Enhancing photocatalytic CO2 reduction activity of ZnIn2S4/MOF-808 microsphere with S-scheme heterojunction by in situ synthesis method

The design of a heterogeneous structure for photocatalysts has attracted significant attention. In this study, a step-scheme (S-scheme) heterojunction was designed using an in-situ synthesis method. The resulting heterojunction comprised 3D microspheres of ZnIn 2 S 4 and octahedral MOF-808 (ZnIn 2 S 4 /MOF-808). During this process, we investigated the impact of the scale of the ZnIn 2 S 4 microspheres on performance by controlling the growth of the ZnIn 2 S 4 microspheres with various scales. The maximum catalytic activity was discovered to be achieved with ZnIn 2 S 4 microspheres of 6 µm when coupled with MOF-808. Compared to pure ZnIn 2 S 4 and MOF-808, the fabricated S-scheme ZnIn 2 S 4 /MOF-808 heterojunction exhibited notably improved photocatalytic CO 2 reduction performance. The performance of the CO yield of the optimized sample could reach 8.21 μmol g −1 h −1 , which was approximately 10 and 8 times higher than those of ZnIn 2 S 4 (0.84 μmol g −1 h −1 ) and MOF-808 (1.03 μmol g −1 h −1 ), respectively. Moreover, ultraviolet photoelectron spectroscopy, ESR, in situ X-ray photoelectron spectroscopy, and density functional theory calculations were used to study the charge transfer mechanism of the S-scheme heterojunction. In-situ FT-IR investigation established the Carbene pathway as the source of CO production (CO 2 → CO 2 * → COOH* → CO* → CO). This study provides an efficient method for designing an S-scheme heterojunction for photocatalytic CO 2 reduction.