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

Abstract 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.