Simulated sunlight enhanced methane-sensing performance based on Au-modified ZnO microsphere under room temperature

It is necessary to explore high-performance CH4 gas sensors with low working temperatures to avoid combustion and explosion accidents. In this work, the strategy of the photo-activation was used and ZnO microspheres modified by Au nanoparticles were synthesized to study their CH4-sensing performance at room temperature. The samples were synthesized via a facile hydrothermal method and an impregnation route. The characterizations indicated that Au nanoparticles with a size of 3–6 nm were deposited on ZnO hollow microspheres, and Au/ZnO composite had good optical properties to use light energy. The methane-sensing properties of all samples were tested under simulated sunlight at room temperature. Results showed that the sensors modified with Au performed light-enhanced gas-sensing performances compared to pure ZnO microspheres at room temperature. Unusually, the sensor based on 0.75 at.% Au/ZnO (atom ratio) exhibited a higher response, faster response/recovery time, and lower detection limit under simulated sunlight. The enhanced mechanism behind the Au/ZnO sensors can be ascribed to the increased electrons on the surface of the material and the improved reaction processes by the loading of Au nanoparticles and illumination. This study demonstrates that Au loading is an efficient and promising route in the development of photo-activated CH4 gas sensors in daily life.