New low-temperature preparations of some simple and mixed Co and Ni dispersed sulfides and their chemical behavior in reducing atmosphere

A series of simple (CoS2, Co9S8, NiS2, NiS, Ni3S2) and mixed sulfides (NiCo2S4, Ni0.33Co0.67S2, Ni3Co6S8, CuCo2S4, Cu0.33Co0.67S2) was prepared using low-temperature procedures. To obtain the mixed sulfides, the mixtures of the solutions of the corresponding salts were precipitated by Na2S and then heated in a sulfiding atmosphere at 300 degreesC. It has been found that the product phase composition depends on the sulfiding atmosphere. Using a H2S/Ar mixture leads to pyrite type sulfides, whereas treatment in H2S/H-2 flow allowed the preparation of Ni-Co and Cu-Co thiospinels. The as prepared highly dispersed single-phase materials were characterized by X-ray powder diffraction, scanning electron microscopy, temperature-programmed reduction (TPR), elemental analysis, and BET surface area measurements.