Highly sensitive NO2 sensor based on mesoporous ZrO2–WO3 nanotubes composite

In this study, two anodic oxidation processes were used to prepare ordered mesoporous zirconia nanotubes. Ammonium metatungstate was introduced into zirconia to obtain mesoporous ZrO2–WO3 composite nanotubes. We performed XRD, TEM, and SEM tests on the material. Furthermore, a mixed electromotive force–based NO2 sensor was fabricated using ZrO2–WO3 nanotubes as sensing materials. The sensor not only has a low working temperature (400°C) and high sensitivity (131.4 mV/decade) but also shows remarkable selectivity, stability, and repeatability. At 400°C, the polarity curve of the sensor in air and under different concentrations of NO2 was measured, which proves the mixed electromotive force mechanism. Moreover, the tubular structure of the mesoporous ZrO2–WO3 composite provides additional electrochemical active sites, improves the catalytic efficiency, enhances the diffusion of NO2, and reduces NO2 consumption in the diffusion process, thus essentially improving the performance of the sensor.