Mechanistic investigation on Ag-Cu2O in electrocatalytic CO2 to CH4 by in situ/operando spectroscopic and theoretical analysis

Silver-copper electrocatalysts have demonstrated effectively catalytic performance in electroreduction CO₂ toward CH₄, yet a revealing insight into the reaction pathway and mechanism has remained elusive. Herein, we construct chemically bonded Ag-Cu₂O boundaries, in which the complete reduction of Cu₂O to Cu has been strongly impeded owing to the presence of surface Ag shell. The interfacial confinement effect helps to maintain Cu⁺ sites at the Ag-Cu₂O boundaries. Using in situ/operando spectroscopy and theoretical simulations, it is revealed that CO₂ is enriched at the Ag-Cu₂O boundaries due to the enhanced physisorption and chemisorption to CO₂, activating CO₂ to form the stable intermediate *CO. The boundaries between Ag shell and the Cu₂O mediate local *CO coverage and promote *CHO intermediate formation, consequently facilitating CO₂-to-CH₄ conversion. This work not only reveals the structure-activity relationships but also offers insights into the reaction mechanism on Ag-Cu catalysts for efficient electrocatalytic CO₂ reduction.