Facile preparation of flower-like NiO/In2O3 composite for sensitively and selectively detecting NO2 at room and lower temperatures

As a typical n-type semiconductor, In2O3 is often used in gas sensors due to the wide band gap, adjustable morphology and good electrical conductivity. However, the pristine In2O3 has some disadvantages, such as higher operating temperature, poor sensing performance to low concentrations of gases. In this work, we fabricated flower-like NiO/In2O3 composites via a facile one-pot hydrothermal method, and investigated their gas sensitivity to various concentrations of NO2 at different temperatures. The responses (Rg/Ra) of NiO/In2O3-0.2 composite to 0.1–80 ppm NO2 are 2.5 ∼ 5.8 times higher than those of pristine In2O3 at the optimum temperature of 150 °C, respectively. The room-temperature response of the NiO/In2O3-0.2 composite to 20 ppb NO2 is 1.82 with the limit of detection (LOD) of 5 ppb, indicating great application potential for NO2 detection. Moreover, the NiO/In2O3-0.2 composite has the excellent reproducibility, good long-term stability and selectivity. The specific morphology with larger surface area and the formation of p-n heterojunction synergistically enhance the sensing properties of NiO/In2O3 composite, demonstrated by DFT calculation and experiments. This work provides a facile fabrication of flower-like In2O3–based composites for room-temperature detection of ppb-level NO2.