Pt single atoms promoting the construction of asymmetric double sites to achieve highly selective photoreduction of CO2 to ethylene

Abstract

In this work, Pt single atoms (SAs) were engineered on the surface of CdIn₂S₄ (CIS) to trigger abundant generation and stable existence of sulfur vacancies (S_v). Through quasi in situ X-ray photoelectron spectroscopy (XPS) and work function analysis, the photogenerated electrons are first captured by Pt SAs and S_v, and then transferred from Pt SAs to S_v, ultimately increasing the electron density of S_v. Meanwhile, S_v have significant advantages in adsorbing CO₂ molecules. According to the number of transferred electrons, the optimized 0.8 %Pt/CIS has 76 times the photocatalytic performance of pristine CIS, and the selectivity of ethylene (C₂H₄) is up to 99.3 %. The carbon–carbon coupling reaction between *CO and *CHO adsorbed on double sites of S_v and In atoms is identified as the rate-determining step. Theoretical calculations suggest that the energy barrier required for coupling of intermediates *CO and *CHO is the lowest, conducive to the selective generation of C₂H₄.