Hydrogen sensors fabricated with sprayed NiO, NiO:Li and NiO:Li,Pt thin films

Hydrogen sensors have been prepared using NiO, NiO:Li and NiO:Li,Pt thin films deposited on alumina substrates by chemical spray deposition. X-ray diffraction indicates grain sizes of the order of 60 nm, which are in agreement with HRSEM images. The electrical response to hydrogen was studied at different work temperature (250 °C–450 °C) and at different hydrogen concentrations (3000–30,000 ppm). The NiO and NiO:Li sensors present maximum sensibilities in the range of work temperatures used, while the NiO:Li,Pt sensor has it at lower temperatures, promising to be a good hydrogen sensor at temperatures close to ambient. When tested at different concentrations the pure nickel oxide sensor and the sensor with platinum present a linear behavior, while the lithium-doped sensor presents a potential relation; in all cases, lithium-doped and with platinum on surface, sensitivity proved to be higher than that of pure nickel oxide. The use of platinum on surface sensors improves the response time from 6.6 min to 1.5 min.