Direct Deposition of Copper Atoms onto Graphitic Step Edges Lowers Overpotential and Improves Selectivity of Electrocatalytic CO2 Reduction

Abstract

Minimizing our reliance on bulk 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 remarkable electrocatalytic properties in CO₂ reduction reaction (CO₂RR), exhibiting selectivity for formate production with a faradaic efficiency of ~ 94% at a low overpotential of 0.17 V and an exceptionally high turnover frequency of 2.78×10⁶ h^− 1. The Cu nanoparticles adhered to the graphitic step edges significantly enhance electron transfer to CO₂, with the formation of CO₂∙− intermediate identifiedas the rate-determining step. 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 disfavour CO₂RR, as confirmed by density functional theory calculations, revealing that CO₂ cannot effectively compete with H₂O for adsorption on single Cu atoms on the graphitic surfaces.