In-situ synthesis of carbon-coated β-NiS nanocrystals for hydrogen evolution reaction in both acidic and alkaline solution

The electrocatalytic hydrogen evolution reaction (HER) performance of carbon-coated β-NiS (NiS@C) nanocrystals has been investigated for the first time. The NiS@C nanocrystals were synthesized via a facile solvothermal method followed by in-situ carbonization process with the solvent (ethylene glycol) as the carbon source. Benefited from the well-dispersed NiS nanocrystals and the formation of carbon layer on NiS nanocrystals, the NiS@C nanocrystals displayed a high HER activity in 0.5 M H2SO4, which needed an overpotential of 85 mV to achieve current density of 10 mA cm−1 with a Tafel slope of 46 mV dec−1, as well as long term stability for HER. Additionally, the NiS@C nanocrystals also showed efficient electrocatalytic activity under alkaline media.