Charge carrier separation and enhanced PEC properties of BiVO4 based heterojunctions having ultrathin overlayers

The photoelectrochemical performance of a BiVO4 photoanode is limited by its poor charge transport properties, despite other useful optical absorption properties. Modifying the surface charge transport properties by forming heterojunction of BiVO4 with other metal oxides layers having ultralow thickness is a promising route, as it may facilitate charge separation/transport without affecting other properties of BiVO4. In this study, the structural, optical and PEC properties of heterojunction of BiVO4 having ultrathin overlayers of Fe2O3, MoO3 and ZnO has been investigated. The electrochemical impedance (via electrochemical impedance spectra in PEC cell) and surface photovoltage (using KPFM) measurements indicates improved charge transport owing to staggered band alignment and favourable band bending in case of BiVO4/MoO3 heterojunction as compared to pristine BiVO4, BiVO4/Fe2O3 and BiVO4/ZnO heterojunctions. Enhanced photocurrent density in BiVO4/MoO3 of similar to 0.22 mA/cm(2) at 1.23 VRHE which is 6 times as compared to pristine BiVO4 layers has been observed. The results of the present study show that by forming heterojunction with a suitable semiconductor material can be used to enhance the PEC response by modifying the surface charge transfer characteristics and there is a large possibility of using other semiconductor materials for further investigations and improvement. (C) 2020 Published by Elsevier Ltd on behalf of Hydrogen Energy Publications LLC.

Automated summary

The photoelectrochemical performance of a BiVO4 photoanode can be enhanced by forming heterojunctions with ultrathin overlayers of Fe2O3, MoO3 and ZnO. In particular, the BiVO4/MoO3 heterojunction shows improved charge transport properties compared to pristine BiVO4, leading to a significant increase in photocurrent density. There is potential for further research and improvement by exploring other semiconductor materials for heterojunction formation.