Tungsten Oxide Nanoplate Film as a Highly Active Solar-Driven Photocatalyst

A WO3 nanoplate-like film with an average edge width of approximately 20 nm and thickness of approximately 250 nm was fabricated via electrochemical anodization of W film at 60 V in a bath with electrolytes composed of ethylene glycol and 0.7 wt% NH4F. The influence of applied potential on the morphology of the anodic oxide was investigated. The growth of the nanoplate-like morphology might be attributed to the competition between electrochemical oxide formation and chemical etching by the corrosive [WFn](n-6) complex ions at minimal applied potential of 60 V. In addition, the presence of tungstite (WO3˙H2O) with an orthorhombic structure was observed within the WO3 nanoplate-like film, which has a layered structure with sheets of distorted W–O octahedral units sharing corners. All of the anodic WO3 nanostructured films were annealed and their electrochemical ability was investigated under solarillumination. A maximum photocurrent density of 1.50 mA/cm2 was observed for the WO3 nanoplate-like film because more incident photons could be harvested to generate photo-induced charge carriers under solar-illumination.