Highly coordinated Ni-N5 sites for efficient electrocatalytic CO2 reduction toward CO with faradaic efficiency exceeding 99%

Abstract

Electrochemical production of high value-added CO from CO2 on transition metal-nitrogen-carbon (M−N−C) catalysts is a promising approach to achieve carbon neutral economy, yet the quest for robust catalysts is driven by achieving > 96 % CO faradaic efficiency (FE) under low overpotential and wide potential range. Herein, we report a novel synthetic approach involving post-metallization of the pre-synthesized N-doped carbon (NC-T) support for the fabrication of robust and efficient Ni@NC-T quasi-molecular catalysts toward CO2 electroreduction reaction (CO2RR). The optimum Ni@NC-1100 catalyst exhibited an extremely high FECO > 99 % at −0.72 V vs. reversible hydrogen electrode (RHE). Of interest is the FECO maintained above 96 % over a wide potential window from −0.52 V to −1.12 V. Density functional theory (DFT) calculation validated that the presence of axial pyrrolic-N significantly enhances the Ni-N5 active site for CO2 activation, resulting in the lowest activation energy for the *COOH intermediate generation compared to other axial ligands.