Large specific surface area S-doped Fe-N-C electrocatalysts derived from Metal-Organic frameworks for oxygen reduction reaction

YIt is highly desired but challenging to develop platinum group metal-free electrocatalysts for oxygen reduction reaction (ORR), which can promote the commercialization of fuel cell technology. To achieve this target, we report a one-step doping method to prepare S-doped Fe-N-C catalysts using zeolite imidazole framework (ZIF-8) and iron (III) thiocyanate (Fe(SCN)3) as precursor. Different from conventional doping approach, i.e. physical mixing, Fe(SCN)(3) is in-situ added during ZIF-8 formation which would encapsulate Fe(SCN)(3) molecules inside ZIF-8 to avoid structure destruction and create potential replacement of Zn ions by Fe ions to form uniform Fe-N-4 complexes. As a result, the prepared S-doped Fe-N-C catalysts own large specific surface areas with a maximum value of 1326 m(2) g(-1) and a dual-scale porous structure that benefits mass transport. Significantly, the composition-optimized catalyst exhibits superior ORR activity in both 0.1 M HClO4 electrolyte and 0.1 M KOH electrolyte, in which the half-wave potential reaches 0.81 V and 0.92 V (vs. RHE), respectively. Remarkable stability is also attained, which loses 2 mV only after 10000 potential cycles in O-2-saturated 0.1 M HClO4 and remains almost constant in O-2-saturated 0.1 M KOH, surpassing commercial Pt/C catalyst in both acidic and alkaline medium.