The Combination of Nickel Oxide (NiO) and Molybdenum Trioxide (MoO3) for Pollutant Gas Detection

The prime objective of the current research was to analyze and utilize the coexistence of basic and acidic metal oxide semiconductors (MOS) for sensing pollutant gases. In the current work, 1 wt.%, 3 wt.%, 5 wt.%, 7 wt.%, and 9 wt.% NiO (basic MOS) was added to MoO 3 (acidic MOS), and thick films were prepared using the screen printing technique. Structural characterization was performed by x-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive x-ray analysis (EDAX). The crystallite size was about 50 nm, with intermediate voids. EDAX analysis confirmed the non-stoichiometric composition of the films. The films were oxygen-deficient as per EDAX data. An electrical analysis involving resistivity, temperature coefficient of resistance (TCR), and activation energy was also performed. NiO3 samples showed maximum resistivity of 103.13 × 10 4 Ω·m and minimum activation energy of 0.3953 eV. The electrical analysis predicted the distinct behavior of the NiO3 sample. A negative TCR value indicated the semiconductor-like behavior of the samples. The pollutant gas response of the samples was analyzed using a static gas sensing apparatus. NiO3 samples showed gas sensitivity of 87% towards the ethanol vapors, with good selectivity, as compared with the responses towards CO, liquid petroleum gas (LPG), NH 3 , and NO 2 gases. The oxygen vacancy-based gas sensing mechanism was the probable reason for the improved ethanol vapor sensing. The response time of the sample was 28 s, while the recovery time was 38 s. Graphical Abstract