Interfacial electric field of BiVO4/WO3 photoanode-induced S-scheme charge transfer for enhanced photoelectrochemical performance

摘要

Type-II heterojunction films are widely applied as photoanodes for photoelectrochemical (PEC) water splitting. However, type-II heterojunctions are disadvantaged by drawbacks such as reduced redox ability and the occurrence of repulsion against photogenerated charge transfer. Herein, it is first proposed that an S-scheme heterojunction be used as a photoanode in the PEC field. The proposed S-scheme BiVO4/WO3 photoanode (S-BiVO4/WO3) is inverse to the typical type-II WO3/BiVO4 heterojunction photoanode (IIWO3/ BiVO4) and shows significantly better PEC performance. The photocurrent density reaches 3.22 mA cm-2 (1.23 VRHE) without a cocatalyst, which is higher than the photocurrent density reported to date for most BiVO4-based photoanodes. The onset potential decreases from 0.97 to 0.82 VRHE. According to the experimental and theoretical calculation results, the internal electric field formed at the heterojunction interface can induce a step-scheme charge transfer mechanism, which promotes the separation of photogenerated charge. Besides, the same direction between the internal electric field and the applied bias can reduce the applied bias voltage. Our results demonstrate that the construction of an S-scheme heterojunction is a preferable strategy that can be applied to design the photoanode for highly efficient PEC water splitting.