Recently, binuclear transition-metal-doped
carbon materials have attracted particular interest because of the
enhanced catalytic activity. Herein, a series of homonuclear (M2, M = Mn–Cu) and heteronuclear (FeM, M = Mn–Cu)
binuclear transition-metal and nitrogen codoped graphene (M2N6/FeMN6-Gra) has been investigated based on
the density functional method. The calculated formation energies and
molecular dynamics simulations indicate that these catalysts are stable
thermodynamically. Scaling relationships, that is, ΔG
*O versus ΔG
*OH, ΔG
*O versus ΔG
*OOH, and ΔG
*OH versus
ΔG
*OOH, are obtained. Interestingly,
there is a strong linear relationship for overpotential and the electronegativity
difference (between Fe and another metal). Volcano plots, that is,
ΔG
*O versus equilibrium potential,
ΔG
*OH versus overpotential, and
d band center versus overpotential, are established. The results show
that FeMN6-Gra (M = Co, Fe and Ni) has high catalytic activity.
This means that ΔG
*O, ΔG
*OH, and the d band center are good descriptors
to evaluate the oxygen reduction reaction (ORR) activity. For FeCoN6-Gra, the working potential is 0.97 V and energy barrier is
0.34 eV in the rate-determining step, which are better than those
of Pt (0.78 V and 0.80 eV). These results suggest that binuclear transition-metal
and nitrogen codoped graphene are good ORR catalysts and further study
toward this direction would provide a novel method for the development
of high efficient electrocatalysts.
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