Accelerating solar driven CO 2 reduction via sulfur-doping boosted water dissociation and proton transfer

Exploring efficient photocatalysts for solar driven CO 2 reduction with water (H 2 O) as a proton donor is highly imperative but remains a great challenge because the synchronous enhancement of CO 2 activation, H 2 O dissociation and proton transfer is hardly achieved on a photocatalyst. Particularly, the sluggish H 2 O dissociation impedes the photocatalytic CO 2 reduction reaction involving multiple proton–electron coupling transfer processes. Herein, a sulfur-doped BiOCl (S-BiOCl) photocatalyst with abundant oxygen vacancies (O V ) is developed, which exhibits broadband-light harvesting across solar spectrum and distinct photothermal effect due to photochromism. For photocatalytic CO 2 reduction with H 2 O in a gas-solid system, the high CO yield of 49.76 µmol·g cat −1 ·h −1 with 100% selectivity is achieved over the S-BiOCl catalyst under a simulated sunlight. The H 2 O-assisted CO 2 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 H 2 O dissociation affects the whole photocatalytic CO 2 reduction process. The presence of oxygen vacancies promotes the adsorption and activation of H 2 O and CO 2 , and the doped S sites play a crucial role in boosting H 2 O dissociation and accelerating the dynamic migration of hydrogen species. As a result, the ingenious integration of O V defects, S sites and photothermal effect in S-BiOCl catalyst conjointly contributes to the significant improvement in photocatalytic CO 2 reduction performance.