Low temperature solventless syntheses of nanocrystalline nickel sulfides with different sulfur sources

• Nanostructured NiS with controllable composition were produced by solventless method.
• Very pure nanocrystalline h-NiS could be formed using thiourea as sulfur source.
• Only pure nanocrystalline NiS2 was produced using elemental sulfur as sulfur source.
• The method is new, one step, low cost and scalable.

This work describes a novel synthesis for the production of very pure nanocrystalline hexagonal nickel sulfide phase (h-NiS) by the solventless route in air at temperatures of only 190 °C. Only the cubic NiS2 nickel sulfide phase is obtained when the sulfur source reacting with the nickel acetate powder (NiAc) is switched from thiourea (TU) to elemental sulfur (SN). When using both TU and SN sulfur sources, phase mixture of h-NiS, NiS2 and Ni3S4 with less aggregated particles was obtained. Relative concentrations of the phases were quantified by the Rietveld refinement of the XRD powder patterns. The thermal evolution of stoichiometric reagents mixture was observed by TG-FTIR and DSC curves.