Photochemically Etching BiVO 4 to Construct Asymmetric Heterojunction of BiVO 4 /BiO x Showing Efficient Photoelectrochemical Water Splitting.

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 .