Synthesis And Gas Properties Of α-Fe₂O₃@SnO₂ Core-shell Nanotubes Heterostructure

As important fundamental materials, a-Fe2O3 and SnO2 possess wide application potentials in gas sensing, Li-ion battery electrodes, and photocatalysis, and have aoused wide research interest due to their unique properties. Especially as conventional gas-sensitive materials, a-Fe2O3 and SnO2 with different structure and morphology have been investigated intensively in the last few decades. In order to to obtain high performance gas sensors, much efforts have done to improve the properties of the two materials. In rencent years, it has been demonstrated that,by combining a-Fe2O3 and SnO2, the heterojunction nanostructures can greatly enhance their application performance. Thus, various a-Fe2O3/SnO2 nanocomposites has been synthesized as gas sensing materials. And it was reported that the structure and morphology of composites played a key role in their gas sensing properties. Based on the above, it’s worth synthizing a-Fe2O3/SnO2 composites with special structure by a simple, low-cost method and exploring the relationship between structure and gas sensing properties.In this thesis, a gas sensor device was constructed using as-prepared a-Fe2O3@SnO2 core-shell heterostructure nanotubes and was tested for its ability to detect acetone and some other compounds, The porous a-Fe2O3@SnO2 core-shell heterostructure nanotubes were synthized by an effective two-step hydrothermal method. The a-Fe2O3 nanotubes were firstly synthesized by a convenient hydrothermal reaction. After going through another hydrothermal process in a reaction system with stannate trihydrate (Na2SnO3"3H2O) and urea dissoved in an ethanol-water mixture, a uniform layer of SnO2 was coated on both the outer and inner surface of the a-Fe2O3 nanotubes, achieving the final a-Fe2O3@SnO2 core-shell heterostructure nanotubes. The as-prepared a-Fe2O3/SnO2 heterostructure nanotubes were used as electrode materials for gas sensors. Compared with pure a-Fe2O3 nanotubes and SnCh nanoparticles, the sensor based on α-Fe2O3@SnO2 nanotubes exhibits much enhanced sensing performances, demonstrating higher response and better selectivity to different gases. When exposed to 100 ppm acetone, the α-Fe2O3@SnO2 sensors show a high sensitivity of 33.4, which is much larger than that of α-Fe203and SnO2sensors. Furthermore, the response/recovery time for the a-Fe2O3@SnO2 sensors is also much shorter than the ones based on pure a-Fe2O3 or SnO2. The perfect repeatability has been demonstrated as well by a series of dynamic response measurements to acetone with different concentrations of 10,50,100 ppm, respectively. The excellent sensing performance can be probably attributed to the unique heterostructure of a-Fe2O3@SnO2 nanotubes.In conclusion, we have discussed the structure, combination, size of α-Fe2O3@SnO2 composite and their effect on the gas sensing properties. Supplemented with the analysis of the experimental data, we preliminarily studied the gas sensing mechanism and the performance of such binary compound materials.