Long Liu’s research while affiliated with Technische Universität Ilmenau and other places

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Publications (27)


A, Abundance of Li, Na, and K metals in the Earth's crust (wt%). B, Schematic illustration of potassium‐ion batteries (KIBs). C, Summary of challenges and their relationships to the KIBs. D, Number of publications on KIBs according to Web of Science
A, GPD profiles of graphite for the initial two cycles between 0.01 and 1.5 V at C/40. B, Cycling performance of graphite at C/2. C, First‐cycle GPD potential profiles at C/10. D, X‐ray diffraction patterns of electrodes corresponding to the marked selected states of charges in (C). Reprinted with permission.⁴⁶ Copyright 2015, American Chemical Society
A, Transmission electron microscopy image of NCNF‐650. (B) XRD patterns and (C) XPS survey spectra of NCNFs. D, CV curves of NCNF‐650. E, Long‐term cycling performance of NCNF‐650 at a high rate of 2 A g⁻¹. F, Rate performance of NCNFs with rates ranging from 0.05 to 20 A g⁻¹. Reprinted with permission.⁹⁴ Copyright 2018, Springer Nature. NCFC, N‐doping soft carbon nanofibers; XPS, X‐ray photoelectron spectroscopy; XRD, X‐ray diffraction
A, Potential profiles recorded at 0.1 C (cycle 10), 1 C (cycle 28), and 10 C (cycle 38) for the HC/CB composite. B, Rate Performance of HC, CB, and HC/CB within 0.02 and 2.0 V range. Reprinted with permission.⁹⁵ Copyright 2016, ECS. D Long cycling performance at 1 C rate of hard carbon spheres (HCS), SC, and HCS‐SC. Reprinted with permission.⁵³ Copyright 2017, John Wiley and Sons; D, Schematic illustration of the activation process. Reprinted with permission.⁵⁵ Copyright 2017, Elsevier. CB, carbon black, HC, hard carbon; SC, soft carbon
A, Voltage profiles of the carbon nanofiber anodes in potassium‐ion batteries. Reprinted with permission.⁶³ Copyright 2017, The Royal Society of Chemistry. B, Selective Raman spectra taken at different states of charge as indicated in the LSV. C, Waterfall plot of all Raman spectra taken between 0.37 and 0.01 V. Reprinted with permission.¹⁰⁰ Copyright 2016, The Royal Society of Chemistry. D, Schematic of the staging and defect storage mechanism in N‐FLG and FLG (E). Reprinted with permission.⁵⁷ Copyright 2016, American Chemical Society. F, Li, or K‐ion diffusion mechanism. Reprinted with permission.⁵⁶ Copyright 2016, American Chemical Society. G, Schematic of phosphorus and oxygen dual‐doped graphene. Reprinted with permission.⁶⁰ Copyright 2017, The Royal Society of Chemistry. FLG, few‐layer graphene

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Anode materials for potassium‐ion batteries: Current status and prospects
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June 2020

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385 Reads

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105 Citations

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Long Liu

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Huaping Zhao

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Potassium‐ion batteries (KIBs) as one of the most promising alternatives to lithium‐ion batteries have been highly valued in recent years. However, progress in KIBs is largely restricted by the sluggish development in anode materials. Therefore, it is imperative to systematically outline and evaluate the recent research advances in the field of anode materials for KIBs toward promoting the development of high‐performance anode materials for KIBs. In this review, the recent achievements in anode materials for KIBs are summarized. The electrochemical properties (ie. charge storage mechanism, capacity, rate performance, and cycling stability) of these reported anode materials, as well as their advantages/disadvantages, are discerned and analyzed, enabling high‐performance KIBs to meet the requirements for practical applications. Finally, technological developments, scientific challenges, and future research opportunities of anode materials for KIBs are briefly reviewed.

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a) Schematic diagram of the preparation process of ZIF‐8‐C@PP; b) SEM, c) TEM, d) HRTEM images of ZIF‐8‐C; e) SEM, f) TEM, and g) HRTEM images of ZIF‐8‐C@PP.
SEM image and corresponding EDX elemental mapping of carbon, nitrogen, phosphorus of ZIF‐8‐C@PP.
a) Nitrogen adsorption/desorption isotherm, b) pore size distribution and c) cumulative pore volume curves of ZIF‐8‐C and ZIF‐8‐C@PP. Pore size distribution and cumulative pore volume were investigated by the DFT method; d) TGA of ZIF‐8‐C and ZIF‐8‐C@PP.
a) CV curves of ZIF‐8‐C@PP at 0.5 mV s⁻¹ after ten cycles of activation; b) EIS of RP, ZIF‐8‐C, and ZIF‐8‐C@PP at open circuit potential; c) discharge and charge curves of ZIF‐8‐C@PP at 0.1 A g⁻¹; d) cycle performance curves of RP and of ZIF‐8‐C@PP at 0.1 A g⁻¹; e) Rate performance of ZIF‐8‐C@PP; f) discharge curve of ZIF‐8‐C@PP at 1 A g⁻¹.
Mild‐Temperature Solution‐Assisted Encapsulation of Phosphorus into ZIF‐8 Derived Porous Carbon as Lithium‐Ion Battery Anode

February 2020

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835 Reads

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54 Citations

Chengzhan Yan

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Huaping Zhao

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Jun Li

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[...]

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The high theoretical capacity of red phosphorus (RP) makes it a promising anode material for lithium‐ion batteries. However, the large volume change of RP during charging/discharging imposes an adverse effect on the cyclability and the rate performance suffers from its low conductivity. Herein, a facile solution‐based strategy is exploited to incorporate phosphorus into the pores of zeolitic imidazole framework (ZIF‐8) derived carbon hosts under a mild temperature. With this method, the blocky RP is etched into the form of polyphosphides anions (PP, mainly P5⁻) so that it can easily diffuse into the pores of porous carbon hosts. Especially, the indelible crystalline surface phosphorus can be effectively avoided, which usually generates in the conventional vapor‐condensation encapsulation method. Moreover, highly‐conductive ZIF‐8 derived carbon hosts with any pore smaller than 3 nm are efficient for loading PP and these pores can alleviate the volume change well. Finally, the composite of phosphorus encapsulated into ZIF‐8 derived porous carbon exhibits a significantly improved electrochemical performance as lithium‐ion battery anode with a high capacity of 786 mAh g⁻¹ after 100 cycles at 0.1 A g⁻¹, a good stability within 700 cycles at 1 A g⁻¹, and an excellent rate performance.


Nanoelectrode design from microminiaturized honeycomb monolith with ultrathin and stiff nanoscaffold for high-energy micro-supercapacitors

January 2020

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467 Reads

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68 Citations

Downsizing the cell size of honeycomb monoliths to nanoscale would offer high freedom of nanostructure design beyond their capability for broad applications in different fields. However, the microminiaturization of honeycomb monoliths remains a challenge. Here, we report the fabrication of microminiaturized honeycomb monoliths—honeycomb alumina nanoscaffold—and thus as a robust nanostructuring platform to assemble active materials for micro-supercapacitors. The representative honeycomb alumina nanoscaffold with hexagonal cell arrangement and 400 nm inter-cell spacing has an ultrathin but stiff nanoscaffold with only 16 ± 2 nm cell-wall-thickness, resulting in a cell density of 4.65 × 109 cells per square inch, a surface area enhancement factor of 240, and a relative density of 0.0784. These features allow nanoelectrodes based on honeycomb alumina nanoscaffold synergizing both effective ion migration and ample electroactive surface area within limited footprint. A micro-supercapacitor is finally constructed and exhibits record high performance, suggesting the feasibility of the current design for energy storage devices. Micro-supercapacitors are promising energy storage systems to power the future electronic devices. Here, the authors utilize honeycomb alumina nanoscaffold as a nanostructuring platform to design nanoelectrodes and construct micro-supercapacitors with impressive performance.


Review on Recent Advances of Cathode Materials for Potassium‐ion Batteries

January 2020

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2,068 Reads

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79 Citations

Potassium‐ion batteries (PIBs) as a promising supplement to lithium‐ion batteries have drawn great attention attributing to the abundant potassium resources, the fast‐ionic conductivity of potassium ions in electrolyte, and the low standard redox potential of potassium. However, the development of PIBs is still in its infancy, which is largely restricted by the fact that the electrode materials, especially the cathode materials of PIBs, are far from satisfactory in practical applications regarding the capacity, voltage, and cycle life. Therefore, most of current research efforts have been devoted to exploring new and high‐performance electrode materials for achieving PIBs with high capacity and voltage as well as excellent cyclability. In this review, the recent advancements on cathode materials for PIBs are specially summarized. Besides, technological developments, scientific challenges, and future research opportunities of cathode materials for PIBs are also briefly outlooked. Recently, potassium‐ion batteries (PIBs) attract considerable attention due to their low cost, fast ion conductivity in electrolyte and high operating voltage. Cathode materials play a significant role in determining the overall electrochemical property of PIBs. This review provides recent advancements of cathode materials for PIBs. Furthermore, challenges and prospects of these cathode materials are also discussed.


Nanoarchitectured Current Collectors: Review on Nanoarchitectured Current Collectors for Pseudocapacitors (Small Methods 8/2019)

August 2019

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46 Reads

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3 Citations

In article number 1800341, Huaping Zhao, Yong Lei, and their co‐worker outline the design philosophy and the design considerations for nanoarchitectured current collectors in pseudocapacitors. The recent achievements in design, fabrication, and utilization of nanoarchitectured current collectors for pseudocapacitors are summarized. Particularly, the roles of nanoarchitectured current collectors in enhancing the electrochemical performance of pseudocapacitors are highlighted. This study gives clues to develop future advanced energy‐storage devices.


CuMnO2-reduced graphene oxide nanocomposite as a free-standing electrode for high-performance supercapacitors

June 2019

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154 Reads

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86 Citations

Chemical Engineering Journal

Free-standing electrodes have attracted wide attention for advanced supercapacitors. Herein, direct deposition of CuMnO2 and CuMnO2-reduced graphene oxide (rGO) nanocomposite on nickel foam (NF) substrates was performed through a simple hydrothermal process. The simultaneous deposition makes full use of the synergistic effect formed by the large pseudocapacitance of CuMnO2 and excellent electrical conductivity of rGO, which results a greater performance improvement of the nanocomposite comparing with that of bare CuMnO2. Remarkably, the CuMnO2-rGO/NF electrode displays a large specific capacitance of 1727 F g⁻¹ at 3 A g⁻¹ and manifests exceptional cycling stability with a retention ratio of 125% of the initial capacitance over consecutive 5000 cycles. Furthermore, a rGO/NF//CuMnO2-rGO/NF asymmetric supercapacitor exhibits great electrochemical performance by delivering high energy density (37.5 Wh kg⁻¹) and high power density (4250 W kg⁻¹) as well as excellent cycling stability (3.3% decay after 4000 cycles). The presented results suggest that CuMnO2-rGO nanocomposite can be considered as a potential candidate for highly stable and high-rate supercapacitors.


Area‐normalized Ragone plot of energy and power density showing the estimated performance of MSCs (marked by the violet rectangle), MBs (marked by the orange rectangle), and some of typical electronic components such as sensors and communication transmitters. MBs, microbatteries; MSCs, micro‐supercapacitors
Schematic of two basic configurations of 3D MSCs: A, Sandwich and B, in‐plane topology, respectively, based on nanostructured electrodes. C, Schematic of the cross‐section of the electrodes highlights the nanoarchitecture of homogeneous or heterogeneous electrode unit. More active materials can be grown along the longitude direction in the limited footprint area leading to improved areal capacitance. MSCs, micro‐supercapacitors
A, Boron‐doped 3D porous carbon pattern (B‐3D‐PCP) electrodes based MSCs and their corresponding electrochemical performances. Reproduced with permission.55 Copyright 2018, Elsevier Ltd. B, MSCs based on 3D Au nanoporous scaffold (AuNPS)/MnO2 electrodes and their corresponding electrochemical performances. Reproduced with permission.65 Copyright 2016, Wiley‐VCH. C, ITO NWs@MnO2 based MSC and its electrochemical performances. Reproduced with permission.73 Copyright 2019, the Royal Society of Chemistry. MSCs, micro‐supercapacitors
Schematic of some promising 3D MSCs based on nanoarchitectured electrodes. The design models were inspired by 3D MBs reported in previous literatures. MBs, microbatteries; MSCs, micro‐supercapacitors
Advances on three‐dimensional electrodes for micro‐supercapacitors: A mini‐review

May 2019

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574 Reads

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144 Citations

Owing to the high power density, long cycle life and maintain‐free, micro‐supercapacitors (MSCs) stand out as preferred miniaturized energy source for the miscellaneous autonomous electronic components. However, the shortage of energy density is the main stumbling block for their practical applications. To solve this energy issue, constructing a three‐dimensional (3D) electrode within the limited footprint area is proposed as a new solution for improving the energy storage capacity of MSCs. In the last few years, extensive efforts have been devoted to developing 3D electrodes for MSCs, and significant progress and breakthrough have been achieved. While, there is still lack of systematic summary on the 3D electrode design strategies. To this end, it is imperative to outline the basic design conception, summarize the current states, and discuss the future research about 3D electrodes in MSCs based on the latest development.


Exploration of Nanowire- and Nanotube-Based Electrocatalysts for Oxygen Reduction and Oxygen Evolution Reaction

November 2018

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164 Reads

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38 Citations

Materials Today Nano

Electrocatalysts for oxygen reduction and/or evolution are key components for proton-exchange membrane fuel cells (PEMFCs) and water electrolysis. However, the slow kinetics of oxygen reduction and/or evolution reactions largely hampers the efficiencies of PEMFCs and water electrolysis. Highly efficient electrocatalysts for oxygen reduction and evolution reactions must meet three requirements: (i) rapid transport of electrons, ions, and products of the reaction; (ii) sufficient catalysts/reactants contact area; and (iii) good intrinsic activity. Nanostructuration of electrocatalysts provides an effective approach to overcome the slow kinetics because nanostructured electrocatalysts with rational design can not only provide sufficient active sites but also promote intrinsic activity of electrocatalysts as well as possess the ability of rapid transport of electrons, ions, and products of the reaction. Especially, electrocatalysts in the form of one-dimensional nanostructures (1D-Nano) such as nanowires (NWs) and nanotubes (NTs) have shown significant advantages, such as high surface area, rapid electron and mass transfer, low vulnerability to dissolution, Ostwald ripening, and aggregation, for oxygen evolution reaction (OER) and oxygen reduction reaction (ORR). In this review, we summarize different strategies for fabricating 1D nanostructure-based electrocatalysts (1D-NanoECs), which are categorized into template-free and template-assisted strategies, and emphasis has been placed on anodic aluminum oxide template–assisted strategies. Then, recent advances of 1D-NanoECs for ORR and OER applications are summarized. Finally, future challenges and opportunities about 1D-NanoECs are discussed.


Optimizing Hydrogen Evolution Activity of Nanoporous Electrodes by Dual-Step Surface Engineering

November 2018

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97 Reads

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25 Citations

Applied Catalysis B Environmental

The hydrogen evolution reaction (HER) from electrocatalytic water splitting represents an important approach for efficient hydrogen production, in which the HER feasibility relies on electrocatalysts as well as the art of electrode design. Herein, a considerate surface engineering strategy is developed for promoting HER process taking place on nanoporous HER electrodes. Cobalt nanopore arrays (CoNPA) are fabricated as the representative nanoporous HER electrode. Then an ultrathin titanium dioxide (TiO2) with optimized thickness is conformally coated onto CoNPA for improving the wettability in order to expose more active sites, followed by a well-dispersed platinum (Pt) nanoparticles with an ultralow mass loading (ca. 54 μg cm⁻²) anchored on TiO2 layer for enhancing the HER activity. The advanced features of nanoporous architecture in combination with the synergistic contribution from ultrathin TiO2 layer and well-dispersed Pt nanoparticles enable [email protected]2@Pt electrode exhibit outstanding HER performance in alkaline conditions, i.e., an overpotential of 29 mV needed to reach the catalytic current density of 10 mA cm⁻² and long-termed performance as well as structure stability. Not limited to the HER electrodes, the similar strategy is also expected to be further applied to the rational design and nanoengineering of electrodes for other electrochemical energy conversion and storage devices.


MoS2 nanosheets with expanded interlayer spacing for enhanced sodium storage

October 2018

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203 Reads

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44 Citations

Inorganic Chemistry Frontiers

Sodium-ion battery technology is a promising alternative to lithium-ion batteries for low-cost and large-scale energy storage applications. The larger size of Na-ion relative to Li-ion imposes kinetic limitation and often results in sluggish Na-ion diffusion. It is a great necessity to explore prominent structural features of materials to overcome the limitation and improve the diffusion. Layered MoS2 has an ideal two-dimensional diffusion pathways because of the weak van der Waals interaction between the layers. However, the limited gallery height of 0.3 nm is insufficient to achieve fast Na-ion diffusion. A facile hydrothermal route at medium-ranged temperatures is reported in this work to obtain interlayer expanded MoS2 naonsheets. The interlayer spacing is greatly expanded to 1 nm and facilitates Na-ion insertion and extraction in the van der Waal gaps. The nanosheet morphology shortens Na-ion diffusion distance from the lateral side. The interlayer expanded MoS2 nanosheets are used as sodium-ion battery anodes in the voltage window of 0.5-2.8 V where intercalation reaction contributes to Na-storage and the layered structure can be preserved. The nanosheets exhibit a high cycling stability by retaining 92% of the initial charge capacity after 100 cycles and a great rate capability 43 mAh g-1 at 2 A g-1. Kinetics study reveals a significant alleviation of diffusional limitation, verifying the improved Na-ion diffusion and enhanced Na-storage. The presented work explores the utilization of the van der Waals gaps to store ions and sheds light on designing two-dimensional materials in other energy systems.


Citations (26)


... × 10 −12 cm 2 s −1 ) and charging (1.2 × 10 −12~1 .65 × 10 −11 cm 2 s −1 ) are significantly higher than micro-sized BiPO 4 electrode (discharging: 7.8 × 10 −13~1 .82 × 10 −14 cm 2 s −1 , charging: 1.2 × 10 −13~3 .5 × 10 −11 cm 2 s −1 ) (Figures 4f and S12), also significantly exceeds some of the reported phosphate anodes [42][43][44]. The high K + values indicate fast potassiation and depotassiation kinetics and excellent rate performance. ...

Reference:

Synergistic Effect of Anionic-Tuning and Architecture Engineering in BiPO4@C Anode for Durable and Fast Potassium Storage
Anode materials for potassium‐ion batteries: Current status and prospects

... Besides, using sodium ethoxide as a nucleophile, the bulk RP can be transformed into soluble polyphosphide (PP) anions (mainly consisting of P 5 − ) in the presence of dimethyl sulfoxide solution. The P 5 − in the solution can be directly adsorbed in pores of CNTs (inner diameter ~5 nm) (Fig. 8G) or porous carbons (<3 nm) carbonized from zeolitic imidazole framework (ZIF-8) (Fig. 8F), and transform into NaP 5 after cooling [56,57]. Although such procedure can achieve good cycle performance, further research is needed to probe the actual size of these anions and make clear the electrochemical behavior of alkaline ion storage. ...

Mild‐Temperature Solution‐Assisted Encapsulation of Phosphorus into ZIF‐8 Derived Porous Carbon as Lithium‐Ion Battery Anode

... However, the development of supercapacitors using cost-effective and eco-friendly materials presents a persistent challenge. Supercapacitor materials are broadly classified into electrochemical double-layer capacitors (EDLCs), which store energy through non-faradaic charge separation, and pseudocapacitive materials, which rely on fast, reversible redox reactions for energy storage [7][8][9][10]. A promising strategy to achieve superior performance involves hybrid capacitors, which combine carbon-based materials with metal oxides and conducting polymers [11]. ...

Nanoelectrode design from microminiaturized honeycomb monolith with ultrathin and stiff nanoscaffold for high-energy micro-supercapacitors

... Recent developments in cathode materials for hydrogen evolution reaction (HER) and oxygen reduction reaction (ORR) applications have spurred significant advancements in electrochemical energy conversion and storage technologies [1][2][3][4][5][6][7][8][9][10][11]. Bifunctional catalysts capable of catalyzing both ORR and HER have garnered considerable attention for their potential application in rechargeable metal-air batteries and water electrolysis. ...

Review on Recent Advances of Cathode Materials for Potassium‐ion Batteries
  • Citing Article
  • January 2020

... In this paper we have highlighted the recent developments in the design and manufacturing of conductive polymer-based aluminum current collectors (CC) for Li-ion batteries. As a result, current collectors with high strength, lightweight, high flexibility, and ultrathin profiles will continue to be developed in the future [63]. Major focus on the increment of energy density should be increased, C-rate should be increased. ...

Nanoarchitectured Current Collectors: Review on Nanoarchitectured Current Collectors for Pseudocapacitors (Small Methods 8/2019)
  • Citing Article
  • August 2019

... Very recently, influence of defects on specific capacitance and electrochemical properties of CuFeO 2 has been studied by our group [25]. On the other hand, hydrothermally synthesized CuMnO 2 nanoplates show reasonably good specific capacitance (381.5 F g − 1 at a current density of 1 A g − 1 ) using 3.0 M NaOH as electrolyte [26,27]. Some author also tried a modified hydrothermal method to prepare different nanostructured CuMnO 2 ; e.g. ...

CuMnO2-reduced graphene oxide nanocomposite as a free-standing electrode for high-performance supercapacitors
  • Citing Article
  • June 2019

Chemical Engineering Journal

... A pertinent strategy consists of lowering the resistance of the electrode materials [53]. In addition, the energy and power densities can also be enhanced through the topology or configuration of the device (the arrangement or geometry of the positive and negative electrodes) [6,132]. The overview of the schematic topologies used in MSCs, including parallel plate, interdigitated, and three dimensional (3D) interdigitated configurations, is shown in Figure 6a. ...

Advances on three‐dimensional electrodes for micro‐supercapacitors: A mini‐review

... Different from the 1D nanostructures array, cobalt nanopore arrays were fabricated by replicating AAO template. Then TiO 2 thin layer and Pt nanoparticles were deposited onto the nanopore arrays, and the composite structure presented excellent HER properties in alkaline conditions [180]. For most of the studies above, the 1D nanostructures arrays remarkably improved the electrocatalytic reaction kinetics, while the electrochemical desorption of hydrogen became the rate-limiting step. ...

Optimizing Hydrogen Evolution Activity of Nanoporous Electrodes by Dual-Step Surface Engineering
  • Citing Article
  • November 2018

Applied Catalysis B Environmental

... Recently, according to one study, it was found that OER performance of a catalyst can be improved with increase in the number of transition metal present in the materials [25]. On this context, in the year 2017, Deka and coworkers [26] have synthesized Co 3 S 4 , CuCo 2 S 4, and Cu 0.5 Co 2.5 S 4 by facile one step hydrothermal process. ...

Exploration of Nanowire- and Nanotube-Based Electrocatalysts for Oxygen Reduction and Oxygen Evolution Reaction
  • Citing Article
  • November 2018

Materials Today Nano

... A peak appearing around 17.8 corresponds to the (004) diffraction provides additional support for the expanded interlayer spacing. 31 Two broadened peaks at centered 32 and 57 can be well indexed to (100) and (110) planes, suggesting the same atomic arrangement along the basal planes. 32 The results indicate that MoS 2 with different lattice expansion were successfully obtained in the regulation of hydrothermal time or guest intercalants. ...

MoS2 nanosheets with expanded interlayer spacing for enhanced sodium storage
  • Citing Article
  • October 2018

Inorganic Chemistry Frontiers