Promoting CO 2 Electroreduction Over Nano-Socketed Cu/Perovskite Heterostructures via A-Site-Valence-Controlled Oxygen Vacancies.

Despite the intriguing potential, nano-socketed Cu/perovskite heterostructures for CO 2 electroreduction (CO 2 RR) are still in their infancy and rational optimization of their CO 2 RR properties is lacking. Here, an effective strategy is reported to promote CO 2 -to-C 2+ conversion over nano-socketed Cu/perovskite heterostructures by A-site-valence-controlled oxygen vacancies. For the proof-of-concept catalysts of Cu/La 0.3-x Sr 0.6+x TiO 3-δ (x from 0 to 0.3), their oxygen vacancy concentrations increase controllably with the decreased A-site valences (or the increased x values). In flow cells, their activity and selectivity for C 2+ present positive correlations with the oxygen vacancy concentrations. Among them, the Cu/Sr 0.9 TiO 3-δ with most oxygen vacancies shows the optimal activity and selectivity for C 2+ . And relative to the Cu/La 0.3 Sr 0.6 TiO 3-δ with minimum oxygen vacancies, the Cu/Sr 0.9 TiO 3-δ exhibits marked improvements (up to 2.4 folds) in activity and selectivity for C 2+ . The experiments and theoretical calculations suggest that the optimized performance can be attributed to the merits provided by oxygen vacancies, including the accelerated charge transfer, enhanced adsorption/activation of reaction species, and reduced energy barrier for C─C coupling. Moreover, when explored in a membrane-electrode assembly electrolyzer, the Cu/Sr 0.9 TiO 3-δ catalyst shows excellent activity, selectivity (43.9%), and stability for C 2 H 4 at industrial current densities, being the most effective perovskite-based catalyst for CO 2 -to-C 2 H 4 conversion.