Study On Gas Sensing Performances And Their Mechanisms Based On Nano-structured TiO₂

As an important wide-energy-gap semiconductor with a band gap of 3.2 eV,nanostructured titanium dioxide has been intensively studied and applied in photocatalysis,lithium ion battery,solar cells,sensors and other fields,because of its good chemical stability,non-toxicity,low cost,abundance and excellent physical and chemical properties.In the thesis,nanostructured TiO2 and its composites were synthesized by a simply hydrothermal method.The as-synthesized products were used as sensing materials to fabricate gas sensors and their gas-sensing performances and sensing mechanisima were studied.The main research contents and results are as following:(1)Synthesis,characterization,acetone sensing performances and sensing mechanisms of nanoporous TiO2 synthesized by the hydrothermal methodNanoporous titanium dioxide was synthesized by a hydrothermal method without using any surfactant or template.The structure,morphology,surface chemical states and specific surface area were characterized by X-ray diffraction(XRD),transmission electron microscopy(TEM),X-ray photoelectron spectroscopy(XPS),and N2 adsorption-desorption isotherms,respectively.The as-synthesized nanoporous TiO2 was used as sensing materials to fabricate gas sensor whose acetone sensing characteristics were investigated.The results show that the nanoporous TiO2 has a good response to acetone,and the gas response towards 500 ppm acetone is 25.97 at the optimum temperature of 370℃.And nanoporous TiO2 has a short response-recovery time,good selecticvity and long-term stability.(2)Synthesis and characterization of WO3/TiO2 nanocomposites and their xylene performances and sensing mechanismsTiOSO4 and(NH4)6H2W12O40·xH2O were used as titanium and tungsten sources,the pure and the different mole ratio of WO3/TiO2 nanocomposites were synthesized by one-step hydrothermal method and the products were characterized by XRD,TEM,EDX,XPS and BET,respectivity.The gas-sensing performances of the pure and the different mole ratio of WO3/TiO2 nanocomposites towards xylene were investigated.The results indicate that the 10.0%WO3/TiO2 nanocomposite has the highest response value for xylene.At the optimum temperature of 160℃,the gas response value to 10 ppm xylene is 92.53.The sensor has an excellent selectivity and long-term stability.(3)Synthesis,characterization,butane sensing properties and sensing mechanisms of Pd functionalized TiO2 nanoparticlesPd functionalized TiO2 nanoparticles were successfully synthesized by a simply hydrothermal process.The microscopic morphology,structure and composition of the products were analyzed by XRD,TEM,EDX and XPS,respectivity.The sensors fabricated by pure and Pd functionalized TiO2 were used to detect butane,respectively.The consequences reveal that the 7.5%Pd/TiO2 nanoparticles have the highest response of 39.32 towards 3000 ppm butane at the optimum temperature of 340℃.And at the temperature of 340℃,the sensor towards 3000 ppm butane shows the short response-recovery time and good long-term stability.