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-Cu_SAC, CeO₂-Cu_SAC, and TiO₂-Cu_SAC) 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 3d_yz orbital of Al₂O₃-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 Al₂O₃-Cu_SAC. The highest occupied 3d_z2 orbital of TiO₂-Cu_SAC 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-Cu_SAC. CeO₂-Cu_SAC with highest occupied 3d_x2-y2 orbital promotes CO₂ activation and its localized electronic state inhibits C-C coupling. The moderate water activity of CeO₂-Cu_SAC facilitates *CO deep hydrogenation without excessively activating HER. Hence, CeO₂-Cu_SAC exhibits the highest CH₄ Faradaic efficiency of 70.3% at 400 mA cm^-2.