Investigation on the effect of NiO content on spray deposited ZnO for selective ammonia detection

Zinc Oxide/Nickel Oxide (ZnO/NiO) heterostructures were deposited using the spray pyrolysis technique by varying NiO content. The X-ray Diffraction (XRD) studies confirmed the polycrystalline nature of various heterostructures. The Field Emission Scanning Electron Microscope (FESEM) studies showed spherical ZnO with a vertical plate-like NiO morphology. The X-ray Photon Electroscopy (XPS) studies showed the existence of Zn²⁺ and Ni²⁺ in ZnO/NiO. The ammonia sensing studies of the various samples were investigated by varying the temperature from room temperature (RT) to 450 °C. Among various nanostructures, ZnO/NiO in mixed form exhibited better sensitivity and selectivity towards ammonia at low temperature (300 °C), when compared to others. The range of detection towards ammonia was found to be 0.5 ppm to 100 ppm for ZnO/NiO mixed oxide. The response of the nanostructures towards different poultry gases such as methane, carbon dioxide, and nitrous oxide was also investigated. The ZnO/NiO mixed oxide also exhibited remarkable selectivity towards ammonia in a mixed vapour environment.