Size-controlled growth of ZnSe nanocrystals for high-performance photocatalytic H2O2 production in pure water

Semiconductor photocatalysis is deemed as a novel and promising process that can produce H₂O₂ from earth-abundant water and gaseous dioxygen using sunlight as the energy supply. The searching of novel catalysts for photocatalytic H₂O₂ production has received increasing attention in the last few years. Herein, size-controlled growth of ZnSe nanocrystals was realized via a solvothermal method by varying the amount of Se and KBH₄. The performance of the as-obtained ZnSe nanocrystals towards photocatalytic H₂O₂ production depends on the mean size of the synthesized nanocrystals. Under O₂-bubbling, the optimal ZnSe sample presented an excellent H₂O₂ production efficiency (8.596 mmol g^-1 h^-1), and the apparent quantum efficiency for H₂O₂ production reaches as high as 2.84% at λ = 420 nm. Under air-bubbling, the accumulation of H₂O₂ was as high as 1.758 mmol L^-1 after 3 h irradiation at the ZnSe dosage of 0.4 g L^-1. The photocatalytic H₂O₂ production performance is far superior to the most investigated semiconductors such as TiO₂, g-C₃N₄, and ZnS.