Simple preparation of Ni/CuO nanocomposites with superior sensing activity toward the detection of methane gas

Composite nanostructures composed of transition metal oxides are promising materials in catalyst, supercapacitor, and gas sensors. Here we have used Ni for the enhancement of the CuO gas sensor toward methane gas. High-quality Nix/CuO nanocomposites (where x = 0.0 to 10%) have been synthesized by the simple method of solid–solid reaction. A nanoparticle structure was obtained. The size of the nanoparticle can be controlled easily by adjusting the relative Ni concentration in Ni/CuO nanoparticles. The relative diffusion amount of Ni to CuO was proved to be the key factor to influence the sensing sample properties. XRD patterns and HRTEM image confirmed the preparation of Nix/CuO phase, which showed a decline in crystallite size from ~ 17.8 to 14.6 nm (XRD). FESEM and TEM images also exhibited the effect of Ni content on the particle size of CuO. EDX mapping confirmed that the NiO fine particles were distributed semi-uniform at low Ni concentration; however, they aggregated at high Ni concentration. The sensing properties were done at different temperatures and various concentrations of methane gas. It was illustrated that the increase of Ni up to 5% showed an improvement in the sensor response of CuO toward methane compared to the pure phase of CuO and NiO, as well. The maximum-response temperature was 250 °C at which the sensor response is ~ 4.9 (390%), which is four times higher than the CuO and NiO pure phases. The present nanocomposites could detect CH4 at lower levels of explosive level (5%). The mechanism of gas sensing is explained depending on the electronic structure changes.