Improved Oxygen Reduction Activity in Heteronuclear FeCo-Codoped Graphene: A Theoretical Study

Recently, binuclear transition-metal-doped carbon materials have attracted particular interest because of the enhanced catalytic activity. Herein, a series of homonuclear (M-2, 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, Delta G(*O) versus Delta G(*OH), Delta G(*O) versus Delta G(*OH), and Delta G(*OOH) versus Delta G(*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, Delta G(*O) versus equilibrium potential, Delta G(*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 Delta G(*O), Delta G(*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.