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

Photoreduction of CO₂ to ethanol (C₂H₅OH) 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 C₂H₅OH 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 C₂H₅OH. The S-scheme TiO_2-x/BNF heterostructure provides spatially separated sites for CO₂ 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. C₂H₅OH dehydration is often difficult within the hydrophilic TiO_2-x/BNF microreactor, thus it tends to produce C₂H₅OH rather than C₂H₄. Through the synergizing effects, the well-constructed microreactor delivers an excellent C₂H₅OH 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 CO₂ conversion to C₂H₅OH using solar energy.