Dual Channel H₂O₂ Photosynthesis in Pure Water over S‐Scheme Heterojunction Cs₃PMo₁₂/CC Boosted by Proton and Electron Reservoirs

AbstractDual channel photo‐driven H2O2 production in pure water on small‐scale on‐site setups is a promising strategy to provide low‐concentrated H2O2 whenever needed. This process suffers, however, strongly from the fast recombination of photo‐generated charge carriers and the sluggish oxidation process. Here, insoluble Keggin‐type cesium phosphomolybdate Cs3PMo12O40 (abbreviated to Cs3PMo12) is introduced to carbonized cellulose (CC) to construct S‐scheme heterojunction Cs3PMo12/CC. Dual channel H2O2 photosynthesis from both H2O oxidation and O2 reduction in pure water has been thus achieved with the production rate of 20.1 mmol L−1 gcat.−1 h−1, apparent quantum yield (AQY) of 2.1% and solar‐to‐chemical conversion (SCC) efficiency of 0.050%. H2O2 accumulative concentration reaches 4.9 mmol L−1. This high photocatalytic activity is guaranteed by unique features of Cs3PMo12/CC, namely, S‐scheme heterojunction, electron reservoir, and proton reservoir. The former two enhance the separation of photo‐generated charge carriers, while the latter speeds up the torpid oxidation process. In situ experiments reveal that H2O2 is formed via successive single‐electron transfer in both channels. In real practice, exposing the reaction system under natural sunlight outdoors successfully results in 0.24 mmol L−1 H2O2. This work provides a key practical strategy for designing photocatalysts in modulating redox half‐reactions in photosynthesis.