A room temperature etching route to tungsten oxide hydrate nanoplates with expanded surface area

Tungsten oxide hydrate nanoplates with expanded surface area have been synthesized through the acid treatment of tungstate−aluminum keggin nanocomposite. According to powder X-ray diffraction and W LIII-edge X-ray absorption spectroscopic analyses, X-ray amorphous nanocomposite is changed into crystalline WO3·2H2O upon the acidic etching of alumina component. Nitrogen adsorption−desorption isotherm and field emission-scanning electron microscopy measurements clearly demonstrated that the surface area of the nanocomposite is increased by the selective etching of alumina component, a result of the formation of the porous stacking assembly of nanoplates. From optoelectrochemical analysis, the etched derivative is found to be applicable as an electrode material for electrochromic devices. Based on the experimental findings, we are able to conclude that the present selective etching method can provide a soft-chemical synthetic route to nanocrystalline metal oxides with expanded surface area.