Gas sensing properties of WO3 based materials with hierarchical structural features

With the increasing requirements from toxic and hazardous gas detection technologies, WO3-based gas sensors have garnered tremendous interest on account of their low operating temperatures, good cycling stability, and short response/recovery time. So far, considerable progress has been made in the design and preparation of different architectures of WO3. The sensing mechanism of WO3-based gas sensors is relatively complex. To further optimize the capabilities of WO3-based gas sensors, the influencing factors of the sensing mechanism need to be deeply understood to seek more effective enhanced strategies. This review probes the application of WO3- based sensors for various dangerous gases and contrastively analyses the sensing behavior of WO3 in detail. In addition, we pay special attention to the interfacial interaction pathways between the sensing material and the target gas. Nowadays, more efforts are being made to strengthen the sensing properties of WO3-based materials so that they can be used in more smart demanding and complex environments. The authors focus on four approaches, namely, morphology control, hybridization, defect engineering, and photoactivation, for enhancing gas sensors and providing a comprehensive study of WO3 for gas-sensing applications. Finally, we discuss the current problems and improvement methods and provide an outlook on the development trend of WO3-based gas sensors.