Understanding Photo(electro)catalysts for Energy Conversion via Operando Functional Imaging.

Understanding the fundamental processes of charge carrier generation, separation, transport, and reactivity on the surface of semiconductors is crucial for the rational design of high-performance photo(electro)catalysts for various energy conversion applications. Nevertheless, the ubiquitous and intricate heterogeneity exhibited by individual catalysts poses a significant obstacle to achieving a comprehensive understanding of the structure-function relationships using bulk-level, ensemble-averaged characterizations. This review highlights the emerging operando imaging techniques capable of providing local functional information, such as surface photovoltage, photoluminescence, charge carrier reaction rate, and photocurrent, at the single particle to subparticle level. By establishing correlations between the acquired local functional information and the specific structural characteristics of the catalyst, a quantitative, holistic understanding of the structure-function relationship in photo(electro)catalysts can be achieved. This understanding can serve as a foundation for guiding the design of photocatalysts with enhanced energy conversion performance.