Air-Stable N-Heterocyclic Carbene Functionalised Copper-Gold Core-Shell Nanoparticles for CO2RR Catalysis

N-heterocyclic carbenes (NHCs) offer a robust alternative to thiol ligands for stabilising and functionalising metal nanoparticles, particularly for catalytic applications, such as the electrochemical reduction of CO2 (CO2RR). Copper nanoparticles are attractive CO2RR electrocatalysts, with notable selectivity towards C2+ products, but suffer from competing hydrogen evolution and rapid oxidation under ambient conditions. Here, we report a bottom-up synthesis of 9 nm copper-gold core-shell nanoparticles (CSNP) with an ~2 nm gold shell, prepared by reducing an NHC-Au complex on pre-formed copper seeds. The resulting samples, denoted as IC12@CSNP and IC12@CSNPNHC, were characterised by X-ray Photoelectron Spectroscopy (XPS) and Surface-Enhanced Raman Spectroscopy (SERS), confirming surface binding of IC12 ligands. Scanning Transmission Electron Microscopy (STEM) and High-Resolution Transmission Electron Microscopy (HRTEM) verified the distinct gold shell and copper core. The gold shell preserves the metallic copper oxidation state even under air exposure. Both IC12@CSNP and IC12@CSNPNHC exhibit electrocatalytic activity for syngas production via CO2RR, with the H2:CO ratio tunable from 0.5:1 to 3.5:1 by varying the applied potential. This work demonstrates a strategic route to stable, NHC-functionalised copper-gold core-shell nanoparticles, offering a versatile platform for future CO2RR catalyst design.