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Electrocatalytic oxidation of methanol on platinum nanoparticles electrodeposited onto porous carbon substrates
Abstract
To achieve methanol fuel cell electrodes allowing a high catalyst use, thin layers of various carbon powders and recast Nafion were electrochemically plated with platinum. The resulting Pt deposits were characterized by hydrogen and carbon monoxide electrosorption, as well as by transmission electron microscopy. Methanol oxidation was then carried out using cyclic voltammetry. The influence of the amount of carbon surface oxides and the effect of Pt specific surface area on the Pt catalytic activity were thus investigated.
... As for as-prepared catalysts, for cycled catalysts, in the presence of CO the performance of the cells with aged catalysts was Pt/N-GNP > Pt/C > Pt/GNS (Figures 6b and 7). In the presence of CO, compared to the cell with as-prepared catalysts, after ageing a decrease of the performance of the cell with Pt/C as anode catalyst was observed, due to the ECSA decrease by Pt particle growth, whereas the cell with for Pt/GNS and Pt/N-GNP as anode catalyst presented a substantial stability, due to a lower ECSA loss, and, in the case of Pt/N-GNP, to the weaker adsorption of CO on the larger Pt particles [43,44], reducing the poisoning of the catalyst. ...
... Both before and after RPC, for current densities > 0.15 A cm −2 , the overpotential was in the order Pt/N-GNP < Pt/C < Pt/GNS. Following ageing, a decrease of the overpotential for all the catalysts, in particular for Pt/N-GNP, which presents the largest Pt particle size, can be observed in Figure 8, due to the weaker adsorption of CO on the larger Pt particles [43,44], reducing the poisoning of the catalyst. At low current density (<0.1 A cm −2 ) following ageing a decrease of the overpotential of the PEMFC with Pt/C as the anode catalyst can be observed in Figure 8, while the effect of RPC on the overpotential of the cells with Pt/GNS and Pt/N-GNP was negligible. ...
... adsorption of CO on the larger Pt particles [43,44], reducing the poisoning of the catalyst. At low current density (<0.1 A cm −2 ) following ageing a decrease of the overpotential of the PEMFC with Pt/C as the anode catalyst can be observed in Figure 8, while the effect of RPC on the overpotential of the cells with Pt/GNS and Pt(N-GNP was negligible. ...
Pt electrocatalysts supported on pristine graphene nanosheets (GNS) and nitrogen-doped graphene nanoplatelets (N-GNP) were prepared through the ethylene glycol process, and a comparison of their CO tolerance and stability as anode materials in polymer electrolyte membrane fuel cells (PEMFCs) with those of the conventional carbon (C)-supported Pt was made. Repetitive potential cycling in a half cell showed that Pt/GNS catalysts have the highest stability, in terms of the highest sintering resistance (lowest particle growth) and the lowest electrochemically active surface area loss. By tests in PEMFCs, the Pt/N-GNP catalyst showed the highest CO tolerance, while the poisoning resistance of Pt/GNS was lower than that of Pt/C. The higher CO tolerance of Pt/N-GNP than that of Pt/GNS was ascribed to the presence of a defect in graphene, generated by N-doping, decreasing CO adsorption energy.
... This is mainly by improved methanol dehydrogenation, higher electrochemical activity, better resistivity to CO poisoning and reduction of costs [14,15]. Taking into account the economical as well as ecological point of view, the strategy of fuel cell should be based on the reduction of metal amount used for anode preparation [7,9,12,[17][18][19]. Hence, in some cases catalysts used for alcohol oxidation constitute metal combination with carbon materials. ...
... Owing to their developed specific surface area, appearance of functional groups, high conductivity, carbon materials are widely applied as adsorbents [20] and/or matrix for catalyst [8,19]. Carbon materials are also used as electrodes for alcohols oxidation [7,9,[17][18][19]21]. Metal catalyst are merge with carbons by variety of methods, a.g. ...
... This result agrees with the statement that after 26th cycle when the activity of electrode slightly decreases, the efficiency of methanol transformation into the inorganic product is lower compared to that observed during the previous 25 cycles. The gentle deactivation of EG/Ni/ Pd electrode probably is associated with its poisoning effect caused by deposited CO [5,8,10,[17][18][19]. It seems that the mechanism of electrode poisoning can be similar to that given by Zhu et al. [32]. ...
This paper try to answer the question, if the exfoliated graphite/nickel/palladium (EG/Ni/Pd) composite can be regarded as a potential anode material in direct methanol fuel cells (DMFCs). For this purpose, process of electrochemical oxidation of methanol on electrode made of EG/Ni/Pd was investigated. Electrochemical investigations were conducted in alkaline medium by cyclic voltammetry and potentiostatic techniques. Informations on catalytic activity of the examined composite were acquired from the comparison of current charges calculated for methanol oxidation peaks. The investigations revealed that electrochemical activity of EG/Ni/Pd composite enhances along the potential cycling. Current charges of methanol oxidation peaks increase with number of conducted cycles up to 26th cycle. The increment in electrochemical activity impacts on the decline in methanol concentration in the investigated electrolyte. The results of electrochemical investigations for EG/Ni/Pd composite were compared to that acquired for EG/Pd. The difference in total organic carbon (TOC) before and after the selected cycles of electrochemical process at EG/Ni/Pd electrode were the source of information on degree of methanol oxidation. Process comprised of 50 cycles of methanol electrooxidation resulted over 50% decrease in its concentration. The interpretation of electrochemical investigations were supported by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and X-ray photoelectron spectroscopy (XPS) analysis.
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... From the results of FA electro-oxidation in Fig. 8a, it is also possible to conduct a more thorough analysis of the effective area of Ptnp on the SS|COP-P1AAQnw-Ptnp surface, based on the information reported by Gloaguen et al. [24]. Since increase of electro-catalytic activity seemed to be enhanced by the inclusion of Ptnp and this in turn depends on the number of available surface sites, the activity referred to the platinum surface area (A r ), has a great physical significance. ...
... It is noteworthy, finally, that the use of electrochemical techniques for each of the steps of the electrode modification guarantee variables control and reproducibility, particularly when generating nanostructures in situ, phenomenon practically impossible when the modified electrodes are prepared adding nanostructures synthesized ex situ. In that case, it is very difficult to control that the surface be perfectly reproducible, as verified by previous studies concerning the characterization of the electrodes prepared and used in the current work [24]. ...
Conducting polymer nanostructuring enables a substantial improvement of many electro-catalytic processes, e.g., formic acid (HCOOH, FA) electro-oxidation. In this case, a stainless steel (SS) electrode is first modified with poly(1-amino-9,10-anthraquinone-co-o-phenylenediamine) (COP) and then, by means of a template that can be chemically removed, poly(1-amino-9,10-anthraquinone) nanowires (P1AAQnw) are electro-synthesized; this procedure has allowed the effective FA electro-catalytic oxidation generating adsorbed CO, which is quickly converted to CO2. Subsequently, when platinum nanoparticles (dispersed by electro-chemical techniques) are also incorporated on the polymeric nanowires, oxidation peaks are observed at ca. 1000 mV, with a current increase up to fourfold. In this way, the method provides a highly reproducible nanostructured electrode that is prepared solely by electro-chemical techniques offering promising results for FA electro-catalytic oxidation.
... 可以分为平板团聚 [40,41] 、柱形团聚 [42,43] 和球形团聚 [44] . ...
... Electrochemical deposition of precious metals is a method that involves the reduction of the desired metal ions from solution to the metallic state on the surface of a substrate in aqueous electrolytes [27]. Gloaguen et al. [28] carried out the electrooxidation of methanol utilising Pt nanoparticles onto porous carbon substrates obtained by potential step electrodeposition experiments. The purpose of the work was to determine the characteristics of Pt electrodeposited on various carbon supports, viz., graphite powder and conventional carbon, mixed with recast Nafion. ...
Fuel cells are a key enabling technology for the future economy, thereby providing power to portable, stationary, and transportation applications, which can be considered an important contributor towards reducing the high dependencies on fossil fuels. Electrocatalyst plays a vital role in improving the performance of the low temperature fuel cells. Noble metals (Pt, Pd) supported on carbon have shown promising performance owing to their high catalytic activity for both electroreduction and electrooxidation and have good stability. Catalyst preparation by electrodeposition is considered to be simple in terms of operation and scalability with relatively low cost to obtain high purity metal deposits. This review emphasises the role of electrodeposition as a cost-effective method for synthesising fuel cell catalysts, summarising the progress in the electrodeposited Pt and Pd catalysts for direct liquid fuel cells (DLFCs). Moreover, this review also discusses the technological advances made utilising these catalysts in the past three decades, and the factors that impede the technological advancement of the electrodeposition process are presented. The challenges and the fundamental research strategies needed to achieve the commercial potential of electrodeposition as an economical, efficient methodology for synthesising fuel cells catalysts are outlined with the necessary raw materials considering current and future savings scenario.
... However, the increase in the affinity of OH chemisorption on Pt occurs with the increase in Pt d-band vacancy [29,30]: the subsequent coverage of Pt atoms with oxygenated species can lead to a decrease in the ethanol oxidation activity. In this regard, the decrease of the EOR activity of Pt for methanol [37][38][39] and ethanol [28] oxidation, with decreasing the particle size, was explained with the increase of the adsorption strength of oxygenated species on Pt with decreasing Pt particle size. On this basis, we can suppose that the decrease of EOR activity with increasing CeO 2 content could be due to the increase of Pt d-band vacancy. ...
Pt/CeO2/C electrocatalysts in different compositions were prepared and their structural characteristics and activities for ethanol oxidation in alkaline media were evaluated. In the presence of CeO2, an increase in the platinum particle size was observed. XANES measurements indicated that the Pt d-band vacancies increased with increasing CeO2 amounts. For the first time, the decrease in electro activity was described to an electronic effect for high CeO2 contents. The dependence of the activity for ethanol oxidation on CeO2 content went to a maximum, due to the counteracting bifunctional and electronic effects of the metal oxide.
... Con esto, la cantidad de Au depositado (W) en g cm −2 se obtiene a partir de la ley de Faraday, mediante la relación [61]: ...
One of the most important reactions for electrochemical science and technology is the electrocatalytic reduction ofoxygen. It is particularly relevant in fuel cells because it is slow to react and requires high overpotentials. This workaims to study electrodes with deposits of Au on Ti obtained by electrodeposition. The substrates have undergone po-tentiodynamic growths of oxides before deposition for some electrodes and after deposition for other electrodes understudy, at different final potentials. Both procedures resulted in the formation of a composite Au layer on the Ti surface.The electrochemical behavior of these composite layers was examined in a 0.01 M HClO4solution, both oxygen-freeand oxygen-saturated, and compared with the behavior of Ti as a target, using the cyclic voltammetry technique. In thepotential region of the oxygen reduction reaction (RRO), the Au layer on the Ti obtained by first performing the Audeposition and then the growth of the anode oxide showed a better response, not only in the onset potential of the RRO,but also in the current densities. In all cases the voltammetry curves of the Au and TiO2 composite layers were similarto those shown by the Au polycrystalline.
... Based on the assumption of the agglomerate shape, the agglomerate model can be further classified as slab [63,64], cylindrical [60] and spherical [52,53] configurations. ...
Computational modeling has played a key role in advancing the performance and durability of polymer electrolyte membrane fuel cells (PEMFCs). In recent years there has been a significant focus on PEMFC catalyst layers because of their determining impact on cost and and durability. Further progress in the design of better performance, cheaper and more durable catalyst layers is required to pave the way for large scale deployment of PEMFCs. The catalyst layer poses many challenges from a modeling standpoint: it consists of a complex, multi-phase, nanostructured porous material that is difficult to characterize; and it hosts an array of coupled transport phenomena including flow of gases, liquid water, heat and charged occurring in conjunction with electrochemical reactions. This review paper examines several aspects of state-of-the-art modeling and simulation of PEMFC catalyst layers, with a view of synthesizing the theoretical foundations of various approaches, identifying gaps and outlining critical needs for further research. The review starts with a rigorous revisiting of the mathematical framework based on the volume averaging method. Various macroscopic models reported in the literature that describe the salient transport phenomena are then introduced, and their links with the volume averaged method are elucidated. Other classes of modeling and simulation methods with different levels of resolution of the catalyst layer structure, e.g. the pore scale model which treats materials as continuum, and various meso- and microscopic methods, which take into consideration the dynamics at the sub-grid level, are reviewed. Strategies for multiscale simulations that can bridge the gap between macroscopic and microscopic models are discussed. An important aspect pertaining to transport properties of catalyst layers is the modeling and simulation of the fabrication processes which is also reviewed. Last but not least, the review examines modeling of liquid water transport in the catalyst layer and its implications on the overall transport properties. The review concludes with an outlook on future research directions.
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... [1][2][3][4] Composite electrodes can be produced from potentiostatic depositions of platinum and/or polyaniline (PANI) directly onto the carbon surface. Carbon supported platinum (C/Pt) is widely used for its known activity toward alcohol oxidation, [5][6][7] and carbon supported PANI (C/PANI), or even carbon-platinum supported PANI (C/Pt-PANI) electrodes are also attractive for the fabrication of composite catalyst materials. 8,9 Previous studies have shown that PANI can be used as a viable matrix for the insertion of catalytically active atomic-sized metal clusters, using platinum as support. ...
Carbon has unique and desirable properties for use in applications such as fuel cells and batteries. The properties can vary widely depending on its structure and surface characteristics. Two types of carbon, a synthetic graphite produced from petroleum coke and an extruded graphite rod, were characterized using Raman spectroscopy and X-ray Photoelectron spectroscopy and the features were correlated with electrochemical properties of the material. The graphite rod was found to have a more disordered structure, greater sp³ character, and a greater surface oxygen content as compared to the synthetic graphite from coke. Our results show that the characteristics of electrodeposited platinum and polyaniline depend on the type of substrate; the preferable carbon for producing composite materials for catalyst applications is the graphite from petroleum coke.
... From the electrochemical results, the electrochemical surface area (ECSA) of the catalysts are calculated from the charge density q Pt (C/cm 2 electrode ) obtained from the CVexperiment before and after electrooxidation of alcohols (Tables 2 and 3). The charge required to reduce a monolayer of protons on catalyst (Pt), Γ = 210 μC/cm 2 Pt and the catalyst content or loading in the electrode, L in g Pt /cm 2 electrode [58][59][60][61]. ...
The platinum-gold bimetallic nanoparticles supported poly(cyclotriphosphazene-co-benzidine)-grafted graphene oxide (poly(CP-co-BZ)-g-GO) composite has been prepared for electrochemical performance studies. Cyclic voltammetry and chronoamperometric studies were carried out to check the electrochemical properties of Pt-Au/poly(CP-co-BZ)-g-GO and Pt/poly(CP-co-BZ)-g-GO catalysts for methanol, ethylene glycol and glycerol in alkaline medium. The morphology and crystalline structure of the prepared Pt-Au/poly(CP-co-BZ)-g-GO and Pt/poly(CP-co-BZ)-g-GO and catalysts have been characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and fourier transform infrared spectroscopy (FT-IR). From the electrochemical results, it was concluded that Pt-Au/poly(CP-co-BZ)-g-GO catalyst shows higher catalytic activity and stability compared to Pt/poly(CP-co-BZ)-g-GO catalyst. The catalytic activity of Pt/poly(CP-co-BZ)-g-GO catalyst has been compared with Pt/poly(CP-co-BZ), Pt/GO and Pt/C catalysts. In addition, oxidation current of ethylene glycol is higher than the methanol and glycerol in alkaline medium on the prepared catalyst.
... It is observed that catalyst with posttreatment revealed well-resolved hydrogen desorption peak, implies an activation of Pt surface. Among the samples, 1 and 3 h treated samples exhibit the strongest hydrogen desorption peak correspond to high electrochemical active surface area (ECSA) which quantitatively can be measured by the following equation [24] : ...
Surfactant removal from the surface of platinumnanoparticles prepared by solution based method is a prerequisite process to accomplish a high catalytic activity for electrochemical reactions. Here, we report a possible approach of combining acid acetic with thermal treatment for improving catalytic performance of formic acidoxidation. This strategy involves conversion of amine to amide in acetic acid followed by surfactant removal via subsequent thermal treatment at 85 °C. This combined activation technique produced monodisperse nanoparticle with the size of 3 to 5 nm with enhanced formic acidoxidation activity, particularly in perchloric acidsolution. Pt treated in 1 h of acetic acid and heat treatment of 9 h shows high electrochemicalsurface area value (27.6 m²/g) compares to Pt without activation (16.6 m²/g). The treated samples also exhibit high current stability of 0.3 mA/cm² compares to the as-prepared mA/cm²). Shorter duration of acid wash and longer duration of heating process result in high electrocatalytic activity. This work demonstrates a possible technique in improving catalytic activity of platinumnanoparticles synthesized using methylamine as surfactant.
... The specific surface area is a useful macroscopic quantity to characterize the dispersed catalysts [35,36]. The specific surface area (S in m 2 g À1 ) can be estimated using Eq. ...
The electrocatalytic performance of reduced graphene oxide-poly(3,4-ethylenedioxythiophene)/platinum (RGO-PEDOT/Pt) nanocomposite for methanol oxidation has been evaluated with respect to PEDOT/Pt and RGO/Pt. The electrocatalysts are characterized by scanning electron microscopy, transmission electron microscopy and cyclic voltammetry. The RGO-PEDOT/Pt has been found to have favorable characteristics in terms of large specific surface area (460.5 m(2) g(-1)) and small particle size (0.61 nm). The methanol oxidation current for RGO-PEDOT/Pt is nearly 3.6 and 12.6 times higher than that for PEDOT/Pt and RGO/Pt respectively. Among the three electrocatalysts, the RGO-PEDOT/Pt nanocomposite shows the best electrocatalytic behavior towards methanol oxidation with a mass specific peak current of 774 mA mg(-1) cm(-2) for a Pt loading of 191.4 mu g cm(-2) at a concentration of 1 M methanol in 0.5 M H2SO4. The effects of Pt loading, methanol concentration and electrode stability have been studied. RGO-PEDOT/Pt-Ru electrodes with a fixed Pt and variable Ru ion concentrations are prepared by chronoamperometry and the Pt-Ru alloy formation was confirmed by X-ray diffraction method. The electrocatalytic performance of the Pt-Ru supported RGO-PEDOT for the oxidation of methanol is evaluated by cyclic voltammetry. The Tafel kinetic analysis indicates that the RGO-PEDOT/Pt-Ru prepared with equal concentrations of Pt and Ru ions (i.e. RGO-PEDOT/Pt-Ru (1:1)) gives the best performance in terms of the lowest onset potential (0.14 V), highest exchange current density (2390 mu A cm(-2)) and highest I-f/I-r ratio (2.33) implying minimum poisoning.
... The extended surface of PtNiNWs (hundreds of nm in diameter, hundreds of µm in length) also potentially benefitted MOR activity by avoiding a previously observed Pt MOR particle size effect. [13][14][15] The specific MOR activity of PtNiNWs offered similar benefits as other extended Pt catalysts using silver and copper nanowire templates. 10,11 A benefit due to the extended surface, however, was potentially reduced by the surface features of the PtNiNWs, which were previously found to be 2-4 nm in diameter. ...
The heat treatment of nickel (Ni) nanowires (NiNWs) in oxygen is examined for its effect on platinum (Pt) galvanic displacement and the activity of Pt-coated NiNWs (PtNiNWs) in the methanol oxidation reaction (MOR). Annealing of NiNWs in oxygen is found to reduce Pt displacement, increasing its resistance to potential-driven dissolution (during electrochemical break-in). In reducing Ni dissolution, oxophilic species are provided in close proximity to Pt sites and the MOR activity of PtNiNWs improves, particularly at low overpotential in rotating disk electrode halfcells.
... However, commercialization of DMFC technology is far from reality due to lots of obstacles such as methanol crossover, low catalytic activity of electrodes, high costs of Pt-based electrocatalysts and susceptibility of the catalysts to be poisoned by CO gas formed during methanol oxidation [8,9]. The reduction in the Pt catalyst amounts; for sake of pricey, as well as size reduction of Pt nanoparticles can be achieved via using high-surface-area carbon support that enables effective utilization and dispersion of Pt nanocatalysts [10,11]. Carbon nanostructures having high surface area such as CNTs and fullerenes can be used as useful candidates for electrooxidation of methanol in fuel cell applications [12,13], based on their unique electrical and structural properties [14]. ...
Titanate-SWCNT; synthesized via exploiting the interaction between TiO2 anatase with oxygen functionalized
SWCNT, supported Ag nanoparticles and Ag/titanate are characterized using XRD, TEM-EDX-SAED, N2 adsorption,
Photoluminescence, Raman and FTIR spectroscopy. These samples are tested for methanol
electrooxidation via using cyclic voltammetry (CV) and impedance measurements. It is shown that Ag/
titanate nanotubes exhibited superior electrocatalytic performance for methanol oxidation (4.2 mA cm−2)
than titanate-SWCNT, Ag/titanate-SWCNT and titanate. This study reveals the existence of a strong metalsupport
interaction in Ag/titanate as explored via formation of Ti–O–Ag bond at 896 cm−1 and increasing
surface area and pore volume (103 m2 g−1, 0.21 cm3 g−1) compared to Ag/titanate-SWCNT (71 m2 g−1,
0.175 cm3 g−1) that suffers perturbation and defects following incorporation of SWCNT and Ag. Embedding
Ag preferably in SWCNT rather than titanate in Ag/titanate-SWCNT disturbs the electron transfer
compared to Ag/titanate. Charge transfer resistance depicted from Nyquist impedance plots is found in
the order of titanate > Ag/titanate-SWCNT > titanate-SWCNT > Ag/titanate. Accordingly, Ag/titanate indicates
a slower current degradation over time compared to rest of catalysts. Conductivity measurements
indicate that it follows the order Ag/titanate > Ag/titanate-SWCNT > titanate > titanate-SWCNT declaring
that SWCNT affects seriously the conductivity of Ag(titanate) due to perturbations caused in titanate
and sinking of electrons committed by Ago through SWCNT.
In the modern era, we all depend on energy for everything. However, we have limited traditional energy sources like coal, petroleum etc. Various alternative energy sources have been developed to fulfill the energy requirements from time to time. Despite this, we are in continuous need of energy sources that are of low cost and cause less environmental pollution. To overwhelm prospective energy concerns, when the world is exploring ways for net carbon zero or negative carbon emissive energy techniques FCs are predicted as one of the clean energy origins with low operating temperatures and high energy modifications. Nevertheless, a superior and steady catalyst for the electrodes is essential for the electrochemical reactions in FCs to work efficiently. Noble and non-noble metal electrocatalysts are extensively utilized as catalysts for the transformation of energy within fuel cells (FCs). For many years many pieces of research have been done to enhance the performance of FC technology. The literature review shows the role of various metal/ polymer-based nanomaterials as anode catalysts to robust fuel cell performance by the electro-oxidation of alcohols. Here, we have demonstrated the different morphology of the stimulus (such as nanowires and nanospheres, nanotubes, nanodendrites, nanofibers and nanosheets) and fabrication methods (such as electrodeposition, electrospinning, wet chemical, chemical vapor deposition, solvothermal, reduction, microwave-assisted polyol synthesis method) in detail. Further, the role of different noble and non-noble metal catalysts in FC application in FC technology and the relationship between morphology, synthesis and composition of catalysts have been discussed. Finally, the advantages of the fuel cell, current challenges, and prospects in this field, with concluding remarks, have been presented at the end.
We report on the fabrication and electrochemical evaluation of a Vitamin B2-riboflavin (RF) sensor based on binary transition metal oxide (ZnO-MnO) core-shell nanocomposites (CSNs) on the surface of the glassy carbon electrode (GCE). The nanocomposites are attained through a one-step hydrothermal synthesis route using zinc acetate and manganese acetate as precursors where ZnO acts as a core and MnO forms as a shell. As-synthesized binary transition metal oxide-based composite was scrutinized through various physicochemical techniques, demonstrating excellent physiochemical features. ZnO-MnO/GCE composite delivers synergistic features of improving the electrochemical properties toward detection of RF at an operational voltage of 0.42 V, with increased active sites because of its structural morphology and high surface area. ZnO-MnO/GCE is examined through electrochemical impedance spectroscopy, cyclic voltammetry, differential pulse voltammetry, and linear sweep voltammetry. Furthermore, ZnO-MnO/GCE shows a remarkable kinetic transfer rate and superior electron transfer rate over other modified electrodes. It also exemplifies a wider linear range (0.05 – 1102 µM), with Nanomolar level detection of 13 nM aided with a sensitivity of 0.3746 µA µM-1 cm-2, respectively. The proposed ZnO-MnO/GCE sensor demonstrates excellent selectivity over the presence of co-interfering species exquisite repeatability, reproducibility, and stability.
Here, N-doped hollow carbon sphere (NHCS)-supported (1 1 1)-plane-engineered sub-5-nm Pt (Pt-NHCS) catalysts regulated precisely by imidazolium ionic liquids were synthesized successfully and used to catalyze oxygen reduction. The (1 1 1)-plane engineered Pt nanocrystals with a diameter of 4.5 ± 0.5 nm were homogeneously deposited on the 3-dimensional spherical nanoshells. The resulting Pt nanocrystals anchored on the carbon skeleton exhibit a stable configuration in both alkaline and acid electrolytes with the help of imidazolium cations and pyrolysis. Among all as-prepared catalysts, the optimized Pt-NHCS shows remarkable long-term durability. Specifically, Pt-NHCS maintains 95.3% of the original current density after 10,000 potential cycles, while Pt/C benchmarks exhibit a retention of 78.5%. Accelerated durability test results indicate that Pt-NHCS exhibits a high efficiency of 96 % in comparison with initial current density, while a value of 86% for Pt/C. Density functional theory calculations demonstrate that reactive Pt(1 1 1) planes with well-defined Schottky defects and vacancies adsorb and activate oxygen molecule rapidly while desorbing the reaction intermediates.
PEM electrochemical analysis and measurements by voltammetry analysis.
As the energy demand and diversity increases human beings need new energy sources or energy converters. Among energy convertion technologies, direct methanol fuel cells (DMFCs) have attracted much attention due to their uniqe advantages. But, high-efficiency and CO poisoning are still the main drawbacks of these systems. In this study, binary CoAg electrocatalyst was fabricated on a carbon felt (C-felt) as promising anode material for DMFCs. Electrocatalytic performance of the binary catalyst for methanol electro-oxidation reaction was studied in 0.1 M KOH solution containing 1 M methanol using cyclic voltammetry (CV) and chronoamperometry (CA) techniques. Time-stability and CO poisoning tolerance of the catalyst were examined with CA technique. The electrocatalysts were characterized using SEM, EDX and XRD techniques. The data of binary eletrocatalysts were compared with the un-coated C-felt and Co-modified C-felt as reference points. It was found that the CoAg binary electrocatalyst has quite good electro-catalytic activity for the methanol electrooxidation reaction. The high-electrocatalytical activity was related to large real surface area, high intrinsic activity of Co and Ag as well as possible synergistic affect between the metals.
Composites of commercially available graphene oxide (GO) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with solvent additive ethylene glycol (EG) were investigated as an alternative support for Pt nanoparticles towards the electrocatalytic reduction of oxygen. The surface characteristics of the materials were examined using atomic force microscopy (AFM), X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), and energy dispersive X-ray spectroscopy (EDS). Cyclic voltammetry (CV) and linear sweep voltammetry (LSV) at rotating disk electrodes (RDEs) and rotating ring-disk electrodes (RRDEs) were used to characterise the electrocatalytic activities of the composites materials. The structural and electrochemical studies reveal that the addition of EG favours the homogeneous distribution of Pt particles with reduced particle size and improves the electrocatalytic properties. A 30% and 16% increase in electrochemically active surface area (ECSA), a 1.2 and 1.1 fold increase in specific area activity (SA), and a 1.5 and 1.2 fold increase in mass activity (MA) were observed for 30% and 40% Pt loading on PEDOT:PSS after the addition of EG. A composite of rGO and PEDOT:PSS(EG) was investigated for different (w/w) ratios of PEDOT:PSS and rGO. The 1 : 2 w/w ratio showed an enhanced catalytic activity with high limiting current, more positive onset potential, higher SA and MA with lower H2O2 yield compared to PEDOT:PSS(EG) and rGO and previously reported values for PEDOT:PSS.
PGM-free catalysts have high initial activity for O2 reduction reaction, but suffer from low stability in acid medium in PEMFC and DMFC. Here, we shed light on the atomic-scale structure of hybrid Pt/FeNC catalysts (1-2 wt% of Pt), revealing by STEM and EDXS the presence of [email protected] particles. The absence of exposed Pt on the surface is confirmed by the suppression of methanol oxidation reaction and CO stripping experiments. The promising application of such Pt/FeNC catalysts, comprising FeNx sites and [email protected] particles, is demonstrated at the cathode of DMFC. To gain fundamental understanding on the stability in acid medium and on the intrinsic ORR activity of [email protected], we constructed model surfaces by depositing FeOx films with controlled thickness (from 1.0 to 6.4 nm), fully covering the Pt(111) surface, which resulted stable in acid medium in the potential range 0.45 – 1.05 V vs. RHE. The specific ORR activity of Fe2O3/Pt(111) increases exponentially with decreasing overlayer thickness, which is explained by the tunneling of Pt electrons through Fe2O3. This special phenomenon sheds light onto recently reported excellent durability of Pt/FeNC composites in PEMFC and identify a promising [email protected] strategy leading to stable PGM-free surfaces in acid medium, and tolerant to methanol.
In this research, the glassy carbon electrode was modified by silver nanoparticles zeolite type A composite, hybridized with the nitrogen-doped graphene (AgNP-“zeolite A”/NG). The electrocatalytic oxidation of methanol was investigated at the surface of the modified electrode in alkaline solution using cyclic voltammetry, chronoamperometry and linear sweep voltammetry methods, and followingly, excellent electrocatalytic activity was observed. The structure and morphology of the resulting AgNP-“zeolite A”/NG were characterized by scanning electron microscopy, dynamic light scattering, X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy techniques. This electrode was found as a good candidate for application in the anode pole of the direct methanol fuel cell. Silver incorporated in this modified electrode played a key role for oxidation of methanol. The results confirmed the adsorption-controlled reaction at the surface of the modified electrode. Also, the effect of some parameters such as pH, scan rate of potential and the concentration of methanol were explored. Moreover, the kinetic parameters such as transfer coefficient (ko) and exchange current (io) were obtained 1.199 × 10−7 and 2.18 × 10−4 A, respectively, for methanol electro-oxidation process by the AgNP-“zeolite A”/NG. The relative standard deviation of ten replicate measurements, performed on a single electrode in 1.5 × 10−4 M of methanol in alkaline setting, was calculated 2.1% too.
In the present work, the three-dimensional ultra-fine platinum nanoflowers are directly deposited on carbon-coated gas diffusion layer electrode (C-GDL) by a single-step electrodeposition method towards the application of polymer electrolyte fuel cells. The surface morphology, particle size distribution, crystallinity, and chemical oxidation state of platinum nanoflowers are examined using various techniques. The morphological features of the Pt nanostructures are highly influenced by the difference in current density. Notabely, the Pt nanospheres converts into three-dimensional nanoflower with an increase in current density from -1.6 to -32 mA cm⁻². Electrodeposited Pt catalyst on C-GDL as the cathode catalyst was fabricated and steady-state polarization studies were carried out. Mainly, the fuel cell performance is analysed considering the electrodeposited Pt morphology. Among the prepared electrocatalysts, the nanoflower shaped Pt catalyst exhibit a high peak power density of 660 mW cm⁻² at 0.6 V in PEFC.
Platinum nanoparticles are an excellent catalyst for oxidation/evolution of hydrogen, oxygen reduction reaction and oxidation of small organic molecules fuels such as ethanol, methanol, and formic acid. In recent years, solutions-based techniques have attracted great interest due to their advantage in controlling reaction parameters. Among the techniques, amine-based seed-mediated solvothermal growth provides a versatile method for the production of various Pt nanoparticles. However, the amine species that functioned as the stabilizing agent would absorb at the surface of Pt, resulting in poor electrocatalytic performance. For this reason, the amine ligand must be removed in order to reveal the expected catalytic performance of Pt. In this work, we proposed a combination strategy that employed acid treatment under gentle heating followed by thermal treatment to remove the amine ligand and investigate their catalytic effect on formic acid oxidation. The acid wash involved in subjecting the catalyst in acetic acid glacial at 85 °C for 1 h + 9 h of heat treatment at 85 °C in air atmosphere. The experimental procedures were repeated by subjecting the Pt to 3 h in acetic acid + 7 h of heat treatment, followed by 5 h in acetic acid + 5 h heat treatment and a single treatment by immersing the Pt nanoparticles in acetic acid for 10 h. We reported that this combined activation technique improves significantly the performance of Pt nanoparticles in catalyzing formic acid oxidation. The results showed that 3 h of acid wash + 7 h of thermal treatment is the optimal condition for a high electrochemical surface area (ECSA) value of 1.006 ± 0.02 m²/g, lower coverage of CO adsorption and a steady-state current of 3.03 mA/cm² made at 0.67 V (vs. SCE) at 1000 s during formic acid oxidation. This approach could become a potential procedure for activating the Pt surface attached by amine ligand.
MoS 2 has been considered as a non-precious alternative to platinum based electrocatalyst for electrochemical hydrogen evolution. Since most of the active site exists on the edges of MoS 2 , a material design that could increase the exposure of the edges could improve its catalytic activity. In this work, we prepared small sized and few-layered MoS 2 that is vertically aligned on three-dimensional interconnected porous carbon nanosheets (IPC). Benefiting from exposure of MoS 2 edges, MoS 2 /IPC composite exhibits a high catalytic activity (225 mA cm ⁻² at −250 mV vs. RHE, and Tafel slope of 38 mV dec ⁻¹ ) and maintains steady performance for several hours. Since the procedure to prepare MoS 2 /IPC composites is scalable and cost-effective, our method of preparing few-layered MoS 2 on porous carbon shows great potential as a competitive electrocatalysts for HER.
Platinum is the best catalyst known so far for the hydrogen evolution reaction (HER) in acidic environments, but it is also a scarce and expensive resource. Maximizing its performance per metal atom is essential in order to reduce costs. The deposition of small Pt nanoparticles (2–3 nm) onto electrically conductive, highly accessible and stable carbon supports leads to active catalysts. However, blocking of pores and active sites by Nafion, which acts as a binding species, reduces the catalytic activity. Moreover, inaccessible Pt located in micropores diminishes an efficient exploitation of the noble metal.
We report a new synthesis approach to ordered mesoporous carbon (OMC) coatings with preformed Pt nanoparticles. The particles are exclusively located inside the mesopores. Furthermore, no Nafion binder is needed. As a consequence, the PtNP/OMC catalyst film outperforms Pt/C catalysts reported in literature particularly at high current densities. PtNP/OMC catalyst films with a geometric Pt loading of 1.6 µgPt/cm² achieve a current density of −100 mA/cm² at an overpotential of ca. −70 mV.
Multiwall carbon nanotubes are modified by urea (MWCNTs-U), as an amide group, through a simple amination method to be used as support for Pt nanoparticles in methanol electrooxidation reaction (MOR). The amination method involves a covalent grafting of urea molecules onto the surface of acid treated multiwall carbon nanotubes (MWCNTs-A) using O-(7-azabenzotriazol-1-yl)-N,N,N′,N′-tetramethyluronium hexafluorophosphate (HATU) as the coupling agent. Platinum nanoparticles are impregnated on the surface of MWCNTs-U using NaBH4. Pt/MWCNTs-U shows an enhanced electrocatalytic activity and durability with exposing larger accessible surface area and 27% higher active surface area compared to Pt/MWCNTs-A. In addition, urea incorporation can improve the electrocatalyst tolerance against CO-poisoning, due to the enhanced formation kinetics of the chemisorbed hydroxyl groups. The onset potential of COads oxidation indicates a decrease from 553 mV to 530 mV for Pt/MWCNTs-A and Pt/MWCNTs-U, respectively. It is observed that in the presence of amide group the forward peak current density and exchange current density, in CV and LSV experiments, respectively increase from 378 to 515 mA/mgPt and 1.59 × 10⁻⁸ A/cm² to 2.12 × 10⁻⁸ A/cm². These results are also in a good agreement with the theoretical activation energies obtained from Arrhenius plots, indicating a decrease from 41.7 to 38.8 kJ/mol methanol in the case of Pt/MWCNTs-A and Pt/MWCNTs-U, respectively.
The electrocatalytic performance of the carbon supported catalysts can be effectively influenced by controlling the atomic structure of carbon materials. Herein, novel graphene nanospheres (GNs) composed of graphene nanoflakes are prepared through a modified arc-discharge method using toluene as carbon source. It is explored that these GNs possess high density of lattice disorder as well as the oxygen-containing functional groups. Attributing to the structural features, the Pt nanoparticles deposited on the prepared GNs exhibit a homogeneous dispersion without obvious aggregation. Such electrocatalyst with a Pt loading of 14.7 wt.% displays remarkable performance with low overpotentials of approximately −25 and −44 mV at the current density of −10 and −100 mA cm⁻² as well as excellent cycling stability for the hydrogen evolution reaction. Thus, our result provides a suggestive way to improve the catalytic performance of the supported catalysts.
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This review explores the recent development in the synthesis process of platinum nanoparticles by electro deposition method. Various developed supporting electrodes used in synthesis process of platinum nanoparticles have been discussed. It is possible to control the particle size by adjusting electrolysis parameters and to improve homogeneity of platinum particles by changing the composition of electrolytic solutions. Various electrolytic compositions also discuss briefly for single or mixed electrodes.
Nanoporous platinum nanoparticles (NPs) have been proposed as promising electrocatalytic materials. Routes to produce them typically consist of chemical synthesis or selective dissolution of one component of a two component mix. Here we show that by employing a pulsed laser heating approach during electrodeposition, whereby the electrode/electrolyte interface is continually heated and cooled, NPs with a nanoporous structure, can be grown directly on the electrode (boron doped diamond) surface. Transmission electron microscopy shows the NPs to be composed of loosely packed aggregates of much smaller crystalline particles of size 2-5 nm, with the porosity increasing with increasing deposition overpotential. In contrast electrodeposition at room temperature (RT) results in particles which show a considerably more compact morphology, and less higher index crystal facets, as revealed by electron diffraction techniques. Pulsed heating also offers a route towards controlling the monodispersity of the electrodeposited NPs. When applied to the oxidation of methanol, the laser heated NPs show considerably higher catalytic current densities compared to RT deposited particles. The highest catalytic activity is observed for the most porous NPs produced at the highest overpotential. Interestingly, the ratio of the forward oxidative current to the backward one is highest for those particles deposited under laser heated conditions but with the smallest overpotential. This suggests that the most catalytically active NPs may also encourage binding of residual adsorbed carbon monoxide and that a compromise must be reached.
For a clean environment, low-temperature fuel cells are particularly important to power familiar devices, such as portable electronics (cell phones, computers, cam recorders, etc.) or electrical vehicles (buses, trucks, and individual cars). Among them, the alkaline fuel cell working at 80 °C with pure hydrogen, the proton exchange membrane fuel cell that can operate at temperatures ranging from ambient to 70–80 °C with hydrogen either produced by water electrolysis or by hydrocarbon reforming, and the direct alcohol fuel cell that realizes at higher temperatures (up to 120–150 °C) the direct electrooxidation of methanol or ethanol are particularly convenient. In these fuel cells, because of the relatively low working temperatures, the kinetics of the electrochemical reactions involved (fuel oxidation and oxygen reduction) is rather slow. Therefore, to improve the reaction kinetics, by a careful design of the electrode catalyst, it is necessary to determine detailed reactionmechanisms, where all the adsorbed species and intermediate products have been clearly identified. The use of purely electrochemical techniques is not at all sufficient to do it, and electrochemical methods have to be coupled with spectroscopic methods (infrared spectroscopy, mass spectroscopy, etc.) and analytical methods (gas chromatography, high-pressure liquid chromatography, radiotracers, etc.) in order to identify the different species involved and to evaluate their concentration or surface amount. After the establishment of the reaction mechanism, particularly the knowledge of the rate determining step, it is important to design suitable electrocatalysts able to activate preferentially the rate determining step.The various methods to prepare such catalysts are first presented. Then, the different physicochemical methods used to evaluate their properties and to determine the reaction mechanisms are discussed. Finally, the reaction mechanisms of the most important electrochemical reactions involved in low-temperature fuel cells, that is, the electrooxidation of hydrogen, carbon monoxide, methanol, and ethanol and the electroreduction of oxygen, have been established.
In this study, Pt catalysts were fabricated on a glassy carbon (GC) electrode Pt/GC using a potentiostatic technique at different reduction potentials in potassium hexachloroplatinate solutions with hydrochloric acid. The compositions of the catalysts were determined using energy dispersive spectroscopy (EDS), the surface morphologies were observed using scanning electron microscopy (SEM), and the crystal structure was confirmed using thin-film X-ray diffraction (XRD). The results show that all the electrodeposited Pt/GC catalysts exhibit a higher electrochemical activity for the oxygen reduction reaction (ORR) when compared with a commercial Pt/C electrode. There is an optimum electrodeposited potential (−0.15 V vs. Ag/AgCl) at which the Pt/GC electrode displays the highest electrochemical activity for the ORR due to the high-index plane and shape effect of the Pt particles. At a lower electrodeposited potential, the applied current density is high enough to form large and coarse metal particles, while at a higher electrodeposited potential, the active sites of Pt particles decrease because of its equiaxed shape.
Direct methanol fuel cell (DMFC) have the advantages of low emissions of carbon dioxide, high power density and high energy density, so they have a great potential to replace fossil fuels. It is well known that Pt with high activity is an ideal catalyst for methanol oxidation in an acidic medium. However, it is an expensive material, and cost of the DMFC containing Pt is prohibitively high and it becomes poisoned by COads which is formed during the methanol oxidation. In this work, for the first time, the preparation of activated carbon(YBC) doped carbon paste electrode (YBCPE) and carbon paste electrode (CPE) were carried out for comparison. The electrochemical properties of YBCPE and CPE were investigated by electrochemical impedance spectroscopy. The electrodes of Pt/YBCPE and Pt/CPE were prepared by electrodeposition of platinum on YBCPE and CPE, respectively, at a constant potential (−0.1 V vs. Ag|AgCl(sat)) in 0.5 M H2SO4 containing 3 mM H2PtCl6. The behavior of electrodeposition of platinum on YBCPE and CPE was studied through the application of theoretical models, and the morphology of Pt/YBCPE and Pt/CPE were characterized by SEM. The electrochemical activities of these catalysts towards methanol electrooxidation were examined by cyclic voltammetry. The influence of YBC mass percentage in YBCPE on both the electrode activity and long-term stability of electrodes in methanol electrooxidation was studied. It was shown that the addition of activated carbon improved the electrocatalytic activity of Pt catalysts on corresponding YBCPE toward methanol electrooxidation.
The practical application of theory to experiment and data analysis is a crucial component of effective advancement of electrochemical systems. This chapter takes the fundamental principles of fuel cell operation and the underlying scientific and engineering principles and applies them to laboratory experiments. Topics covered include experiments showing how fuel cell performance varies with test conditions, methodology to fit experimental data to a simple empirical model to extract physically meaningful parameters that govern fuel cell performance, impedance spectroscopy as a diagnostic for fuel cell performance, and data analyses methods to determine the performance of fuel cells. Methods are also given for the practical measurement of relevant items from cell assembly and cell pinch to relative humidity. While the lessons are relevant to all electrochemical systems, this chapter is primarily targeted at new entrants into this arena wishing to learn the basics of fuel cell operation and testing.
Pt nanoparticles supported on Vulcan XC-72R were synthesized by water-in-oil microemulsion method. By incorporating different amounts of HCl as a capping agent in the precursor-containing water phase, nanoparticle shape was varied. Influencing the growth of certain facets leads to the changes of the particle shape depending on the preferential facets. As a result, nanoparticles exhibit some of the electrochemical features typical for single crystals. Commonly employed synthesis procedure for water-in-oil microemulsion method was altered with the addition of catalyst support in the system and changing the catalyst cleaning steps. Prepared catalysts were characterized by thermogravimetric analysis (TGA), transmission electron microscopy (TEM) and electrochemical methods. Activity and stability for methanol oxidation reaction (MOR), a structure-sensitive reaction, were tested. Electrochemical results reveal the influence of particle size, shape and exposed facets on the electrochemical processes. TEM investigations confirm electrochemical findings, while TGA verifies Pt loading in catalyst powder. Based on the results, optimal HCl concentration for cubic particle formation is determined, and structural effect on MOR activity and stability was tested. Cuboidal NPs show very good reaction activity and fair stability under applied experimental conditions.
Platinum (Pt) nanocrystals of cubic and octopod structures were synthesized via seed-mediated solvothermal growth with monoethanolamine as the solvent. The combination of nanocube and octopod structures was formed using 0.025 ml seeds loading, while increasing the seeds volume to 0.050 ml and 0.100 ml produced nanocube as the primary product. The octopod structure evolves from the overgrown nanocube via kinetic growth mechanism. Pt nanocube formed with 0.050 ml seeded solution has the potential to serve as a catalyst in formic acid oxidation by virtue of its high electrochemical surface area of 10.93 m2/g, over that of Pt black at 8.62 m2/g and resistance to poisonous CO. Nonetheless, it is less catalytically active in ethanol oxidation as depicted by the small electrochemical surface area of 8.64 m2/g and low current density in longer period.
nPd0 · (Hx–2n
MoO3)/GC electrodes (0 < n < 1) were obtained by currentless redox reaction between hydrogen-containing molybdenum bronzes and palladium(II) chloride. The composites were characterized by electrochemical methods and by SEM, TEM, XRD, XPS, and AES–ICP. The morphology, structure, and composition of the electrodes depend on the degree of reduction of the starting molybdenum bronze. The use of red molybdenum bronze Hx
MoO3 (x ≈ 1.55) led to the formation of a composite characterized by longer palladium/molybdenum oxide compound boundaries than in the case of green molybdenum bronze (x ≈ 1.9). On the nPd0 · (Hx–2n
MoO3)red/GC electrodes, the catalytic effect with respect to methanol electrooxidation (MEO) was significant, while formic acid electrooxidation (FAEO) was accelerated insignificantly. Possible reasons for the difference in the effect of Pd modification with molybdenum bronzes on MEO and FAEO were discussed.
Here we studied the formation of Platinum hierarchical microstructure by varying the synthesis time using amine assisted growth via solvothermal method. A small cluster of particles was produced at a shorter synthesis time (5h) while fully grown flower-like microstructure were formed at 9h of reaction. The synthesized Pt particles exhibit high absorption peak at 230 nm corresponding to Pt absorption peak. The catalytic property of the synthesized Pt is greatly influenced by its geometrical shape. The fully grown flower-like particles exhibit large electrochemical surface area (4.88 cm−2 g−1) and catalytic stability at a longer period, which can serve as a potential catalyst for electro-oxidation of formic acid.
Development of polymer electrolyte membrane (PEM) fuel cells throughout the years is established through its component optimization. This is especially true of its catalyst layer, where structuring of the layer has led to many breakthroughs. The catalyst layer acts as the heart of the cell, where it controls the half-cell reactions and their products. The complex nature of various transport phenomena simultaneously taking place in the layer requires the layer to be heterogeneous in structure. Hence, a delicate balance of the layer's ingredients, coupled with the understanding of the ingredients' interaction, is required. State-of-the-art catalyst layers are composed of a catalyst, its support, a solvent and a binder. Changes in the morphology, structure or material of any of these components ultimately affects the layer's activity and durability. In this review paper, we provide an overview of the various works tailored to understand how each component in the catalyst's ink affects the stability and life-time of the layer.
Carbon nanotubes with diameters ranging between 140-220nm was synthesized with chemical vapor deposition method, and treated using nitric acid as oxidant. Pt/C catalysts were prepared using untreated and treated carbon nanotubes as supports, respectively. TEM and FT-IR differential spectra showed that treated carbon nanotubes become short and possess more oxygen-containing surface groups. The electrochemical studies indicated that the Pt/treated carbon-nanotubes catalyst possessed much higher electrocatalytic activity for the oxidation of methanol than that of the Pt/untreated carbon-nanotubes catalyst.
Electrochemical Quartz Crystal Microbalance (EQCM) was used to investigate the events occurring during current-on (Ton) and current-off (Toff) for pulse current electrodeposition of Pt in both air and Ar atmospheres. The EQCM profiles indicated a transient mass loss when the current was turned on, followed by a linear mass gain associated with the Pt electrodeposition from the H2PtCl6 plating bath. During the Toff, the mass revealed a steady increase until it leveled off after 10 sec. The minute transient mass loss during the initial stage of Ton was attributed to the reduction of the adsorbed PtCl62- whereas the mass gain during the Toff was due to the absorption of PtCl62- onto the freshly-deposited Pt surface. In air atmosphere, the parasitic oxygen reduction reaction consumed part of the reduction current and thus, reduced the Pt plating efficiency by 6%. In addition, smaller mass gains during Toff and Ton were observed for the Pt plating in air atmosphere.
Oxidn. of MeOH was studied on foamed Ni-based Pt-Ru electrodes in 6 M KOH contg. 0.3 M CH3OH to assess their usefullness for alk. fuel cells. In the 1st cycle, the electrocatalytic activities toward MeOH oxidn. at low potentials followed the descending order: Ni/(4:2)Pt-Ru > Ni/Pt > Ni/(4:1) Pt-Ru > Ni/(4:3)Pt-Ru > Ni. In subsequent cycles, the activity of the Ni/Pt decreased, whereas that of the Ni/Pt-Ru electrodes rose.
Platinum microparticles electrodeposited at a glassy carbon surface (Pt/GC) and within a poly-ortho-aminophenol film formed on a GC substrate (Pt/PoAP/GC) have been used for investigating their catalytic activity towards hydrogen evolution reaction and methanol oxidation by cyclic voltammetry, impedance spectroscopy and chronoamperometry. The effect of the deposition time (t dep) of the Pt particles dispersed into GC and PoAP electrodes and of the acid anions (SO42-, ClO4- on the hydrogen adsorption/desorption peaks and hydrogen evolution reaction has been studied. It has been shown that the main cause of immediate blocking of the PoAP-SO42- pores with platinum microparticles is its smaller scaling yardstick. The higher electrocatalytic activity of the PoAP as compared to that of GC due to its higher surface area for the methanol oxidation has been proved by a substantial improvement in transition current in chronoamperometric and in the maximum anodic current of the methanol in cyclic voltammetric measurements.
The nanoTiO2-CNT-PtNi complex catalysts were prepared by the direct hydrolysis of electrosynthetic precursor Ti(OEt)4 and electrochemical scan electrodepositing method. The results of XRD and SEM show that the PtNi nanoparticle of average size 8 nm was dispersed uniformly on nanoTiO2-CNT complex film surface. The electrocatalytic activity of the nanoTiO2-CNT-PtNi complex catalysts was investigated by cyclic voltammetry and chronopotentiogram. The results indicated that the nanoTiO 2-CNT-PtNi complex catalysts with Pt loading of 0.32 mg/cm 2 exhibited high electrochemically active surface area of 90 m 2/g and very high electrocatalytic activity and stability for electro-oxidation of methanol. The oxidation peak potential of methanol was 0.67 and 0.44 V at room temperature in atmosphere pressure, respectively, and shifted to 0.64 and 0.30 V at 60 °C and the oxidation peak current of methanol was 1.38 A/cm2. The high electrocatalytic activity and good stability can be attributed to the synergistic catalytic effect of nanocomposite, which leads to the weak adsorption of CO on complex nanostructure catalysts, avoiding poisoning of the catalysts.
Pt-stabilized catalysts with platinum crystallites sizes between 1-20 nm were prepared using an organometallic approach and three different amino ligands; tert-butylamine, 1,3-diaminopropane and anthranilic acid. The electrochemical oxidation of methanol was investigated on Pt stabilized nanoparticles in acid solutions and the results were compared with commercial PtBlack to analyze the feasibility of applying a tailored stabilizer to improve the dispersion and electrocatalytic activity. The particle size and the degree of dispersion of the resultant nanoparticles were observed by transmission electron microscopy (TEM) and selected area electron diffraction (SAED) patterns. Dispersion differences, lattice parameters and interplanar distances were caused by the coordination of the functional groups contained in the ligands at the Pt surface. The current density peaks on methanol oxidation reaction (MOR), appearing at different potentials and are increased in the following order PtBlack ≈ PtTBA< PtDAP < PtAA. The different tendency to form aggregates and scattered particles is the result of the divergence in their sterical shapes rather than different acid-base interactions. It has been also found that stabilized Pt nanoparticles using TBA or even DAP exhibit an interesting electrocatalytic activity, and can facilitate the MOR.
The modification of a glassy carbon (GC) electrode with platinum (PtNPs) and gold (AuNPs) nanoparticles was intended to fabricate efficient anodes for the formic acid electro-oxidation (FAO). A suitable deposition sequence of PtNPs and AuNPs was adjusted to enhance the electrocatalytic activity of the electrode in such a way suppressing the CO poisoning that usually deteriorates the electrode's catalytic activity during FAO. Morphologically, PtNPs were deposited in a spherical shape (with an average diameter of 37 nm), while AuNPs appeared in granules (with an average diameter of 43 nm) both were uniformly dispersed on the GC surface. The highest electrocatalytic activity was obtained at the Au-Pt/GC electrode (for which PtNPs was deposited first on the GC electrode then AuNPs). Interestingly, AuNPs could successfully interrupt the contiguity of Pt surface sites in a way preventing the CO poisoning. Moreover, the Au-Pt/GC electrode exhibited excellent tolerance against poisoning influenced by chloride ions, which usually contaminate the fuel cell and have a similar impact as CO. The relationship between the degree of electrode's tolerance against the catalytic deactivation and the chloride ion concentration was addressed.
Titanate-SWCNT; synthesized via exploiting the interaction between TiO2 anatase with oxygen functionalized SWCNT, supported Ag nanoparticles and Ag/titanate are characterized using XRD, TEM-EDX-SAED, N2 adsorption, Photoluminescence, Raman and FTIR spectroscopy. These samples are tested for methanol electrooxidation via using cyclic voltammetry (CV) and impedance measurements. It is shown that Ag/titanate nanotubes exhibited superior electrocatalytic performance for methanol oxidation (4.2 mA cm-2) than titanate-SWCNT, Ag/titanate-SWCNT and titanate. This study reveals the existence of a strong metal-support interaction in Ag/titanate as explored via formation of Ti-O-Ag bond at 896 cm-1 and increasing surface area and pore volume (103 m2 g-1, 0.21 cm3 g-1) compared to Ag/titanate-SWCNT (71 m2 g-1, 0.175 cm3 g-1) that suffers perturbation and defects following incorporation of SWCNT and Ag. Embedding Ag preferably in SWCNT rather than titanate in Ag/titanate-SWCNT disturbs the electron transfer compared to Ag/titanate. Charge transfer resistance depicted from Nyquist impedance plots is found in the order of titanate > Ag/titanate-SWCNT > titanate-SWCNT > Ag/titanate. Accordingly, Ag/titanate indicates a slower current degradation over time compared to rest of catalysts. Conductivity measurements indicate that it follows the order Ag/titanate > Ag/titanate-SWCNT > titanate > titanate-SWCNT declaring that SWCNT affects seriously the conductivity of Ag(titanate) due to perturbations caused in titanate and sinking of electrons committed by Ago through SWCNT.
Energy and environment issues are of paramount importance to achieve the sustainable development of our society. Alcohol-fuelled direct oxidation fuel cells (DOFCs), as a clean and highly-efficient energy harvesting engine, have attracted intensive research activity over recent decades. Electrocatalysts are the material at the very heart of the cell that determines the performance of DOFCs. The rapid advances in electrocatalysts, particularly nano-sized ones, have left current information only available in scattered journals. To be truly useful to both present and future researchers, a new book is needed to present an insightful review of the reaction nature of this research and to systematically summarize recent advances in nanocatalysts, and convey a more global perspective. Catalysts for Alcohol-fuelled Direct Oxidation Fuel Cells will present a state-of-the-art review on recent advances in nanocatalysts and electrocatalysis in DOFCs, including both proton and hydroxide ion exchange membrane fuel cells. The main topics covered include a molecular-level understanding of electrocatalysis, the design principles of electrocatalysts, recent advances in nanocatalysts and future perspectives for DOFCs. The book presents a cutting-edge collection on nanocatalysts for alcohol-fuelled direct oxidation fuel cells and brings together the most authoritative researchers in the field from both industry and academia, filling the gap between both sides. Finally, the book will provide an insightful review on electrocatalysis at the molecular- level, which will be useful for postgraduate students and junior researchers in this field. It will be an essential resource for postgraduates, researchers and policy-makers globally in academia, industry, and government institutions.
The theory of the potentiostatic current transient for three-dimensional multiple nucleation with diffusion controlled growth is discussed. Reliable values of nuclear number densities and nucleation rates are obtained from the analysis of the current maximum, and good agreement is obtained with experimental data for nucleation in several electrochemical systems. The termination of the nucleation process by the expansion of diffusion fields is considered, as well as the deviations from randomness observed in the distribution of nuclei on the electrode surface.
Of the several factors which influence electrocatalytic activity, particle size and structural effects are of crucial importance, but their effects and mechanism of interaction,vis-a-vis overall performance, have been, at best, vaguely understood. The situation is further aggravated by the use of a wide range of experimental conditions resulting in non-comparable data. This paper attempts systematically to present the developments to date in the understanding of these structural interactions and to point out areas for future investigation. The entire content of this review has been examined from the context of the highly dispersed Pt electrocatalyst, primarily because it has been examined in the greatest detail. In the first two sections a general idea on the correlations between surface microstructure and geometric model is presented. Subsequently, indicators of a direct correlation between particle size and catalyst support synergism are considered. The structural and particle size effect on electrocatalysis is examined from the point of view of anodic hydrogen oxidation and cathodic oxygen reduction reactions. The hydrogen and oxygen chemisorption effects, presented with the discussion on the anodic and cathodic electrocatalytic reactions, provide important clues toward resolving some of the controversial findings, especially on the dependence of particle size on the anodic hydrogen oxidation reaction. Finally, the effect of alloy formation on the cathodic oxygen reduction reaction is discussed, providing insights into the structural aspect.
The fourth volume of Modern Aspects of Electrochemistry is being prepared at a time of great growth of interest in electro chemistry. The situation can be summarized by saying that the realization is spreading among scientists that electrochemistry represents a broad interdisciplinary field, which has applications to many areas in physics, chemistry, metallurgy, and biology. Among the reasons for this awakening is the reorientation of what is understood under electrochemistry toward electrodics "the study of charged interfaces"-with the ionic-solution aspects of electrochemistry being regarded increasingly as aspects of physical chemistry which are helpful auxiliaries to the broad subject of charged interfaces. The pervasiveness of electrochemistry be comes clearer when one recalls that most interfaces carry a charge, or undergo local charge transfers, even though they are not con nected with a source of power. A further reason for the rapid increase in electrochemical studies arises from the technological aspects, in particular in energy conversion and storage, syntheses, extractions, devices, the stability and finishing of surfaces, the treatment of water, etc. The fact that electrodics allows the conversion of chemical to electric energy and the storage of the latter, at the same time producing fresh water as a by-product, presents an aspect of the subject which appears to have far-reaching significance.
The efficiency of platinised porous-carbon electrodes for the electrooxidation of methanol in H2SO4 is found to vary quite markedly with the method used to deposit the platinum. This is shown to be a consequence of both the size and the electronic nature of the platinum crystallites. The most efficient electrodes are those that possess both small crystallite sizes, ∼ 20 Å diameter, and a minimum amount of ionic platinum species as identified by XPS studies. A comparison is drawn with optimised platinised carbon electrodes for oxygen reduction, and an explanation for the different requirements of these two types of electrode suggested.
In order to characterize the surface structure of electrochemically modified polycrystalline platinum, the voltammograms of underpotential deposited copper and of formic acid are studied. The operating conditions are chosen in such a way that a direct comparison to results on single crystal platinum electrodes is possible. It is shown that UPD copper in HF solution and formic acid oxidation are well suited to characterize the modified structure of platinum surfaces.
The influence of platinum crystallite dispersion on the electrocatalytic oxidation of methanol in sulphuric acid has been examined with different carbon black supports. There are no platinum “crystallite size” effects, even for crystallites as small as 1.4 nm in diameter, which corresponds to ca. 70% dispersion of the platinum. The mass activity increased proportionally with the specific surface area of the platinum crystallites. No inter-crystallite distance effect for platinum on the catalytic activity was found either, unlike the electroreduction of oxygen found previously. Therefore, increasing the dispersion of platinum on carbon surfaces is a significant factor for achieving a much higher catalytic activity of methanol oxidation than the present level.
A method that allows one to selectively electrodeposit catalyst within the thin active layer of a membrane-electrode assembly is described. The active layer corresponds to the location of electrochemical reaction in a fuel cell. The method is based on the unique chemistry of the membrane/gas-diffusion-electrode interface, where metal deposits tend to concentrate if dilute-electrolyte solutions are used for deposition. Examples of copper and platinum deposition from aqueous copper sulfate and tetrammine platinum (II) chloride, respectively, demonstrate the generality and effectiveness of the method. Electron probe microanalysis, backscattered electron images, and electrochemical experiments are used to characterize the catalyzed membrane-electrode assemblies. Transport and kinetic parameters are obtained for the Pt(NHâ)âClâ electrolyte; the parameters can be used in future modeling work to understand and optimize the catalyzation process.
The electro-oxidation of methanol on a Pt(111) surface in both sulfuric and perchloric acid solutions was investigated by combined apparatus under both ultra-high vacuum and electrochemical environments. In sulfuric acid solution, a strong lateral interaction was observed between adsorbed bisulfate and CO derived from methanol. Coadsorption of CO derived from methanol with bisulfate ion yielded a (√7 × √7)-R19.1°-CO-bisulfate structure. In perchloric acid solution, however, no lateral interaction between adsorbed CO and perchlorate was seen. The difference in reaction rates of methanol oxidation in both solutions was explained by these specific anion adsorption effects.
The electrodeposition of platinum particles into Nafion films on a glassy carbon electrode is described. The particles are dispersed three-dimensionally throughout the polymer layer. The active platinum surface area is determined by the charge required for the adsorption of hydrogen. The mass specific surface area of the particles grown in the Nafion film is surprisingly large, suggesting that the platinum particles are highly dispersed in the Nafion film. The average crystal size of the platinum clusters is in the range 10–20 nm. The exchange current density of the hydrogen evolution reaction has been determined in an acidic solution.
EMIR spectra of methanol electroadsorbates on smooth and rough polycrystalline, monocrystalline and preferentially oriented platinum electrodes are reported. The (100)-type preferred oriented platinum behaves approximately as Pt (100) single crystals. On electrodispersed platinum electrodes the poisoning phenomena due to CO adsorbates appear to be reduced as compared to smooth platinum electrodes. EMIRS results correlate well with the electrochemical behaviour of the different platinum electrodes for methanol electrooxidation.
The effects of carbon supports for platinum‐ruthenium (Pt‐Ru) catalysts on anode performance of direct methanol fuel cells
(DMFC) were investigated. Good polarization characteristics of the methanol electrode were obtained for a Pt‐Ru catalyst supported
on an acetylene black with high specific surface area and a pore size distribution in the range of 3 to 8 nm. The performance
of the methanol electrode increased with the increase in pore volume for the pore size distribution of 3 to 8 nm. Analyses
of various carbon blacks and supported catalysts were carried out with several techniques:
adsorption (Brunauer‐Emmett‐Teller (BET) and Barrett‐Joyner‐Halenda (BJH) methods),
adsorption, transmission electron microscope, and scanning electron microscope observations. The effects of the heat‐treating
temperature, time, and atmosphere on the polarization curves of the methanol electrodes with the acetylene black were investigated.
The heat‐treatment in air at 370°C improved not only methanol oxidation but the durability of the Pt‐Ru catalyst.
The particle size effect for oxygen reduction kinetics on highly dispersed Pt particles in acid electrolytes are discussed.
It is suggested that the change in the fraction of surface atoms on the (100) and (111) crystal faces of Pt particles, which
are assumed to be cubo‐octahedral structures, can be correlated to the mass activity (A/g Pt) and specific activity (μA/cm2 Pt) of highly dispersed Pt electrocatalysts. The maximum in mass activity that is observed at ∼3.5 nm in several studies
is attributed to the maximum in the surface fraction of Pt atoms on the (100) and (111) crystal faces, which results from
the change in surface coordination number with a change in the average particle size. The reduction of oxygen on supported
Pt particles in acid electrolytes is classified as a demanding or structure‐sensitive reaction; the specific activity increases
with an increase in particle size.
Direct methanol fuel cells (DMFCs) using Pt‐Ru electrocatalysts and perfluorosulfonic acid membranes provide high performances
if operated above 100°C with optimized catalyst layers. A decal transfer method is used to apply thin‐film catalyst/ionomer
composite layers to Nation® membranes. A Nation 112 membrane/electrode assembly operating on 5 atm oxygen at 130°C yields
a current of 670 mA/cm2 at 0.5 V cell voltage. Peak power density is 400 mW/cm2. The same cell operating on 3 atm air at 110°C yields 370 mA/cm2 at 0.5 V and provides a maximum power density of 250 mW/cm2.
Platinum was electrochemically deposited within a Nafion film coated on glassy carbon (GC) to form a well adherent and high-platinum utilization electrode. Two potential-control procedures were evaluated to form a deposit: a cyclic potential scan and a constant potential, with Pt loadings ranging for each from 60–750 μg Pt cm−2 GC obtained by varying the coulombs discharged. The Pt/Nafion/GC electrodes were annealed at 170 °C before use. Transmission electron microscopy studies revealed that Pt grows as a dispersed, three-dimensional deposit within the film for both techniques. The average particle size for a loading of 60 μg cm−2 is 7.3 nm, which is in good agreement with that (7.1 nm) estimated from electrochemical formation of adsorbed hydrogen. With a Pt loading an order-of-magnitude greater, the particle number density increased, and the observed average particle is larger at 9.8 nm which is smaller than that (19.0 nm) evaluated from electrochemical hydrogen adsorption. The deposit thickness increased with loading and, for a given Pt loading, was less thick when using the steady-potential method; the latter technique, however, yielded a deposit which covered more of the GC-Nafion interface. The mass specific surface area of Pt decreased with loading and ranged from 32-8 m2g−1 as the loading varied from 60–640 μg cm−2. The Pt/Nafion/GC structure is robust in that the electrode can be used to evolve hydrogen or oxygen without damaging the film. In contrast, a Nafion film on smooth Pt is lifted off the surface under similar gas-evolution conditions.
Kinetic data are presented for the adsorption of a hexaamminecobalt(III) ion from an aqueous solution onto several kinds of carbon and for the base hydrolysis catalyzed by carbon. The content of surface acidic groups of carbons, including a carbon black and an active carbon, was modified by oxidation or methylation. The pH value of solution has a significant effect on the adsorption rate: an addition of NaOH increases the rate, and HC1 retards the adsorption. The observed rate constant increases with the amount of surface acidic groups and the amount of carbon. These results are consistent with the proposed mechanism which involves adsorption of complex ion on such acidic groups of carbon. Apparent activation energy for adsorption on carbon was estimated at 21 ∼ 23 kcal/mol. The rate constant for base hydrolysis of the same complex ion was also found to have a close relation to the amount of surface acidic groups of carbon catalysts. It is suggested that the active sites for hydrolysis may be such acidic groups which are also the active sites for the adsorption.
The objective of the study was to investigate the effect of particle size on the catalytic activity for oxygen reduction reaction at platinum/recast ionomer interface. To obtain experimental evidence of this effect, porous electrodes of well-defined geometry and very well calibrated Pt particles on graphite were used. The catalytic powders were prepared by cationic exchange and characterised by TEM and H and CO electrochemical adsorptions. For oxygen reduction, a loss of catalytic activity with the decreased platinum particle size is confirmed. This activity loss is correlated to the stronger adsorption of oxygenated species under inert atmosphere and during oxygen reduction. No effect of the inter-particles distance was found even when the particles are 1.2nm in diameter and about 10nm away; the use of graphite powder also prevents a too strong shielding effect of the catalyst support.
The objective of the following study was to test proton exchange membrane fuel cell catalysts. A mixture of supported catalyst and recast ionomer (Nafion) was deposited on a rotating disc electrode (RDE). The resulting thin active layer was immersed in a dilute sulphuric acid solution. The RDE technique allows correction of mass transfer limitation in solution. To calculate the kinetic parameters from the current-potential relation, a mathematical model was written taking into account gas diffusion, ohmic drops and interfacial kinetics within the thin layer. Analytic and/or numerical expressions for the effectiveness factor and for the current-potential relation were obtained. The oxygen reduction reaction at various Pt/C-recast Nafion interfaces demonstrates the validity of this test procedure.
This paper describes the results of transmission electron microscopic, scanning electron microscopic and/or Rutherford backscattering spectroscopic analyses of platinum electrocatalysts supported on carbon, and of low catalyst loading gas-diffusion electrodes used in proton-exchange-membrane (PEM) fuel cells. We looked for correlations between the performance of PEM fuel cells and the morphology of low-catalyst-loading electrodes, taking into account the thickness of the catalyst layers, the crystallite sizes of the platinum electrocatalyst supported on carbon and the increased Pt catalyst content near the front of the electrodes. We reached the conclusion that the use of electrodes with thin catalyst layers (made by using platinum on carbon electrocatalysts with a high Pt/C weight ratio) and with more platinum localized near the front surface had the effect of diminishing the overpotentials in PEM fuel cells.
The effect of various electrode pretreatments on the properties of Pt microparticles (dia. ca. 0.1 μm) electrodeposited on glassy carbon (GC) is evaluated. On freshly polished GC surfaces, Pt particles are not observed by scanning electron microscopy (SEM) after the electrodeposition process. In addition, these electrodes exhibit very low catalytic activity toward hydrogen generation. Heat treatment of GC, prior to deposition at 0.185 V, markedly improves the catalytic activity of the electrode, and Pt particles are observed on the GC surface by SEM. It is believed that a thin layer of finely divided carbon is formed by the polishing procedure. Reduction of Pt onto this layer either did not produce Pt particles or produced particles which are removed when the electrode is washed with water. Heat treatment of the GC prior to deposition removes the carbon layer, allowing Pt reduction to occur on the intrinsic carbon surface with concomitant particle formation.Cyclic voltammograms show multiple reduction waves for the deposition of Pt on GC. In the potential range of 0.2 to 0.5 V, the first reduction exhibits a double peak which is assigned to the reduction of Pt(IV) to Pt(II). However, Pt microparticles are observed by SEM on the GC surface when the deposition potential is held within the limits of the first wave. A slow chemical step (probably disproportionation of Pt(II) to Pt0 and Pt(IV)) is involved in the nucleation and growth of the Pt particles at ⪢- 50 mV. For electrodes exhibiting high particle stability, hydrogen evolution, with exchange current densities comparable to bulk platinum, is achieved at loading levels of 10 to 20 μg cm−2 Pt.
The electrocatalytic oxidation of CO, HCOOH and CH3OH is compared on Pt(100), Pt(110) and Pt(111) single crystals. The similarity of behaviour of CH3OH and CO on the three single crystal planes leads to the conclusion that the oxidation of both compounds involves CO-like intermediates. On the other hand, HCOOH behaves quite differently, particularly on Pt(100) and Pt(111) electrodes, i.e its oxidation involves different adsorbed intermediates, some of them being poisoning species formed in the hydrogen region.
This review paper aims to show how the electrochemical behaviour of CO plays a key role in the understanding of the reaction mechanism of many electrocatalytic oxidations of small organic molecules. For that purpose, the adsorption of CO on noble metal electrodes, eventually modified by foreign metal adatoms, is reviewed, taking into account both experimental (electrochemical and spectroscopic techniques) and theoretical (Extended Hückel Model) approaches. Data from the gas phase—solid metal interface are also considered.
The effect of particle size of ultrafine platinum particles, which were prepared by vacuum evaporation onto a glassy carbon rod, on the electrochemical oxidation of methanol and formic acid has been examined by a cyclic voltammetry. The specific activity for the oxidation of methanol decreased by decreasing the platinum particle size, whereas that of the formic acid increased as the particle size decreased. Features of the cyclic voltammograms of the latter reaction suggested that the ratio of the exposed Pt(100) plane of platinum particles increased with decreasing the platinum particle size, while that of Pt(110) decreased.
The effect of the particle size of carbon-supported Pt catalysts on the electrooxidation of methanol was studied. Different methods were used to prepare catalysts with particle sizes ranging between 1.2 and 10 nm. The possible interaction of Pt with carbon surface groups was also investigated by preparing catalysts on oxidized and non-oxidized carbon supports. The specific activity was found to decrease with decreasing particle size in the range 4.5–1.2 nm. Carbon-supported Pt particles appear to be more active than non-supported particles and the presence of an acidic group on the support slightly enhances this effect. The dependence of the activity on the particle size can be explained in terms of either its effect on the formation of an adsorbed hydroxy species or its effect on the number of methanol adsorption sites.
The O2 reduction reaction on Pt (111), (100) and (110) planes is found not to be very sensitive to the structure of the surface in l M HClO4 solution, for which the anion adsorption is weak. On the contrary, the results are orientation and structure-sensitive in 1 M H2SO4, 1 M H3PO4 and 0.1 M HC1+1 M H2SO4: the anion adsorption not only decreases the kinetics of this reaction for a given structure, but also seems to be very structure-sensitive. In sulphuric and phosphoric acid solutions the reaction rate is slower on a Pt (111) plane than on a Pt (110) or on an average Pt (100) plane; in sulphuric acid solutions various treatments, which are known to provide a smaller amount of superficial defects on Pt (100) or (111), induce a slower reaction rate. With Cl− anions, the reaction rate decreases in the order (111) ⪢ (110) ⪢ (100).
Razaq and D. Tryk, in `Structural Effects in Electrocatalysis and Oxygen Elec-trochemistry
- M E Yeager
- D Razaq
- A Gervasio
Abberdam, in `Symposium on Oxygen Electrochemistry', The Electro-chemical Society
- R R Durand
- F Faure
- D Gloaguen