Ethanol Synthesis by CO2 Photoreduction Catalyzed by Self-Optimized Tiδ+-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 TiO2-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 TiO2-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 TiO2-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 TiO2-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.