Research On WO₃ Based Gas Sesors For H₂S Detection Of SF₆ Decompodsition Products

The performance of SF₆ electrical insulation equipment is closely related to the purity of SF₆ in the gas chamber.During the production and long-term operation of the equipment,there are inevitably some insulation defects inside the gas chamber,leading to malfunctions in the gas chamber,such as partial discharge,spark discharge,arc discharge and local overheating.These faults will cause SF₆ to decompose to varying degrees,reducing the insulation performance of the equipment.In addition,SF₆ and its decomposition products of varying degrees can react with trace amounts of water and oxygen in the gas chamber to produce a variety of stable decomposition products,such as SO2F2,SOF2,SOF4,SO2,and H₂S,severely reducing the insulating properties of SF₆ gas.It has been shown that these steadily present decomposition products can be used as characteristic decomposition products for diagnosing the type of fault and the degree of discharge,while H₂S can be used to assess the amount of discharge from the fault and whether the fault has solid insulating material involved.Therefore,the development of a high-performance gas sensor that can be used for H₂S detection will help to achieve the identification and concentration of H₂S molecules inside the SF₆ gas chamber and to detect the internal failure of the SF₆ gas chamber in time.As a typical n-type semiconductor,WO₃ has high gas-sensitive activity and has become an important research object in the field of gas sensing due to its non-chemical measurement properties.The shape and physical phase of the material largely determine the gas-sensitive properties of the material.In addition,techniques such as load catalysts,precious metal modifications,construction of heterogeneous junctions and photoexcitation can further enhance the gas-sensitive properties of the materials.In this paper,WO₃ is used as a sensitive material to design and prepare gas sensors for H₂S detection of SF₆ decomposition products.Focused on the controllable design of WO₃ morphology/structure and the gas sensing performance of H₂S.The main studies are as follows:Sphere-like and sphere WO₃ with different morphology and different maximum exposed crystal planes were prepared by solvothermal method combined with high temperature treatment technology,the morphology and structure of the product were studied,and the gas sensing performance and sensing mechanism of H₂S were also discussed.Sphere-like WO₃ is made of aggregated nano-particles around 50 nm.Sphere WO₃ has a smooth surface and is assembled from particles of 30-80 nm.The two materials show an excellent H₂S gas sensing performance at a lower operating temperature,including fast response,good linear relationship,high response value and selectivity.Sphere-like and sphere WO₃ have shown a different optimal selectivity,which has a great relationship with the morphology and maximum exposed surface of the two materials.In addition,the detection limit of Sphere-like WO₃ can reach 100 ppb.A series of WO₃ sensitive materials was prepared by solvothermal synthesis method to control the synthesis precursor and combined with the subsequent calcination treatment.The effect of different solvothermal synthesis conditions on the product was systematically studied,and the growth mechanism of the material was analyzed.It was found that WO₃ with hierarchical flower-like structure is assembled from two-dimensional nanosheets and can be prepared at a lower reaction temperature.The additive diammonium citrate will increase the viscosity of the solution and inhibit the heterogeneous growth of nanosheets,thus affecting the morphology of WO₃.The gas sensing performance and response mechanism of the above series of WO₃ sensitive materials to H₂S were explored.The results show that at a lower operating temperature of 140?,the hierarchical flower-like structure WO₃,the two-dimensional nanosheet WO₃,and WO₃ with both flower-like structure and the irregular loose spherical structure show a high response to H₂S,fast response and recovery,100 ppb detection limit and excellent selectivity.These excellent sensing performances are mainly dominated by the three special morphologies of WO₃.In general,WO₃ sensitive materials can be prepared at milder synthesis temperatures by the solvent thermal method.WO₃-based gas sensor can be used to detect SF₆ decomposition products H₂S at a low operating temperature,which has shown potential application value.