The enhancement in oxygen reduction reaction (ORR) activity is achieved by the introduction of Fe species via the Fe electrochemical deposition-dissolution treatment into a metal-free nitrogen-doped carbon (P-PI) catalyst, which is prepared by the pyrolysis of polyimide fine particles. The thus-obtained Fe-containing P-PI catalyst suffers activity decay during the durability test, evidenced by the negative shift of half-wave potential, the decrease in limiting current density, the number of electrons transferred, and the ratio of the rate constant for 4-electron ORR to that for 2-electron process, and the increase in H2O2 production percentage. The decayed ORR activity can be recovered by another Fe electrochemical deposition-dissolution treatment, demonstrating the predominant role of Fe leaching in activity degradation as well as the effectiveness of the electrochemical treatment in activity restoration. (C) 2016 Elsevier Ltd. All rights reserved.