Fig. 1: Schematic diagram of the HPs suppression mechanism.

Figure 1 illustrates the formation and suppression mechanism of HPs. The orange, blue, yellow, and red spheres represent Bi, V, O, and In atoms, respectively. The green and purple spheres denote electrons and holes, respectively. In the BiVO₄ photoanode, the self-trapping of photogenerated carriers leads to the formation of EPs (VO₄ sites) and HPs (BiO₈ sites), with HPs significantly limiting the utilization of surface hole carriers (highlighted in the blue dashed box). By selectively substituting Bi³⁺ with In³⁺, the formation energy of polarons is increased, thereby suppressing the generation of HPs and releasing more hole carriers (highlighted in the orange dashed box).