Engineering the Local Coordination Environment and Density of FeN 4 Sites by Mn Cooperation for Electrocatalytic Oxygen Reduction.

Single atom sites (SAS) of FeN 4 are clarified as one of the most active components for the oxygen reduction reaction (ORR). Effective strategies by engineering the local coordination environment and site density of FeN 4 sites are crucial to further enhance the electrocatalytic ORR performance. Herein, the integration of a second metal of Mn with Fe to construct Fe&Mn/N-C catalysts with enhanced density of FeN 4 active sites and modulated electronic structure is reported. The formation of MnN 4 centers modulates the local environment of FeN 4 sites and reserves more FeN 4 embedded in carbon substrate by forming the possible FeN 4 -O-MnN 4 configurations. Density functional theory calculations demonstrate that the overall energy barrier of ORR is decreased over the FeN 4 -O-MnN 4 moieties. Therefore, the Fe&Mn/N-C catalyst exhibits enhanced ORR performance both in alkaline and acidic solution (half-wave potentials are 0.904 and 0.781 V). This work provides an effective strategy by modulating the local electronic structure and density of FeN 4 active sites to improve the ORR activity and stability through Mn cooperation.