Fabrication and enhanced carbon monoxide gas sensing performance of p-CuO/n-TiO₂ heterojunction device

The p-CuO/n-TiO₂ heterojunction sensor was fabricated by using CuO and TiO₂ nanoparticles. The physicochemical properties of the sensor materials were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), elemental mapping, and energy dispersive spectroscopy (EDS). As-fabricated heterojunction sensors were investigated for sensing carbon monoxide (CO) in the range of 50–800 ppm and showed a highest response of 854 % for 800 ppm CO at 250 °C, whereas 177 % response for 50 ppm CO. The sensor selectivity was tested for gases such as CO, carbon dioxide (CO₂), nitrogen dioxide (NO₂), ethanol (C₂H₅OH), hydrogen (H₂) and methane (CH₄), which showed remarkable selectivity for CO. The CO sensors were examined for different operating temperatures and gas concentrations to elucidate their transient response, repeatability and stability. Furthermore, the plausible sensing mechanism of the p-CuO/n-TiO₂ heterojunction device was proposed.