Catalytic-induced Sensing Effect of Triangular CeO2 Nanoflakes for Enhanced BTEX Vapor Detection with Conventional ZnO Gas Sensors

It is really difficult to detect inert gaseous chemicals such as BTEX (i.e., benzene, toluene, ethylbenzene and xylene) vapors by using conventional metal-oxide-semiconductor (MOS) gas sensors. CeO2 is a widely used catalyst for benzene and its homologues cracking. However, CeO2 catalyst cannot be directly added into MOS-based materials for sensing applications due to its insulating characteristic. Herein, a novel bi-layer sensing structure is proposed for trace BTEX detection, where insulated CeO2 catalyst is coated onto the top-surface of ZnO sensing layer. Our study verifies that the top-layer of CeO2 catalyst only has a negligible influence on the resistance of the bottom ZnO sensing layer. To achieve high sensing performance to trace-level BTEX, two nanomaterials of triangular CeO2 nanoflakes as well as nano-porous ZnO are used to construct the bi-layer gas sensor. The fabricated ZnO-CeO2 sensor exhibits satisfied sensing performance to BTEX vapors and its limit of detection (LOD) to toluene reaches 10 ppb. The catalytic-induced cracking mechanism of CeO2 nanoflakes is further revealed by using online mass spectrum (online MS).