Synthesis and Gas Sensitivity of In2O3/CdO Composite

Indium oxide (In2O3) was synthesized using a hydrothermal process. The crystallography and microstructure of the synthesized samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and transmission electron microscopy (TEM). The In2O3 had a flower-like hierarchical nanostructure and was composed of tiny near-spherical crystals with a diameter of approximately 20 nm. When In2O3 was mixed with CdO in a 1:1 molar ratio, it was found that the resulting In2O3/CdO composite showed an interesting grape-like porous microstructure following calcinations at elevated temperatures. A gas sensor using this In2O3/CdO composite as the sensing material showed higher sensitivity to different concentration of formaldehyde than the gas sensor based on pure flower-like In2O3 nanomaterials. The In2P3/CdO-based sensors showed a high sensitivity to a concentration of 0.05x10(-6) formaldehyde at the optimized operating temperature of 410 degrees C and a good level of selectivity over other possible interference gases such as ethanol, toluene, acetone, methanol, and ammonia. The gas sensing mechanism of In2O3/CdO sensor has been discussed in detail.