Photoswitchable Chlorine Vacancies in Ultrathin Bi4O5Cl2 for Selective CO2 Photoreduction

Abstract

CO2 photoreduction 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 CO2 photoconversion. However, surface vacancies in this catalyst are easily deactivated during the reaction. CO2 photoreduction relies on sufficient active sites; hence, we synthesized ultrathin Bi4O5Cl2 nanoplates 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 O2 atmosphere after turning off the irradiation. These photoswitchable vacancies enabled Bi4O5Cl2 to produce 58.49 μmol g–1 CO 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 CO2 photoreduction 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.