Room-temperature gas sensors based on three-dimensional Co3O4/Al2O3@Ti3C2Tx MXene nanocomposite for highly sensitive NOx detection

A self-sacrificial template and a hydrothermal method were utilized to successfully synthesize Ti3C2Tx MXene-supported Co3O4/Al2O3 assembled with nanosheets derived from layered double hydroxides. Within three-dimensional Co3O4/Al2O3@Ti3C2Tx MXene composite, Co3O4, as the active center component, was evenly distributed on Ti3C2Tx MXene nanosheets and Al2O3 as the addition. The 3D structure could expose more active center sites on the surface of Co3O4/Al2O3@Ti3C2Tx MXene and provide more gas diffusion channels, which were beneficial to the gas sensing performance. Comparing to CoAl-LDH@Ti3C2Tx MXene (CAM, and CoAl-LDH represents the cobalt-aluminum layered double hydroxide), Co3O4/Al2O3@Ti3C2Tx MXene (CAM-AC) exhibited an enhancing response (S = R0/Rg = 40.3) and a shorter response time of 1.3 s to 100 ppm NOx. Besides, CAM-AC also showed an ultra-low detection limit of 10 ppb and excellent repeatability, selectivity and long-term stability. The outstanding gas sensing performance could be attributed to the 3D structure, porous structure and the heterostructure between Co3O4/Al2O3 and Ti3C2Tx MXene. Therefore, the Co3O4/Al2O3@Ti3C2Tx MXene is an excellent NOx gas sensor candidate. [Display omitted] •3D hierarchical CAM-AC with high specific surface area and porous structure.•Oxygen-rich holes of CAM-AC can significantly improve the gas sensitivity to NOx.•The gas sensing performance and mechanism of CAM-AC were studied.•The excellent performance ascribed to a heterojunction and hierarchical structure.