Promoting CO₂ Electroreduction Over Nano-Socketed Cu/Perovskite Heterostructures via A-Site-Valence-Controlled Oxygen Vacancies

Despite the intriguing potential, nano-socketed Cu/perovskite heterostructures for CO₂ electroreduction (CO₂RR) are still in their infancy and rational optimization of their CO₂RR properties is lacking. Here, an effective strategy is reported to promote CO₂-to-C₂₊ 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-xSr_0.6+xTiO_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 C₂₊ present positive correlations with the oxygen vacancy concentrations. Among them, the Cu/Sr_0.9TiO_3-δ with most oxygen vacancies shows the optimal activity and selectivity for C₂₊. And relative to the Cu/La_0.3Sr_0.6TiO_3-δ with minimum oxygen vacancies, the Cu/Sr_0.9TiO_3-δ exhibits marked improvements (up to 2.4 folds) in activity and selectivity for C₂₊. 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_0.9TiO_3-δ catalyst shows excellent activity, selectivity (43.9%), and stability for C₂H₄ at industrial current densities, being the most effective perovskite-based catalyst for CO₂-to-C₂H₄ conversion.