Preparation Of Fe Doped WO₃ And CuO/WO₃ Composites And Their Gas Sensing Properties And Photocatalytic Activity

Tungsten oxide(WO₃)and its composites can be widely used in many fields such as gas sensors,photocatalytic degradations of organic dyes,electrochromic,and photochromism.In this thesis,WO₃ nanoplates,series of Fe-doped WO₃ nanoplates,Cu₂O/WO₃ and Cu O/WO₃ composites were synthesized by a simple hydrothermal method.Gas sensing properties of the series of Fe doped WO₃ nanoplates and Cu O/WO₃ composites were investigated systematically,and the corresponding sensing mechanisms were proposed.The photocatalytic activities of the series of Fe doped WO₃nanoplates as well as Cu₂O/WO₃ composites were investigated and the reaction mechanisms were proposed.The details are as follows.1.A series of Fe doped WO₃ nanoplates with different Fe contents(0.5%-5%)were successfully prepared by hydrothermal method.The samples were characterized by XRD,SEM,TEM,XPS with BET,and their gas-sensitive and visible light degradation properties were systematically investigated to explore the effect of Fe doping on the gas sensing and photocatalytic performance of tungsten oxide.The results show that the Fe-WO₃ nanoplates have excellent gas sensing performance to acetone and good visible light degradation activity to methylene blue(MB)dye.The addition of Fe³⁺to the WO₃ nanoplates significantly accelerated the charge transfer rate of the samples,which may be responsible for the improved gas sensing performance.The 0.5%Fe-WO₃sample exhibited the highest photodegradation activity,which may be related to the enhanced charge transfer rate as well as charge separation efficiency and enhanced absorbance to visible light.In addition to O^2-·as the primary active species,·OH as a secondary active species was also involved in the photodegradation of MB.2.A series of Cu₂O/WO₃ composites were prepared by ultrasonic and hydrothermal treatment of the WO₃ synthesized by hydrothermal method and the Cu₂O synthesized by liquid phase reduction method.The samples were characterized by XRD,SEM,TEM,XPS and BET.The visible photocatalytic activity of the Cu₂O/WO₃composites was systematically investigated,and the corresponding photocatalytic mechanism was proposed by overall considering the specific surface area,light absorption,charge transfer rate and the active species involved in photocatalysis.The results show that the formation of heterojunctions between Cu₂O and WO₃ inhibits the recombination of photogenerated carriers,resulting in improvement in the photocatalytic activity.The material exhibits the highest activity when the molar ratio of the Cu₂O and WO₃ is 1:2.·OH,O₂^-·and h⁺are all involved in the photodegradation of MB as active species.3.A series of Cu O/WO₃ composites were obtained from the as-prepared Cu₂O/WO₃ composites by calcination in air.The samples were analyzed by XRD,SEM,TEM,XPS and N₂ adsorption-desorption isotherm.The gas sensing properties of the Cu O/WO₃ composites were systematically investigated,and the gas sensing mechanism was proposed.The results show that the sensor has the best gas sensing performance to acetone when the molar ratio of the Cu O to WO₃ is 1:2,which could be attributed to the formation of p-n heterojunction that enhanced the charge transfer rate.