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.

_{银-铜电催化剂已在CO 2}电还原成CH ₄方面表现出有效的催化性能，但对反应途径和机制的揭示仍然难以捉摸。在此，我们构建了化学键合的Ag-Cu ₂ O边界，其中由于表面Ag壳的存在， Cu _{2 O完全还原为Cu受到强烈阻碍。}界面限制效应有助于保持Ag-Cu _{2 O边界处的Cu} ⁺位点。利用原位/操作光谱和理论模拟，揭示了由于对CO 2 的物理吸附和化学吸附增强，CO _2在Ag-Cu ₂ O边界富集，活化CO ₂形成稳定的中间体*CO。_{Ag壳和Cu 2} O之间的边界介导局部*CO覆盖并促进*CHO中间体形成，从而促进CO ₂至CH ₄转化。这项工作不仅揭示了结构-活性关系，还为Ag-Cu催化剂上有效电催化CO ₂还原的反应机制提供了见解。