Boosting Photocatalytic CO2 Reduction with H2O by Oxygen Vacancy- and Hydroxyl-Tailored SrBi2Ta2O9 Surface-Frustrated Lewis Pairs

The photocatalytic reduction of CO2 into high-value-added fuels is an extremely desirable process, but its practical application is limited by the weak adsorption and activation of inert CO2 molecules. Herein, oxygen vacancies (VOs) are formed on SrBi2Ta2O9 (SBT) by annealing in Ar gas at 400 °C and can spontaneously react with adsorbed H2O to form surface hydroxyls. Therefore, frustrated Lewis pairs (FLPs) are fabricated on SBT, where the surface VO and proximal surface hydroxyl serve as the Lewis acid and base, respectively. Experimental results indicate that the obtained FLPs can act as catalytic sites to adsorb, activate, and convert CO2 under low-intensity LED light irradiation (420 nm). Consequently, a CO2-to-CO conversion rate of 9.9 μmol g–1 h–1 is achieved in pure water on VO-SBT-OH without any sacrificial agents or cocatalysts, which is ∼4× higher than that of pristine SBT. Moreover, the surface hydroxyl can self-replenish by dissociating H2O during the reaction, thereby achieving a long-term CO2 conversion for 60 h. Our study demonstrates the potential of FLPs as a platform to decrease barriers to reducing CO2 and provides valuable insights into the underlying photocatalytic mechanism.