Constructing asymmetric dual active sites through symbiotic effect for achieving efficient and selective photoreduction of CO2 to C2H4

Abstract

One of the biggest obstacles to the light-driven conversion of greenhouse gas CO₂ into high value-added multi-carbon compounds is manipulating the C–C coupling reaction. Herein, we propose using a symbiotic effect to construct asymmetric dual active sites, namely doping CuInS₂ (CIS) with single atomic Ag, accompanied by the formation of sulfur vacancies (S_v). Thus, S_v and the neighbouring In metal atom double sites are constructed, and CO₂ photoreduction products undergo a transformation from C₁ products to C₂H₄. Meanwhile, the doped Ag plays a role in capturing and transferring photogenerated electrons, improving the reduction rate. The generation rate of C₂H₄ is 53.8 μmol g⁻¹ h⁻¹ with a selectivity of 98.8%. Based on the number of transferred electrons, the catalytic activity of 2%Ag/CuInS₂ (2%Ag/CIS) is 90 times that of CIS. Experimental and theoretical calculations verify that the key intermediates *CO and *CHO adsorbed on S_v and In sites, respectively, are propitious to promote the occurrence of the C–C coupling reaction owing to the reasonable distance, asymmetric electron distribution and distinct adsorption capacity. Accordingly, the findings provide a new strategy for designing asymmetric catalytic active sites for the selective photosynthesis of multi-carbon products from CO₂.