Direct formation of copper nanoparticles from atoms at graphitic step edges lowers overpotential and improves selectivity of electrocatalytic CO₂ reduction

A key strategy for minimizing our reliance on precious metals is to increase the fraction of surface atoms and improve the metal-support interface. In this work, we employ a solvent/ligand/counterion-free method to deposit copper in the atomic form directly onto a nanotextured surface of graphitized carbon nanofibers (GNFs). Our results demonstrate that under these conditions, copper atoms coalesce into nanoparticles securely anchored to the graphitic step edges, limiting their growth to 2–5 nm. The resultant hybrid Cu/GNF material displays high selectivity in the CO₂ reduction reaction (CO₂RR) for formate production with a faradaic efficiency of ~94% at -0.38 V vs RHE and a high turnover frequency of 2.78 × 10⁶h^-1. The Cu nanoparticles adhered to the graphitic step edges significantly enhance electron transfer to CO₂. Long-term CO₂RR tests coupled with atomic-scale elucidation of changes in Cu/GNF reveal nanoparticles coarsening, and a simultaneous increase in the fraction of single Cu atoms. These changes in the catalyst structure make the onset of the CO₂ reduction potential more negative, leading to less formate production at -0.38 V vs RHE, correlating with a less efficient competition of CO₂ with H₂O for adsorption on single Cu atoms on the graphitic surfaces, revealed by density functional theory calculations.