Microwave-assisted synthesis of bifunctional multiphase nickel sulfide (Ni-S) and NiCo2S4 electrocatalysts for water splitting

Abstract

Water splitting into hydrogen and oxygen with non-noble and efficient electrocatalysts is crucial for green energy demands. The transitional metal-based sulfides are owing to the interest due to their high activity in electrochemical processes, low cost, and earth abundance. Herein, we report the bi-functional catalytic performance of multiphase Nickel Sulfide NiS2 and Ni9S8 (Ni-S) and Nickel Cobalt Sulfide (NiCo2S4), synthesized with the one-step microwave-assisted (MWA) method, for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The flower-like nanosheets of Ni-S show effective HER performance at a low overpotential 152 mV at 50 mA cm-2, because of the surface morphology and electron adsorption ability. Furthermore, the bimetallic nanospheres of NiCo2S4 give a high current density of 160 mA cm-2 at 275 mV overpotential for OER, because of the incorporation of nickel and cobalt species by stabilizing the sulfur phase for further improved activity and charge transfer capacity. Moreover, the NiCo2S4 has faster reaction kinetics with a low Tafel slope of 76 mV dec‑1 for OER and 37 mV dec‑1 for HER, rather than the Ni-S at 167 mV dec‑1 and 65 mV dec‑1 respectively. © 2025 Elsevier Ltd