Mechanism on BiVO4 photoanode photoelectrochemical performance improving: Based on surface electrochemical reduction method

Highlights: • Amorphous layer on BiVO₄ can be controlled by surface electrochemical reduction. • Amorphous layer formed on BiVO₄ by the boosting of the dislocation line defect. • Homojunction built-in electric field will fabricated between amorphous layer and bulk BiVO₄. • Scanning Kelvin Probe technique was employed to verify the homojunction built-in electric field. • IMPS/IMPS and transient PEC technique were employed to research the separation and transfer process of the photo carriers. -- Abstract: In this work, a typical BiVO₄ photoanode is employed to explore the performance improving mechanism by surface electrochemical reduction. Corresponding results demonstrate some new information that nanoparticle-like amorphous layer is formed on the surface of BiVO₄ and its thickness is positive correlation with the SER force. Furthermore, Scanning Kelvin probe results indicate that the Fermi level of the amorphous layer is shifted positively, inducing a homojunction built-in electric field between the amorphous layer and the bulk BiVO₄. The transfer ability of photogenerated holes from the bulk to the surface of photoanode can enhance obviously. In addition, due to the quasi-oxygen vacancy defects in the amorphous layer, the enhanced hydrophilicity improves the PEC performance synergistically. However, as the thickness of amorphous layer increasing, it raises the migration time and secondary recombination rate of the photogenerated carriers. Therefore, a controllable amorphous surface and PEC performance of BiVO₄ photoanode can realize by adjusting the SER force.