An-Liang Wang

Co3O4/Ni(OH)2 composite mesoporous nanosheet networks as a promising electrode for supercapacitor applications

Co3O4/Ni(OH)2 composite mesoporous nanosheet networks (NNs) grown on conductive substrates were synthesized by heat treatment of Co(OH)2/Ni(OH)2 NNs that were synthesized on Ti substrates by a facile electrochemical deposition route. The prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FT-IR), and micro-Raman spectroscopy. The above products were directly functionalized as supercapacitor electrodes without using any ancillary materials such as carbon black or binder. Co3O4/Ni(OH)2 composite mesoporous NNs achieved a high specific capacitance (Csp) of 1144 F g−1 at 5 mV s−1 and long-term cyclability. The electrochemical measurements showed Co3O4/Ni(OH)2 composite mesoporous NNs exhibited much better electrochemical performances than single Co3O4 or Ni(OH)2. The binary redox couples of Ni2+/Ni3+ and Co2+/Co3+, nanosheet networks with porous structures, the mesoporous structure within nanosheets, the interconnections among nanosheets, together with the excellent electrical contact with the current collector (substrate) are responsible for the improved electrochemical performances of Co3O4/Ni(OH)2 composite mesoporous NNs. With the ease of large scale fabrication and superior electrochemical characteristics, Co3O4/Ni(OH)2 composite mesoporous NNs grown on Ti substrates will be good candidates for supercapacitor applications.

Porous Pt-Ni-P Composite Nanotube Arrays: Highly Electroactive and Durable Catalysts for Methanol Electrooxidation

Porous Pt-Ni-P composite nanotube arrays (NTAs) on a conductive substrate in good solid contact are successfully synthesized via template-assisted electrodeposition and show high electrochemical activity and long-term stability for methanol electrooxidation. Hollow nanotubular structures, porous nanostructures, and synergistic electronic effects of various elements contribute to the high electrocatalytic performance of porous Pt-Ni-P composite NTA electrocatalysts.

Design of Pd/PANI/Pd Sandwich-Structured Nanotube Array Catalysts with Special Shape Effects and Synergistic Effects for Ethanol Electrooxidation

Low cost, high activity, and long-term durability are the main requirements for commercializing fuel cell electrocatalysts. Despite tremendous efforts, developing non-Pt anode electrocatalysts with high activity and long-term durability at low cost remains a significant technical challenge. Here we report a new type of hybrid Pd/PANI/Pd sandwich-structured nanotube array (SNTA) to exploit shape effects and synergistic effects of Pd-PANI composites for the oxidation of small organic molecules for direct alcohol fuel cells. These synthesized Pd/PANI/Pd SNTAs exhibit significantly improved electrocatalytic activity and durability compared with Pd NTAs and commercial Pd/C catalysts. The unique SNTAs provide fast transport and short diffusion paths for electroactive species and high utilization rate of catalysts. Besides the merits of nanotube arrays, the improved electrocatalytic activity and durability are especially attributed to the special Pd/PANI/Pd sandwich-like nanostructures, which results in electron delocalization between Pd d orbitals and PANI π-conjugated ligands and in electron transfer from Pd to PANI.

Palladium–Cobalt Nanotube Arrays Supported on Carbon Fiber Cloth as High‐Performance Flexible Electrocatalysts for Ethanol Oxidation

PdCo nanotube arrays (NTAs) supported on carbon fiber cloth (CFC) (PdCo NTAs/CFC) are presented as high-performance flexible electrocatalysts for ethanol oxidation. The fabricated flexible PdCo NTAs/CFC exhibits significantly improved electrocatalytic activity and durability compared with Pd NTAs/CFC and commercial Pd/C catalysts. Most importantly, the PdCo NTAs/CFC shows excellent flexibility and the high electrocatalytic performance remains almost constant under the different distorted states, such as normal, bending, and twisting states. This work shows the first example of Pd-based alloy NTAs supported on CFC as high-performance flexible electrocatalysts for ethanol oxidation.

Ni2P–CoP hybrid nanosheet arrays supported on carbon cloth as an efficient flexible cathode for hydrogen evolution

Here we report a new type of Ni2P–CoP hybrid nanosheet array (HNSAs) supported on carbon cloth (CC) (Ni2P–CoP HNSAs/CC) as an efficient flexible cathode for the hydrogen evolution reaction (HER). This synthesized Ni2P–CoP HNSAs/CC shows excellent electrocatalytic performance for the HER in both acid and alkaline solutions compared with Ni2P/CC and CoP/CC cathodes that have been considered to be good candidates for the HER. The significantly improved electrocatalytic performance of Ni2P–CoP HNSAs/CC can be attributed to the special surface effects of hybrid nanosheet arrays and synergistic effects between Ni2P and CoP. The Ni2P–CoP HNSAs/CC shows excellent flexibility and exhibits unchangeable electrochemical performance under the various distorted states, such as bending and twisting sates.

Hierarchical Pd-Sn Alloy Nanosheet Dendrites: An Economical and Highly Active Catalyst for Ethanol Electrooxidation

Hierarchical alloy nanosheet dendrites (ANSDs) are highly favorable for superior catalytic performance and efficient utilization of catalyst because of the special characteristics of alloys, nanosheets, and dendritic nanostructures. In this paper, we demonstrate for the first time a facile and efficient electrodeposition approach for the controllable synthesis of Pd-Sn ANSDs with high surface area. These synthesized Pd-Sn ANSDs exhibit high electrocatalytic activity and superior long-term cycle stability toward ethanol oxidation in alkaline media. The enhanced electrocataytic activity of Pd-Sn ANSDs may be attributed to Pd-Sn alloys, nanosheet dendrite induced promotional effect, large number of active sites on dendrite surface, large surface area, and good electrical contact with the base electrode. Because of the simple implement and high flexibility, the proposed approach can be considered as a general and powerful strategy to synthesize the alloy electrocatalysts with high surface areas and open dendritic nanostructures.

Pt–MoO3–RGO ternary hybrid hollow nanorod arrays as high-performance catalysts for methanol electrooxidation

Here we design and synthesize novel Pt–MoO3–RGO (reduced graphene oxide) ternary hybrid hollow nanorod arrays (HNRAs) as anode catalysts for methanol electrooxidation. These fabricated Pt–MoO3–RGO HNRAs have highly dispersive MoO3, RGO, and Pt nanocrystals (∼3 nm), which leads to rich heterogeneous interfaces and strong synergistic effects among Pt, MoO3 and RGO. The Pt–MoO3–RGO HNRAs exhibit a high electrochemically active surface area (ECSA) of 71.20 m2 per (g, Pt), which is much higher than those of Pt–MoO3 HNRAs (34.23 m2 per (g, Pt)) and commercial Pt/C catalysts (52.89 m2 per (g, Pt)). Because of the strong synergistic effects and structural advantages, these Pt–MoO3–RGO HNRAs show much enhanced electrocatalytic activity, durability and CO anti-poisoning ability compared with Pt–MoO3 HNRAs and commercial Pt/C catalysts. Besides, the electrocatalytic activity of Pt–MoO3–RGO HNRAs also exceeds those of many Pt-based catalysts reported in the literature. Our finding demonstrates the importance of the interfacial and structural effects in harnessing the true electrocatalytic potential of Pt-based catalysts and will open up new strategies for the development of high-performance catalysts for methanol electrooxidation.

Multi-layered Pt/Ni nanotube arrays with enhanced catalytic performance for methanol electrooxidation

Novel Pt/Ni multi-layered nanotube arrays (MLNTAs) are synthesized by template-assisted layer-by-layer electrodeposition. The unique multi-layered structures in nanotube walls provide a new method to study the effects of heterointerfaces and structures on methanol electrooxidation. For the fabricated Pt/Ni MLNTAs, especially Ni@Pt@Ni@Pt NTAs, we observed obvious enhancements in the catalytic activity and durability compared with the monometallic Pt nanotube arrays (NTAs) and many Pt-based catalysts reported in the literature studies. Our synthesis approach presents a strategy to broaden the heterointerfacial and structural effects for harnessing the true catalytic potential of Pt-based electrocatalysts and may lead to wide applications for energy conversion and storage.

High-performance supercapacitors based on MnO2 tube-in-tube arrays

MnO2 tube-in-tube arrays supported on carbon fiber cloth (MnO2 TTAs/CFC) were designed and synthesized. As a robust integrated 3D electrode with high utilization rate and fast ion transport, the MnO2 TTAs/CFC exhibits a high areal specific capacitance (Csp) of 322 mF cm−2 (∼1007 F g−1 for MnO2 at 0.125 A g−1) and superior cycling stability (95.1% retention of the initial Csp after 2000 cycles) at a high scan rate of 100 mV s−1. The assembled flexible all-solid-state symmetric supercapacitors (SSCs) based on MnO2 TTAs/CFC electrodes show a high volumetric energy density of 0.073 mW h cm−3 at a power density of 25 W kg−1 and high cycling stability (96.4% retention of the initial Csp after 2000 cycles). This study demonstrates that the 3D MnO2 TTAs/CFC electrodes hold great potential for use in flexible energy storage devices.

In Situ Derived NixFe1–xOOH/NiFe/NixFe1–xOOH Nanotube Arrays from NiFe Alloys as Efficient Electrocatalysts for Oxygen Evolution

Herein, NixFe1-xOOH/NiFe/NixFe1-xOOH sandwich-structured nanotube arrays (SNTAs) supported on carbon fiber cloth (CFC) (NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC) have been developed as flexible high-performance oxygen evolution reaction (OER) catalysts by a facile in situ electrochemical oxidation of NiFe metallic alloy nanotube arrays during oxygen evolution process. Benefiting from the advantages of high conductivity, hollow nanotube array, and porous structure, NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC exhibited a low overpotential of ∼220 mV at the current density of 10 mA cm-2 and a small Tafel slope of 57 mV dec-1 in alkaline solution, both of which are smaller than those of most OER electrocatalysts. Furthermore, NixFe1-xOOH/NiFe/NixFe1-xOOH SNTAs-CFC exhibits excellent stability at 100 mA cm-2 for more than 30 h. It is believed that the present work can provide a valuable route for the design and synthesis of inexpensive and efficient OER electrocatalysts.