Promoting CO2 and H2O activation on O-vacancy regulated In-Ti dual-sites for enhanced CH4 photo-production

Engineering the specific active sites of photocatalysts for simultaneously promoting CO2 and H2O activation is important to achieve the efficient conversion of CO2 to hydrocarbon with H2O as a proton source under sunlight. Herein, we delicately design the In/TiO2-VO photocatalyst by engineering In single atoms (SAs) and oxygen vacancies (VOs) on porous TiO2. The relation between structure and performance of the photocatalyst is clarified by both experimental and theoretical analyses at the atomic levels. The In/TiO2-VO photocatalyst furnish a high CH4 production rate up to 35.49 μmol g−1 h−1 with a high selectivity of 91.3% under simulated sunlight, while only CO is sluggishly generated on TiO2-VO. The combination of in situ spectroscopic analyses with theoretical calculations reveal that the VO sites accelerate H2O dissociation and increase proton feeding for CO2 reduction. Furthermore, the VO regulated In-Ti dual sites enable the formation of a stable adsorption conformation of In-C-O-Ti intermediate, which is responsible for the highly selective reduction of CO2 to CH4. This work demonstrates a new strategy for the development of effective photocatalysts by coupling metal SA sites with the adjacent metal sites of support to synergistically enhance the activity and selectivity of CO2 photoreduction.