The Overlooked Solvent Effects: Reconsider the Paradigm in Semiconductor Photocatalysis

Semiconductor photocatalysis has seen decades of development, with most attention focused on two key elements: semiconductors Semiconductor photocatalysis has seen decades of development, with most attention focused on two key elements: semiconductors and solutes. However, the third “S” — solvents — which play a crucial role in condensed-phase reactions, has been surprisingly largely overlooked in this field. Despite its significant impact on chemical reactions, solvents have not received the attention they deserve in semiconductor photocatalysis. By reviewing the historical development of this area, we argue that the limitations on solvent selection are becoming increasingly impractical. We explore the fundamental effects solvents have on semiconductor photocatalysis, breaking down their complex influence into three areas: semiconductor properties, interfacial charge transfer, and chemical reactions in the solution. This perspective highlights the urgent need for more comprehensive and systematic research on solvent effects. Although not often the main focus of many studies, several examples are provided to demonstrate the importance of solvent effects. Future research directions are also discussed. Ultimately, this review calls for a rethinking of the current approach to semiconductor photocatalysis, stressing the critical role of solvents.