Solvent dependent in situ growth of NixSy supported on nickel foam as electrocatalysts for oxygen evolution reaction

In situ growth of NixSy on nickel foam (NixSy/NF) has been investigated by hydrothermal or solvothermal process in water, ethanol and their mixture. XRD shows that the obtained NixSy is consisted of Ni3S2 and NiS in the three solvents. NixSy synthesized in ethanol has weaker peak intensities and more NiS planes, implying lower crystallinity and different electrocatalytic properties from the other two smaples. SEM images confirm regular morphology transform of NixSy/NF affected by different solvents. Nanorods and polyhedron structure of NixSy can be observed in water and ethanol, respectively. For mixture solvents, obvious transition morphology including some nanorods and polyhedron structures can be observed. Electrochemical measurements for oxygen evolution reaction (OER) reveal that NixSy/NF synthesized in ethanol has the earliest onset potential (1.24 V vs. RHE) and the largest current density, which may be derived from different crystal structure and morphology of NixSy. Therefore, the solvent dependent activity may provide a new way to prepare excellent electrocatalysts for OER.