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

Abstract BiVO 4 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 BiVO 4 /BiO x asymmetric heterojunction from faceted BiVO 4 crystal arrays. Compared with the BiVO 4 photoanode, the resulting BiVO 4 /BiO x 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 BiVO 4 . Moreover, the Faraday efficiency for water splitting is determined to be nearly 100% for the BiVO 4 /BiO x photoanode. The controllable photochemical etching process may shed light on the construction of homologous heterojunction on other photoelectrode materials that have similar properties to BiVO 4 .