Synthesis And Gas-sensing Properties Of Fe₂O₃ Nanocomposites

As is known to all,with the expansion of industrial production scale,the continuous improvement of human living standards and the development and extension of science and technology,people are increasingly demanding for gas sensors.Metal oxide semiconductors have been widely used in the field of gas sensors due to their outstanding advantages.Iron oxide is an important metal oxide semiconductor material and has a wide range of application prospects.However,a single iron oxide gas sensor still has many defects,forcing people to carry out research and improvement.The cube is a relatively stable three-dimensional structure that can be composite with different nanostructures and construct complex structures.Therefore,this paper mainly uses cubic Fe₂O₃ as the main material,by building the construction of P-N heterojunction,N-N heterojunction,in order to use its Fermi energy level effect and the synergy between different components to enhance the gas-sensing performance;by constructing the yolk-shell structure to increase the specific surface area and enhance the contact with the gas,lowering the working temperature of the material and increasing the sensitivity of the material.The materials were characterized by SEM,EDS,XRD,TEM,XPS and BET.The main work of this thesis is as follows:?1?Cube Fe₂O₃ was prepared with regular morphology and good crystallization.Gas sensing performance was measured by WS-30A gas sensor system.The sample had response to triethylamine at 300°C.?2?NiO/Fe₂O₃ P-N heterojunction nanocomposites were successfully synthesized.As the P-N contact surface forms a new electron depletion layer,the resistance of the material exhibits a more significant change in the dynamic process of adsorption and desorption of the reducing gas,thereby exhibiting a higher gas-sensing response.Therefore,the composite product had response to high concentration of ethanol gas at 300°C.In addition,the product had better response and stability.?3?SnO₂/Fe₂O₃ N-N heterojunction nanocomposites with uniform size and good crystallinity were synthesized by hydrothermal method.Not only due to the enhancement effect of N-N heterojunction,the material itself also exposed more high-energy crystal faces,so the active sites were increased.Gas sensing performance test showed that the composite material has good selectivity to ethanol and the best working temperature is reduced by 60°C,the gas sensitivity is nearly 2 times higher than that of pure Fe₂O₃.?4?Prepared SnO₂/Au/Fe₂O₃ nanocomposites with core-shell structure.Due to the combined effect of the larger specific surface area and the catalytic performance of the Au nanoparticles,the SnO₂/Au/Fe₂O₃ nanocomposites were found to have excellent gas sensitivities to triethylamine,and the working temperature was reduced by 60°C.The response to 100 ppm triethylamine reached 126.841,which was 12 times higher than pure Fe₂O₃.