Dual Channel H₂O₂ Photosynthesis in Pure Water over S-Scheme Heterojunction Cs₃PMo₁₂/CC Boosted by Proton and...

Dual 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 g_cat. ^-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.