Preparation and mechanism of high-performance ammonia sensor based on tungsten oxide and zinc oxide composite at room temperature

Based on ZnO and WO3·H2O composite (ZW), a high performance ammonia (NH3) gas sensor was synthesized by hydrothermal method. Compared with WO3·H2O, ZW sensor has good selectivity and sensitivity for NH3 gas detection at room temperature, with fast response/recovery time of 2.4 s/1.2 s, low detection limit of 0.76 ppm, excellent endurance to humidity and good stability for a long time. With smaller size in it, ZW provides more active sites to absorb NH3 molecules. More free oxygens on surface of ZW will react with more NH3 molecules, thus to improve the sensitivity of ZW. Furthermore, the heterojunction structure of ZW compound can enhance resistance modulation at the interface between ZnO and WO3·H2O, which further improves the sensitivity of WO3·H2O for NH3 detection. This study shows the combination of ZnO can significantly improve the performance of NH3 gas sensor based on WO3·H2O at RT.