Conformal Electrochemical Deposition of Intermetallic AuCu Thin Films for Convergent C-N Coupling

Abstract

Intermetallic AuCu alloys exhibited enhanced selectivity and activity for urea (CO(NH2)2) production compared to their parent metals. Intermetallic AuCu alloy thin films were grown electrochemically over a Ti foil substrate and evaluated for their capacity to enable electrochemical C-N coupling. Varying the Au and Cu stoichiometry provided a synthetic handle to tune the film electronics (i.e., d-band position) while maintaining overall film stability. The AuCu alloy with the highest Au loading of 75% proved to be the most electrochemically stable and possessed the highest selectivity (~68%) for urea formation. Copper K-edge X-ray Absorption Spectroscopy (XAS) revealed that the Cu in alloys with more Au content maintained a higher oxidation state (in the form of Cu-O states) under electrochemically relevant conditions. This observation suggests enhanced anion (NO3-/NO2-) adsorption and retention at the surface. This work highlights the utility of using intermetallic alloys to enable complex electrochemical coupling reactions by finely tuning material properties while also maintaining stability.