Solution Combustion Synthesis of NiS-NiS₂ Nanoparticles for Catalytic Reduction of Nitro Aromatics

Exploring an efficient and economic reductant for nitro aromatics is of great significance for environmental remediation. In this work, nickel sulfide catalysts have been prepared by simple solution combustion method from a mixture of nickel(II) nitrate hexahydrate as oxidant (O) and thiourea as fuel (F) in different ratios. The phase and crystallinity, composition and morphology of synthesized samples were obtained by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and Fourier transform infrared (FTIR) techniques. The catalytic efficiency of as synthesized nickel sulfide nanoparticles towards reduction of 4-nitrophenol (4-NP) as a model compound using sodium borohydride as the reducing agent was explored. The catalyst prepared with 1 : 3 O/F ratio that composed of NiS and NiS2 phases exhibited highest efficiency towards catalytic reduction of 4-NP and the rate constant was found to be 0.429 min(-1). Further, the catalyst could effectively reduce the nitro group in 2-nitroaniline, 4-nitroaniline and picric acid also. Reduced products of 2-nitroaniline and 4-nitrophenol were employed for the synthesis of benzimidazole and paracetamol successfully.