Preparation of Tunable Cu-Ag Nanostructures by Electrodeposition in a Deep Eutectic Solvent

The green transition requires new, clean, inexpensive, and sustainable strategies to prepare controllable bimetallic and multimetallic nanostructures. Cu-Ag nanostructures, for example, are promising bimetallic catalysts for different electrocatalytic reactions such as carbon monoxide and carbon dioxide reduction. In this work, we present the one-step preparation method of electrodeposited Cu-Ag with tunable composition and morphology from choline chloride plus urea deep eutectic solvent (DES), a non-toxic and green DES. We have assessed how different electrodeposition parameters affect the morphology and composition of our nanostructures. We combine electrochemical methods with ex-situ scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) to characterize the nanostructures. We have estimated the electrochemically active surface area (ECSA) and roughness factor (R) by lead underpotential deposition (UPD). The copper/silver ratio in the electrodeposited nanostructures is highly sensitive to the applied potential, bath composition, and loading. We observed that silver-rich nanostructures were less adherent whereas the increase in copper content led to more stable and homogenous films with disperse rounded nanostructures with tiny spikes. These spikes were more stable when the deposition rate was fast enough and the molar ratio of Cu and Ag was no greater than approximately two to one. This study presents the sustainable, clean, and inexpensive preparation of Cu-Ag nanostructures by metal electrodeposition from a urea and choline chloride deep eutectic solvent for their use as electrocatalysts. Size, morphology, and composition are tuned by adjusting applied potential, circulated charge, and bath composition. Electrochemical, microscopy, and spectroscopy techniques are combined to characterize the nanostructures. image