Conformal electrochemical deposition of intermetallic AuCu thin films for convergent C–N coupling

Abstract

Intermetallic AuCu alloy thin films were grown electrochemically onto Ti foil substrates and exhibited enhanced selectivity and activity for electrochemical C–N coupling to form urea (CO(NH₂)₂) compared to their parent metals. Varying the Au and Cu stoichiometry provided a synthetic handle to tune the film electronics (i.e., d-band position, oxophilicity) 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. 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) 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.