Hierarchical SnO2-Sn3O4 heterostructural gas sensor with high sensitivity and selectivity to NO2

Considering the high harmfulness of NO2 to the environment and human healthy, it is pressing to develop NO2 sensors with high sensitivity and selectivity. In this work, we successfully fabricated a novel hierarchical SnO2-Sn3O4 n-n heterostructure through the solvothermal method and subsequent annealing. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), field-emission scanning electron microscopy (FESEM), and high-resolution transmission electron microscopy (HRTEM) characterization of the material confirmed the hierarchical microsphere structure and the formation of SnO2-Sn3O4 n-n heterojunction. The gas sensing experiment demonstrated that the sample annealed at 600 degrees C exhibited excellent NO2 sensing performances at 150 degrees C. Its sensitivities to 5 and 10 ppm NO2 were as high as 48 and 43.6 ppm(-1) respectively, and its limit of detection was lower than 20 ppb. Additionally, it possessed excellent selectivity to NO2 as well as good repeatability and stability. With further exploration of the sensing mechanism of hierarchical SnO2-Sn(3)O(4 )n-n heterostructure, we proposed that the unique microstructure with a large specific surface area and the formation of n-n-type heterojunctions contribute to the excellent NO2 sensing performance.