High-Throughput Calculation Investigations on the Electrocatalytic Activity of Codoped Single Metal-Nitrogen Embedded in Graphene for ORR Mechanism

摘要

Two types of single metal atoms embedded in graphene were investigated as a potential electrocatalyst for oxygen reduction reaction (ORR) for the application in a fuel cell. ORR was considered in the four elementary reaction steps of oxygen hydrogenation, perhydroxyl production, atomic oxygen hydrogenation, and final water form. All calculations of catalytic activity were performed with the Vienna Ab Initio Simulation Package (VASP) on an M@Gra (M = Mn, Fe, Co, and Ir)-embedded structure, indicating that high-efficiency catalytic activity in the oxidation reaction takes place on the top of metal atom sites. Our calculations revealed that ORR is profiled via four-electron transfer pathway. Activity of these catalysts is closely related to the same scaling linear relations between the adsorption energies of the ORR intermediates on different catalytic surfaces; this can improve their catalytic activity for O-2 reduction through a high-efficiency 4e reaction path. Mn- and Ir-doped of cell A graphene exhibited excellent ORR catalytic performance in case of their small overpotential (less than 0.23 V) and low-energy barrier (less than 0.64 eV) of the Ir-doped graphene rate-determining step. Mn@Gra and Fe@Gra of cell B monolayers showed poor ORR catalytic performance due to the strong interaction between various ORR-involved species. Based on the free energy change and activation energy of each intermediate reaction in ORR, Fe@Gra and Ir@Gra are promising catalysts for ORR processes in fuel cells. This provides useful guidance for different types of catalysts in applications to fuel cells.