NHC-CDI ligands boost multicarbon production on Cu electrocatalysts by increasing the accumulated surface charge and promoting *CO dimerization

Copper-based materials have shown significant potential as catalysts for the electrochemical CO2 reduction reaction (CO2RR) due to their inherent ability to produce multicarbon products. The functionalization of Cu electrodes with organic additives represents a simple yet powerful strategy for improving the intrinsic activity of these electrocatalysts by tailoring the microenvironment around the Cu active sites to favor specific reaction pathways. In this work, we introduce NHC-CDI-functionalized Cu catalysts, which demonstrate a remarkable increase in activity for multicarbon product formation, surpassing bare Cu electrodes by more than an order of magnitude. These hybrid catalysts operate efficiently in a gas diffusion configuration, achieving a multicarbon product selectivity of 58% with a partial current density of −80 mA/cm2. Using modified pulsed voltammetry measurements, we found that the activity for multicarbon product formation is closely linked to the surface charge that accumulates during electrocatalysis, resulting from the buildup of CO2RR intermediates. We further supported our findings with in situ Raman spectroscopy measurements, which unveiled a preference for car- bon monoxide binding on Cu step sites, which are known to promote C─C coupling, in the best-performing hybrid catalysts. Additionally, we observed a general preference for atop- bound *CO intermediates over bridge-bound ones in the molecularly functionalized catalysts. Our study underscores the significant potential of molecular tuning in developing efficient electrocatalysts for CO2 reduction and emphasizes the utility of surface charge as a descriptor of multicarbon product activity.