Femtosecond transient absorption spectroscopy investigation on ultrafast electron transfer in S-scheme ZnO/CdIn2S4 photocatalyst for H2O2 production and benzylamine oxidation
Yi Yang , Xin Zhou , Miaoli Gu , Bei Cheng , Zhen Wu , Jianjun Zhang
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引用次数: 0
Abstract
Photocatalytic hydrogen peroxide (H2O2) production is a crucial process for clean energy conversion, involving the reduction of O2 through two electrons. However, this process is often hampered by the sluggish water oxidation involving the photogenerated holes. To address this challenge, we have constructed a dual-functional S-scheme ZnO/CdIn2S4 heterojunction systerm coupling the H2O2 generation with a value-added benzylamine (BA) oxidation reaction. In this dual-functional photocatalytic system, photogenerated electrons in CdIn2S4 efficiently reduce O2 to produce H2O2, while photogenerated holes in ZnO selectively oxidize BA to N-benzylidenebenzylamine. Leveraging the advantages of the S-scheme heterojunction, the optimized ZnO/CdIn2S4 photocatalyst displays an enhanced H2O2 production rate (386 μmol·L−1·h−1) and BA oxidation fraction (81 %) than pure ZnO or CdIn2S4. Femtosecond transient absorption (fs-TA) spectroscopy confirm the ultrafast S-scheme electron transfer from the ZnO conduction band (CB) to the CdIn2S4 valence band (VB) upon photoexcitation of the ZnO/CdIn2S4 composite. Besides, timely depletion of VB holes in ZnO and CB electrons in CdIn2S4 can accelerate the interfacial electron transfer in the ZnO/CdIn2S4 S-scheme heterojunction. The innovative design of the ZnO/CdIn2S4 S-scheme photocatalyst provides new insights for developing efficient dual-functional heterojunction photocatalytic systems and introduces a novel method for studying S-scheme heterojunctions using fs-TA spectroscopy.