Hierarchical NiCo2S4 nanosheets grown on graphene to catalyze the oxygen evolution reaction

Efficient transition metal-based electrocatalysts for oxygen evolution reaction (OER) are vital for water splitting to make H-2 fuel. Here, the hierarchical NiCo2S4 nanosheets/reduced graphene oxide (NiCo2S4/RGO) architecture composite was designed and synthesized. The constitution and morphology of NiCo2S4/RGO composites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscope and transmission electron microscope. Then, the electrochemical performance of as-prepared NiCo2S4/RGOs for OER was studied. The optimal composite (NiCo2S4/RGO-2) exhibited the best improved compared to raw NiCo2S4 on OER performance, which afforded a small overpotential (366 mV at current density of 10 mA cm(-2)) and a low Tafel slope of 65 mV dec(-1) and good stability in 1.0 M KOH electrolyte. The hierarchical architecture of the NiCo2S4/RGO system endows more active sites and enhances charge transfer. This work provided a general strategy to design more efficient NiCo-based chalcogenide OER electrocatalysts.