Theoretical Insights into Nitrogen-Doped Graphene-Supported Fe, Co, and Ni as Single-Atom Catalysts for CO₂ Reduction Reaction

Abstract

Using single-atom catalysts for the electrochemical reduction of carbon dioxide is a promising method for excess renewable electricity as chemical energy in fuels. In this study, we have investigated single non-noble metal atoms supported on nitrogen-doped graphene (M-N4@Gr, where M = Fe, Co, Ni) as catalysts for the electrocatalytic reduction of CO2 using first-principles density functional theory and the computational hydrogen electrode model. The results show that HCOOH is the preferred product of CO2 reduction on the Ni-N4@Gr catalyst with an overpotential of 1.511 V, while Fe-N4@Gr and Co-N4@Gr prefer to reduce CO2 to CH4 with the overpotential of 0.877 and 0.687 V, respectively. The computational results revealed that the coordination environment affects d orbital occupations, leading to a difference in the spin polarization of the systems and thus affecting the performance and selectivity of catalysts. Our work may pave the way for extending single non-noble atom catalysts, which consist of earth-abundant elements, toward electrocatalytic CO2 reduction reaction by regulating coordination environments.

Theoretical Understanding of Potential-Dependent Electrocatalytic CO2RR and Competition with HER upon Cobalt Single Atom Supported by Phthalocyanine Monolayer

“…After identified the physical meaning of the ΔΩ­(eV)– U (V) slope, we also calculated the HER competition upon other reported heterogeneous catalysts, ,,, including Cu(211), Ag(110), iron doped in 2D phthalocyanine (Fe-Pc), cobalt in 2D porphyrin (Co–Pr), and cobalt doped in nitrogen-doped (4N) graphene (Co-Gra@N4), shown in Figure b and Figure S9. Generally, larger electron transfer can be observed in *H formation (larger (ΔΩ– U ) slope) than CO 2 chemisorption; thus, these catalysts will show the coverage crossover as discussed above, HER will also completely suppress CO 2 RR at high applied potential, the current dilemma of realization of industrial electrocatalytic CO 2 RR.…”

Spontaneous FeIII/FeII redox cycling in single-atom catalysts: Conjugation effect and electron delocalization

“…During the interaction between the adsorbate (PMS) and iron center, delocalized electrons accepted by 3d orbitals of Fe from the ligand are further back-donated to the lowest unoccupied molecular orbital. 62 The adsorbed PMS are therefore activated for the generation of radicals by accepting the electrons. For an in-depth assessment of the synergism between the iron center and ligands for spontaneous Fe III /Fe II redox cycling, the ligand-field theory was employed.…”

Influence of the molecular structure of metal-phthalocyanine on electrocatalytic reactions

“…NiPc functionalized with NH 2 , a representative electron-donating group, shows improved adsorption of CO 2 at active sites and better CO 2 reduction efficiency of 99.8% compared with the pristine NiPc. The functional group donates electrons to the Ni center with an interior inductive effect, leading to a higher degree of electron localization [30,31]. The primary step for the CO 2 RR is the reduction from CO 2 to CO.…”