Synthesis of Co nanotubes by nanoporous template-assisted electrodeposition via the incorporation of vanadyl ions

Electrochemical preparation of nano/micron structure transition metal-based catalysts for the oxygen evolution reaction

Electrochemical water splitting is a promising technology for hydrogen production and sustainable energy conversion, but the existing electrolytic cells lack a sufficient number of robust and highly active anodic electrodes for the oxygen evolution reaction (OER). Electrochemical synthesis technology provides a feasible route for the preparation of independent OER electrodes with high utilization of active sites, fast mass transfer, and a simple preparation process. A comprehensive review of the electrochemical synthesis of nano/microstructure transition metal-based OER materials is provided. First, some fundamentals of electrochemical synthesis are introduced, including electrochemical synthesis strategies, electrochemical synthesis substrates, the electrolyte used in electrochemical synthesis, and the combination of electrochemical synthesis and other synthesis methods. Second, the morphology and properties of electrochemical synthetic materials are summarized and introduced from the viewpoint of structural design. Then, the latest progress regarding the development of transition metal-based OER electrocatalysts is reviewed, including the classification of metals/alloys, oxides, hydroxides, sulfides, phosphides, selenides, and other transition metal compounds. In addition, the oxygen evolution mechanism and rate-determining steps of transition metal-based catalysts are also discussed. Finally, the advantages, challenges, and opportunities regarding the application of electrochemical techniques in the synthesis of transition metal-based OER electrocatalysts are summarized. This review can provide inspiration for researchers and promote the development of water splitting technology.

Hydrogen Bubble-Directed Tubular Structure: A Novel Mechanism to Facilely Synthesize Nanotube Arrays with Controllable Wall Thickness

Nanowire arrays can be conveniently fabricated by electrodeposition methods using porous anodized alumina oxide templates. They have found applications in numerous fields. Nanotube arrays, with their hollow structure and much enhanced surface-to-volume ratio, as well as an additional tuning parameter in tube wall thickness, promise additional functions compared with nanowire arrays. Using a similar fabrication method, we have developed a facile and general method to fabricate metallic nanotubes (NTs). Using Ni NTs as a model system, the mechanism of the hydrogen-assisted NT growth was postulated and confirmed by controlling the hydrogen formation with conductive salts in an electrodeposition solution, which improves the H₂ concentration but prevents the large H₂ bubbles from blocking the nanochannel of a template. The controlled hydrogen generation forces the growth along the wall of nanochannels in the templates, leading to the NT formation. The magnetic properties can be controlled by the NT wall thickness, making these NTs useful for various applications.

Electrodeposition of (hydro)oxides for an oxygen evolution electrode

Electrochemical water splitting is a promising technology for hydrogen production and sustainable energy conversion, but the electrolyzers that are currently available do not have anodic electrodes that are robust enough and highly active for the oxygen evolution reaction (OER). Electrodeposition provides a feasible route for preparing freestanding OER electrodes with high active site utilization, fast mass transport and a simple fabrication process, which is highly attractive from both academic and commercial points of view. This minireview focuses on the recent electrodeposition strategies for metal (hydro)oxide design and water oxidation applications. First, the intrinsic advantages of electrodeposition in comparison with traditional technologies are introduced. Then, the unique properties and underlying principles of electrodeposited metal (hydro)oxides in the OER are unveiled. In parallel, illustrative examples of the latest advances in materials structural design, controllable synthesis, and mechanism understanding through the electrochemical synthesis of (hydro)oxides are presented. Finally, the latest representative OER mechanism and electrodeposition routes for OER catalysts are briefly overviewed. Such observations provide new insights into freestanding (hydro)oxides electrodes prepared via electrodeposition, which show significant practical application potential in water splitting devices. We hope that this review will provide inspiration for researchers and stimulate the development of water splitting technology.

Preparation of Porous Carbon Nanofibers with Tailored Porosity for Electrochemical Capacitor Electrodes

Porous carbon electrodes that accumulate charges at the electrode/electrolyte interface have been extensively investigated for use as electrochemical capacitor (EC) electrodes because of their great attributes for driving high-performance energy storage. Here, we report porous carbon nanofibers (p-CNFs) for EC electrodes made by the formation of a composite of monodisperse silica nanoparticles and polyacrylonitrile (PAN), oxidation/carbonization of the composite, and then silica etching. The pore features are controlled by changing the weight ratio of PAN to silica nanoparticles. The electrochemical performances of p-CNF as an electrode are estimated by measuring cyclic voltammetry and galvanostatic charge/discharge. Particularly, the p-CNF electrode shows exceptional areal capacitance (13 mF cm^-2 at a current of 0.5 mA cm^-2), good rate-retention capability (~98% retention of low-current capacitance), and long-term cycle stability for at least 5000 charge/discharge cycles. Based on the results, we believe that this electrode has potential for use as high-performance EC electrodes.