In situ Growth of Phase-Controlled Nickel Sulfide Nanostructures on Reduced Graphene Oxide Nanosheets : A Improved Cost-effective Catalyst for 4-Nitrophenol Reduction

Reduced graphene oxide (rGO)-functionalized nickel sulfide nanoparticles were synthesized using a temperature-controlled injection method. Syntheses were carried out in single (oleylamine) and mixed (oleylamine, oleic acid, and octadecene) solvents. Phase-controlled NiS, NiS2, or Ni3S4 nanocrystals were decorated on rGO sheets through the single-step temperaturecontrolled injection processes. Problems with the synthesis of rGO/nickel sulfide yielding mixed phases were overcome by adjusting the solvent mixture and source concentrations. X-ray diffraction and transmission electron microscopy were used to study the crystal structures and phases of nickel sulfide on the rGO sheets. The catalytic performances of rGO/nickel sulfide structures containing different nickel sulfide phases were analyzed by measuring the degradation rate of 4-nitrophenol. Catalytic activity of as synthesized rGO/NiS, rGO/NiS2 and rGO/Ni3S4 were higher activity than pure NiS, among them rGO/NiS was showed better activity than those of rGO/NiS2 and rGO/Ni3S4.