Synthesis Of Bi₂WO₆-based Functional Nanomaterials And Their Gas-sensitive Properties

Currently,environmental problems associated with a wide range of toxic and hazardous gases,which pose a serious threat to sustainable human development due to the rapid development of industry.Gas sensors have been increasingly used in industrial environment production and daily life.It uses a specific mechanism to identify various gas-related information in the surrounding environment and converts it into electrical signals or other forms of information analysis output by rationally designing the device structure,therefore,gas sensing can be realized in many harsh environments,meeting various needs in various fields,and has a wide range of applications.Monometallic oxides represented by Sn O₂ have been used in practically used,but their application in devices is limited due to low selectivity and high operating temperature.Little has been reported about the composite metal oxides Bi₂WO₆、Bi₂VO₆、Bi₂Mo O₆、Cd In₂O₅、Ni Fe₂O₄.Bi₂WO₆ is a multifunctional layered chalcogenide like material with a stable crystal structure and has been widely used in catalysis,piezoelectricity and ferroelectricity.Currently,it is of great interest to researchers in the field of gas sensing.In this paper,Bi₂WO₆ is selected as a gas-sensitive sensing material and characterized by X-ray diffractometer（XRD）,Raman spectroscopy（Raman）,scanning electron microscope（SEM）,energy dispersive spectrometer（EDS）,transmission electron microscope（TEM）,etc.for its structure,morphology and composition.A gas-sensitivity tester is used for gas-sensitive testing experiments.The gas-sensitive mechanism is also described in detail,which provides clues for further Bi₂WO₆ based gas sensing research.1.The bulk Bi₂WO₆ nanoparticles were prepared by hydrothermal method.The p H of the precursor solution was adjusted with sodium hydroxide solution and ammonia water,and the bulk Bi₂WO₆ nanoparticles with cracks on the surface were obtained.The results show that the cracked Bi₂WO₆ surface corresponds to an ultra-fast response and recovery time of 7s/8s when the triethylamine gas is introduced and withdrawn,which is a result of the crack providing more active sites.At an optimum operating temperature of240°C,the sensitivity to 100 ppm triethylamine reached 30.14.2.To optimise the above experiments,a two-step hydrothermal composite of other typical functional materials,Zn O,was used to construct heterojunctions to maximise the performance parameters,and the samples were tested by various characterisation means and the gas-sensitive performance of the composite samples,Zn O/Bi₂WO₆ and Bi₂WO₆,was compared.The response of the Zn O composite Bi₂WO₆ sensor for triethylamine detection was increased by 5 times and the operating temperature was significantly reduced,reaching a response value of 3.18 at room temperature.It shows that this sensor has practicality at room temperature.The gas-sensitive mechanism is described in detail using an electron depletion layer model.The formation of a heterojunction allows the depletion layer to be depleted again,thus effectively improving the gas-sensitive performance.3.In order to further improve the microscopic morphology of Bi₂WO₆ and explore the effect of hydrothermal reaction time on the material,self-assembled Bi₂WO₆ curds composed of nanosheets with an average size of 1μm were successfully synthesized by a simple solvothermal method.The results showed that the crystallinity of the samples gradually became stronger with the increase of reaction time.Gas sensors based on these products were fabricated for ethanol detection.The layered stack-based sensor with a reaction time of 9H-Bi₂WO₆ nanostructures has better sensing performance than others.The significant improvement in the sensing performance of the Bi₂WO₆ sensor may be attributed to its unique structure,good crystallinity...