High-performance room temperature NO2 gas sensor based on visible light irradiated In2O3 nanowires

Abstract

A batch of In2O3 nanowires (NWs) samples were prepared through a simple electrospinning method and the following sintering procedure. The X-ray powder diffraction (XRD) analysis identified their high purity and crystallinity. Furthermore, the field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) revealed the high quality of the synthesized products. The nanowires were homogeneous and of uniform diameter. The X-ray photoelectron spectroscopy (XPS) data showed that the oxygen vacancies and surface chemisorbed oxygen species occupied a large proportion in the total oxygen content. O2-temperature-programmed desorption (TPD) experiments identified the affinity of oxygen to In2O3 nanowires´ surface at room temperature and concrete adsorbed oxygen species. The above results were positive signals of their gas-sensing performance. In the subsequent gas-sensing test, we found that the sensor based on In2O3 NWs exhibited a high selectivity toward NO2 under room temperature. What's more, the response of the sensor toward 5 ppm NO2 at 25 ℃ in dark could reach as high as 740 and its detection limit was as low as 10 ppb. However, like most reported literatures on low-temperature gas sensors, the In2O3 NWs sensor likewise had a significant defect of long recovery process. Fortunately, we successfully solved this defect through the introduction of visible light irradiation during the recovery process. We detailedly explored the relationship between the light intensity and wavelength and the recovery properties of the sensor. Based on an in-depth analysis on the above two parameters and O2-TPD data, we proposed two different action mechanisms of photons according to their energy difference when accelerating the recovery of the sensor.