N-Heterocyclic Carbene Coordinated Cu Single Atoms on Poly(ionic Liquid) for Selective Electroreduction of CO2 to CH4 at High Current Density

Finely adjusting the local environment of Cu single atom (SA) is crucial but challenging for the fabrication of electrocatalysts for the CO2 reduction reaction (CO2RR) to produce clean energy methane (CH4). Herein, poly(ionic liquid)s-stabilized Cu SAs with tunable Br-Cu-C-x configuration were directly synthesized through the self-polymerization of the ionic liquid monomer, a bis-vinylimidazolium salt, in the presence of Cu precursor. Synchrotron X-ray absorption fine structure, soft X-ray absorption, and X-ray photoelectron spectroscopy analyses showed that the Cu SAs were coordinated with N-heterocyclic carbene derived from the imidazole ring. The optimal catalyst Cu@P-2 with moderate Cu loading afforded a high Faradaic efficiency of similar to 70% at a high current of -250 mA cm(-2) in the CO2RR to CH4, associating with a turnover frequency as high as 1.0 s(-1.) This outstanding performance is assigned to the high density Cu SAs reaching strong affinity towards *CO intermediates in the case of moderate Cu loading, as revealed by in situ attenuated total reflection surface-enhanced infrared absorption spectroscopy analysis and theoretical calculated free energy profiles of CO2 RR to CH4.