Large specific surface area S-doped Fe–N–C electrocatalysts derived from Metal–Organic frameworks for oxygen reduction reaction
Xiaohui Yan, Xiaolin Li, Cehuang Fu, Chen Lin, Huanming Hu, Shuiyun Shen, Guanghua Wei, Junliang Zhang
Abstract
It 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–N4 complexes. As a result, the prepared S-doped Fe–N–C catalysts own large specific surface areas with a maximum value of 1326 m2 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 O2-saturated 0.1 M HClO4 and remains almost constant in O2-saturated 0.1 M KOH, surpassing commercial Pt/C catalyst in both acidic and alkaline medium.