A density functional study on the oxygen reduction reaction mechanism on FeN2-doped graphene

The rational design of heteroatom doped graphene as a highly active and non-noble oxygen reduction reaction (ORR) electrocatalyst is significant for the commercial applications of the fuel cells. In this work, the catalytic activity for the ORR and the reaction mechanism on the surface of FeN2 doped graphene (FeN2-Gra) have been studied by using density functional theory. The results indicate that the ORR is a four-electron process on FeN2-Gra, similar to FeN3-Gra and FeN4-Gra. But FeN2-Gra shows quite different reaction mechanisms compared with FeN3-Gra and FeN4-Gra. For FeN2-Gra, the OOH hydrogenation to form OH + OH is the kinetically most favorable pathway, in which the O-2 hydrogenation to form OOH is the rate-determining step with an energy barrier of 0.47 eV. This energy barrier is smaller than 0.56 eV for FeN4-Gra, and much smaller than 0.87 eV for FeN3-Gra and 0.86 eV for pure Pt. The predicted working potential is 0.18 V. FeN2-Gra also has better capability of resisting CO poisoning compared with pure Pt. Consequently, the FeN2-Gra is a good ORR catalyst.