Effect of Surface Modification of Cu Electrodes by Ag Nanoparticle Spray Coating on the Products and Electrolytic Potential of Electrochemical CO2 Reduction

Electrochemical CO2 reduction reaction (eCO2RR) is a promising technology for carbon utilization, yet achieving high product selectivity and long-term stability remains a critical challenge. In this study, we investigated the performance and surface stability of Cu electrodes modified with Ag nanoparticles using a spray-coating method. While a bare Cu reference electrode exhibited an initial starting period dominated by hydrogen evolution before shifting toward hydrocarbon production after two hours, the Ag-spray-coated Cu electrode demonstrated immediate and stable catalytic activity. Electrode potential remained stable throughout the 12 h evaluation, in contrast to the negative shifts observed with the bare Cu electrode. Ambient pressure hard X-ray photoelectron spectroscopy (AP-HAXPES) revealed that while the bare Cu surface remained metallic, the Ag-spray-coated Cu surface existed as Cu2O during the reaction. The enhanced selectivity and stability are attributed to a spillover mechanism, where CO generated on the Ag nanoparticles migrates to adjacent Cu2O sites, inhibiting hydrogen evolution and facilitating efficient reduction to methane and ethylene from the onset of electrolysis. These findings demonstrate that surface modification via nanoparticle spray coating is a highly effective strategy for achieving selective and stable CO2 conversion on bimetallic catalysts.