Nanosheet-like Ternary Metal Sulfide as a pH-Universal Catalyst for the Hydrogen Evolution Reaction

A ternary nickel-cobalt-molybdenum-based sulfide nanosheet-like catalyst supported on Ni foam (Ni-Co-Mo-S/NF) is synthesized by a hydrothermal method. This catalyst shows superior performances of the hydrogen evolution reaction in both acidic and alkaline media. In an acidic medium (0.5 M H2SO4), the catalyst requires a very low overpotential of 63 mV at a current density of 10 mA cm–2 (η10), with a Tafel slope of 46.7 mV dec–1, which is even comparable to the noble platinum catalyst. This catalyst also shows excellent activity in an alkaline medium (1 M KOH) and delivers a Tafel slope of 122.6 mV dec–1, and η10 of 92 mV. The high activity is further verified by electrochemical impedance spectroscopy and electrochemical surface area measurements. The roles of the three metal elements (Ni, Co, and Mo) in the Ni–Co–Mo–S/NF catalyst are investigated by X-ray photoelectron spectroscopy. This work produces a good pH-universal catalyst for water-splitting processes and demonstrates a facile vulcanization method for developing ternary metal catalysts.