Crystal-Face-Dependent Charge Dynamics on a BiVO₄ Photocatalyst Revealed by Single-Particle Spectroelectrochemistry

The performance of semiconductor materials in solar water splitting and other applications is strongly influenced by the structure-related dynamics of charge carriers in these materials. In this study, we assessed the trapping, recombination, and surface reactions of photogenerated and electrically injected charges on specific facets of the promising visible active photocatalyst BiVO₄ by using single-particle photoluminescence (PL) spectroscopy. Evaluation of the electric-potential-induced PL properties and the PL response to charge scavengers revealed that the visible PL bands observed during visible laser irradiation originate from radiative recombination between holes trapped at the intraband states above the valence band and mobile (free or shallowly trapped) electrons. Furthermore, the trapped holes are preferentially located on the lateral {110} facets of the BiVO₄ crystal, while the electrons are uniformly distributed over the crystal. The methodology described in this study thus provides us with a unique opportunity to explore whether or not the crystal faces affect the charge carrier dynamics in the photocatalysis and the photoelectrocatalysis.