Gas Sensing Studies On Silver Decorated Graphene Detecting Sulfur Hexafluoride Decomposed Components

Detection of decomposition products of sulfur hexafluoride?SF₆?is one of the best ways to diagnose early latent insulation faults in gas-insulated equipment.Development on gas sensor array,constituted by a series of high-performance gas sensors,used to detect all kinds of decomposition products of sulfur hexafluoride?SF₆?at the same time is material precondition of realizing on-line monitoring and fault diagnosis for SF₆ gasinsulated equipment.With the wide application of SF₆ gas-insulated equipment in power grid,the development of this technology not only reduce fault rate and maintenance cost for equipment,but also ensure the operation safety of power grid.Functionalized graphene,a kind of gas sensing material,shows a good application prospect in the gas sensor field.Supported by the National Natural Science Foundation of China,this paper proposed a related subject——gas sensing studies on silver decorated graphene detecting SF₆ decomposed components.Choose SF₆ decomposed components as the detection object,and synthesizing new gas sensing material——Ag-decorated graphene?Ag-graphene?by chemical redox method.Fabricate resistance-type gas sensor by spraying method,and the sensor was characterized by different methods to test its microstructure and structural feature.Based on theself-designed test platform in our group,we have fully studied the gas sensing properties of Ag-graphene to SF₆ decomposed components?SO₂F₂?SOF₂?SO₂?.Meanwhile,Ag-graphene and gas adsorption models are build based on the First Principle of Density Functional Theory and a series of parameters on gas-sensing properties duringadsorbing process werecalculated respectively,including adsorption energy,net charge transfer,electronic state density,andthe highest occupied andlowest unoccupied molecular orbital.The results of the study are as follows:?1?This paper use chemical redox method to synthesize new gas sensing material,Ag graphene,which shows good crystallinity and uniform silver nanoparticles distribution on the surface of the graphene by covered or wrapped manner.The Aggraphene sensor produced by spraying method process achieve good gas-sensing properties at room condition.From the point of macro,there are obvious difference in response properties between different gases with different concentrations.Their absolute values of sensitivity reduce in following order: SO₂F₂?SO₂?SOF₂.Ag-graphene showed the best selectivity and sensitivity to SO₂F₂.From the point of micro,the silvernanoparticles decoration on the graphene can effective change the electron cloud distribution of the surface and become active site for absorption between gas molecule and graphene surface to reduce the activation energy of gas molecule chemisorption.The silvernanoparticles provide adsorption site for gas molecule that enhances the interaction between gas molecule and Ag-graphene system.?2?Based on the First Principle of Density Functional Theory,Ag-graphene and gas adsorption system are built and investigated to analyze a series of parameters on gassensing properties duringadsorption process,including single gas molecule?SO₂F₂,SOF₂,SO₂?and double gas molecules?2SO₂F₂,2SOF₂,2SO₂?adsorption on Ag-graphene.Both results showed that SO₂F₂ andSO₂ gas molecules on Ag-graphenepresented chemisorption,and the adsorption strength was SO₂F₂>SO₂,while SOF₂ absorption on Ag-graphene was physisorption.?3?The interaction intensity between SF₆ decomposed components?SO₂F₂?SOF₂?SO₂?and Ag-graphene from theoretical calculation is consistent with the results from experiment.As the gas molecules?SO₂F₂?SOF₂?SO₂?attached to the surface of Aggraphene,an induced pull electron effect occurs,the electrons on Ag-graphene transfer partly to gas molecules,so the increased electron hole on the surface enhance conductivity,which corresponds to the decrease of system resistance value after adsorbing gas molecules.This process is called P type adsorption.Ag-graphene exhibits characteristic as P-type semiconductor.