Nanograin-Boundary-Abundant Cu2O-Cu Nanocubes with High C2+ Selectivity and Good Stability during Electrochemical CO2 Reduction at a Current Density of 500 mA/cm2

Surface and interface engineering, especially the creationof abundantCu(0)/Cu+ interfaces and nanograin boundaries,is known to facilitate C2+ production during electrochemicalCO(2) reductions over copper-based catalysts. However, preciselycontrolling the favorable nanograin boundaries with surface structures(e.g., Cu(100) facets and Cu[n(100)x(110)] stepsites) and simultaneously stabilizing Cu-0/Cu+ interfaces is challenging, since Cu+ species are highlysusceptible to be reduced into bulk metallic Cu at high current densities.Thus, an in-depth understanding of the structure evolution of theCu-based catalysts under realistic CO2RR conditions isimperative, including the formation and stabilization of nanograinboundaries and Cu-0/Cu+ interfaces. Herein wedemonstrate that the well-controlled thermal reduction of Cu2O nanocubes under a CO atmosphere yields a remarkably stable Cu2O-Cu nanocube hybrid catalyst (Cu2O(CO)) possessinga high density of Cu-0/Cu+ interfaces, abundantnanograin boundaries with Cu(100) facets, and Cu[n(100)x(110)] step sites. The Cu2O(CO) electrocatalystdelivered a high C2+ Faradaic efficiency of 77.4% (56.6%for ethylene) during the CO2RR under an industrial currentdensity of 500 mA/cm(2). Spectroscopic characterizationsand morphological evolution studies, together with in situ time-resolved attenuated total reflection-surface enhancedinfrared absorption spectroscopy (ATR-SEIRAS) studies, establishedthat the morphology and Cu-0/Cu+ interfacialsites in the as-prepared Cu2O(CO) catalyst were preservedunder high polarization and high current densities due to the nanograin-boundary-abundantstructure. Furthermore, the abundant Cu-0/Cu+ interfacial sites on the Cu2O(CO) catalyst acted to increasethe *CO adsorption density, thereby increasing the opportunity forC-C coupling reactions, leading to a high C2+ selectivity.