Stepwise pyrolysis treatment as an efficient strategy to enhance the stability performance of Fe-NX/C electrocatalyst towards oxygen reduction reaction and proton exchange membrane fuel cell

Metal-nitrogen/carbon (M-NX/C) materials have been hailed as promising electrocatalysts toward oxygen reduction reaction (ORR). However, most reported promising Fe-NX/C catalysts are prohibited by their low stability in acidic media. Here we report a rational stepwise pyrolysis strategy for stabilizing isolated Fe-NX sites on highly graphitized N-doped carbon (NC) supports. The NC support derived from a harsh thermal treatment of 1100 °C can apparently enhance the graphitization degree of catalysts. The targeted catalyst, Fe-NX/C-NC1100 achieved a half-wave potential (E1/2) of 0.811 V and displayed superior stability in both ORR (only 25 mV loss of E1/2 after 30000 cycles) and fuel cell (71 % current retention at a voltage of 0.5 V after 100 h) tests. High graphitization degree of carbon support was responsible for the enhancement of stability, which empowers strong antioxidant ability to Fe-NX/C catalyst.