Pyrrolic nitrogen coordinated Ni2+ dual-atom catalyst for boosting CO2 electroreduction

Abstract

Nitrogen-doped carbon materials have been widely used for the constructions of single-atom catalysts, while the effect of different species of doped nitrogen on the catalytic activity of CO₂ electroreduction has rarely been investigated. Here we found that pyrrolic-N coordinated Ni²⁺ catalysts display much higher electrocatalytic CO₂-to-CO activity and selectivity than the corresponding pyridinic-N coordinated low valent Ni⁽⁰⁻⁺²⁾ catalysts, and pyrrolic-N coordinated Ni₂ dual-atoms catalyst of Ni₂/N-CNTs exhibits the best electrocatalytic performance, with over 90% Faradaic efficiencies in a broad potentials from −0.6 to −1.2 V vs. reversible hydrogen electrode, as well as an outstanding CO specific current of 56.2 A/mg_Ni and high turnover frequency of 6.2 × 10⁴ h⁻¹, over 7-times higher than those of pyridinic-N coordinated Ni catalysts. Electrochemical results indicate the weak electron-donor nature of pyrrolic-N facilitates the generation of a reduced active site at low overpotential for boosting CO₂ electroreduction. Density functional theory calculations reveal that the reaction free energy for the *COOH formation on pyrrolic-N coordinated Ni catalysts are lower than those on pyridinic-N coordinated Ni catalysts, and a H₂O-adsorbed Ni₂/N-CNTs displays the optimized reaction free energy for both *COOH formation and CO desorption, which derive the best catalytic performance.