Methane gas-sensing and catalytic oxidation activity of SnO2–In2O3 nanocomposites incorporating TiO2

The InO1.5–SnO2 nanocomposites incorporating TiO2 were synthesized by a controlled co-precipitation method as sensing materials of a novel semiconductor CH4 sensor. Through manipulating the total salt concentration, cation ratio, precipitation pH, aging time and calcination temperature, the nanocrystalline composites were successfully derived with chemical homogeneity and superior thermal stability compared to tin oxide. The gas-sensing and catalytic activity for methane oxidation were examined in a micro fixed bed reaction system. The experimental results showed that the nanocomposites exhibited high gas-sensing and catalytic activity, and these performances depended on composition of composites, calcination temperature of precursors and sensor operating temperature. It was found that the sensing behavior was straightforwardly related to the catalytic activity. The sensing and catalytic activity was greatly enhanced by the introduction of metal elements or oxide surface coatings. To guide for the search of better sensor materials or suitable additives, it is necessary to understand the sensing mechanism of the semiconductor oxide gas sensors by temperature-programmed desorption (TPD) study and X-ray photoelectron spectroscopic (XPS) analysis.