Microenvironment Modulation of Ultrathin Bronze‐Phase TiO2 Nanosheets for Highly Selective Photocatalytic CO2 Reduction in Water

Photocatalytic reduction of CO2 with H2O provides a promising and sustainable pathway to produce valuable chemicals and fuels. However, the low efficiency of CO2 reduction and the concomitant competition of H2 evolution pose serious challenges to practical applications. Herein, a novel approach is proposed to modulate the surface microenvironment of photocatalysts by utilizing hydrogen peroxide (H2O2). A bronze‐phase TiO2 (TB) composed of ultrathin nanosheet with a thickness of ∼3 nm is fabricated and employed as the model catalyst for photocatalytic CO2 reduction. H2O2 molecules are presumed to be bonded to the ultrathin TB surface to form the TB‐H2O2 (TBHO) active specie. The newly generated TBHO enhances the CO2 adsorption and accelerates mass transfer, and the weakly acidic microenvironment of the catalyst surface serves the purpose of mediating the proton‐coupled electron transfer path. Consequently, ultrathin TB nanosheets assisted by H2O2 show an excellent CO generation rate of 29.1 µmol−1 g−1 h−1 (which is 11.2‐fold higher than that of pure TB) in water, and the selectivity toward CO is nearly 100%. This work underscores the importance of tailoring the catalyst surface microenvironment to promote the CO2 reduction while minimizing the H2 generation in pure water. A novel approach is proposed to promote CO2 reduction and suppress the generation of H2 in water. H2O2 is presumed to be bonded to the bronze‐phase TiO2 nanosheet, which improves carrier separation efficiency, increases CO2 adsorption and mass transport, and mediates a proton‐coupled electron transfer route for enhanced CO2 reduction.