Accelerating solar driven CO2 reduction via sulfur-doping boosted water dissociation and proton transfer

Exploring efficient photocatalysts for solar driven CO2 reduction with water (H2O) as a proton donor is highly imperative but remains a great challenge because the synchronous enhancement of CO2 activation, H2O dissociation and proton transfer is hardly achieved on a photocatalyst. Particularly, the sluggish H2O dissociation impedes the photocatalytic CO2 reduction reaction involving multiple proton–electron coupling transfer processes. Herein, a sulfur-doped BiOCl (S-BiOCl) photocatalyst with abundant oxygen vacancies (OV) is developed, which exhibits broadband-light harvesting across solar spectrum and distinct photothermal effect due to photochromism. For photocatalytic CO2 reduction with H2O in a gas-solid system, the high CO yield of 49.76 µmol·gcat−1·h−1 with 100% selectivity is achieved over the S-BiOCl catalyst under a simulated sunlight. The H2O-assisted CO2 reduction reaction on S-BiOCl catalyst is triggered by photocatalysis and the photothermal heating further enhances the reaction rate. The kinetic isotope experiments indicate that the sluggish H2O dissociation affects the whole photocatalytic CO2 reduction process. The presence of oxygen vacancies promotes the adsorption and activation of H2O and CO2, and the doped S sites play a crucial role in boosting H2O dissociation and accelerating the dynamic migration of hydrogen species. As a result, the ingenious integration of OV defects, S sites and photothermal effect in S-BiOCl catalyst conjointly contributes to the significant improvement in photocatalytic CO2 reduction performance.