MoO3/SnO2Nanocomposite-Based Gas Sensor for Rapid Detection of Ammonia

Ammonia is harmful to human health, however, the detection limit of the sensor based on traditional semiconductor gas sensors is high and the speed is slow. Constructing heterostructure is an effective method to improve the performance of sensors. In this paper, one-dimensional MoO3 nanorods and SnO2 nanoparticles are successfully combined to obtain MoO3/SnO2 nanocomposite. The one-dimensional structure can increase the speed of electron transport, while the nanoparticles on the surface increase the specific surface area, more importantly, the structure maximizes the interface area between the two materials which can transfer electronic more efficient. SEM, TEM, HRTEM, SAED, EDS, XPS, XRD, BET, and BJH are used to analyze the microstructure and elemental composition of MoO3/SnO2. The diameter of MoO3/SnO2 nanocomposite is approximately 200 nm and the distribution is uniform. The response of MoO3/SnO2 nanocomposite to 100 ppm NH3 is 12.7 at 280 °C, and the response/recovery time is 13/2 s. The detection limit for NH3 can reach 10 ppb (response 1.3), which enables rapid detection of NH3 at low concentration. Electron transport requires more energy to overcome the contact barrier between pure SnO2 nanoparticles, which can also lead to electron emission and noise increase. However, the sensitive electrons of MoO3/SnO2 nanocomposite can transmit electrons along the one-dimensional rod-like structure of MoO3, which undoubtedly accelerates the efficiency of electron transmission. Moreover, n-n heterojunction formed between MoO3 and SnO2 to bend the SnO2 band and show better sensitivity to NH3. Therefore, MoO3/SnO2 nanocomposite shows a low detection limit and a rapid response/recovery speed. Nevertheless, the nanoparticles on the surface of MoO3/SnO2 nanocomposite begin to agglomerate with the increase of SnO2 content, which leads to the decrease of gas-sensitive response. The formation process of MoO3/SnO2 composites are also discussed in this paper. The excellent gas sensing results show that MoO3/SnO2 composites is a promising gas sensing material.