Electronic metal-support interaction modulates Cu electronic structures for CO2 electroreduction to desired products

In this work, the Cu single-atom catalysts (SACs) supported by metal-oxides (Al2O3-CuSAC, CeO2-CuSAC, and TiO2-CuSAC) are used as theoretical models to explore the correlations between electronic structures and CO2RR 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 3dyz orbital of Al2O3-CuSAC enhances the adsorption strength of CO and weakens C-O bonds through 3dyz-π* electron back-donation. This reduces the energy barrier for C-C coupling, thereby promoting multicarbon formation on Al2O3-CuSAC. The highest occupied 3dz2 orbital of TiO2-CuSAC accelerates the H2O activation, and lowers the reaction energy for forming CH4. This over activated H2O, in turn, intensifies competing hydrogen evolution reaction (HER), which hinders the high-selectivity production of CH4 on TiO2-CuSAC. CeO2-CuSAC with highest occupied 3dx2-y2 orbital promotes CO2 activation and its localized electronic state inhibits C-C coupling. The moderate water activity of CeO2-CuSAC facilitates *CO deep hydrogenation without excessively activating HER. Hence, CeO2-CuSAC exhibits the highest CH4 Faradaic efficiency of 70.3% at 400 mA cm−2.