Au-Loaded Hierarchical MoO3 Hollow Spheres with Enhanced Gas-Sensing Performance for the Detection of BTX (Benzene, Toluene, And Xylene) And the Sensing Mechanism

Monodisperse, hierarchical alpha-MoO3 hollow spheres were fabricated using a facile template-free solvothermal method combined with subsequent calcination. Various quantities of Au nanoparticles (NPs) were deposited on the alpha-MoO3 hollow spheres to construct hybrid nanomaterials for chemical gas sensors and their BTX sensing properties were investigated. The 2.04 wt % Au-loaded alpha-MoO3 sensor can detect BTX effectively at 250 degrees C, especially, its responses to 100 ppm toluene and xylene are 17.5 and 22.1, respectively, which are 4.6 and 3.9 times higher than those of pure alpha-MoO3 hollow spheres at 290 degrees C. Besides, Au loading decreased the response times to toluene and xylene from 19 and 6 s to 1.6 and 2 s, respectively, lowered the working temperature from 290 to 250 degrees C as compared with those of pure alpha-MoO3. The surface status of Au/alpha-MoO3 hollow spheres before and after contacting with toluene at 250 degrees C was analyzed through XPS technique. Possible oxidization product of toluene was confirmed by GC for the first time. The gas-sensing mechanism of the Au/alpha-MoO3 was speculated as the oxidation of toluene to water and carbon dioxide by chemisorbed oxygen and lattice oxygen. The possible reason related with improved gas-sensing properties of the Au-functionalized alpha-MoO3 was discussed.