Effect of calcination temperature on NiO for hydrogen gas sensor performance

In this work, we have synthesized the nickel oxide (NiO) nanopowders via twofold facile solvothermal synthesis. Later, the products are calcined at 300 °C, 400 °C, and 500 °C in an air atmosphere to form NiO nanopowders, which are deposited onto the SiO2/Si substrate via the spin coating technique. The morphological studies depict the high porosity at 400 °C calcinated NiO thin film than other conditions. Further, the Brunauer-Emmett-Teller (BET) surface analysis reveals that at 400 °C calcinated NiO sample exhibits a higher surface area of 52.3 m2g-1 due to the existence of porous grain-like surface morphology. To examine the gas sensing performance, Ag/NiO/Ag hydrogen gas sensor device is fabricated by depositing planar-type silver (Ag) electrodes onto the NiO thin film via thermal evaporation technique. The gas sensing behaviour of the fabricated gas sensor test-devices has been examined at various operating temperatures (100 °C–300 °C) and concentrations (100 ppm–300 ppm). The hydrogen gas sensor test-device fabricated using NiO nanopowder calcined at 400 °C shows good crystalline nature, a highly porous surface with efficient oxygen vacancies, and narrowed bandgap, which results in the maximum responsivity of 97.2% at the operating temperature of 250 °C with response and recovery time of 56 s and 21 s, respectively. Therefore, the Ag/NiO/Ag gas sensor test-device can be a potential route toward the development of hydrogen gas sensor devices.