Mechanistic understanding on effect of doping nitrogen with graphene supported single-atom Fe toward electrochemical CO2 reduction: A computational consideration

Abstract

In this study, we constructed single-atom Fe materials (Fe-Nx-Cyv) as the electrocatalysts for CO2 electrochemical reduction reaction (CO2ERR) and examined the reduction mechanisms on the basis of periodic density functional theory computations. The adsorption strength of HCOO* and COOH* species is found to play an important role for CO2ERR. The formation of HCOO* on the Fe-C1v, Fe-N3-C1v, and Fe-C2v catalysts is much preferred than the COOH* formation resulting in the production of CH4 with limiting potentials of −0.41 V for the potential-determining step (PDS) of HCOOH* → H2COOH* on the Fe-C1v, −0.63 V for the PDS of HCO* → H2CO* on the Fe-N3-C1v, and −0.68 V for the PDS of H3CO* → O* + CH4(g) on the Fe-C2v. While the COOH* formation on the Fe-N4-C2v catalyst becomes more favorable leading to the production of CO with a limiting potential of −0.20 V for the PDS of CO2 → COOH*. In addition, nitrogen doping effect on the adsorption of important intermediates are also investigated. It is found that the adsorption of CO* and COOH* is enhanced that facilitates CO generation of CO2ERR on the Fe-N4-C2v. Therefore, Fe-N4-C2v materials is a promising single-atom catalyst for CO2 electro-reduction to CO.