Promoting CO 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 electroreduction (CORR) are still in their infancy and rational optimization of their CORR properties is lacking. Here, an effective strategy is reported to promote CO-to-C conversion over nano-socketed Cu/perovskite heterostructures by A-site-valence-controlled oxygen vacancies. For the proof-of-concept catalysts of Cu/LaSrTiO (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 present positive correlations with the oxygen vacancy concentrations. Among them, the Cu/SrTiO with most oxygen vacancies shows the optimal activity and selectivity for C. And relative to the Cu/LaSrTiO with minimum oxygen vacancies, the Cu/SrTiO exhibits marked improvements (up to 2.4 folds) in activity and selectivity for C. 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/SrTiO catalyst shows excellent activity, selectivity (43.9%), and stability for CH at industrial current densities, being the most effective perovskite-based catalyst for CO-to-CH conversion.