A Mn single atom catalyst with Mn–N2O2 sites integrated into carbon nanosheets for efficient electrocatalytic CO2 reduction

Abstract

The electrocatalytic reduction of CO₂ using electricity produced from renewable resources is a strategy for achieving CO₂ emission reduction and sustainable energy development. Further, the reaction has a large number of industrial practical applications, since CO₂ can be converted to fuels via downstream chemical processing of the CO product. Herein, we successfully synthesized a low Mn-content single-atom catalyst (SAC) with Mn–N₂O₂ sites, covalently integrated into carbon nanosheets (Mn–NO/CNs) using a one-pot synthesis method. The Mn–NO/CN catalyst displays efficient electrocatalytic performance for the CO₂ reduction reaction (CO₂RR). Using an H-type electrolytic cell, the maximum CO Faraday efficiency (FE) at −0.460 V (V vs. RHE) reaches 96.0% in 0.5 M KHCO₃ electrolyte. In the flow cell measurements, Mn–NO/CNs exhibits a current density of 28 mA cm⁻² at a very low potential of −0.425 V (V vs. RHE) for the CO₂RR with 1.0 M KOH as the mobile phase. The FE_CO remains above 80% even after 70 h, demonstrating the excellent durability of the catalyst even at a very low potential. The X-ray absorption spectra (XAS) and DFT calculations show that the Mn–N₂O₂ site is the active catalytic center, which facilitates the adsorption of CO₂ and significantly lowers the free energy barrier leading to the formation of the critical intermediate *COOH. The presence of dual N and O coordinated to the single atom metal sites embedded in the 2D carbon nanosheet significantly improves catalytic activity for the reduction of CO₂. Therefore, the catalytic performance of the single atom metal catalyst can be enhanced by adjusting the coordination environment.