Construction of WO3/InWO4 heterojunction for NO2 detection at room temperature under UV activation

Background Nitrogen dioxide (NO 2 ) is a hazardous atmospheric pollutant, driving demand for highly sensitive and reliable monitoring sensors. A significant challenge in this field is enhancing the performance of metal-oxide-based gas sensors, particularly their response and operating temperature. Current materials often exhibit insufficient sensitivity at room temperature, limiting their practical application. This work addresses the problem of developing a high-performance NO 2 gas sensor that operates effectively at room temperature. Results We present a novel WO 3 /InWO 4 heterojunction sensor that demonstrates dramatically enhanced NO 2 sensing under UV activation. The key result is a response value of 116.03 to 3 ppm NO 2 at room temperature, which is 3.55 times higher than that of a pure InWO 4 sensor. The composite sensor showed a response time of 68 s and a recovery time of 43 s, representing a slight increase and decrease, respectively, compared to the pure material. This performance is attributed to the synergistic effects of the constructed heterojunction, which promotes charge separation, alongside optimized oxygen vacancy concentration and UV light activation. The method was comprehensively validated through material characterization and gas-sensing tests, confirming that this composite structure effectively improves surface reactions with NO 2 molecules. Significance This study conclusively demonstrates that the WO 3 /InWO 4 heterojunction strategy is highly effective for NO 2 sensing. The significance lies in achieving exceptional sensor response at room temperature, providing a valuable pathway for developing low-power, high-performance gas sensing devices.