[en] Highlights: • Bimetallic Ag/Cu nanowire fabricated via Cu anodization and Ag displacement. • Varying Ag displacement time effective to modulate the Ag surface contents. • Ag coverage estimated by numerical and experimental methods ranged from 70% to 94.3%. • CO selectivity of Ag/Cu nanowire closely related and scaled with Ag coverage. Herein, bimetallic Ag/Cu nanowires (NWs) are prepared by electrochemical synthesis of Cu NWs and subsequent Ag galvanic displacement for the electrochemical reduction of CO₂ to CO. The delicate execution of the displacement fabricates bimetallic NWs that possess controlled surface composition. The surface composition of NW is precisely controlled by varying the displacement time, and it is revealed by numerical and experimental methods that the catalytic activity is closely affected by the composition. The surface coverage of Ag measured based on under potential deposition according to the displacement time ranges from 70% to 94.3%. An increase in the Ag surface composition results in an improvement in the CO Faradaic efficiency from 29.8% to 39.6% and a significant increase in CO partial current density compared with Cu NWs and Ag foil. Namely, the catalytic activity of Ag/Cu NWs is dependent on the Ag coverage, and is governed by scaling relation.

[en] Electrodeposition of Cu-based alloys has been researched for a variety of applications due to Cu-based alloys having superior properties compared to pure Cu, including higher chemical resistance, mechanical hardness, and electrocatalytic activity. Cu-Ag is the most electrically conductive among Cu-based alloys, and it has higher mechanical hardness and oxidation resistance compared to pure Cu. Cu-Ag co-deposition in cyanide-based electrolytes has been previously reported; however, the toxicity of cyanide limited its use. In this study, we introduce an ammonium hydroxide-based electrolyte for Cu-Ag electrodeposition and the properties of Cu-Ag films deposited in this electrolyte. Electrochemical measurements were performed to determine the potential range for co-electrodeposition of Cu and Ag, and the effect of nitrate reduction on the film deposition was examined. The effects of deposition potential and concentration of Ag ions in the electrolytes on the electrical resistivity and Ag contents of the films were investigated. The modulation of Ag ion concentration was found to be a more effective way to control Ag contents in the deposited films. Co-deposition of 4 at% Ag with Cu in the ammonium-hydroxide electrolyte markedly improved mechanical hardness and oxidation resistance compared to a pure Cu film without severe deterioration of electrical conductivity.