Preparation of MoS2-Graphene-NiO@Ni foam composite by sol coating for (photo)electrocatalytic hydrogen evolution reaction

Ni foam was first preoxidized by hydrogen peroxide to form a thin NiO layer, and subsequently deposited with graphene and molybdenum disulfide (MoS2) by a facile sol assisted dip-coating method to obtain MoS2-Graphene-NiO@Ni composite. XRD, SEM, TEM, HRTEM, and XPS measurements were performed to analyze the crystal phase, morphology, and surface elemental chemical states of the as-prepared MoS2-Graphene-NiO@Ni composite. The results show that MoS2 nanosheets and graphene were well dispersed on the surface of the preoxidized Ni foam with intimate interfacial contact. The electrocatalytic hydrogen evolution reaction (HER) performance of the Ni foam based electrocatalysts were tested in concentrated alkaline aqueous electrolyte (1 M KOH). Compared with bare Ni foam, NiO@Ni and MoS2-NiO@Ni sample, the MoS2-Graphene-NiO@Ni electrode delivered superior HER performance with a lower overpotential of 150 mV at 10 mA cm−2, a smaller Tafel slope of 80 mV dec−1, and a charge transfer resistance (Rct) of 15.14 Ω. Under simulated sunlight irradiation (150 W Xenon lamp with AM 1.5 optical filter), the overpotential and Tafel slope of the MoS2-Graphene-NiO@Ni composite was further slightly reduced. The enhanced HER performance of the MoS2-Graphene-NiO@Ni composite is dominantly attributed to the synergistic effect of preoxidized Ni foam substrate, high conductive graphene and electrocatalytic active MoS2.