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

Abstract Photocatalytic reduction of CO 2 with H 2 O provides a promising and sustainable pathway to produce valuable chemicals and fuels. However, the low efficiency of CO 2 reduction and the concomitant competition of H 2 evolution pose serious challenges to practical applications. Herein, a novel approach is proposed to modulate the surface microenvironment of photocatalysts by utilizing hydrogen peroxide (H 2 O 2 ). A bronze‐phase TiO 2 (TB) composed of ultrathin nanosheet with a thickness of ∼3 nm is fabricated and employed as the model catalyst for photocatalytic CO 2 reduction. H 2 O 2 molecules are presumed to be bonded to the ultrathin TB surface to form the TB‐H 2 O 2 (TBHO) active specie. The newly generated TBHO enhances the CO 2 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 H 2 O 2 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 CO 2 reduction while minimizing the H 2 generation in pure water.