Electron transfer dynamics and enhanced H2 production activity of hydrangea-like BiOBr/Bi2S3-based photocatalysts with Cu-complex as a redox mediator

A composite photocatalyst consisting of the BiOBr/Bi2S3 heterojunction and a Cu complex exhibited high H-2 production activity through an efficient transport of charge by redox couple Cu(II)/Cu(I) of the complex. BiOBr was prepared by a microwave solvothermal method. Then, the BiOBr/Bi2S3 composite was prepared as a heterojunction photocatalyst by an ion-exchange process. The copper complex was then introduced as a co-catalyst or a redox mediator. The morphology, crystal properties, optical properties, surface chemistry, photocurrent response, and photocatalytic activity of these BiOBr/Bi2S3/copper complex composites were investigated. The formation of a BiOBr/Bi2S3 heterojunction and the introduction of Cu complex improved the performance of the photocatalysts. For the first time, operando X-ray absorption spectra were recorded in situ to unveil the local interaction at the reactant-photocatalyst interface toward the photocatalysis reaction of BiOBr/Bi2S3-Cu complex photocatalyst in the sacrificial agent solution (Na2S, Na2SO3).