Low-temperature controlled synthesis of Ni 3 S 4 /NiS 2 composite powder in deep eutectic solvent

Ni 3 S 4 /NiS 2 composite powder with controllable morphology and proportion is synthesized without using any surfactant in choline chloride-ethylene glycol (ChCl-EG) deep eutectic solvent (DES) at 120 °C. The products are characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) to reveal the effects of reaction time, and reactant concentration on their composition and structure. The reaction mechanism for synthesizing Ni 3 S 4 /NiS 2 in ChCl-EG DES is also elaborated. The results show that different proportions of wrinkled, lamellar and layer-rolled Ni 3 S 4 /NiS 2 can be obtained by controlling the concentration of NiCl 2 ·6H 2 O and Na 2 S 2 O 3 ·5H 2 O. The analysis found that the reaction mechanism of Ni 3 S 4 /NiS 2 is Ni(II) reacting with S 2 O 3 2− and H 2 O to form Ni 3 S 4, NiS 2, SO 4 2−, and H +. The NMR hydrogen spectrum ( 1 H NMR), NMR carbon spectrum ( 13 C NMR) and FT-IR tests of ChCl-EG indicate that it is structurally stable, and acted as a solvent and template during the reaction process.