Bimetallic atomic Fe–Mn metal-nitrogen active sites for synergistic enhancement of CO2 electroreduction efficiency

Abstract

Electrocatalytic reduction of CO₂ is important for mitigating global warming and energy crisis, and the key to an economical and promising CO₂ conversion technology lies in the development of catalysts with high catalytic activity. Here, we report a N-doped carbon-based bimetallic single-atom catalyst (Fe/Mn–N–C) to improve the selectivity of electrocatalytic reduction of CO₂ products by combining with highly active iron-manganese bimetals. At the carbonation temperature of 800 ​°C and the Fe/Mn mass ratio of 1:2 in the precursor, the catalyst Fe/Mn–N–C was able to achieve a Faraday efficiency (FE) of 94% for CO in 0.1 ​M KHCO₃ electrolyte at an overpotential of −0.5 ​V (RHE), which was much higher than that of the Fe–N–C (40%), Mn–N–C (25%), and N–C (25%). And after 12 ​h of continuous catalysis, the FECO was still maintained at more than 80%, demonstrating the good stability of the Fe/Mn–N–C. X-ray absorption spectroscopy (XAS) results confirmed the diatomic dispersed M_xN_y active centers embedded in the exposed substrate of the carbon surface and their dispersion was confirmed by high angle angular dark field-scanning transmission electron microscopy (HAADF-STEM) with atomic resolution. Density functional theory (DFT) calculations showed that the reaction potential for COOH∗ formation and CO desorption was reduced by the synergistic effect of the adjacent Fe–Mn centers. This work provides a great possibility for the preparation of bimetallic single atom catalysts for efficient catalytic conversion of CO₂.