Synergistic Electrocatalytic Hydrogen Evolution in Ni/NiS Nanoparticles Wrapped in Multi-Heteroatom-Doped Reduced Graphene Oxide Nanosheets

Hydrogen production is a key driver for sustainable and clean fuels used to generate electricity, which can be achieved through electrochemical splitting of water in alkaline solutions. However, the hydrogen evolution reaction (HER) is kinetically sluggish in alkaline media. Therefore, it has become imperative to develop inexpensive and highly efficient electrocatalysts that can replace the existing expensive and scarce noble-metal-based catalysts. Herein, we report on the rational design of nonprecious heterostructured electrocatalysts comprising a highly conductive face-centered cubic nickel metal, a nickel sulfide (NiS) phase, and a reduced graphene oxide (rGO) doped with phosphorous (P), sulfur (S), and nitrogen (N) in one ordered heteromaterial named Ni/NiS/P,N,S-rGO. The Ni/NiS/P,N,S-rGO electrode shows the best performance toward HER in 1.0 M KOH media among all materials tested with an overpotential of 155 mV at 10.0 mA cm-2 and a Tafel slope of 135 mV dec-1. The performance is comparable to the herein used Pt/C-20% benchmark catalyst examined under the same experimental conditions. The chronoamperometry and chronopotentiometry measurements have reflected the high durability of the Ni/NiS/P,N,S-rGO electrode for technological applications. At the same time, the current catalyst showed a high robustness and structure retention after long-term HER performance, which is reflected by SEM, XRD, and XPS measurements.