NiS-FeS/N, S co-doped carbon hybrid: Synergistic effect between NiS and FeS facilitating electrochemical oxygen evolution reaction

A series of NiS-FeS/N, S co-doped carbon (NixFey-S/NSC) for electrochemical oxygen evolution reaction (OER) were synthesized by a co-precipitation method and followed by pyrolysis in N-2 atmosphere. NiS-FeS hybrid was uniformly integrated with N, S co-doped carbon in NixFey-S/NSC. NixFey-S/NSC showed high OER catalytic activity, and the optimized Ni60Fe40-S/NSC afforded an OER overpotential of similar to 239 mV to deliver a current density of 10 mA cm(-2) and showed a corresponding Tafel slope of similar to 30.9 mV dec(-1) in 1 M KOH. Such OER catalytic activity was not only higher than that of IrO2, but also comparable with that of the most recently reported NiFe-based sulfides for OER. Further study indicated that hybridizing NiS with FeS resulted in a synergistic effect for OER. The hybridization increased total amount of sulfides as active species, therefore enhancing the OER catalytic activity. In addition, the hybridization benefited the formation of petal-like morphologies that contributing much to higher electrochemically active surface area (ECSA), and also boosted the content of graphitic and N, S co-doped carbon that improving charge transfer efficiency.