Optimization of hydrogen-ion storage performance of tungsten trioxide nanowires by niobium doping

The transport and storage of ions within solid state structures is a fundamental limitation for fabricate more advanced electrochemical energy storage, memristor, and electrochromic devices. Crystallographic shear structure can be induced in the tungsten bronze structures composed of corner-sharing WO₆octahedra by the addition of edge-sharing NbO₆octahedra, which might provide more storage sites and more convenient transport channels for external ions such as hydrogen ions and alkali metal ions. Here, we show that Nb₂O₅·15WO₃nanowires (Nb/W = 0.008) with long length-diameter ratio, smooth surface, and uniform diameter have been successfully synthesized by a simple hydrothermal method. The Nb₂O₅·15WO₃nanowires do exhibit more advantages over h-WO₃nanowires in electrochemical hydrogen ion storage such as smaller polarization, larger capacity (71 mAh g^-1, at 10C, 1C = 100 mA g^-1), better cycle performance (remain at 99% of the initial capacity after 200 cycles at 100C) and faster H⁺ions diffusion kinetics. It might be the crystallographic shear structure induced by Nb doping that does result in the marked improvement in the hydrogen-ion storage performance of WO₃. Therefore, complex niobium tungsten oxide nanowires might offer great promise for the next generation of electrochemical energy and information storage devices.