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 (≈3.2 mA cm-2 ) and ≈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 ≈2.0 mA cm-2 even after 12 h consecutive operation, while only ≈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 .