Dual Channel H 2 O 2 Photosynthesis in Pure Water over S-Scheme Heterojunction Cs 3 PMo 12 /CC Boosted by Proton and Electron Reservoirs.

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.