Constructing bridging oxygen vacancies in SnTa2O6_x for efficient and stable photocatalytic CO2 reduction under visible light irradiation

Construction of oxygen vacancies is a common strategy to improve the performance of metal oxide photocatalysts. However, the oxygen vacancies can be easily filled and consumed by the oxygen atoms of CO2 molecules during CO2 photoreduction reactions, resulting in deactivation of the catalyst. In this study, bridging oxygen vacancies were introduced into SnTa2O6 nanosheets, which remarkably enhanced the photocatalytic performance with good stability. The SnTa2O6_x obtained after 40 s of flame reduction treatment showed 7.5 times higher visible-light-activity than pristine SnTa2O6 (21.1 & mu;mol h_ 1 g_ 1 of CO), and sustained good stability even after five cycles. Accompanied by a positive shift in the d-band center, the adsorption configuration of CO2 on the catalysts changed from monodentate to bidentate after the introduction of bridging oxygen vacancies into SnTa2O6, which is beneficial for CO2 adsorption and activation. Furthermore, the bridging oxygen vacancies in SnTa2O6_ x can reduce the Gibbs free energy of COOH*, and facilitate the photo conversion of CO2 by receiving photogenerated electrons. The good stability of SnTa2O6_x can be attributed to the distinct molecular configuration of CO2, which avoids filling and consuming the oxygen vacancies.