Elucidating the roles of grain boundary and facet in electrochemical CO 2 reduction

The electrochemical reduction of CO2 (CO2RR) facilitates the sustainable synthesis of fuels and chemicals. Grain-boundary-rich nanoparticles show superior CO2RR performance, however, the nature of active sites remains elusive. Here, we utilize in situ attenuated total reflectance surface-enhanced infrared absorption spectroscopy to identify the active sites and achieve structure-activity correlations, by taking advantage of synthesizing colloidal nanoparticles with well-defined shapes. It indicates that grain boundaries selectively convert CO2 to CO during the CO2RR, and the terrace sites on Cu(100) facets are the active sites for the conversion of CO to C2+ products. Density functional theory calculations show that the optimal adsorption energies of CO2 and CO on grain boundaries facilitate the conversion of CO2 into CO, while the terrace sites on Cu(100) facets selectively convert CO to C2+ products by lowering the activation energy of C-C coupling process. This work provides experimental evidences for the rational design of highly selective catalysts to produce C2+ products via the CO2RR.