Hydrogenated MnO Octahedron And Sn_xTi_1-xO₂-Ti_xSn_{1- Enhanced Gas Sensing Performance And Mechanism Of X}O₂ Quasi-homotype Boundary Nanosheets

In this paper,the MnO octahedron exposed to the crystal plane of {111} and the SnxTi1-xO2-TixSn1-xO2 morphotropic phase boundary nanosheets exposed to the crystal plane of {001} and {010} were prepared by simple hydrothermal method,respectively.After hydrogen treatment,the hydrogenated MnO octahedron and SnxTi1-xO2-TixSn1-xO2 morphotropic phase boundary nanosheets were obtained.The samples after hydrogenation were characterized by transmission electron microscopy(TEM),multifunctional imaging photoelectron spectroscopy(XPS),infrared spectrometer(IR),X-ray diffractometer(XRD)and field emission electron microscopy(FESEM).The gas sensing reaction mechanism between MnO octahedron and SnxTi1-xO2-TixSn1-xO2 composite nano-sheet with quasi-homomorphic phase boundary was studied before and after hydrogenation,and the relationship between material properties and structure was discussed.The results are as follows:(1)The MnO octahedron exposed to {111} crystal plane was obtained by hydrothermal reaction at 200? for 48 h.Then the products were heated in 600?hydrogen for 12 h,24 h,36 h,44 h and 48 h respectively to obtain the hydrogenated products.The results show that the gas sensing performance of the hydrogenated samples is higher than that of the unhydrogenated samples,and the sensitivity of the samples increases with the increase of hydrogen passage time.However,when the hydrogen passage time increases to 48 h,the sensitivity of the samples is only higher than that of the original samples.Therefore,we believe that the unsaturated 2,3 or 5 coordination Mn atoms are the active sites of the sensing reaction,which explains the mechanism of the gas sensing reaction at the atomic and molecular level.(2)Using solvent hot method,using anhydrous ethanol-five hydrated stannic chloride-butyl titanate is mixed solution under the condition of 200? for 24 h reaction,get exposed to {001} and {010} crystal SnxTi1-xO2-TixSn1-xO2,morphotropic phase boundary nanosheets,will get the samples under the condition of 200?,respectively,thermal insulation in hydrogen atmosphere,12 h,24 h,36 h,48 h after hydrogenated samples.Then the gas sensing performance of the sample was studied,and it was found that the gas sensing performance of the sample increased with the increase of hydrogen passing time.By studying the relationship between the atomic structure and sensing performance on the surface of SnxTi1-xO2-TixSn1-xO2 morphotropic phase boundary nanosheets,the unsaturated Sn atom and the unsaturated Ti atom on the polar crystal plane are the active sites of gas sensor reaction,and the mechanism of enhancing related gas sensing at the molecular and atomic level is proposed.