Bifunctional NiCo/rGO Bimetallic Nanocomposites for Efficient Alkaline Hydrogen and Oxygen Evolution Reaction

Recently, efficient and robust electrocatalysts for alkaline HER and OER are essential for water splitting applications. In the present work, the combination of nickel (Ni) and cobalt (Co) bimetallic nanocomposites embedded on rGO were prepared by the solid-state sintering process. X-ray diffraction analysis shows a single face–centered–cubic metallic phase together with the (002) diffraction of reduced graphene oxide (rGO), consistent with the NiCo phase being supported on rGO. The field emission scanning electron microscopy analysis shows sub-micrometer metallic particles anchored on the layered rGO sheets in the NiCo/rGO bimetallic nanocomposite. The core-level spectrum of Ni and Co metals confirmed the existence of more oxidation on the surface of rGO. The NiCo/rGO bimetallic nanocomposites show an OER overpotential at 10 mA/cm² of 358 mV vs. RHE and a Tafel slope of 92 mV/dec. The HER overpotential is observed at 10 mA/cm² of −136 mV vs. RHE with a Tafel slope of 95 mV/dec. Both HER and OER stability analyses were performed for 25 h. Finally, full cell analysis of NiCo/rGO revealed that it requires 1.9 V to reach 10 mA/cm² and shows stable operation for 10 h. The present work paves the way for the formation of NiCo/rGO bimetallic nanocomposites for bifunctional electrocatalytic applications.