Hierarchically structured, oxygen deficient, tungsten oxide morphologies for enhanced photoelectrochemical charge transfer and stability†
The role of non-stoichiometry in a hierarchically structured WO3−x electrode, constituted from nanoscale fuzziness as well as microscale wire morphology, on the photoelectrochemical response is investigated. Through X-ray photoelectron spectroscopy (XPS) studies, the relative amounts of the various oxidation states of the constituent W are probed with respect to the observed response. It is concluded that an intermediate/optimal number of vacancies, yielding a W6+/(W5+ + W4+) ratio of around 2, would be beneficial for increasing the photocurrent. It is posited that defect engineering combined with optimized band structure modulation could be used for enhanced photocurrent density as well as electrode stability. The work would help considerably elucidate the role of defects as well as charge carriers for oxygen evolution reaction (OER) efficiency increase.