Nickel Sulfide Synthesis Lab Report

Reduced graphene oxide functionalized structure controlled nickel sulfide (NiS, NiS2, Ni3S4) nanoparticles were synthesized using a temperature-controlled injection method. In single-solvent experiments oleylamine was used as solvent, in the case of multi-solvent oleylamine, oleic acid and octadecine were mixed together. The respective nickel sulfide phases were synthesized on the reduced graphene oxide (rGO) sheets through the single-step temperature controlled injection processes. The complications in the synthesis of rGO/nickel sulfide phases were overcome by adjusting the solvent and source concentrations. The x-ray diffraction and transmission electron microscopy were used to study the phase control of nickel sulfide on rGO supports. The

23 shows the UV-visible spectroscopy measurements for the reduction of 4-nitrophenol to 4-aminophenol. The reduction measurements of rGO/NiS, rGO/Ni3S2 and rGO/Ni3S4 were carried out and compared with pure NiS phase. The reduction of absorption peak at 400 nm was measured for about 30 min. The corresponding appearance of 4-nitrophenolate ion was observed from the peak position of 400 nm. The peak position of 293 nm was related to 4-aminophenol. For the same concentration of NaBH4 in 4-nitrophenol solution, rGO samples were tested. Fig. 23 (a) shows that the complete reduction of 4-nitrophenolate ions required about 300 s for the sample rGO/NiS phase of nickel sulfide. Similarly, for the nickel-rich phase of rGO/Ni3S2, reaction completed less than 500 sec and sulfur-rich phase of rGO/Ni3S4 were finished within 260 s. Fig. 24 shows the reduction rate percentage with respect to time for different materials. The reaction rate linearly increased with respect to time. The reduction rate constant (kobs) was calculated using the absorption values for the 4-nitrophenol reduction reaction.
K_obs=ln⁡[(A_∞-A_0)/(A_∞-A_t

The products were uniform-sized nanocrystals. Multi-solvent experiment was preferred to form structure controlled nickel sulfide on rGO supports. The injection method enabled the sulfur ions to react slowly with the well-dispersed nickel ions in the presence of multi-solvent, to form nickel sulfide nanoparticles on rGO. This enabled formation of the desired phase instead of mixed phases. The complications in the synthesis of rGO functionalized nickel sulfide nanoparticles were overcome by adjusting the solvent and source concentrations. XRD and TEM analyses confirmed the presence of single-phase nanoparticles of sizes less than 20 nm for all the synthesized products. The catalytic activities of the synthesized rGO/nickel sulfide nanoparticles were investigated and it was found that the rGO/NiS phase had the best