NO2 Detection Using Hierarchical WO3 Microflower-Based Gas Sensors: Comprehensive Study of Sensor Performance

Monitoring nitrogen dioxide (NO2) in various scenarios is crucial due to its significant environmental impact as a hazardous gas which is emitted by several industrial sectors. This study reports the optimized synthesis of WO3 flower-like structures using the microwave-assisted hydrothermal method under various experimental conditions, resulting in the optimized sample designated MF-WO3-K2. Structural, morphological, and chemical characterizations revealed that WO3 microflowers (MF-WO3-K2) exhibit a hexagonal crystalline phase, a bandgap of 2.4 eV, and a high specific surface area of 61 m2/g. The gas-sensing performance of WO3 microflowers was investigated by electrical measurements of six similarly fabricated MF-WO3-K2 sensors. The MF-WO3-K2 sensors demonstrated a remarkable sensor signal of 225 for 5 ppm NO2 at 150 °C and response/recovery times of 14.5/2.4 min, coupled with outstanding selectivity against potential interfering gases such as CO, H2, C2H2, and C2H4. Additionally, the sensors achieved a low detection limit of 65 ppb for NO2 at 150 °C. The exceptional sensing properties of WO3 microflowers are attributed to the abundance of active sites on the surface, large specific surface area, and the presence of pores in the material that facilitate the diffusion of NO2 molecules into the structure. Overall, the WO3 microflowers demonstrate a promising ability to be used as a sensitive layer in high-performance chemiresistive gas sensors due to their high sensor performance and good reproducibility for NO2 detection.