Preparation and Bifunctional Gas Sensing Properties of Porous In2O3-CeO2 Binary Oxide Nanotubes

The porous binary In2O3-CeO2 oxides nanotubes (NTs) in cubic phase were first fabricated by electrospinning (ESP) method and characterized by SEM, TEM, XRD, XPS and UV-vis absorption techniques. By adjusting the In2O3 and CeO2 molar ratio, the out diameters and wall thicknesses of the final composites were tuned ranging of 90-180 nm and 15-9 nm, respectively. The band gap of the binary oxides gradually decreases, and the ratio of Ce3+ to Ce4+ increases with the increase of CeO2, implying that surface oxygen vacancies gradually increase. The gas sensing test reveals that when the content of CeO2 is appropriate, the as fabricated In2O3-CeO2 NTs could be bifunctional gas sensors to detect H2S at low temperature(25-110 degrees C) while acetone at relative high temperature (300 degrees C). The In75Ce25 NTs sensor is an optimum one, which exhibits the highest response of 498 to H2S at 80 degrees C and the highest response of 30 to acetone at 300 degrees C. In contrast to the pure In2O3 sensor, the response and recovery times, as well as the sensing reaction barrier height, for In75Ce25 both degrade considerably. The above temperature-dependent sensing properties were attributed to two different gas sensing mechanisms, sulfuration at low temperature and adsorption at high temperature.