Reaction Pathway Regulation for Gaseous and Liquid Products of Electrocatalytic CO₂ Reduction under Adsorbate...

Halide anion adsorption on transition metals can improve the performance of electrochemical CO₂ reduction reaction (CO₂RR), while the specific reaction mechanisms governing selective CO₂RR pathways remain unclear. In this study, we reveal for the first time the distinct pathway switching between gaseous (CO) and liquid products (formate and ethanol) on the well-defined Ag-Cu nanostructures with controlled chlorination. We show that CO₂ conversion to CO on Ag/AgCl can be tuned by adjusting the thickness of AgCl layer, achieving a high selectivity over a broad potential range in a 0.5 M KHCO₃ using flow cell. In contrast, the optimized Cl-Ag/Cu system enables the conversion of CO₂ into liquid products including formate and ethanol with a total Faradaic efficiency (FE) nearing 100 %, delivering high current densities of 136.3 and 20.8 mA cm^-2 at -1.3 V, respectively. In situ infrared experiments and theoretical calculations indicate that the lateral adsorbate of *OCHO intermediate facilitates the thermodynamics of both the CO pathway on Cl-Ag(111) and the formate pathway on Cl-Ag/Cu(111) by reducing Gibbs free energy barriers of each potential-limit step. This work uncovers the role of chlorination in the tuning of C-bound or O-bound intermediates during CO₂RR on Ag-Cu catalysts, determining the reaction pathway under lateral adsorbate effects.