Origin of Metal–Support Interactions for Selective Electrochemical CO2 Reduction into C1 and C2+ Products

The design of metal–support interaction (MSI) is an essential strategy in developing classical heterogeneous catalysts and recently for electrocatalysts. Particularly, for the electrochemical CO2 reduction reaction (CO2RR), metal–oxide-supported Cu catalysts have demonstrated remarkable selectivity improvements toward C1 and C2+ products, whereas the exact regulatory mechanism remains debated. Herein, we elucidate that the stabilization of the Cu+/Cu interface is likely the dominant mechanism for the selectivity improvement rather than the perceived formation of Cu–O–M dual sites. We designed two CeO2-modified Cu nanocube catalysts with a similar Cu/CeO2 heterogeneous interface yet distinct high selectivity toward CH4 (40 ± 1.4%) and C2H4 (52 ± 0.57%), offering ideal models for in-depth mechanistic studies. In situ spectroscopy characterized a notable presence of adsorbed CO (COads) at the formed Cu/CeO2–x interface. Yet, these COads only account for less than 5% of the total COads population for both catalysts, with most COads remaining at the Cu/Cu+ sites. Further characterization revealed a varied electronic interaction between Cu and CeO2 for these two catalysts, generating different surface Cu+ under operational conditions, which subsequently tune the CO2RR selectivities by regulating the surface COads populations. These results provide an in-depth understanding of MSI for its further utilization in the CO2RR and other electrocatalysis processes.