Constructing Z-Scheme WO3–CeO2 Heterojunctions for Selective Sensing of NO2 or Acetone Gas under UV Light Irradiation

Light assistance and the construction of heterojunctions between two semiconductors with matching band structures are effective strategies for obtaining efficient gas sensors. Recently, Z-scheme heterojunctions have shown marked potential in promoting the separation and transfer of photogenerated carriers as well as possessing strong redox capability. In this study, two types of nanocomposites of WO3/CeO2 and CeO2/WO3 with Z-scheme heterojunctions were designed and prepared with WO3 and CeO2 as host materials, respectively. In the case of the WO3/CeO2 nanocomposite, the CeO2 nanoparticles are evenly distributed and attached to the WO3 host. Conversely, in the CeO2/WO3 nanocomposite, WO3 is completely covered by the CeO2 nanoparticles, forming a core–shell structure. The construction of Z-scheme heterojunctions effectively suppresses the recombination of photogenerated carriers, generates more active sites, and enhances redox capability. Resultantly, under UV light assistance, the sensors based on heterojunctions of WO3/CeO2 and CeO2/WO3 exhibit a selective response toward the oxidizing gas of NO2 and the reducing gas of acetone, respectively, at room temperature. The WO3/CeO2 sensor exhibits a response of 6.82 toward 100 ppb NO2, while the CeO2/WO3 sensor exhibits a response of 6.45 toward 10 ppm acetone at room temperature (RT) under UV irradiation. The dynamic response/recovery characteristics of both heterojunction sensors were improved by UV irradiation, with an obvious shortening of the response/recovery time compared to the case in the dark. The experimental results demonstrate that the two sensors are capable of detecting NO2 and acetone gases at RT, respectively. This work expands the application of Z-scheme heterojunctions in gas sensing and provides a strategy based on the design of special Z-scheme heterojunctions for developing high-performance gas sensors toward selective detection of oxidizing or reducing gas.