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

Halide anion adsorption on transition metals can improve the performance of electrochemical CO reduction reaction (CORR), while the specific reaction mechanisms governing selective CORR 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 CO 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 KHCO using flow cell. In contrast, the optimized Cl-Ag/Cu system enables the conversion of CO 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 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 CORR on Ag-Cu catalysts, determining the reaction pathway under lateral adsorbate effects.