Solvent-Guided Galvanic Replacement of Ag on Cu Nanowires: Dynamic Structural Evolution for CO₂ Electrolysis

Galvanic replacement is a powerful strategy for incorporating heterometal atoms into preformed metallic nanostructures. However, the resulting architectures are highly sensitive to the reaction environment, which influences the relative stability and solubility of the redox species involved. Previous studies on Cu-Ag nanocatalysts synthesized via galvanic replacement have reported diverse product selectivities, underscoring the need for a systematic investigation of the process. In this work, we performed galvanic replacement of Cu nanowires with Ag ions in various solvents and evaluated the resulting nanostructures and their performance in CO₂ electroreduction. The choice of solvent significantly affected the dispersity of the nanocomposites, the size of Ag nanocrystals, and the structure and chemical state of oxidized Cu species. Among these factors, the size of the Ag nanocrystals emerged as the dominant parameter influencing CO₂ electrolysis selectivity, despite notable variations in the Cu species oxidized in different solvents. The results suggest that methane production sites are formed during electrolysis via the reconstruction of Cu nanoparticles on the surface of large Ag crystal facets. This highlights the critical role of copper structural reconstruction during CO₂ electroreduction, particularly when the initial Cu species are readily deformable due to their nanoscale dimension.