Construction of Co 3 O 4 nanorods/In 2 O 3 nanocubes heterojunctions for efficient sensing of NO 2 gas at low temperature

The development of NO2 gas sensor with high sensitivity, low detection limit and high selectivity is highly required. This article reports a NO2 gas sensor based on Co3O4/In2O3 heterojunction structure fabricated by a two-step hydrothermal method. Particularly, morphological and structural analysis of the Co3O4 nanorods/In2O3 nanocubes nanocomposite was examined by SEM, TEM, XRD, EDS and XPS measurements. The Co3O4/In2O3 nanocomposite sensor was tested toward NO2 gas (1–200 ppm) under different operation temperature. The sensor exhibited excellent gas sensing properties for NO2 sensing at an optimal temperature of 150 °C. The corresponding response is 27.9 to 10 ppm NO2 at 150 °C, 1.2 times higher than that of pure In2O3 and 10 times higher than that of pure Co3O4. Moreover, the Co3O4/In2O3 sensor shows sub-ppm level detection ability, good selectivity and long-term stability at low temperature. The enhanced sensing performance can be attributed to the Co3O4/In2O3 heterojunction structure formed at the interfaces of n-type In2O3 nanocubes and p-type Co3O4 nanorods.