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Fabrication and characterization of composite TiO2 nanotubes/boron-doped diamond electrodes towards enhanced supercapacitors
... (2) NTs are partially decomposed and converted to Ti 2 O 3 and TiC fractions. Finally, TiO 2 NTs, which demonstrate high ordering attained by a simple, rapid and controllable anodic oxidation method, can be used as the conductive BDD layer deposited on a substrate and then embedded into the structure of a supercapacitor [70,105,106]. Most recently, Miroslav et al. [41] reported on the development of a unique photoelectrochemical electrode consisting of a nanostructured BDD layer covering an n-type TiO2 film ( Figure 20). ...
... Schematic illustration for composite TiO2 NTs/BDD electrode. Cyclic voltammetry plots: (a) combination electrodes TiO2 NTs/BDD-10 k, with pure TiO2 and BDD immersed in 0.1 M NaNO3 (ν = 50 mV/s), (b) the curve of peak currents versus the square root of the scan rate for different BDD-covered electrodes[70,105,106]. ...
... Schematic illustration for composite TiO 2 NTs/BDD electrode. Cyclic voltammetry plots: (a) combination electrodes TiO 2 NTs/BDD-10 k, with pure TiO 2 and BDD immersed in 0.1 M NaNO 3 (ν = 50 mV/s), (b) the curve of peak currents versus the square root of the scan rate for different BDD-covered electrodes[70,105,106]. ...
This review is mainly focused on the optoelectronic properties of diamond-based one-dimensional-metal-oxide heterojunction. First, we briefly introduce the research progress on one-dimensional (1D)-metal-oxide heterojunctions and the features of the p-type boron-doped diamond (BDD) film; then, we discuss the use of three oxide types (ZnO, TiO2 and WO3) in diamond-based-1D-metal-oxide heterojunctions, including fabrication, epitaxial growth, photocatalytic properties, electrical transport behavior and negative differential resistance behavior, especially at higher temperatures. Finally, we discuss the challenges and future trends in this research area. The discussed results of about 10 years’ research on high-performance diamond-based heterojunctions will contribute to the further development of photoelectric nano-devices for high-temperature and high-power applications.
... After laser treatment, for almost all the examined cases, the appearance of several peaks is visible (Fig. 6). For the all analyzed samples we found the characteristic peaks near 142 cm −1 and mediumintensity peak 197 cm −1 , derived to anatase [41][42][43] (Table 3). Weak signals near 494 cm −1 for samples manufactured in the focal plane, can also form the anatase. ...
... Similarly, the moderate-intensity peak near 326, 335 cm −1 and the medium-intensity 439 cm −1 were observed for the symmetric bending vibrations at OeTieO bond from Ti 2 O 3 [44]. The broad medium-intensity peak near 439 cm −1 with, according to the literature [41,44], are the symmetry stretching vibrations for the Ti 2 O 3 . For the set of samples created out of the focal plane (4d), near 446 cm −1 the broad medium-intensity peak can be found, which may be from the TieO vibrations [41]. ...
... The broad medium-intensity peak near 439 cm −1 with, according to the literature [41,44], are the symmetry stretching vibrations for the Ti 2 O 3 . For the set of samples created out of the focal plane (4d), near 446 cm −1 the broad medium-intensity peak can be found, which may be from the TieO vibrations [41]. According to the literature [42,45], rutile has a characteristic peak near 446 and 611 cm −1 . ...
This study presents an analysis of the impact of the oxide layers, prepared by means of laser radiation in ambient air with different process parameters, on the morphology, corrosion resistance and adhesion properties of titanium grade 2. The samples were irradiated in and out of the focal plane, using a commonly-available fiber laser (Yb:glass) system. The microscopic examination, colorimetry, roughness, chemical Raman analysis, electrochemical tests (electrochemical impedance spectroscopy) as well as adhesion, wettability and scratch-tests were conducted. The study has shown that laser oxidation, depending on the choice of process parameters, can contribute to both the improvement and deterioration of the surface quality, including the size and amount of microcracks, other defects or heterogeneities, roughness, and adhesion. The samples manufactured in the focal plane exert a higher corrosion resistance, higher adhesion and lower roughness, compared to those irradiated out of the focal plane. The aim of this study was to broaden the knowledge about the nature and influence of laser-induced oxidation in and out of the focal plane on selected properties of oxide layers.
... Recently, nanomaterials such as metal oxides have drawn a large attention for electrode materials. Among these metal oxides TiO 2 nanomaterial are one of the most attractive candidate for their easy synthesis, chemical stability, abundance in nature, low environmental impact and larger surface area [10]. TiO 2 nanotube arrays are widely being used in the field of catalysis [11,12]. ...
... Low electrochemical activity and inadequate conductivity of TiO 2 are associated from the semi conductive origin of TiO 2 and leads to restrict its use for high performance supercapacitors. Inspite of high exterior area and lineal transportation of charge, TiO 2 nano-tubes, without doping, provide the SC which is generally confined to less than 1 mF/ cm 2 [10]. Lu et al. [13] and Salari et al. [14,15] have informed that semiconducting behavior of TiO 2 can be changed by a thermal treatment that associates an incorporation of oxygen vacancies (Ti 3+ sites) to attain amended capacitive behavior. ...
... Moreover, metal oxide nanoparticles (MONPs) such as transition metal oxides (e.g. titanium dioxide [5], manganese oxide [6], and iron oxide [7]), perovskites (e.g. bismuth-iron oxide [8]), spinel type oxides (e.g. ...
... Titanium dioxide (TiO 2 ) is an electrode material of choice for the pseudocapacitors due to their abundance in nature, facile synthesis routes, chemical stability, and relatively large surface area [5]. Substitution of oxygen anions in the structure of TiO 2 with dopants such as nitrogen, sulfur and carbon has been shown to increase the electrical conductivity [17] which can boost the supercapacitive performance of TiO 2 [18,19]. ...
Titanium dioxide (TiO2) is one of the most commercialized metal oxides due to its abundance, low cost, and environmental friendliness. However, its potential for application in electrochemical energy storage devices especially as an electrode material for supercapacitors is limited. In this study, Nitrogen-doped TiO2 (N-doped TiO2) nanoparticles are synthesized through a sol–gel method and their supercapacitive performance is compared with that of TiO2 nanoparticles. X-ray photoelectron spectroscopy (XPS) analysis of N-doped TiO2 proves successful doping of nitrogen into the crystal lattice of the TiO2 nanoparticles with a concentration of 4.1 atom%. Electrochemical properties of the synthesized materials are investigated with a three-electrode system in 3.0 M KCl as the aqueous electrolyte. Electrochemical characterizations proved that nitrogen doping of TiO2 nanoparticles provided an enhanced supercapacitive performance including, specific capacitance of 311 F g⁻¹ at 1 A g⁻¹, 98.9% capacitance retention after 4000 cycles, and a better rate capability than that of bare TiO2 nanoparticles. Results of this study clearly demonstrate that small amount of nitrogen doping into the crystal lattice of TiO2 nanoparticles significantly improves their supercapacitive performance. © 2018 Springer Science+Business Media, LLC, part of Springer Nature
... MONPs typically enclose low electrical conductivity 19,20 , but by adding conductive materials to (MONPs), their electrical conductivity is increased, which in turn improves their capacitance 21,22 . The TiO 2 NPs are preferred electrode material for pseudocapacitors because of its natural abundance, easy manufacturing methods, chemical stability, and comparatively large surface area 23 . It has been demonstrated that adding dopants like carbon, sulphur, or nitrogen to the structure of TiO 2 increases its electrical conductivity 24,25 , which in turn improves the material's supercapacitive properties 26,27 . ...
The development of multifunctional nanomaterials for environmental remediation and energy storage is critical for sustainable technologies. In this study, we synthesized strontium-doped titanium dioxide (Sr-TiO2) nanoparticles (NPs) via a green method and investigated their structural, optical, and electrochemical properties to enhance photocatalytic and supercapacitive performance. Characterization results confirmed successful Sr incorporation into the TiO2 lattice. X-ray diffraction (XRD) analysis revealed a slight shift in peak positions, indicating lattice distortion due to Sr doping. Scanning electron microscopy (SEM) showed uniform, well-dispersed nanoparticles, while energy-dispersive X-ray (EDX) spectra confirmed elemental composition. UV-visible spectroscopy (UV-Vis) demonstrated a redshift in absorption, reducing the bandgap and enhancing visible-light absorption. Fourier transform infrared (FTIR) spectroscopy identified characteristic functional groups, and Brunauer–Emmett–Teller (BET) analysis indicated increased surface area, favoring photocatalytic and electrochemical activity. The photocatalytic performance of Sr-TiO2 NPs was assessed through Methylene Orange (MO) and Congo Red (Con-R) degradation under visible light at different pH levels. Under optimized conditions, Sr-TiO2 NPs achieved 94.48% MO removal in 100 min and 97.89% Con-R removal in 70 min, following pseudo-first-order kinetics, demonstrating their efficiency as visible-light-driven photocatalysts for wastewater treatment. Electrochemical studies, including cyclic voltammetry (CV), charge-discharge tests, and electrochemical impedance spectroscopy (EIS), revealed improved charge storage and lower charge transfer resistance compared to bare TiO2. The Sr-TiO2 NPs exhibited enhanced specific capacitance and good electrochemical stability, underscoring their potential as high-performance electrode materials for supercapacitors. These findings highlight a sustainable approach to environmental remediation and energy storage by leveraging Sr-doped TiO2 nanomaterials for dual-functional applications.
... With the invention of the deposition of a CVD diamond film onto a non-diamond substrate, this problem was solved. The fabrication of conductive diamond films with various shapes has reached a promising development stage [41][42][43][44]. The fundamental CVD growth mechanism of diamond film is the pyrolysis of a hydrocarbon to deposit sp 3 -bonded carbon and simultaneously suppress the formation of graphitic sp 2 -bonds with the presence of atomic hydrogen. ...
Boron-doped diamond (BDD) is considered as a high-performance electrode material for electrochemical oxidation (EO) of organic compounds or pathogens in wastewater. With its excellent physical, chemical properties and wide potential window, BDD surpasses the capabilities of classical electrodes. The present chapter provides an overview on the general issues of using BDD electrodes for such applications. It starts with a small discussion on different types BDD electrodes and their preparation methods. The main factors that affect the performance of BDD electrode have been discussed and evaluated. Then, we focus on the degradation mechanisms and reactor design that based on EO. More attention is paid to recent applications of electrochemical oxidation using BDD electrodes in various organic water treatment and disinfection. Finally, the prospective and challenge of BDD electrode in the upcoming future are discussed according to the existing problems in water treatment.
... In recent years, considerable efforts have been made by various researchers to discuss the effect of doping of rare earth and transition metal elements in TiO 2 to enhance the physical and chemical properties [37][38][39][40][41][42]. However, according to our best knowledge, no report is to be found in the literature on the dual doping of various rare earth elements such as lanthanum (La), neodymium (Nd), and transition metals yttrium (Y), vanadium (V) for supercapacitor electrode. ...
Nanostructured TiO2 has been extensively used for environmental and energy storage applications because of its high chemical stability, economical, non-toxic, and significant charge density. However, the poor electrical conductivity of TiO2 restricts its widespread practical application for high-performance supercapacitors. Hereby, in the present work, we investigated the influence of rare-earth/transition metal ions dual doping on electrochemical performance of TiO2 by synthesizing Ti0.90La0.05M0.05O2 (M = Y, Nd, V) nanostructures via facile sol–gel method. The effect of dual doping on the prepared TiO2-based nanostructures was studied for structural, electrical, and morphological characteristics by using XRD, FTIR, IV, and FESEM measurements. The XRD and FTIR results confirmed the successful dual doping with tetragonal phase formation of TiO2, and FESEM images revealed the formation of interconnected nanosphere type morphology by La/V doping. The CV, GCD, LSV, and EIS were performed to assess the electrochemical behavior of grown TiO2-based nanostructures for supercapacitor application. The electrochemical results exhibited the Faradic charge storage mechanism in all the fabricated nanostructures with pseudocapacitive nature. The CV results showed the highest specific capacitance (1070 F/g) for TiLaVO2 nanostructure than other grown samples. TiLaVO2 electrode also exhibited superior specific capacitance (803 F/g), energy density (28 Wh/kg), and power density (0.3 KW/kg), at a current density of 1 A/g in 1 M KOH electrolyte with better cycling stability 93% retention after 1000th cycle. The superior performance of TiLaVO2 electrodes was attributed to the formation of nanospheres that offer more electroactive sites for ion/electron transportation, higher electrical conductivity (IV results), higher current density (LSV results), and lower resistance and fast charge transfer (EIS results). The dual doping of different ions provoked size tunability, electrical conductivity improvement, and superior electrochemical characteristics of TiO2. Moreover, the facile strategy (dual doping) discussed in the present findings would provide insights for enhancing the electrochemical properties of TiO2 for use as supercapacitor electrode material.
Graphical abstract
... The presence of C-O species on the pristine CFE is due to surface contamination and partial oxidation in the air atmosphere. These results agree with the literature findings (Sobaszek et al., 2016;Kunuku et al., 2022). The oxidised to non-oxidised carbon share, C ox = 0.40 for pristine CFE, is based on C 1s spectral deconvolution. ...
Carbon felts are flexible and scalable, have high specific areas, and are highly
conductive materials that fit the requirements for both anodes and cathodes in
advanced electrocatalytic processes. Advanced oxidative modification processes
(thermal, chemical, and plasma-chemical) were applied to carbon felt anodes to
enhance their efficiency towards electro-oxidation. The modification of the porous
anodes results in increased kinetics of acetaminophen degradation in aqueous
environments. The utilised oxidation techniques deliver single-step, straightforward,
eco-friendly, and stable physiochemical reformation of carbon felt surfaces. The
modifications caused minor changes in both the specific surface area and total pore
volume corresponding with the surface morphology.
A pristine carbon felt electrode was capable of decomposing up to 70% of the
acetaminophen in a 240 min electrolysis process, while the oxygen-plasma treated
electrode achieved a removal yield of 99.9% estimated utilising HPLC-UV-Vis. Here,
the electro-induced incineration kinetics of acetaminophen resulted in a rate constant
of 1.54 h-1, with the second-best result of 0.59 h-1 after oxidation in 30% H2O2. The
kinetics of acetaminophen removal was synergistically studied by spectroscopic and
electrochemical techniques, revealing various reaction pathways attributed to the
formation of intermediate compounds such as p-aminophenol and others.
The enhancement of the electrochemical oxidation rates towards acetaminophen was
attributed to the appearance of surface carbonyl species. Our results indicate that the
best-performing plasma-chemical treated CFE follows a heterogeneous mechanism
with only approx. 40% removal due to direct electro-oxidation. The degradation
mechanism of acetaminophen at the treated carbon felt anodes was proposed based
on the detected intermediate products. Estimation of the cost-effectiveness of removal
processes, in terms of energy consumption, was also elaborated. Although the study
was focussed on acetaminophen, the achieved results could be adapted to also
process emerging, hazardous pollutant groups such as anti-inflammatory pharmaceuticals.
... These two species represent 37 at.% of all FA constituents. The next three peaks, present in the core energy levels, are typical for oxidized carbon bonds as C-O (285.9 eV), C=O (287.8 eV) and O=C-O (289.3 eV) [32,34,35]. A similar analysis carried out for the FA-TiO 2 composite revealed a significant decrease in the total share of all carbon forms. ...
Fly ash (FA) is a waste product generated in huge amounts by coal-fired electric and steam-generating plants. As a result, the use of FA alone or in conjunction with other materials is an intriguing study topic worth exploring. Herein, we used FA waste in conjunction with titanium oxide (TiO2) to create (FA-TiO2) nanocomposites. For the first time, a cathodic polarization pre-treatment regime was applied to such nanocomposites to efficiently produce hydrogen from an alkaline solution. The FA-TiO2 hybrid nanocomposites were prepared by a straightforward solvothermal approach in which the FA raw material was mixed with titanium precursor in dimethyl sulfoxide (DMSO) and refluxed during a given time. The obtained FA-TiO2 hybrid nanocomposites were fully characterized using various tools and displayed a cenosphere-like shape. The synthesized materials were tested as electrocatalysts for the hydrogen evolution reaction (HER) in 0.1 M KOH solution in the dark, employing various electrochemical techniques. The as-prepared (unactivated) FA-TiO2 exhibited a considerable HER electrocatalytic activity, with an onset potential (EHER) value of −144 mV vs. RHE, a Tafel slope (−bc) value of 124 mV dec−1 and an exchange current density (jo) of ~0.07 mA cm−2. The FA-TiO2′s HER catalytic performance was significantly enhanced upon cathodic activation (24 h of chronoamperometry measurements performed at a high cathodic potential of −1.0 V vs. RHE). The cathodically activated FA-TiO2 recorded HER electrochemical kinetic parameters of EHER = −28 mV, −bc = 115 mV dec−1, jo = 0.65 mA cm−2, and an overpotential η10 = 125 mV to yield a current density of 10 mA cm−2. Such parameters were comparable to those measured here for the commercial Pt/C under the same experimental conditions (EHER = −10 mV, −bc = 113 mV dec−1, jo = 0.88 mA cm−2, η10 = 110 mV), as well as to the most active electrocatalysts for H2 generation from aqueous alkaline electrolytes.
... Cyclic voltammeter was used for the electrochemical properties for pure and N-doped DWCNTs, and at different scan rates (mV/s), pseudocapacitance behaviour was observed for N-DWCNTs. Similarly, PPy/ MnO2 [166], TiO2 nanotubes/boron-doped diamond electrodes [167], CNTs on graphene [168], and NGF/CNT/MnO2 [169] were also prepared as electrode materials for supercapacitors. Figure 10 describes the chemical vapor deposition process for the preparation of CNTs and nitrogen-doped carbon nanotubes for supercapacitors. ...
Supercapacitors (SCs) have received much interest due to their enhanced electrochemical performance, superior cycling life, excellent specific power, and fast charging–discharging rate. The energy density of SCs is comparable to batteries; however, their power density and cyclability are higher by several orders of magnitude relative to batteries, making them a flexible and compromising energy storage alternative, provided a proper design and efficient materials are used. This review emphasizes various types of SCs, such as electrochemical double-layer capacitors, hybrid supercapacitors, and pseudo-supercapacitors. Furthermore, various synthesis strategies, including sol-gel, electro-polymerization, hydrothermal, co-precipitation, chemical vapor deposition, direct coating, vacuum filtration, de-alloying, microwave auxiliary, in situ polymerization, electro-spinning, silar, carbonization, dipping, and drying methods, are discussed. Furthermore, various functionalizations of SC electrode materials are summarized. In addition to their potential applications, brief insights into the recent advances and associated problems are provided, along with conclusions. This review is a noteworthy addition because of its simplicity and conciseness with regard to SCs, which can be helpful for researchers who are not directly involved in electrochemical energy storage.
... These three types of chemical bonds are commonly identified in the C 1s spectra as signals peaking at a binding energy of 284.6 eV (C2), 286.0 (C3), and 288.1 eV (C4), Table 2 The electric parameters obtained for CB-PLA electro-activation in 1 M NaOH for each studied electrochemical polarization condition. respectively [21,33,34]. Furthermore, their expected ratio for PLA matrix should be 1:1:1. ...
Additive manufacturing, also known as 3D printing, is beginning to play an unprecedented role in developing many applications for industrial or personalized products. The conductive composite structures require additional treatment to achieve an electroactive surface useful for electrochemical devices. In this paper, the surfaces of carbon black/poly(lactic acid) CB-PLA printouts were activated by electrolysis or enzymatic digestion with proteinase K, or a simultaneous combination of both. The proposed modification protocols allow the tailoring of electrochemically active surfaces and electron transfer kinetics determined by electrochemical techniques (CV, EIS) by [Fe(CN)6]4-/3- redox probe. X-ray photon spectroscopy and SEM imaging were applied to determine the delivered surface chemistry. CB-PLA hydrolysis under alkaline conditions and anodic polarization greatly impacted the charge transfer kinetics. The enzymatic hydrolysis of PLA with proteinase K led to highly efficient results, yet requires an unsatisfactory prolonged activation duration of 72 h, which can be efficiently reduced by electrolysis carried out in the presence of the enzyme. Our studies hint that the activation protocol originates from surface electropolymerization rather than a synergistic interaction between the electrolysis and enzymatic hydrolysis. The detailed mechanism of CB-PLA hydrolysis supported by electrolysis is a promising new route to achieve a time-efficient and environmentally-friendly activation procedure.
... a,b) XPS spectra registered in a) C 1s and b) O 1s binding energy range for the untreated CB-PLA electrode and after its electro-activation using various protocols, c-e) SEM micrographs of CB-PLA electrode surface after hydrolysis in c) 1M HCl and d) 1M NaOH, and e) electrolysis in 1M NaOH (-1.4 to +1.2 V vs. Ag|AgCl polarization range).The polylactide chemistry includes three different carbon chemical states, namely C-C, C-O, and C=O. These three types of chemical bonds are commonly identified in the C 1s spectra as signals peaking at a binding energy of 284.6 eV (C2), 286.0 (C3), and 288.1 eV (C4), respectively[21,32,33]. ...
Additive manufacturing, called 3D printing, starts to play an unprecedented role in developing many applications in industrial or personalized products. The conductive composite structures require additional treatment to achieve an electroactive surface useful for electrochemical devices. In this paper, the surfaces of carbon black/poly(lactic acid) CB-PLA printouts were activated by electrolysis or enzymatic digestion with proteinase K, or a simultaneous combination of both. Proposed modification protocols allowed for tailoring electrochemically active surface area and electron transfer kinetics determined by electrochemical techniques (CV, EIS) with [Fe(CN)6]4-/3- redox probe. The X-ray photon spectroscopy and SEM imaging were applied to determine the delivered surface chemistry. The CB-PLA hydrolysis in alkaline conditions and under anodic polarization greatly impacts the charge transfer kinetics. The enzymatic hydrolysis of PLA with proteinase K has led to highly efficient results yet requiring an unsatisfactory prolonged activation duration of 72 h, efficiently reduced by the electrolysis carried out in the presence of the enzyme. Our studies hint that the activation protocol originates from surface electropolymerization rather than synergistic interaction between electrolysis and enzymatic hydrolysis. The detailed mechanism of CB-PLA hydrolysis supported by electrolysis has been elaborated since it pawed a new route towards a time-efficient and environmentally-friendly activation procedure.
... Furthermore, noticeable broad signals centered around 416 and 627 cm -1 suggest the existence of TiC in the nanotube structure36 . These signals, together with those around 150 and 516 cm -1 , can be attributed to the internal stress of the crystalline structure generated by the TiO 2 and TiC clusters37 . In their studies on amorphous carbon nanocomposite films doped by titanium, Zemek et al.38 reported a similar effect, with sp 2 hybridization within subsurface TiC clusters. ...
The long cycle life stability jointly with high energy density are limiting broader feasible applications of supercapacitors. The novel diamondized titania nanocomposite supercapacitors deliver high power and energy densities along with high capacitance retention rates. Supercapacitor electrodes were fabricated utilizing a combination of Ti anodization followed by chemical vapor deposition resulting in simultaneous growth of complex BDD/TiC interface. The first-principles simulations along with extended molecular investigations conducted by BF-TEM and HR-SEM revealed that capacitive phenomena are delivered by nanoporous, multi-faceted, and substoichiometric TiC, forming clusters at the lateral surfaces of titania nanotubes. Next, TiC mechanical stability and effective charge transfer electrode-electrolyte are efficiently provided by highly conductive although discontinuous BDD overlayer. The assembled two-electrode supercapacitor devices exhibited capacitance 15 mF cm−2, which were stable at 0.1 V s−1 scan rate in various neutral aqueous electrolytes. The composite TiO2NT-BDD supercapacitors showed outstanding long-term cycling stability with capacitance retention of 93% after 100,000 chronopotentiometry cycles verified by post-aging cyclic voltammetry tests. In parallel, the energy and power density calculated at a current density of 3 A g-1 achieved levels as high as 14.74 Wh kg-1 and 24.68 kW kg-1, revealing the superior performance of the assembled devices compared to recently reported supercapacitors.
... Currently, there are very few researches related to the study of nÀp heterojunctions using BDD as a p-type material and different methods; some of them are shown in Table 10À1. Those methods, such as sputtering [65], liquid phase deposition [66], MOCDV [58], MWPECVD [70], and anodic hydrolysis [72] seem to be expensive, and they are only possible with the high-cost equipment. Recently, different authors have concerned about developing new methods that do not require highly specialized equipment to make TiO 2 films, keeping their properties, and they can be made with simple equipment. ...
... Currently, there are very few researches related to the study of nÀp heterojunctions using BDD as a p-type material and different methods; some of them are shown in Table 10À1. Those methods, such as sputtering [65], liquid phase deposition [66], MOCDV [58], MWPECVD [70], and anodic hydrolysis [72] seem to be expensive, and they are only possible with the high-cost equipment. Recently, different authors have concerned about developing new methods that do not require highly specialized equipment to make TiO 2 films, keeping their properties, and they can be made with simple equipment. ...
... The Raman spectra of the samples Black, Tran-1 and Tran-2 are presented in Fig. 5. The sample Black shown in Fig. 5a has characteristic peaks of five bending modes (E g ) and two stretching modes (A 1g ), all matching well results of previous works based upon tistarite, a Ti 2 O 3 mineral recently discovered in the Allende Meteorite [47], and the synthetic Ti 2 O 3 [48]. The details of the peaks position are shown in Table 3. ...
In the present work, a simple route to control the growth of different crystalline titanium oxides thin films prepared by reactive sputtering is reported. Using the film pumping speed, the oxygen consumption or “oxygen gettering” in the reactive process is monitored, obtaining different titanium suboxides (TSO's) films with high deposition rate in the metallic zone of the reactive process. On the other hand, it was also obtained titanium dioxide (TiO2) thin films at the beginning of the oxidative region, without using postdeposition thermal annealing. X-ray diffraction and Raman spectroscopy were used to determine the different titanium oxides according to the oxygen percentage added to the chamber during the reactive process.
... Nanostructured materials have the potential to considerably reduce the impact of energy production, storage and use [1]. Supercapacitors are encouraging energy storage devices because of their high power density, fast charging/discharging rate, and excellent cycle stability [2][3][4]. Such exceptional properties make supercapacitors promising material for wide range of applications, where extraordinary power density and good cycle-life are highly desirable. ...
Mixed transition metal oxides with hierarchical and porous structures are considered to be the promising electrodes for high-performance supercapacitors. Nickel-Tin-Oxide (NiSnO3) thin films are deposited by spray pyrolysis for electrochemical supercapacitors. The films are characterized by X-ray diffraction (XRD), scanning electron microscopy and UV–Vis spectrophotometer. XRD patterns confirm formation of Perovskite NiSnO3. NiSnO3 thin films show flake and spongy type of morphology. The band gap energy is found to be in the range of 3.31–3.56 eV. The pseudocapacitive behavior of NiSnO3 electrodes has been investigated through cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) measurements in 2 M aqueous KOH. NiSnO3 electrode shows maximum specific capacitance of 386 F g− 1 at scan rate 5 mV s− 1. Further, 92.63% retention in specific capacitance is observed after 1000 charge/discharge cycles. EIS study reveals low solution and charge transfer resistance. These features make NiSnO3 electrode attractive for high-performance supercapacitors.
... It is known that TiO 2 exhibits n-type semiconductor properties, which can composite with a p-type semiconductor to form a p-n type heterojunction [18,22]. The electric field integrally formed at the heterojunction interface can effectively separate the photoelectrons/holes in TiO 2 [23][24][25][26]. Therefore, a p-type substrate may be used to form a p-n type heterojunction. ...
Rutile TiO2 nanorod (TiNR) arrays were fabricated on a boron-doped diamond (BDD) substrate by a simple hydrothermal synthesis method. A fluorine-doped tin oxide (FTO) electrode grown with TiNR arrays was also prepared using the same technology for comparison. Field-emission scanning electron microscopy results show that oriented TiNR arrays can grow vertically on the surface of BDD and FTO electrodes. TiNR arrays grown on both electrodes had the same length (3 μm). In comparison with the TiNR/FTO electrode, the TiNR/BDD electrode demonstrated a higher photoelectrocatalytic activity for the degradation of water and organic compounds, which is mostly attributed to the formation of a p-n heterojunction between the TiNR arrays and BDD at high potential, apart from the density of TiNR. A linear relationship between the photoelectrocatalytic current and the organic concentration can be observed on both electrodes. However, the linear range between net photoelectrocatalytic current values and organic compound concentrations for the TiNR/BDD electrode are much greater than those for the TiNR/FTO electrode, which makes the TiNR/BDD electrode a versatile material for the photocatalytic degradation and sensing of organic compounds.
... Supercapacitors offer unique features owing to their high power density, fast charge-discharge rate, superior cycle-lifetime, simple charging circuit and free from chemical pollution. Due to these reasons, supercapacitors have become attractive power sources for industrial and domestic applications [4][5][6][7]. Supercapacitors have 10 to 100 times higher power density than battery [2]. In the Super capacitors energy density is much higher than the conventional energy sources but less than fuel cell [5]. ...
... Unlike its related thick SiO 2 crystalline phase, fused silica is amorphous material with a macroscopic inversion symmetry that promotes growth of non-diamond phases. Besides, it could be easier dehydrated by hydrogen rich plasma generating oxygen species [98,99] responsible for boron incorporation saturation [100]. Furthermore, the smaller resistivity might also be caused by charge tunnelling effect to the Si wafer substrate, which is driven by the impurities in thermally fabricated thick oxide films. ...
This paper presents boron-doped diamond (BDD) film as a conductive coating for optical and electronic purposes. Seeding and growth processes of thin diamond films on fused silica have been investigated. Growth processes of thin diamond films on fused silica were investigated at various boron doping level and methane admixture. Two step pre-treatment procedure of fused silica substrate was applied to achieve high seeding density. First, the substrates undergo the hydrogen plasma treatment then spin-coating seeding using a dispersion consisting of detonation nanodiamond in dimethyl sulfoxide with polyvinyl alcohol was applied. Such an approach results in seeding density of 2 x 1010 cm -2 . The scanning electron microscopy images showed homogenous, continuous and polycrystalline surface morphology with minimal grain size of 200 nm for highly boron doped films. The sp3 /sp2 ratio was calculated using Raman spectra deconvolution method. A high refractive index (range of 2.0-2.4 @550 nm) was achieved for BDD films deposited at 500 ºC. The values of extinction coefficient were below 0.1 at λ=550 nm, indicating low absorption of the film. The fabricated BDD thin films displayed resistivity below 48 Ohm cm and transmittance over 60% in the visible wavelength range.
... Supercapacitors offer unique features owing to their high power density, fast charge-discharge rate, superior cycle-lifetime, simple charging circuit and free from chemical pollution. Due to these potentials supercapacitors are becoming attractive sources of power for industrial and domestic applications [4][5]. ...
Mn3O4 thin film electrodes with various mass-loadings are deposited by spray pyrolysis using aqueous/organic solvent mixture. The influence of mass-loading on the electrochemical properties of Mn3O4 thin film electrodes is studied. The results showed that, the as-prepared Mn3O4 exhibited ideal capacitive behavior in a voltage window of - 0.2 to 0.4 V. With increasing of Mn3O4 mass-loading from 0.47 mg cm- 2 to 0.64 mg cm- 2, the specific capacitance calculated from the cyclic voltammetry curves at 5 mV s- 1 increased from 520 to 597 F·g- 1. The specific energy and specific power are found to be 3735 Wh kg- 1 and 12.45 W kg- 1 respectively at a current density of 4.0 A·g- 1 for film having 0.64 mg cm- 2 mass-loading. Ragone plots indicated that the Mn3O4 electrode with 0.64 mg cm- 2 mass-loading possessed good power-energy density characteristics. The electrochemical performances of 0.64 mg cm- 2 mass-loading Mn3O4 thin film electrode suggest suitability of this material as a potential electrode material for supercapacitors.
... The sensitivity threshold, selectivity and operating speed are heightened due to deposition of Pt nanoparticles onto the surface of CNTs as compared to sensors produced with undeposited C N Ts. T h e nanocomposites consisting of carbon nanotubes modified with Pt are appropriate for production o f e l ectrodes, they a l so may b e u s ed in a catalysis process of different chemical reactions and in fuel cells333435363738394041. ...
Purpose: The main purpose of the article is to present interesting forms of platinum at a nanometric scale. There are multiple fabrication methods of nanoparticles, nanowires and other forms of platinum, and the methods proposed in the article are simple and effective. They employ carbon nanotubes in the form of a so-called forest, manufactured by CVD methods and nanotubes dispergated (in a water or ethylene glycol solution) as templates for deposition of Pt nanoforms. Design/methodology/approach: Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were applied for showing the structure and morphology of platinum nanoforms deposited on carbon nanotubes, and Energy Dispersive Spectroscopy (EDS) was used for confirming the chemical composition of the analysed structures. Findings: The microscope examinations carried out with scanning electron microscopy have shown that platinum may crystallise by assuming the form of, notably, nanoparticles, nanowires and nanocubes. The structure of carbon nanotubes covered with nanoparticles of Pt at a nanoscale could have been observed by applying high-resolution transmission electron microscopy. Practical implications: Carbon nanotubes decorated with Pt nanoparticles and platinum at a nanometric scale are used as, in particular, an active layer of chemical and biochemical sensors. In addition, excellent catalytic properties of platinum are used in various industrial processes, including chemical, automotive and petroleum industry. Originality/value: Chloroplatinic acid H2PtCl6 is an input substance for producing various forms of platinum. Platinum exhibits unique physiochemical properties at a nanoscale, different than its properties at a macro scale. It was confirmed that the selected fabrication method of platinum nanoforms is effective and simple.
This work introduces a novel, scalable methodology for rapidly fabricating sulfur-doped laser-induced graphene with enhanced porosity and wetting characteristics, targeting advanced supercapacitor applications. An infrared laser scribing technique was employed to create a three-dimensional porous graphene network, with in-situ sulfur doping achieved through physical evaporation using powder precursor. A second-pass laser process ensured uniform sulfur integration and optimized graphene structure. Sulfur incorporation facilitated the formation of a hierarchical porous network, significantly improving hydrophilicity and surface chemistry. This modification enhanced ion transport and charge storage mechanisms through synergistic double-layer and pseudo-capacitance effects. Physicochemical characterization revealed a dramatically increased ID/IG ratio post-sulfur doping and plasma treatment, indicating increased crystal plane defects and promising capacitive properties. Systematic optimization of sulfur loading, synthesis temperature, and electrolyte composition yielded remarkable electrochemical performance. The optimized S-doped electrodes achieved a high areal capacitance of 30.18 mF/cm2 at 0.08 mA/cm2 using a PVA/H2SO4 gel electrolyte. Notably, the developed supercapacitors demonstrated mechanical flexibility, maintaining 84.7 % of their initial capacitance after 5000 cycles, highlighting the potential for scalable, flexible energy storage technologies.
Diamond nanomaterials are renowned for their exceptional properties, which include the inherent attributes of bulk diamond. Additionally, they exhibit unique characteristics at the nanoscale, including high specific surface areas, tunable surface structure, and excellent biocompatibility. These multifaceted attributes have piqued the interest of researchers globally, leading to an extensive exploration of various diamond nanostructures in a myriad of applications. This review focuses on non‐zero‐dimensional (non‐0D) diamond nanostructures including diamond films and extended diamond nanostructures, such as diamond nanowires, nanoplatelets, and diamond foams. It delves into the fabrication, modification, and diverse applications of non‐0D diamond nanostructures. This review begins with a concise review of the preparation methods for different types of diamond films and extended nanostructures, followed by an exploration of the intricacies of surface termination and the process of immobilizing target moieties of interest. It then transitions into an exploration of the applications of diamond films and extended nanostructures in the fields of biomedicine and electrochemistry. In the concluding section, this article provides a forward‐looking perspective on the current state and future directions of diamond films and extended nanostructures research, offering insights into the opportunities and challenges that lie ahead in this exciting field.
In this present study, CuO/TiO2/rGO (CTG) hybrid ternary composite was synthesized via a single-step hydrothermal route for an asymmetric supercapacitor application. The PXRD pattern and XPS analysis confirms the formation of prepared ternary composites. As analyzed by FE-SEM and HR-TEM techniques, both CuO and TiO2 nanoparticles were anchored on the conducting two-dimensional rGO matrix, which facilitates efficient electron transport during electrochemical tests. From the electrochemical investigations, the CTG-2 composite revealed a high rise in capacitance value of 1077 Fg-1, overcoming the individual capacitance of CuO (173.4 Fg-1), TiO2 (206.2 Fg-1), rGO (269 Fg-1), and composite CTG-1 (690 Fg-1) at a current density of 1 Ag-1 with an unveiled remarkable capacitance performance of 88.4 % over the 5000 cycles at 5 Ag-1. Further, an asymmetric supercapacitor device was also assembled in two-electrode system with a specific capacitance of 563.7 Fg-1 at 1 Ag-1, with an energy and power density of 50.2 Wh Kg-1 and 498.2 W Kg-1. This research provides a novel approach for synthesizing CTG ternary nanocomposite, which could have an impact on contemporary electrical vehicles and portable electronics that are used for energy storage applications.
In this study, the Ni nanoparticles grafted TiO2 nanotubes electrode improved by surface reconstruction (s-Ni/TiO2/Ti) shows the facile hydrogen evolution reaction (HER) in the alkaline and chloride solutions. Nickel nanoparticles were electrochemically grafted on the anodic TiO2 nanotubes under different conditions. The heat treatment of TiO2 nanotubes contributes to the enhancement of electrical conductivity and template adherence. The surface reconstruction is indicated to create heterojunction intermediates, Ni(OH)2 and NiOOH, on the surface of Ni nanoparticles. An extremely low overpotential of 126 mV is required for HER on the s-Ni/TiO2/Ti electrode in 1.0 M KOH solution, showing higher activity than Pt/C. Besides, the developed electrode exhibits an overpotential of 127 mV for HER in 1.0 M KOH + 0.5 M NaCl solution. The long-term stability over 100 h suggests a highly active and inexpensive material choice for substituting the precious electrocatalysts in corrosive media such as seawater.
In this study, photolysis and immobilization of bis(aminopyridine)-Cu on the surface of SiO2-coated Fe3O4 nanoparticles were used to create core-shell composites of magnetite (Fe3O4) and Fe3O4@SiO2-bis(aminopyridine)-Cu. FTIR, ICP-AES, XRD, XPS, FESEM-EDS-mapping, and TEM were used to identify the structural characteristics of the catalyst. TGA was used to test the prepared materials' thermal stability, and CV, GCD, and EIS were used to assess their electrochemical characteristics. The successful shelling of SiO2 around Fe3O4 with a size of 20 nm was confirmed by the TEM images. The results of the electrochemical tests demonstrate that the performance of the synthetic materials is typical for supercapacitors. The shell of SiO2-bis(aminopyridine)-Cu can boost Fe3O4's reversibility and storage energy. After 1000 cycles at 5 A/g, the Fe3O4. The Fe3O4@SiO2-bis(aminopyridine)-Cu electrode exhibits good specific capacitance of 265 F/g and excellent cyclic stability with a retention ratio of 85% compared to pure magnetite's 67 percent.
Abstract The objective of this chapter is to describe our work in developing various strategies of surface modification in order to (i) enhance the adsorption capacity of the organic pollutants, (ii) accelerate the kinetic of degradation, (iii) shift the light activation towards visible and solar light, and (iv) facilitate the catalyst recovery to be able to reuse easily the catalyst. The different options are compared towards the degradation of methyl orange under the same experimental conditions. In order to enhance the adsorption capacity of the organic pollutants (i), two original approaches have been developed. The first one leads to the modification of the hydrophilic/hydrophobic properties of the catalyst via the grafting of organosilane onto TiO2. The aim of the second approach is to increase the surface area of the photocatalyst thanks to the immobilization of the TiO2 onto bentonite clay. To accelerate the kinetic of degradation of the pollutant (ii), the mixing of TiO2 and ZnO to produce ZnO/TiO2 systems has been evaluated. To improve the photochemical properties of the catalyst (iii), the grafting of photosensitizers such as monocarboxylic tetraphenyl porphyrin, chlorin e6, tetrakis(4-carboxyphenyl)porphyrin, and protoporphyrin IX has been conducted. Those photosensitizers serve as visible light antenna to modify the UV-limited photoresponse properties of the hybridized TiO2 nanoparticles towards visible activation. In order to facilitate the catalyst recovery (iv), the use of thermoresponsive photocatalyst is developed. Thermoresponsive copolymers based on 2-(2-methoxyethoxy) ethyl methacrylate (MEO2MA) and oligo (ethylene glycol) methacrylate (OEGMA) have been grown from the surface of the ZnO photocatalyst. The recovery of the particles is based on the aggregation of the particles at high temperature and their redispersion at low temperature.
High performance supercapacitors (SCs) need to employ superior capacitor electrodes. Among various capacitor electrodes, diamond and related materials have been recognized as one of the best capacitor electrodes. This is because of their excellent stability, large potential windows, rich surface chemistry, varied surface terminations, and the possibility to enhance their surface areas. Herein, this article summarizes recent progress and achievements regarding the synthesis of nanostructures, particles, hybrid materials and pseudocapacitive composites of diamond and related materials. The applications of these materials for the SC construction are then overviewed. The performance of reported diamond electrical double layer capacitors, pseudocapacitors, redox-electrolyte-enhanced SCs, and metal-ion capacitors is reviewed in detail. Some diamond SC devices and demonstrators are highlighted. The future perspectives of diamond SCs are further outlined and discussed.
Graphene (G) and ternary nanocomposites of Mn3O4, TiO2, and reduced graphene oxide(rGO) electrodes have been prepared for supercapacitor applications. The as-synthesized samples were characterized using several techniques including XRD, SEM, TEM, XPS, and Raman spectroscopy. Electrochemical characterizations were studied via cyclic voltammetry (CV), galvanostatic charge–discharge (GCD), and electrochemical impedance spectroscopy (EIS). XRD patterns of TiO2 and Mn3O4 showed the formation of anatase and hausmannite tetragonal nanoparticles, respectively, whereas rGO and G showed an amorphous structure. The TEM analysis showed spherical shaped particles with less than 50 nm sizes for Mn3O4, nanotube for TiO2, fiber structure for rGO, and layered structure for graphene. The Mn3O4/TiO2/rGO ternary nanocomposite electrode presented a much higher specific capacitance than its single individual constituents. The ternary nanocomposite has a specific capacitance of 356 F g⁻¹ in 6 M KOH aqueous electrolyte and respectable cycling performance, with 91% capacitance retained over 3000 cycles referring to its suitability for supercapacitor applications. An asymmetric supercapacitor (ASC) was constructed using a Mn3O4–TiO2–rGO (MTrGO) as a positive electrode and G as a negative electrode. The organized (ASC) works steadily under the potential window of 0–1.8 V and provides a high-energy density of 31.95 Wh kg⁻¹ at a power density of 7188 W kg⁻¹ complemented by satisfactory cycle stability with 87% capacitance retention over 1000 cycles.
Graphical Abstract
Nowadays, the photocatalytic degradation of air pollutants such as carbon monoxide (CO) has threatened human health by reducing oxygen transport to the body. Other pollutants such as nitrogen oxides (NOx family) or volatile organic carbons (VOCs) that are exhausted from automobiles or factories in large cities are harmful for public health. From this aspect, the study on photocatalysts for the degradation of gaseous pollutants has been recommended. Photocatalysts are key intermediates in environmental applications since they undergo reactions in transforming pollutants to harmless products, benefitting from light energy. The photon energy produces free radicals of •O−2ads or H2O2 from semiconductors and molecular oxygen. These reactions generate other products such as holes which then produce OH•. These reactive species are initiators of photocatalytic reactions. For this purpose, a number of photocatalysts have been explored. These phenomena correspond to a wide variety of metal oxides or semiconductors such as TiO2, ZnO, and WO3. The properties of photocatalysts can be elaborated using appropriate doping metals. The doping may reduce the bandgap and increase the photocatalyst activity by shifting the corresponding irradiation light to a visible area. Another suggestion to overcome the large bandgap of photocatalysts is to make mesoporous materials according to their high surface area. By reducing pore size to meso range (2–50 nm) and increasing surface area, the photocatalytic characteristics could be greatly enhanced. Synthesis of porous photocatalysts with high surface area could be achieved by involving ionic liquids (ILs) as both environmentally benign media and structure-directing materials. ILs have the excellent solubility of inorganic reactants, and at the same time, they have low toxicity and are flameless. The composites of graphene oxide and photocatalysts have been recognized as efficient heterogeneous catalysts, due to their layered spaces that provide accessible catalytic active sites. This chapter first presents air pollutants and then introduces the most important photocatalysts for air purification. The modification of the photocatalyst even at the synthesis level or in the process is the final discussion.
Photocatalysis is a multifaceted phenomenon that can be used for various applications, which include pollutants degradation, organic synthesis, H2 production, CO2 reduction, N2 fixation, antimicrobial applications, and biomass conversion. However, materials are key ingredients to achieve an effective photocatalytic conversion. The meticulous understanding of photocatalytic process reveals that the band edge position, bandgap energy, recombination process, and surface reactions are the four fundamental parameters that need to be controlled to enhance the efficiency of a photocatalyst. In this direction, ferroelectric materials have drawn significant interests due to their internal electrical field, surface polarization properties, and effective band-bending process, which largely govern the abovementioned properties of a photocatalyst. The phenomenon of ferroelectrics essentially helps to reduce the charge recombination possibilities in the system and effortlessly promotes the excited charge carriers to the surface with active sites. However, most of the ferroelectric photocatalysts are ultraviolet light–driven and therefore it has the scope for the bandgap reduction strategies by means of controlling particle size, doping, composite formations, etc. In this context, this chapter intends to provide insights into the various ferroelectric materials that can be used for photocatalytic applications, working mechanism, and their applications in photocatalysis along with a conclusion that highlights the future prospects in the field of ferroelectric photocatalysis.
Conductive diamonds, especially boron‐doped diamonds, own unique advantages over other sp2 nano‐carbon materials. For example, diamond electrodes possess wide electrochemical potential window, low and stable background current, high mechanical and chemical stability, various surface terminations and rich surface chemistry, etc. They have thus been recognized as promising electrodes or electrode supports for various electrochemical applications, including energy storage and conversion, as well as electrocatalysis. In this chapter, recent progresses of conductive diamonds in the areas of supercapacitors, batteries, fuel cells, solar cells and CO2 conversion, etc. are summarized. Challenges for those applications are outlined and discussed, followed by the discussion on several potential directions for future studies.
Uniform three-dimensional porous boron-doped diamond (P-BDD) film is deposited on titanium substrate through chemical vapor deposition and employed as an efficient potential electrode for electrochemical double-layer supercapacitor. The electrochemical responses of BDD electrodes are evaluated by cyclic voltammetry and galvanostatic charge/discharge techniques. P-BDD film delivers a specific capacitance of 6.02 mF cm−2 under scan rate 10 mV s−1, 12.4 times of flat BDD film in 0.1 M H2SO4 electrolyte in three-electrode configuration. Furthermore, operating voltage window of the symmetric device composing of two pieces of P-BDD electrodes could expand to 2.0 V and lighten a yellow light-emitting diode, where the single device presents an admirable energy density of 1.45 μWh cm−2 and power density of 0.5 mW cm−2. Moreover, P-BDD film exhibits favorable self-discharge behavior with low leakage current as small as 14.9 µA and presents remarkable cycling stability with capacitance retention of 91.6% after 10000 continuous cycles. The boosting electrochemical performances can be attributed to the synergistic effect between BDD film itself possessing excellent physical-chemical features and three-dimensional porous structure, which corroborate the P-BDD film potential candidate as future supercapacitor application.
This chapter reviews the construction, modification, and physical characteristics of two types of diamond electrodes: nanoparticle-modified diamond electrodes (NMDE) and detonation nanodiamond-based electrodes (DNDE). These particular types of diamond electrodes show great promise for improving the performance of diamond electrodes via the incorporation of nano-scale chemistry at their surfaces. The construction of both types of electrodes is reviewed, along with the resultant physical and electronic effects. The methods reviewed here are particularly applicable for electroanalytical and electrocatalytic applications of nanoparticle-based diamond electrodes. A brief review of progress on the interactions between metals and diamond at nanoparticle-based electrodes is also included. Finally, an outline of the present state-of-the art research in this field is presented.
Many efforts have been dedicated to develop and study different catalysts supported materials for energy storage and conversion. Polymer electrolyte membranes (PEM) and capacitors have been topics of special interest for the scientific community, then, the research to find excellent catalyst-supports has constantly increased. The use of conductive diamond films has been proposed due to their mechanical and chemical stability properties. In this context, the application of BDD-catalyst surfaces for PEM fuel cells as well as the production of electrochemical capacitors using BDD materials have been summarized and discussed in this chapter.
Boron (a metalloid) has been chosen as the doping agent in the titanium dioxide structure via in situ anodizing method in this work. FE-SEM, XPS, Raman spectroscopy, XRD, EDX and UV–visible techniques were used to investigate the morphology, structure and optical properties of the samples prepared. XPS and UV–visible techniques were used to confirm the presence of boron in the nanotubes and the reduction in band gap, respectively. Afterward, the impact of the concentration of the doping agent on the photoelectrocatalytic and anticorrosion properties of the nanotubes was studied through different electrochemical techniques such as linear sweep voltammetry, chronoamperometry, open-circuit potential and Tafel under visible light. Better photocatalytic performance and anticorrosion properties are shown by nanotubes modified by boron compared with bare titanium dioxide nanotubes, according to the results. The photo-response increases dramatically as boric acid concentration in anodizing electrolyte is increased from samples BT1 to BT10 and slowly decreases for samples BT10-BT25. The best photoelectrocatalytic performance in photoelectrochemical water splitting studies was shown by samples BT10 and BT15. Ultimately, the photo-generated cathodic protection of 403 stainless steel (403SS) has been studied in a corrosion cell using a 3.5% NaCl solution under visible light by the photocatalysts prepared. The photocatalytic activity of TiO 2 under visible light illumination was enhanced by doping of boron, based on the results.
The energy densities of most supercapacitors (SCs) are low, hindering their practical applications. To construct SCs with ultrahigh energy densities, a porous titanium carbide (TiC)/boron‐doped diamond (BDD) composite electrode is synthesized on a titanium plate that is pretreated using a plasma electrolytic oxidation (PEO) technique. The porous and nanometer‐thick TiO2 layer formed during PEO process prevents the formation of brittle titanium hydride and enhances the BDD growth during chemical vapor deposition processes. Meanwhile, the in situ conversion of TiO2 into TiC is achieved. Combination of this capacitor electrode with soluble redox electrolytes leads to the fabrication of high‐performance SCs in both aqueous and organic solutions. In 0.05 m Fe(CN)63−/4− + 1 m Na2SO4 aqueous solution, the capacitance is as high as 46.3 mF cm⁻² at a current density of 1 mA cm⁻²; this capacitance remains 92% of its initial value even after 10 000 charge/discharge cycles; the energy density is up to 47.4 Wh kg⁻¹ at a power density of 2236 W kg⁻¹. The performance of constructed SCs is superior to most available SCs and some electrochemical energy storage devices like batteries. Such a porous capacitor electrode is thus promising for the construction of high‐performance SCs for practical applications.
Petal-like architecture TiO2 mixed oxide (PATMO) nanotubes were readily fabricated by anodization of Ti-4Al-0.005B (TA5) alloy followed by chemical etching in phosphoric acid solution. The formation of PATMO can be attributed to the combined effect of the water-assisted crystallization of TiO2 and the dissolution of alumina component in TiO2 mixed oxides during etching process. The specific capacitance for the PATMO annealed at 450 °C in argon is about 6 times greater than that of the nanotube counterparts. The PATMO show excellent rate capability and cycling stability with a maximum specific capacitance of 110.78 F cm⁻³ at 0.1 mA cm⁻².
Conductive diamond possesses unique features as compared to other solid electrodes, such as a wide electrochemical potential window, a low and stable background current, relatively rapid rates of electron-transfer for soluble redox systems without conventional pretreatment, long-term responses, stability, biocompatibility, and a rich surface chemistry. Conductive diamond microcrystalline and nanocrystalline films, structures and particles have been prepared using a variety of approaches. Given these highly desirable attributes, conductive diamond has found extensive use as an enabling electrode across a variety of fields encompassing chemical and biochemical sensing, environmental degradation, electrosynthesis, electrocatalysis, and energy storage and conversion. This review provides an overview of the fundamental properties and highlights recent progress and achievements in the growth of boron-doped (metal-like) and nitrogen and phosphorus-doped (semi-conducting) diamond and hydrogen-terminated undoped diamond electrodes. Applications in electroanalysis, environmental degradation, electrosynthesis electrocatalysis, and electrochemical energy storage are also discussed. Diamond electrochemical devices utilizing micro-scale, ultramicro-scale, and nano-scale electrodes as well as their counterpart arrays are viewed. The challenges and future research directions of conductive diamond are discussed and outlined. This review will be important and informative for chemists, biochemists, physicists, materials scientists, and engineers engaged in the use of these novel forms of carbon.
Owing to the popularity of carbon-based supercapacitors, diamond has also been examined as a potential candidate with unique advantages such as a wide electrochemical potential window and stable capacitive behavior in both aqueous and non-aqueous electrolytes. Moreover, its chemical stability in harsh environments at extreme applied potential and current provides rare opportunities for designing new supercapacitors. Owing to the intrinsic low surface area of diamond, it is necessary to increase the electrochemically active surface area or to produce diamond based composites ensuring capacitance improvement for the practical applications. According to the literature reports, the nano-engineered diamond structures can achieve a specific capacitance as high as 10 mF cm-2 with a specific energy of 10-100 Wh kg-1 in aqueous electrolyte. The present manuscript reviews the recent advancements in this topic of research by highlighting the potentials and challenges of diamond-based supercapacitors. The special attention was paid to fabrication methods and electrochemical performance of particular materials in view of further application for supercapacitor construction.
Enhanced performance of electrochemical capacitors can be achieved by larger capacitances as well as higher power and energy densities. In this work, such battery-like supercapacitors were fabricated using a three-dimensional and conductive diamond network as the capacitor electrode and water-soluble redox couples as the electrolyte. In 0.05 M Fe(CN)63−/4− + 1.0 M Na2SO4 aqueous solution, a capacitance of 73.42 mF cm⁻² was obtained at a current density of 1 mA cm⁻². This value is 10000 times higher than the capacitance of diamond electric double layer capacitors (EDLCs). The energy and power densities of a fabricated diamond network symmetric pseudocapacitor were up to 56.50 W h kg⁻¹ and 13.7 kW kg⁻¹, respectively. Compared with those of diamond EDLCs obtained with the same cell voltage, they are enhanced about 3500 and 1440 fold, respectively. Therefore the combination of diamond networks and water-soluble redox electrolytes is a novel approach to construct electrochemical capacitors and thus bridges the gap between normal dielectric capacitors and rechargeable batteries.
Au nanoparticles and TiO2 nanotube hybrid materials were prepared electrochemically. The Ti wire was used to form TiO2 nanotube arrays via anodization and subsequent annealing process. The Au nanoparticles were then electrodeposited in chloroauric acid solution to form Au/TiO2 hybrid layers. These two steps were repeated to prepare Au/TiO2, TiO2/Au/TiO2 and Au/TiO2/Au/TiO2 hybrid materials, and the preparation mechanism is discussed. The Au/TiO2 hybrid materials also exhibited different photoelectrocatalytic activities for decomposing methyl orange. The application of the Au/TiO2/Au/TiO2 hybrid material as a photo-anode has been simultaneously examined toward electrochemical-oxidation, photo-oxidation, and photoelectro-oxidation of methyl orange. The photoelectrocatalytic mechanism of Au/TiO2/Au/TiO2 hybrid material and its degradation reaction mechanism for methyl orange were evaluated.
Black TiO2 attracts enormous attention due to its large solar absorption and induced excellent photocatalytic activity. Herein, a new approach assisted by hydrogen plasma to synthesize unique H-doped black titania with a core/shell structure (TiO2@TiO2-xHx) is presented, superior to the high H2-pressure process (under 20 bar for five days). The black titania possesses the largest solar absorption (≈83%), far more than any other reported black titania (the record (high-pressure): ≈30%). H doping is favorable to eliminate the recombination centers of light-induced electrons and holes. High absorption and low recombination ensure the excellent photocatalytic activity for the black titania in the photo-oxidation of organic molecules in water and the production of hydrogen. The H-doped amorphous shell is proposed to play the same role as Ag or Pt loading on TiO2 nanocrystals, which induces the localized surface plasma resonance and black coloration. Photocatalytic water splitting and cleaning using TiO2-xHx is believed to have a bright future for sustainable energy sources and cleaning environment.
Nanoporous carbon (NPC) materials with high specific surface area have attracted considerable attention for electrochemical energy storage applications. In the present work, we have designed novel symmetric supercapacitors based on NPC by direct carbonization of Zn-based metal–organic frameworks (MOFs) without using an additional precursor. By controlling the reaction conditions in the present study, we synthesized NPC with two different particle sizes. The effects of particle size and mass loadings on supercapacitor performance have been carefully evaluated. Our NPC materials exhibit excellent electrochemical performance with a maximum specific capacitance of 251 F g À1 in 1 M H 2 SO 4 electrolyte. The symmetric supercapacitor studies show that these efficient electrodes have good capacitance, high stability, and good rate capability.
We report on the novel composite nanostructures based on boron-doped diamond thin film grown on top of TiO2 nanotubes. The nanostructures made of BDD-modified titania nanotubes showed an increase in activity and performance when used as electrodes in electrochemical environments. The BDD thin films (textasciitilde200-500 nm) were deposited using microwave plasma assisted chemical vapor deposition (MW PA CVD) onto anodically fabricated TiO2 nanotube arrays. The influence of boron-doping level, methane admixture and growth time on the performance of Ti/TiO2/BDD electrode was studied in detail. Scanning electron microscopy (SEM) was applied to investigate the surface morphology and grain size distribution. Moreover, the chemical composition of TiO2/BDD electrodes was investigated by means of micro-Raman Spectroscopy. The composite electrodes TiO2/BDD are characterized by the significantly higher capacitive current comparing to BDD film deposited directly onto Ti substrate. The novel composite electrode of TiO2 nanotube array overgrown by boron-doped diamond (BDD) immersed in 0.1 M NaNO3 can deliver specific capacitance of 2.10, 4.79, 7.46 mF cm-2 at a scan rate of 10 mV/s for [B]/[C] ratio 2k, 5k and 10k, respectively. The substantial improvement of electrochemical performance and excellent rate capability could be attributed to synergistic effect of TiO2 treatment in CH4:H2 plasma and high electrical conductivity of BDD layer. Analysis of electrochemical impedance spectra according to electric equivalent circuit allows to determine surface area on the basis of value of constant phase element.
Tremendous development in the field of portable electronics and hybrid electric vehicles has led to urgent and increasing demand in the field of high-energy storage devices. In recent years, many research efforts have been made for the development of more efficient energy-storage devices such as supercapacitors, batteries, and fuel cells. In particular, supercapacitors have great potential to meet the demands of both high energy density and power density in many advanced technologies. For the last half decade, graphene has attracted intense research interest for electrical double-layer capacitor (EDLC) applications. The unique electronic, thermal, mechanical, and chemical characteristics of graphene, along with the intrinsic benefits of a carbon material, make it a promising candidate for supercapacitor applications. This Review focuses on recent research developments in graphene-based supercapacitors, including doped graphene, activated graphene, graphene/metal oxide composites, graphene/polymer composites, and graphene-based asymmetric supercapacitors. The challenges and prospects of graphene-based supercapacitors are also discussed.
Surface oxidation processes play a key role in understanding electrochemical properties of boron-doped diamond (BDD) electrodes. The type of surface termination groups, which create the potential window of electrolytic water stability or hydrophobicity, influences such properties.
In this study the kinetics of oxidation process under anodic polarization were studied in situ by means of Dynamic Electrochemical Impedance Spectroscopy (DEIS) technique. This novel approach allows for obtaining the impedance data for non-stationary systems. It has been proven that for [B] dopant level of 10k ppm, polarization to 1.5 V vs. Ag|AgCl is sufficient to initiate transformation of the film terminating BDD electrodes. XPS analysis and wettability measurements confirmed oxidation under given conditions.
The most widely used oxide for photocatalytic applications owing to its low cost and high activity is TiO2. The discovery of the photolysis of water on the surface of TiO2 in 1972 launched four decades of intensive research into the underlying chemical and physical processes involved. Despite much collected evidence, a thoroughly convincing explanation of why mixed-phase samples of anatase and rutile outperform the individual polymorphs has remained elusive. One long-standing controversy is the energetic alignment of the band edges of the rutile and anatase polymorphs of TiO2 (ref. ). We demonstrate, through a combination of state-of-the-art materials simulation techniques and X-ray photoemission experiments, that a type-II, staggered, band alignment of ~ 0.4 eV exists between anatase and rutile with anatase possessing the higher electron affinity, or work function. Our results help to explain the robust separation of photoexcited charge carriers between the two phases and highlight a route to improved photocatalysts.
The boron dopant distribution in individual heavily boron-doped nanocrystalline diamond film grains, with sizes ranging from 100 to 350nm in diameter, has been studied using a combination of high resolution annular dark field scanning transmission electron microscopy and spatially resolved electron energy-loss spectroscopy. Using these tools, the boron distribution and local boron coordination have been determined. Quantification results reveal embedding of B dopants in the diamond lattice, and a preferential enrichment of boron at defective areas and twin boundaries. Coordination mapping reveals a distinct difference in coordination of the B dopants in "pristine" diamond areas and in defective regions. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4738885]
Anatase TiO(2) nanotube (TiNT) arrays have been fabricated on a p-type boron-doped diamond substrate by a liquid phase deposition method using a ZnO nanorod template. The n-type TiNT/p-type diamond heterojunction structures which are realized show significantly enhanced photocatalytic activities with good recyclable behavior, with respect to the cases of sole TiNTs.
Carbon supercapacitors, which are energy storage devices that use ion adsorption on the surface of highly porous materials to store charge, have numerous advantages over other power-source technologies, but could realize further gains if their electrodes were properly optimized. Studying the effect of the pore size on capacitance could potentially improve performance by maximizing the electrode surface area accessible to electrolyte ions, but until recently, no studies had addressed the lower size limit of accessible pores. Using carbide-derived carbon, we generated pores with average sizes from 0.6 to 2.25 nanometer and studied double-layer capacitance in an organic electrolyte. The results challenge the long-held axiom that pores smaller than the size of solvated electrolyte ions are incapable of contributing to charge storage.
In this paper diamond foam (DF) is introduced as a new material for thin-film supercapacitor application. Geometrical, structural, and electrical and electrochemical properties with respect to capacitance, electrochemical window and power are discussed in details. Diamond foam shows a 2.5 V potential window in aqueous solution. Discharge rate as high as 1000 V s−1 was measured which is three magnitudes higher than conventional supercapacitors. The power performance of diamond foam (807 W cm−3) approaches that of electrolytic capacitors, but the energy storage is more than one magnitude higher. Therefore, this new material is very promising for high-power micro-supercapacitor applications.
A new two-step method is successfully developed for the synthesis of MWNTs-TiO2 nanotube hybrid electrodes. The resulting (3-aminopropyl)triethoxysilane (APS) film was chemisorbed on the surface of TiO2 nanotubes. TiO2 nanotubes surface modified by 5, 10, and 20 mg ml−1 APS ethanol solution can determine the morphology of MWNTs-TiO2 nanotube electrodes. The morphology and surface composition were characterized by scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) techniques. The zeta potential results confirm that MWNTs were deposited on APS-TiO2 nanotubes by the electrical attractive force. The electrochemical performances were evaluated by using cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge–discharge measurements. The MWNTs-TiO2 nanotube hybrid electrodes (5, 10, and 20 mg ml−1 APS) exhibited a high specific capacitance of 3.5, 4.4, and 3.4 mF cm−2 in 1 M H2SO4 aqueous solution at a charge–discharge current density of 0.1 mA cm−2, respectively. Cyclic voltammetric studies indicated that the electrode has excellent stability even after 1000 consecutive CV cycles. Moreover, the galvanostatic charge–discharge experiments conducted on the MWNTs-TiO2 nanotube hybrid electrodes (10 mg ml−1 APS) exhibited long-term cycle stability, retaining about 75% specific capacitance after 1000 cycles, which suggests that it has potential as an electrode material for high-performance electrochemical supercapacitors.
TiO2 nanotube(TiNT) arrays were deposited on boron-doped diamond films by a liquid-phase deposition method with ZnO nanorod arrays as the template. The different morphologies of TiNTs have been obtained by controlling the morphology of ZnO template. The X-ray diffraction and energy-dispersive X-ray analysis show that the ZnO nanorod arrays template has been removed in the TiNTs formation process. The crystalline quality of the TiNTs is improved by increasing the annealing temperature. The band gap of the TiNTs is about 3.25 eV estimated by the UV-Vis absorption spectroscopy, which is close to the value of bulk TiO2. In the photoluminescence spectrum, a broad visible emission in a range of ca. 550–750 nm appears due to the surface oxygen vacancies and defects.
A two-step thermal treatment method was developed for the fabrication of porous conductive boron-doped diamond (BDD) electrodes. The first step involved graphitization of the BDD thin film surface to form a fine microstructure by heating in an argon atmosphere at 1000 degrees C. The second step was removal of the graphitic components by oxidation in air at 425 degrees C. The heat treatment resulted in the formation of dense pores with several tens to several hundred nanometer sizes or smaller on the BDD surface. The pore formation mechanism was discussed by microscopic observation of the (111) and (100) crystal facets on the treated BDD surface. The porous BDD electrode exhibited a double-layer capacitance (C-dl) of ca. 140 mu F cm(-2), which was estimated from cyclic voltammetry (CV) and galvanostatic measurements in an aqueous electrolyte. This C-dl value was approximately 40 times larger than that for the as-deposited BDD electrode, while the potential window remained wide at ca. 3 V.
Coaxial carbon nanotube-nickel hydroxide (CNT/Ni(OH)2) composites are prepared by a simple, one step and inexpensive chemical coprecipitation method. The coaxial coating of nickel hydroxide provides a three dimensional (3D) structure for easy access of electrolyte. Asymmetric supercapacitors (ASCs) are fabricated using coaxial CNT/Ni(OH)2 composites as positive electrode and reduced graphene oxide (rGO) as negative electrode. The operation voltage is expanded to 1.8 V in spite of the use of aqueous electrolyte, revealing a high energy density of 35 W·h·kg−1 at a power density of 1.8 kW·kg−1. This strategy for choice of coaxial metal hydroxide CNT composites provides a promising route for next generation supercapacitors with high energy as well as power densities.
Electrochemically active diamond-like carbon (DLC) electrodes featuring high specific surface area have been prepared by plasma-enhanced chemical vapour deposition (CVD) onto densely packed forests of vertically aligned multiwall carbon nanotubes (VACNTs). The DLC:VACNT composite film exhibits a complex topography with web like features and ridges generated by partial coalescence of the DLC over the CNT arrays. DLC:VACNT electrodes exhibit low background responses over a large potential window, low uncompensated resistance, as well as low charge-transfer impedance in the presence of ferrocyanide as a redox probe. The interfacial capacitance associated with the DLC:VACNT electrode is in the range of 0.6 mF cm−2, a value two orders of magnitude larger than in conventional flat carbon electrodes. DLC films grown onto single-crystal Si(1 0 0) under identical conditions resulted in essentially insulating layers. Conducting-atomic force microscopy studies reveal that the film electro-activity does not arise from specific topographic features in the highly corrugated film. The ensemble of experimental results suggests that the enhanced electrochemical responses are not connected to areas in which the CNT support is exposed to the electrolyte solution. This is remarkable behaviour considering that no dopants have been included during the DLC film growth.
This is the first investigation on electrically conducting polymersebased supercapacitor electrodes over a
wide temperature range, from �-18 �C to 60 �C. A high-performance supercapacitor electrode material consisting of TiC nanocube core and conformal crystalline polypyrrole (PPy)/poly-vinyl-alcohol (PVA) lamellar shell has been synthesized by heterogeneous nucleation-induced interfacial crystallization. PPy is induced to crystallize on the negatively charged TiC nanocube surfaces via strong interfacial interactions. In this organiceinorganic hybrid nanocomposite, the long chain PVA enables enhanced cycle life due to improved mechanical properties, and the TiC nanocube not only contributes to electron conduction, but also dictates the PPy morphology/crystallinity for maximizing the chargingedischarging performance. The crystalline PPy/PAV layer on the TiC nanocube offers unprecedented high capacity (>350 F/g�-PPy at 300 mV/s� with potential window = 1.6 V) and cycling stability in a temperature range from �-18 C to 60 �C. The presented hybrid-filler and interfacial crystallization strategies can be applied to the exploration of new-generation high-power conducting polymer-based supercapacitor materials.
The aim of the present study was to investigate the electrochemical degradation of sodium dipyrone in aqueous medium using a flow-by reactor equipped with anodes comprising boron-doped diamond film supported on titanium. The system was operated under electrolyte flow conditions that produced laminar (50 L h−1) or turbulent (300 L h−1) regimes in the internal section of the reactor. Spectroscopic and chromatographic analyses revealed that dipyrone was degraded completely within 120 min of electrolysis at applied potentials ⩾+4.0 V independent of the flow regime. The highest rate of removal of total organic carbon was achieved at an applied potential of +5.0 V and an electrolyte flow rate of 300 L h−1. Under these conditions, 52% of the initial organic load was removed after 2 h of electrolysis and 95.2% was eliminated after 8 h reaction. It is concluded that electrochemical technology is effective for the degradation of dipyrone and its possible products formed in aqueous medium.
The application of highly ordered TiO2 nanotube arrays (NTAs) for energy storage devices such as supercapacitors has been attractive and of great interest owing to their large surface area and greatly improved charge-transfer pathways compared to those of nonoriented structures. Modification of the semiconductor nature of TiO2 is important for its application in constructing high-performance supercapacitors. Hence, the present study demonstrates a novel method involving fabrication of self-doped TiO2 NTAs by a simple cathodic polarization treatment on the pristine TiO2 NTAs to achieve improved conductivity and capacitive properties of TiO2. The self-doped TiO2 NTAs at −1.4 V (vs SCE) exhibited 5 orders of magnitude improvement on carrier density and 39 times enhancement in capacitance compared to those of the pristine TiO2 NTAs. Impedance analysis based on a proposed simplified transmission line model proved that the enhanced capacitive behavior of the self-doped TiO2 NTAs was due to a decrease of charge-transport resistance through the solid material. Moreover, the MnO2 species was introduced onto the TiO2 NTAs by an impregnation–electrodeposition method, and the optimal specific capacitance achieved (1232 F g–1) clearly confirmed the suitability of self-doped TiO2 NTAs as effective current collector materials for supercapacitors.
A novel rapid fabrication method was developed for the first time to prepare hollow manganese oxide nanotubes with porous walls, using sacrificial carbon nanotube templates. Multiwalled carbon nanotubes (CNTs) are coated with amorphous manganese oxide layers by acidic reduction of potassium permanganate solution. The rapid synthesis process with the evolution of gaseous byproduct yields very high porosity in the coated manganese oxide layers. Subsequent heat treatment leads to the removal of CNT templates, resulting in the formation of amorphous and crystalline hollow manganese oxide nanotubes with highly porous walls. The porous hollow nanotubes were found to provide excellent catalytic performances in the degradation of organic dye at ambient conditions by virtue of the very high surface reaction sites within the porous hollow tubular structures. These novel nanostructures of hollow nanotubes with porous walls are promising for a series of applications such as hydrogen storage, sensing, supercapacitance, and catalysis, among others.
Sub-micron black titanium oxides powders Ti2O3 and Ti3O5 were synthesized via a facile and economical sol–gel method in this paper. Relatively pure Ti3O5 and Ti2O3 can be obtained by annealing the as-prepared PEG600-based gel with a heating rate of 10 °C min−1 and maintaining the temperature at 1,000 and 1,200 °C, respectively, under high pure (99.999 %) argon atmosphere for 4 h. The FESEM images reveal that the morphologies of the as-prepared Ti3O5 and Ti2O3 are sphere-like and plate-like mixed type structures. The particle size of Ti3O5 sample is in the range of 50–200 nm. However, the appearance of Ti2O3 is 200–500 nm irregular flake structures covered with 20–50 nm spherical particles. This PEG600-based sol–gel approach has a low reaction temperature of 1,000 °C herein for the preparation of Ti3O5, which is ascribed to that, the molecular PEG-600 was distributed well in the homogeneous gel through secondary cross-linking of the organic molecules, and with the increasing of heating temperature, molecular PEG-600 was carbonized. These nanoscaled and homogeneous mixtures of carbon and TiO2 made the carbon thermal reduction reaction occur subsequently at 1,000 °C. The Raman vibrational wavenumbers of as-prepared Ti3O5 and Ti2O3 are perfectly coincident with those of calculated results of pure Ti3O5 and Ti2O3. Besides, the Fourier transform infrared spectra of Ti3O5 and Ti2O3 were also investigated in this article. Finally, the powder electrical resistivity of Ti3O5 and Ti2O3 is 4.7 × 10−3 and 2.5 × 10−3 Ω m, respectively.
Nanostructuring boron-doped diamond (BDD) films increases their sensitivity and performance when used as electrodes in electrochemical environments. We have developed a method to produce such nanostructured, porous electrodes by depositing BDD thin film onto a densely packed “forest” of vertically aligned multiwalled carbon nanotubes (CNTs). The CNTs had previously been exposed to a suspension of nanodiamond in methanol causing them to clump together into “teepee” or “honeycomb” structures. These nanostructured CNT/BDD composite electrodes have been extensively characterized by scanning electron microscopy, Raman spectroscopy, cyclic voltammetry, and electrochemical impedance spectroscopy. Not only do these electrodes possess the excellent, well-known characteristics associated with BDD (large potential window, chemical inertness, low background levels), but also they have electroactive areas and double-layer capacitance values 450 times greater than those for the equivalent flat BDD electrodes.
A novel nanocomposite (PANI–TiC) prepared from polyaniline (PANI) and titanium carbide (TiC) was synthesized through an in situ chemical oxidative polymerization method. Detected by scanning electron microscopy and Fourier transform infrared spectra, morphologies and compositions of the nanocomposite were characterized. Experimental results of cyclic voltammetry (CV) indicated that PANI–TiC on PANI–TiC/GCE showed three pairs of redox peaks in acid medium and a pair of obvious redox peak in neutral medium. Electrocatalysis for ascorbic acid (AA) revealed good catalytic performance with the linear range from 50 μM to 2.25 mM and a sensitivity of 13.3 μA mM−1 cm−2 in neutral medium. This simple synthesis technique of preparing PANI–TiC nanocomposites showed great potential applications in sensor, catalysis, biomedical, environmental analysis, and so on.
In this study the efficiency of electrochemical oxidation of aromatic pollutants, such as reactive dyes, at boron-doped diamond on silicon (Si/BDD) electrodes was investigated. The level of [B]/[C] ratio which is effective for the degradation and
mineralization of selected aromatic pollutants, and the impact of [B]/[C] ratio on the crystalline structure, layer conductivity and
relative sp3/sp2 coefficient of a BDD electrode were also studied. The thin film microcrystalline electrodes have been deposited on highly doped silicon substrates via MW PE CVD. Si/BDD electrodes were synthesized for different [B]/[C] ratios of the gas phase.
Mechanical and chemical stability of the electrodes was achieved for the microcrystalline layer with relatively high sp3/sp2 band
ratio. Layer morphology and crystallite size distribution were analyzed by SEM. The resistivity of BDD electrodes was studied using four-point probe measurements. The relative sp3/sp2 band ratios were determined by deconvolution of Raman and X-ray photoelectron spectra. The efficiency of degradation and mineralization of the reactive azo dye rubin F-2B was estimated based on
the absorbance measurements at 545 nm. The influence of commonly used electrolytes NaCl and Na2SO4 on the dye removal
efficiency was also investigated. The results suggest that, in general, the oxidation occurs indirectly at the anode through generation of hydroxyl radicals •OH, which react with the dye in a very fast and non-selective manner. In NaCl electrolyte the dye was also
decomposed by more selective, active chlorine species (Cl2, HOCl). However the efficiency of this process in BDD depended on
the electrode's doping level. Higher amounts of dopant on the surface of BDD resulted in the higher efficiency of dye removal in both electrolytes.
The many applications of high energy storage devices have forged an increasing interest in research areas related to electrochemical capacitors. Here, in this work, we present a facile method for the fabrication of self-organized titaniananotubes grown by anodic oxidation of titanium foil with different subsequent heat-treatment regimes for use as binder-free working electrodes in supercapacitor applications. The capacitance of these highly ordered titaniananotubes, when exposed to a reductive atmosphere during annealing, was determined to be well above 900 µF cm−2, confirming that the capacitance contribution was pseudocapacitive in nature. The behaviour of oxygen depleted titania in the anatase to rutile (A → R) phase transformation and also in electrochemical charge storage has been studied in detail. It was found that upon the reduction of Ti4+ to Ti3+, with oxygen depletion of the structure, the A → R phase transformation was promoted. In addition, the fabricated electrodes showed highly reversible charge–discharge stability.
In this work, we have used X-ray photoelectron spectroscopy (XPS) to investigate the nature of surface adsorbed species and their sensitivity to the boron concentration [B] in two sets of as-grown diamond films: homoepitaxial {111} and polycrystalline. These sets cover each one at least three of the four doping ranges: low doping (5 x 10(16)<[B] <1.5 x 10(19) cm(-3)), high doping (1.5 x 10(19)<[B] <3 x 10(20) cm(-3)), heavy doping (3 x 10(20)<[B]<2 x 10(21) cm(-3)), and phase separation ([B]>2 x 10(21) cm(-3)). The results are compared to those we have previously obtained on (100) homoepitaxial films in the same doping ranges. A detailed description of both the nature and the relative concentrations of the main surface chemical species on every set of films is reported. Besides the usual CHx bonds on the diamond surface, the following oxygen-related groups: Ether (C-O-C), hydroxyl (C-OH, only on polycrystalline films), carbonyl (>C=O) and carboxyl (HO-C=O) have been found on the surface of grown diamond films, upon spontaneous oxidation under air (no oxidation treatment has been applied). The evolution of each surface chemical group according to the boron concentration in the films is.
Compositional changes induced by 3.5 keV Ar+ sputtering in TiO2, NiO, NiTiO3 and a (TiO2 + NiO) mixture have been quantitatively studied by XPS. Although all the samples show important changes in their stoichiometry, the extent of the decomposition depends on the compound. The stability of Ti4+ appears to be enhanced by the presence of Nisu2+ cations which, on the other hand, are more easily reduced to Ni0 than in pure NiO. To explain these results a redox solid state reaction between the intermediate phases formed during sputtering is proposed, which tends to preserve the most stable phases.
This work presents a systematic study on how pore size and specific surface area (SSA) of carbon effect specific capacitance and frequency response behavior. Carbide derived carbons (CDC) produced by leaching metals from TiC and ZrC at temperatures from 600 to 1200°C have highly tailorable microstructure and porosity, allowing them to serve as excellent model systems for porous carbons in general. BET SSA and average pore size increased with synthesis temperature and was 600–2000m2g−1 and 0.7–1.85nm, respectively. Maximum specific capacitance in 1M H2SO4 was found to occur at an intermediate synthesis temperature, 800°C, for both ZrC and TiC derived carbons and was 190 and 150Fg−1, respectively. Volumetric capacitance for TiC and ZrC derived carbons was maximum at 140 and 110Fcm−3. These results contradict an oft-reported axiom that increasing pore size and SSA, all other things being held constant, increases specific capacitance. A correlation between specific capacitance and SSA of micropores (less than 2nm in diameter) has been shown. As expected, increasing pore size was found to improve the frequency response. However, CDCs with similar pore size distributions but obtained from different starting materials showed noticeable differences in impedance behavior. This highlights the importance of not only the pore size and specific surface area measured using gas sorption techniques, but also the pore shape or tortuousity, which is non-trivial to characterize, on energy storage.
This review describes the possibilities of using hard templates to create nanostructured “soft” materials, for example, polymer networks, carbon nitrides, or carbonaceous materials, that is, materials which are still organic in their nature. Examples are given for the whole range of hard templates described in the literature, starting from silica nanoparticles, zeolites, and periodic mesoporous silicas to aluminum oxide membranes and colloidal crystals.
In the present paper, we report on the processing of titanate nanotubes using the hot filament chemical vapour deposition (HF-CVD) method to synthesize titania–carbon nanotube–wire composites. The titanate nanotubes are prepared using a chemical route, and then deposited on silicon using an electrodeposition method. The HF-CVD is used to process these coatings at different temperatures in vacuum as well as in different concentrations of hydrogen (H2) and methane (CH4) gas mixtures. The evolutions of the surface and precipitation for various phases have been monitored using different characterization techniques. It is observed that titanate nanotubes start disintegrating above Ts~500 °C, and exhibit different types of phase precipitation depending upon the temperature and gas ambient. Under appropriate conditions, the presence of activated hydrogen and carbon radicals leads to the formation of novel architectures of mixtures of nanophases such as carbide, nonstoichiometric titania, carbon nanotubes, and titania decorated carbon nanowires. The results are discussed in terms of reduction in the thermal reaction barrier due to the presence of atomic hydrogen, and the formation of energetic sites during disintegration of titania nanotubes to facilitate nucleation of nanotube and nanowire structures.
Die carbothermale Reduktion von anodischen TiO2-Nanoröhrenschichten in Acetylen wandelt die Röhrenwände in leitfähige und beständige Oxycarbid-Strukturen um. So werden halbmetallische TiO2-Nanoröhrenschichten (TiOxCy) erhalten, die als Elektrodenmaterialien andere Eigenschaften als TiO2-Nanoröhren zeigen (siehe Bild). Sie verfügen über eine hohe Sauerstoff-Überspannung und können als Katalysatorträger, z. B. in der Methanoloxidation, eingesetzt werden.
Highly ordered TiO2/Ti nanotube arrays were fabricated by anodic oxidation method in 0.5 wt% HF. Using prepared TiO2/Ti nanotube arrays deposited Ni nanoparticles as substrate, high quality diamond-like carbon nanorods (DLCNRs) were synthesized by a conventional method of chemical vapor deposition at 750 °C in nitrogen atmosphere. DLCNRs were analyzed by filed emission scanning electron microscopy and Raman spectrometer. It is very interesting that DLCNRs possess pagoda shape with the length of 3–10 μm. Raman spectra show two strong peaks about 1332 cm−1 and 1598 cm−1, indicating the formation of diamond-like carbon. The field emission measurements suggest that DLCNRs/TiO2/Ti has excellent field emission properties, a low turn-on field about 3.0 V/μm, no evident decay at 3.4 mA/cm2 in 480 min.
The advanced plasma immersion ion implantation and deposition (PIII&D) method has been used to deposit TiN, TiC and TiCN films on the surface of Ti–50.6 at.% Ni alloys. Smooth surface with root mean square (RMS) roughness of values 2.672 nm for the TiN, 1.517 nm for the TiCN film and 5.339 nm for the TiC film have been obtained. The XPS Ti 2p, C 1s and N 1s peaks and the valence band spectrum show that the nitrogen, carbon, carbon combined with nitrogen is fully bonded to titanium as nitride, carbide and carbonitride, respectively. Based on the electrochemical measurement and ion releasing tests, we can conclude that the treated samples exhibit better corrosion resistance and depress Ni ion release from the NiTi alloys in the Hank's solution at 37 °C.The suppression of Ni ion by the films is a beneficial phenomenon for the future application of NiTi alloys in the biomedical field.
Supercapacitors (also known as 'ultracapacitors') offer a promising alternative approach to meeting the increasing power demands of energy-storage systems in general, and of portable (digital) electronic devices in particular. Supercapacitors are able to store and deliver energy at relatively high rates (beyond those accessible with batteries) because the mechanism of energy storage is simple charge-separation (as in conventional capacitors). The vast increases in capacitance achieved by supercapacitors are due to the combination of: (i) an extremely small distance that separates the opposite charges, as defined by the electric double-layer; (ii) highly porous electrodes that embody very high surface-area. A variety of porous forms of carbon are currently preferred as the electrode materials because they have exceptionally high surface areas, relatively high electronic conductivity, and acceptable cost. The power and energy-storage capabilities of these devices are closely linked to the physical and chemical characteristics of the carbon electrodes. For example, increases in specific surface-area, obtained through activation of the carbon, generally lead to increased capacitance. Since only the electrolyte-wetted surface-area contributes to capacitance, the carbon processing is required to generate predominantly 'open' pores that are connected to the bulk pore network. While the supercapacitors available today perform well, it is generally agreed that there is considerable scope for improvement (e.g., improved performance at higher frequencies). Thus it is likely that carbon will continue to play a principal role in supercapacitor technology, mainly through further optimization of porosity, surface treatments to promote wettability, and reduced inter-particle contact resistance. © 2006 Published by Elsevier B.V.
Hybrid three-dimensional electrodes produced from microcrystalline boron-doped diamond (BDD) and/or nanocrystalline diamond
films were grown on porous titanium (Ti) substrate by hot filament chemical vapor deposition (HFCVD) technique. Powder metallurgy
technique was used to obtain the Ti substrates provided by interconnected and open pores among its volume. Diamond growth
parameters were optimized in order to provide the entire substrate surface covering including the deeper surfaces, pore bottoms,
and walls. The morphology and structure of these electrodes were studied by scanning electron microscopy (SEM) and visible
Raman spectroscopy techniques, respectively. Electrochemical response was characterized by cyclic voltammetry measurements.
Results showed a wide working potential window and low background current characteristic of the diamond electrodes. The kinetic
parameters also pointed out to a quasi-reversible behavior for these hybrid three-dimensional diamond/Ti electrodes.
Nanocrystalline diamond (NCD) films were successfully grown on micrometric porous silicon (PS) substrate in a hot filament chemical vapor deposition (HFCVD) reactor. The films were deposited at substrate temperature of 920 K and 6.5 kPa, after seeding pretreatment. The gas flow rate was set in a 50 sccm for Ar–CH4–H2 mixture. PS substrates were produced by anodic etching using n-type silicon wafers. The morphology, quality and electrochemical response of NCD have been analyzed by scanning electron microscopy (SEM), Raman scattering spectroscopy and cyclic voltammetry (CV) measurements. SEM images have shown faceted nanograins with average size from 30 to 50 nm and uniform surface texture covering all the supports among the pores resulting in an apparent micro honeycomb structure. Raman spectra have exhibited a shoulder at 1550 cm−1, that is NCD characteristic and have confirmed the good quality films with diamond purity around 90%. Electrochemical response and capacitance behavior of NCD/PS electrodes immersed in aqueous electrolyte solution without redox-active reagents has been explored. The work potential window remains large for NCD, in a similar way of boron doped diamond (BDD), but with a large capacitive background current compared to BDD. NCD/PS presented capacitance values from 230 to 990 μF cm−2, while such capacitance values for BDD were between 20 and 40 μF cm−2 in the potential range of −0.5 up to 1.0 V × Ag/AgCl.
The electrical double-layer (EDL) performance of three different TiC-derived nanoporous carbon materials was tested in prismatic capacitor assembly filled with 1.2 M triethylmethylammonium tetrafluoroborate (TEMA) acetonitrile solution. The electrical double-layer characteristics of supercapacitors were studied using the cyclic voltammetry (CV) and the electrochemical impedance spectroscopy (EIS) methods. Energy density versus power density, i.e. Ragone plots were constructed from the constant resistance and constant power (CP) charge/discharge data. The 1450F supercapacitor with novel nanoporous carbon made by halogen treatment of TiC/TiO2 composite demonstrated the energy density of more than 10 Wh dm−3 at the cell voltage of 2.7 V.
High surface area nanoporous carbon has been prepared by thermo-chemical etching of titanium carbide TiC in chlorine in the temperature range 200–1200 °C. Structural analysis showed that this carbide-derived carbon (CDC) was highly disordered at all synthesis temperatures. Higher temperature resulted in increasing ordering and formation of bent graphene sheets or thin graphitic ribbons. Soft X-ray absorption near-edge structure spectroscopy demonstrated that CDC consisted mostly of sp2 bonded carbon. Small-angle X-ray scattering and argon sorption measurements showed that the uniform carbon-carbon distance in cubic TiC resulted in the formation of small pores with a narrow size distribution at low synthesis temperatures; synthesis temperatures above 800 °C resulted in larger pores. CDC produced at 600–800 °C show great potential for energy-related applications. Hydrogen sorption experiments at −195.8 °C and atmospheric pressure showed a maximum gravimetric capacity of ∼330 cm3/g (3.0 wt.%). Methane sorption at 25 °C demonstrated a maximum capacity above 46 cm3/g (45 vol/vol or 3.1 wt.%) at atmospheric pressure. When tested as electrodes for supercapacitors with an organic electrolyte, the hydrogen-treated CDC showed specific capacitance up to 130 F/g with no degradation after 10 000 cycles.
We report a new and general strategy for improving the capacitive properties of TiO(2) materials for supercapacitors, involving the synthesis of hydrogenated TiO(2) nanotube arrays (NTAs). The hydrogenated TiO(2) (denoted as H-TiO(2)) were obtained by calcination of anodized TiO(2) NTAs in hydrogen atmosphere in a range of temperatures between 300 to 600 °C. The H-TiO(2) NTAs prepared at 400 °C yields the largest specific capacitance of 3.24 mF cm(-2) at a scan rate of 100 mV s(-1), which is 40 times higher than the capacitance obtained from air-annealed TiO(2) NTAs at the same conditions. Importantly, H-TiO(2) NTAs also show remarkable rate capability with 68% areal capacitance retained when the scan rate increase from 10 to 1000 mV s(-1), as well as outstanding long-term cycling stability with only 3.1% reduction of initial specific capacitance after 10,000 cycles. The prominent electrochemical capacitive properties of H-TiO(2) are attributed to the enhanced carrier density and increased density of hydroxyl group on TiO(2) surface, as a result of hydrogenation. Furthermore, we demonstrate that H-TiO(2) NTAs is a good scaffold to support MnO(2) nanoparticles. The capacitor electrodes made by electrochemical deposition of MnO(2) nanoparticles on H-TiO(2) NTAs achieve a remarkable specific capacitance of 912 F g(-1) at a scan rate of 10 mV s(-1) (based on the mass of MnO(2)). The ability to improve the capacitive properties of TiO(2) electrode materials should open up new opportunities for high-performance supercapacitors.
Titanium/diamond-like carbon multilayer (TDML) films were deposited using a hybrid system combining radio frequency (RF)-sputtering and RF-plasma enhanced chemical vapor deposition (PECVD) techniques under a varied number of Ti/diamond-like carbon (DLC) bilayers from 1 to 4, at high base pressure of 1 × 10(-3) Torr. The multilayer approach was used to create unique structures such as nanospheres and nanorods in TDML films, which is confirmed by scanning electron microscopy (SEM) analysis and explained by a hypothetical model. Surface composition was evaluated by X-ray photoelectron spectroscopy (XPS), whereas energy dispersive X-ray analysis (EDAX) and time-of-flight secondary ion mass spectrometer (ToF-SIMS) measurements were performed to investigate the bulk composition. X-ray diffraction (XRD) was used to evaluate the phase and crystallinity of the deposited TDML films. Residual stress in these films was found to be significantly low. These TDML films were found to have excellent nanomechanical properties with maximum hardness of 41.2 GPa. In addition, various nanomechanical parameters were calculated and correlated with each other. Owing to metallic interfacial layer of Ti in multilayer films, the optical properties, electrical properties, and photoluminescence were improved significantly. Due to versatile nanomechanical properties and biocompatibility of DLC and DLC based films, these TDML films may also find applications in biomedical science.
Titanate nanotubes were synthesized under hydrothermal conditions. The optimized synthesis (100-180 degrees C, longer than 48 h), thermal and hydrothermal stability, ion exchangeability and consequent magnetic and optical properties of the titanate nanotubes were systematically studied in this paper. First, nanotubes with monodisperse pore-size distribution were prepared. The formation mechanism of the titanate nanotubes was also studied. Second, the thermal and hydrothermal stability were characterized with X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR), and Raman spectroscopy. Results showed that sodium ions played a significant role in the stability of the frameworks. Third, the selective ion exchangeability was demonstrated with a series of ions. The ion substitution also enlarged the BET surface area of the titanate nanotubes to 240 m(2) x g(-1). Combination of these two features implied that these nanotubes might be functionalized by substitution of different transitional-metal ions and consequently used for selective catalysis. Magnetism, photoluminescence, and UV/Vis spectra of the substituted titanate nanotubes revealed that the magnetic and optical properties of the nanotubes were modifiable.
The combined experimental and theoretical study of intrinsic hydrogen diffusion on bridge-bonded oxygen (BBO) rows of TiO 2(110) is presented. Sequences of isothermal scanning tunneling microscopy images demonstrate a complex behavior of hydrogen formed by water dissociation on BBO vacancies. Different diffusion rates are observed for the two hydrogens in the original geminate OH pair suggesting the presence of a long-lived polaronic state. For the case of separated hydroxyls, both theory and experiment yield comparable temperature-dependent diffusion rates. Density functional theory calculations show that there are two comparable low energy diffusion pathways for hydrogen motion along the BBO from one BBO to its neighbor, one by a direct hop and the other by an intermediate minimum at a terrace O. The values of kinetic parameters (prefactors and diffusion barriers) determined experimentally and theoretically are significantly different and indicate the presence of a more complex diffusion mechanism. We speculate that the hydrogen diffusion proceeds via a two-step mechanism: the initial diffusion of localized charge, followed by the diffusion of hydrogen. Both experiment and theory show the presence of repulsive OH-OH interactions.