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

Nitrogen dioxide (NO₂) 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 NO₂ gas sensor that operates effectively at room temperature.

We present a novel WO₃/InWO₄ heterojunction sensor that demonstrates dramatically enhanced NO₂ sensing under UV activation. The key result is a response value of 116.03 to 3 ppm NO₂ at room temperature, which is 3.55 times higher than that of a pure InWO₄ 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 NO₂ molecules.

This study conclusively demonstrates that the WO₃/InWO₄ heterojunction strategy is highly effective for NO₂ 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.