Cu–S Bonds as an Atomic-Level Transfer Channel to Achieve Photocatalytic CO2 Reduction to CO on Cu-Substituted ZnIn2S4

Due to the intrinsic chemically inert CO2 with the dissociation energy of C═O bond as high as 750 kJ mol–1, low efficiency and selectivity have become the most significant restraints for the practical application of photocatalytic CO2 reduction. Renewing the electronic structure of adsorbed CO2 on the catalyst surface through a rational catalyst design is crucial to achieving performance improvement. Herein, we prepared ZnIn2S4 and Cu-substituted ZnIn2S4 containing both Lewis acid and Lewis base sites as a model system for investigating the activation of CO2 by M–S chemical bonds (M represents a metal site). The Cu–S chemical bond can effectively activate CO2 as a vital electron channel and lower the Gibbs free energy for generating the essential intermediate *COOH. Besides, the Cu0.7-ZnIn2S4 sample displays 74.8% selectivity for reducing CO2 to CO with a rate of 47.2 μmol g–1 h–1, roughly 7.14 times that of ZnIn2S4.