Synthesis and hydrogen gas sensing properties of pure NiS and Au-coated NiS

NiS nanostructures were synthesized using a microwave-assisted wet chemical hydrothermal technique. XRD analysis of the product obtained after washing the product and drying it at 90°C for 6 hours confirmed that α-NiS and β-NiS phases were formed. Au nanostructures were deposited on the surface of the NiS product via a microwave-assisted impregnation technique. H₂ gas sensitivity of NiS or Au/NiS was measured by recording a change in resistance of the sample with time in the presence and absence of the analyte gas, at 300°C. The materials were exposed to H₂ gas of different flow rates relative to N₂ gas flow. Fast response due to reduced H₂ gas flow over similar time intervals was observed which was suggestive of a reliable sensing behavior of the Au/NiS material. Post sensing phase analysis of the materials showed that NiS phase was reduced to the more stable phase of nickel sulfide (Ni₃S₂).