Anodic Formation of Ti-V Binary Oxide Mesosponge Layers for Supercapacitor Applications

摘要

Over the last decade, TiO_(2) nanotube arrays grown by anodization of titanium in fluoride-containing electrolytes have been widely investigated. The material provides a highly aligned oxide structure on a conductive metal substrate and thus directly provides a back-contacted oxide electrode. Therefore, these structures were explored for applications in various fields, such as photocatalysis, photovoltaics, biomedicine, and energy-storage materials. Recently, 3D nano-architectures, TiO_(2) mesosponge layers with controllable pore structure and diameter, have been grown by anodization of titanium in hot glycerol electrolyte. These structures have already shown promising properties and some have shown superb performance compared to nanotubes; as such, these structures are promising candidates for photochemical applications, such as photovoltaics and photocatalysis. Another tempting application is the use of these materials in high-performance reversible-storage materials, especially supercapacitors (also known as electrochemical capacitors or ultracapacitors) that are based on faradaic processes (reversible redox reactions, pseudo-capacitors). In practice, various transition metal oxides have been investigated as supercapacitors because they have either high conductivity or perform reversible redox reactions between different valence states. Among these transition metal oxides, both TiO_(2) and V_(2)O_(5) are usually regarded as very promising active electrode materials for energy-storage applications, owing to their variable oxidation states. Most recently, remarkable achievements have been reported for V_(2)O_(5)-TiO_(2) nanotubular supercapacitors. In these nanotubes, the highly ordered structure reduces the diffusion resistance of electrolytes inside the three dimensional nanotubes and considerably high specific capacitance values can be reached.