Low-potential driven fully-depleted BiVO4/ZnO heterojunction nanodendrite array photoanodes for photoelectrochemical water splitting

Abstract To enhance photoelectrochemical water splitting performance of the intrinsic BiVO 4 , a low-potential driven fully-depleted intrinsic BiVO 4 -based photoanode is realized in this work by the conformal formation of thin BiVO 4 layers ( 4 /ZnO ND photoanode is fully-depleted at 0.8 V vs. the reversible hydrogen electrode (RHE) by the electric fields developed in radial directions of the nanorods and branches. Driven by the electric fields, the photogenerated electron-hole pairs in the whole electrode are efficiently separated and then the holes swiftly drift to the photoanode/electrolyte interface for oxygen evolution. Rather than diffusion, charge transport mechanism is governed by drift in the fully-depleted ND heterojunction array photoanode. As a result, in the high-light-harvesting BiVO 4 /ZnO ND array photoanode, the obstacle of slow charge transport in BiVO 4 can be surmounted due to the construction of the light absorption and hole drifting paths in different directions. The photocurrent density of the Co-Pi/BiVO 4 /ZnO ND photoanode is optimized to be 3.5 mA cm −2 at 1.23 V vs. RHE.