Time-Resolved Photoelectrochemical Measurements To Study Band Bending of BiVO₄ Photoanodes

The oxide semiconductor BiVO₄ is a promising photoanode for the oxygen evolution reaction (OER) under visible light. It is a well-suited model photoanode for the time-resolved investigation of light-pulse-induced space charge layer reorganization and electron-transfer chemistry at the BiVO₄–electrolyte interfaces. In order to study the different time scales of the photocapacitive and photochemical processes including the effect of defect states, a time-resolved photoelectrochemical rotating ring-disk electrode setup with a time resolution of better than 1 ms is developed. Measurements were performed under dark, continuous, and stroboscopic illumination using a LED array that simulates the AM 1.5G spectrum. Cyclic voltammetry measurements revealed four different regions for the photocurrents, which can be associated with different states of band bending and allow for the determination of the flat band potential. The photocurrent transients during switch-on and -off of the LED array show an exponential time evolution with three time constants that are attributed to (1) fast reorganization of the space charge layer, (2) slower onset/relaxation of the photocatalytic OER, and (3) very slow photocorrosion. These findings help to understand the interplay between photoinduced space charge reorganization and OER-related charge transfer in the electrochemical double layer during photocatalytic water splitting. © 2026 The Authors. Published by American Chemical Society