Ethanol Synthesis by CO 2 Photoreduction Catalyzed by Self‐Optimized Ti δ+ ‐Based Heterojunction

Abstract Photoreduction of CO 2 to ethanol (C 2 H 5 OH) is a promising carbon‐neutral technology for renewable energy. Nevertheless, low efficiency of multielectron utilization and high C─C coupling energy barrier cause poor performance in C 2 H 5 OH production. Here, we report a TiO 2−x /BNF (boron nitride flower) S‐scheme heterojunction microreactor to steer the asymmetric Ti active sites configuration and redox potential, thereby enhancing the thermodynamic and kinetic formation of C 2 H 5 OH. The S‐scheme TiO 2−x /BNF heterostructure provides spatially separated sites for CO 2 reduction and water oxidation with efficient charge carrier utilization. The flower‐like structure of BNF improves the local concentration of *CO within microreactors originated from confinement effect to satisfy the coupling process. Self‐generated oxygen vacancy in TiO 2−x brought by BNF leads to different electron densities of adjacent Ti sites, which strengthens the adsorption of *CO and reduces the *CO‐CHO formation energy. C 2 H 5 OH dehydration is often difficult within the hydrophilic TiO 2−x /BNF microreactor, thus it tends to produce C 2 H 5 OH rather than C 2 H 4 . Through the synergizing effects, the well‐constructed microreactor delivers an excellent C 2 H 5 OH production rate of 51.4 µmol g −1 h −1 with a selectivity of 99% and unprecedented global stability. Our work can serve as inspiration for developing Ti‐based catalysts for CO 2 conversion to C 2 H 5 OH using solar energy.