N-heterocyclic carbenes (NHCs) are excellent ligands that bind to a variety of transition metals with extremely high binding strength via σ donation. In my talk, I will highlight the use of two polymeric N-heretocyclic carbenes (NHC) (polydentate and monodentate) to stabilize metal nanocatalysts (Au and Pd) for efficient CO₂ electroreduction in aqueous solution. Compared with other conventional ligands including thiols and amines, metal-NHC bonds are stable under reductive potentials prevent the nanoclustering of nanoparticles, which is of key importance for any practical application. In particular, Au nanocatalysts modified by polymeric NHC ligands show an activity retention of 86% after CO₂ reduction at -0.9 V for 11 h, while it is less than 10% for unmodified Au. We demonstrate that the hydrophobicity of polymer ligands and the enriched surface electron density of metal NPs through σ-donation of NHCs substantially improve the selectivity for CO₂ reduction over proton reduction. As a passive coating on the surface of metal nanocatalysts, NHC-terminated polymers can control the accessibility of substrates, i.e., CO₂ vs. H₂O, as a means to improve the Faradic efficiency toward CO₂ reduction. Our results provide guideline to improve catalytic efficiency and stability of metal nanocatalysts for CO₂ electroreduction and, more generally, as cathodic materials for other electroreduction reactions.