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

Abstract Dual channel photo‐driven H 2 O 2 production in pure water on small‐scale on‐site setups is a promising strategy to provide low‐concentrated H 2 O 2 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 Cs 3 PMo 12 O 40 (abbreviated to Cs 3 PMo 12 ) is introduced to carbonized cellulose (CC) to construct S‐scheme heterojunction Cs 3 PMo 12 /CC. Dual channel H 2 O 2 photosynthesis from both H 2 O oxidation and O 2 reduction in pure water has been thus achieved with the production rate of 20.1 mmol L −1 g cat. −1 h −1 , apparent quantum yield (AQY) of 2.1% and solar‐to‐chemical conversion (SCC) efficiency of 0.050%. H 2 O 2 accumulative concentration reaches 4.9 mmol L −1 . This high photocatalytic activity is guaranteed by unique features of Cs 3 PMo 12 /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 H 2 O 2 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 H 2 O 2 . This work provides a key practical strategy for designing photocatalysts in modulating redox half‐reactions in photosynthesis.