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 MxNy 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.