Gold/vanadium–tin oxide nanocomposites prepared by co-precipitation method for carbon monoxide gas sensors

The gas sensor investigated is constituted by gold/vanadium–tin oxide (Au/V–SnO2) nanocomposite powders, prepared by a co-precipitation method, and evaluated for carbon monoxide detection at low temperature. The Au-loaded sensor exhibited a higher response and shorter response and recovery time than the V–Sn oxide sensor and had good stability. The responses obtained in both air and nitrogen atmospheres increased with increasing sensor temperatures or CO concentrations. X-ray photoelectron spectroscopy (XPS) revealed the presence of gold in the metallic state and vanadium cations with multiple valences on the oxide surface. The gold addition induced an interaction between gold and vanadium and enhanced oxygen adsorption on the sensor surface under electrical field, as indicated by electron paramagnetic resonance (EPR) and electrical analyses. Results demonstrate the viability of the Au/V–SnO2 sensor to detect CO gas in ambient and oxygen-deficient environments. It is postulated that gold and adjacent vanadium or oxygen vacancy sites facilitate oxygen activation for CO oxidation in air or CO chemisorption under nitrogen. Sensing mechanisms that discuss the roles of these active sites and oxygen in the CO detection are proposed.