Semiconductor photocatalyst particles are widely used in transforming sunlight into fuels like H2. A common strategy to improve the efficiency of the photocatalysts is to deposit HER/OER electrocatalysts on bare semiconductor particles. However, a precise understanding of how charge-carrier-selective interface transport emerges and how it can be improved by the rational design of the cocatalyst-semiconductor interface is missing. Here, we design a combination of ex-situ and in-situ conducting-AFM experiments and illustrate heterogeneity in charge-carrier selectivity in a CoOx decorated BiVO4 model catalyst. We discover that the presence of water/electrolytes is critical to induce hole selectivity under irradiation at the interface between the CoOx OER catalyst and the BiVO4 light absorber. Measurements as a function of pH and ionomer chemistry suggest that negative surface charge on the semiconductor particles is central to inducing this hole selectivity. This work provides a fundamental understanding of the mechanism of charge transfer at the catalyst-semiconductor interface and lays the ground for the rational design of high-efficiency photocatalysts in the future.

Nanoscale measurements of charge transfer at cocatalyst-semiconductor interfaces on particle photocatalysts

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