Abstract
In this work, the Cu single-atom catalysts (SACs) supported by metal-oxides (Al(2)O(3)-Cu(SAC), CeO(2)-Cu(SAC), and TiO(2)-Cu(SAC)) are used as theoretical models to explore the correlations between electronic structures and CO(2)RR performances. For these catalysts, the electronic metal-support interaction (EMSI) induced by charge transfer between Cu sites and supports subtly modulates the Cu electronic structure to form different highest occupied-orbital. The highest occupied 3d(yz) orbital of Al(2)O(3)-Cu(SAC) enhances the adsorption strength of CO and weakens C-O bonds through 3d(yz)-π* electron back-donation. This reduces the energy barrier for C-C coupling, thereby promoting multicarbon formation on Al(2)O(3)-Cu(SAC). The highest occupied 3d(z2) orbital of TiO(2)-Cu(SAC) accelerates the H(2)O activation, and lowers the reaction energy for forming CH(4). This over activated H(2)O, in turn, intensifies competing hydrogen evolution reaction (HER), which hinders the high-selectivity production of CH(4) on TiO(2)-Cu(SAC). CeO(2)-Cu(SAC) with highest occupied 3d(x2-y2) orbital promotes CO(2) activation and its localized electronic state inhibits C-C coupling. The moderate water activity of CeO(2)-Cu(SAC) facilitates *CO deep hydrogenation without excessively activating HER. Hence, CeO(2)-Cu(SAC) exhibits the highest CH(4) Faradaic efficiency of 70.3% at 400 mA cm(-2).