Porous ZnO/rGO Nanosheet‐Based NO2 Gas Sensor with High Sensitivity and ppb‐Level Detection Limit at Room Temperature

Abstract High‐performance gas sensors are highly desirable for environmental monitoring, clinical medicine, and industrial production. Herein, a gas sensor with excellent sensing response at room temperature is presented based on zinc oxide/reduced graphene oxide (ZnO/rGO) composites. The ZnO/rGO composites with various contents of rGO and the pure ZnO are successfully fabricated by a facile hydrothermal method. Particularly, the ZnO/rGO sensor with 1.5 mL of the rGO exhibits highest sensing response in a wide range from 5 ppb to 10 ppm NO2 concentration and its response arrives at 13.46 when exposed to 2 ppm NO2 at room temperature. Furthermore, ZnO/rGO sensors show short response time (2 ppm, 26 s) and recovery time (2 ppm, 164 s) at room temperature. The proposed ZnO/rGO sensors present high sensitivity, excellent reproducibility, and stability. In addition, the density functional theory (DFT) calculations show that the increased electrical conductivity under exposure of NO2 gas are attributed to the numerous reactive sites and carrier mobility of rGO. These results demonstrate that ZnO/rGO gas sensor has huge potential for applications in industrial and environmental monitoring.