Ni-reduced graphene oxide composite cathodes with new hierarchical morphologies for electrocatalytic hydrogen generation in alkaline media

Ni-reduced graphene oxide (rGO) composite cathodes were successfully prepared by composite electrodeposition under supergravity fields. The synthesized composite cathodes exhibit unique hierarchical structure with large numbers of Ni nanoparticles anchoring on the rGO surface. Specifically, the sample prepared from the electrolyte containing 0.7 g L-1 GO at rotational speed 3000 rpm displays a favorable activity toward the hydrogen evolution reaction (HER) in 1 M NaOH solution with a high exchange current density of 741.3 mu A cm(-2) and a low Tafel slope of 120 mV dec (-1). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetric (CV) tests demonstrate that the superior catalytic activity should be ascribed to the enhanced active surface area and the improved intrinsic activity. Furthermore, the morphology and microstructure properties of Ni-rGO cathodes synthesized from various GO concentrations and supergravity fields are systematically investigated.