Tailoring oxygen sensing characteristics of Co3O4 nanostructures through Gd doping

Abstract

Detection of oxygen plays an important role in food industry, medicine and controlling automotive exhaust. Here, we have developed a Co₃O₄ nanoparticle-based oxygen gas sensor. Effect of Gadolinium (Gd) doping on oxygen sensing is investigated using the variation in electrical resistance method which clearly reveals improvement in the sensitivity with the increase in Gadolinium doping in Co₃O₄. X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) studies were systematically performed, to understand the effect of the morphology and crystallographic phase on the level of sensitivity with Gadolinium doping. XRD studies reveal a distortion in the Co₃O₄ lattice as the lattice parameters increase with increasing Gd doping. SEM and TEM show a change in particle shape and size with Gd doping. Presence of both Co⁺² and Co⁺³ oxidation states were confirmed by XPS. Gd doping, up to 6%, improved the gas sensing response of Co₃O₄ nanoparticles which is attributed to the decrease in particle size and an increase in oxygen adsorption with Gd doping. Minimum response time of 4 s, 6 s, 10 s and 14 s were observed for pure Co₃O₄ in 1%, 2%, 3% and 4% oxygen environment respectively. Pure Co₃O₄ nanoparticles also showed minimum recovery time which was 6 s, 7 s, 9 s and 11 s in 1%, 2%, 3% and 4% oxygen environment respectively. All the prepared compositions were selective to oxygen at 240 °C.