Photochemically Etching BiVO4 to Construct Asymmetric Heterojunction of BiVO4/BiOx Showing Efficient Photoelectrochemical Water Splitting

BiVO4 as a promising semiconductor candidate of the photoanode for solar driven water oxidation always suffers from poor charge carrier transport property and photo-induced self-corrosion. Herein, by intentionally taking advantage of the photo-induced self-corrosion process, a controllable photochemical etching method is developed to rationally construct a photoanode of BiVO4/BiOx asymmetric heterojunction from faceted BiVO4 crystal arrays. Compared with the BiVO4 photoanode, the resulting BiVO4/BiOx photoanode gains over three times enhancement in short-circuit photocurrent density (approximate to 3.2 mA cm(-2)) and approximate to 75 mV negative shift of photocurrent onset potential. This is due to the formation of the strong interacted homologous heterojunction, which promotes photo-carrier separation and enlarges photovoltage across the interface. Remarkably, the photocurrent density can remain at approximate to 2.0 mA cm(-2) even after 12 h consecutive operation, while only approximate to 0.1 mA cm(-2) is left for the control photoanode of BiVO4. Moreover, the Faraday efficiency for water splitting is determined to be nearly 100% for the BiVO4/BiOx photoanode. The controllable photochemical etching process may shed light on the construction of homologous heterojunction on other photoelectrode materials that have similar properties to BiVO4.