Sol–gel processed (Zn_xNi_1−x)O binary composite characterized for gas sensing and photocatalytic applications

Metal oxides have received consideration in recent times due to their outstanding properties and diverse applications with their composites exhibiting unique electrical and magnetic features, photocatalytic degradation, and gas sensing properties. This research was carried out to investigate the properties of sol–gel synthesized (Zn_xNi_1−x)O binary composites since there has been no published paper yet on this. The zinc oxide, ZnO and nickel oxide, NiO samples were mixed at varied volume ratios of (0.8:0.2), (0.5:0.5), and (0.2:0.8) using Zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and Nickel (II) acetate tetrahydrate (Ni(CH₃CO₂)₂·4H₂O) as their respective precursors. A hexagonal crystal structure of the binary composite was gotten at an average crystallite size of 5.88 nm. Uniformly distributed nanolumps over the surface were observed in the morphology due to even dispersion in the Zn–Ni matrix. TEM images showed compact nanoclusters while the energy band gap values gotten were 3.2, 3.3, and 3.6 eV were obtained for the ZnO_0.8NiO_0.2, ZnO_0.5NiO_0.5, and ZnO_0.2NiO_0.8 composites, respectively. The functional groups present in the composites were shown in the FTIR graph with high PL counts obtained in the visible spectrum. Variation in the volume ratio of the composites gave Raman shifts at high intensity. Results obtained from the elemental analysis confirmed the presence of as-deposited elements and ascertained that the composites were synthesized in the right proportion. The composites were found to be highly sensitive most especially at high temperatures to CO₂, H₂S, and Cl₂ at 100 ppm and 10 V. The photocatalytic efficiency obtained was above 50% at 10 ppm.