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

• A novel hierarchical SnO 2 -Sn 3 O 4 n-n heterostructure was successfully fabricated through the solvothermal method and subsequent annealing. • The SnO 2 -Sn 3 O 4 heterostructure exhibited excellent NO 2 sensing performance in terms of sensitivity, limit of detection and selectivity. • The formation of SnO 2 -Sn 3 O 4 n-n heterojunction played crucial role in enhancing the sensing performance. Considering the high harmfulness of NO 2 to the environment and human healthy, it is pressing to develop NO 2 sensors with high sensitivity and selectivity. In this work, we successfully fabricated a novel hierarchical SnO 2 –Sn 3 O 4 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 SnO 2 –Sn 3 O 4 n–n heterojunction. The gas sensing experiment demonstrated that the sample annealed at 600 °C exhibited excellent NO 2 sensing performances at 150 °C. Its sensitivities to 5 and 10 ppm NO 2 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 NO 2 as well as good repeatability and stability. With further exploration of the sensing mechanism of hierarchical SnO 2 –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 NO 2 sensing performance. [ABSTRACT FROM AUTHOR]