Photoswitchable Chlorine Vacancies in Ultrathin Bi4O5Cl2for Selective CO2Photoreduction

Abstract

CO2photoreduction currently faces two challenges: low photoreduction efficiency and poor product selectivity. Ultrathin two-dimensional bismuth oxyhalide, with a large number of surface vacancies (active sites), is an ideal material for regulating CO2photoconversion. However, surface vacancies in this catalyst are easily deactivated during the reaction. CO2photoreduction relies on sufficient active sites; hence, we synthesized ultrathin Bi4O5Cl2nanoplates via a water-assisted self-assembly process with sufficient photoswitchable surface Cl vacancies for solar-driven CO2-to-CO reduction. The surface Cl vacancies were generated under light irradiation and filled again with migrated Cl-under an O2atmosphere after turning off the irradiation. These photoswitchable vacancies enabled Bi4O5Cl2to produce 58.49 μmol g-1CO after 4 h of irradiation with high stability and lowered the energy barriers of the rate-determining (CO2-to-COOH-) and selectivity-determining steps (COOH--to-CO), enabling 100% product selectivity. The reversible, photoswitchable Cl vacancies have a higher potential as active sites for CO2photoreduction than synthetically introduced static surface vacancies, which could provide a feasible strategy for the creation of highly dynamic, active-defective catalysts for solar-energy conversion.