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Functional Assembly And Macro Structrue Regulation Of Carbon-based Nano Materials Towards Electrochemical Performance Study

Posted on:2018-05-12Degree:DoctorType:Dissertation
Country:ChinaCandidate:J L XueFull Text:PDF
GTID:1361330596964285Subject:Chemistry
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Due to their high conductivity and mechanical property,carbon-based materials especially for graphene and conductive polymer have been attracted tremendous intersting in electrochemical energy transformation and energy storage.In this work,amorphous carbon?carbon fibers network?,graphene or graphene/polypyrrole?PPy?composites and PPy has been obtained by means of reasonable design and appropriate operation.Then their macro structure has been further regulated forimproving the performance.This method may widen their application and develop their new fields.?1?Amorphous carbon--the network of carbon fibersThe neat,clean and size controled cotton mats?CMs?can be obtained simply by removing of seeds and impurity from natural cotton.Then they were carbonized at 1000? for about 2h with flow of 300 sccm Ar gas for the carbonized cotton mats?CCMs?.After the thermal treatment,the formed CCMs becomes highly conductive.Interestingly,they keep the flexible property of cotton which can be folded and rolled into a multilayer structure.Due to the morphologic compatibility of CM and CCM,the sandwich configuration of a CM within two CCMs has sufficient integrity and flexibility for arbitrary deformation.Even folded at180°,the performance of the supercapacitor remain almost unchanged.Furthermore,the capacitance of the device remains almost unchanged during 10000 charging-discharging cycles whether flat or folded.And it can be flat-folded 1000 times without any changing of performance.It is also interesting that,the as-prepared supercapacitor features a high rate with a rapid frequency response.?2?Three demensional?3D?graphene and graphene/PPy composites3D graphene hydrogel?GH?was fabricated by the hydrothermal treatment of homogeneous graphene oxide?GO?.And 3D graphene-polypyrrole hydrogel?G-PH?was fabricated also by hydrothermal treatment of commixture about fresh pyrrole?Py?monomer and GO.Py was then polymerized into PPy by elcetrochemical polymerization.After that,a cylinder of GH or G-PH was loaded into a syringe which containning enough water to keep a wet condition.It is worth saying that,the diameter of syringe is the same with GH or G-PH to prevent the swell from crosswise.To maintain the stable reshaped structure,the final RSGH or RG-PH sample was left in the container for 2-3Days for solidifying its shape before release of the compression force.The distance between the layers can be controled by compression degree.The sample with different compression in height is obtainedby releasing of the compression force.The re-shaped hybrid actuator exhibits excellent actuation behavior in response to electrochemical potential variation.Even under stimulation at a voltage as low as 0.8 V,actuators based on the re-shaped G-PH exhibit a maximum strain response of up to13.5%,which is the highest value reported to date for graphene-based materials.?3?3D network of PPy sheeta)The 3D network of PPy sheets was obtained by template-assisted chemical polymerization.3D V2O5 nanosheets foam was used as template.At first,a solvothermal process prompted the Py uniform distributing on the sheet of V2O5.Then the FeCl3 was added to induce polymerization of Py.After that,the product was successively washed with 0.1 M HCl and water for several times.The multifunctional PPy has been used as adsorbent,compressive materials and shape memory materials.It aslo can be used as elctrode materials for supercapicitor,even for compressible supercapacitor.After freeze-drying,the ultralight PPy foam was obtained.This synthetic method has universality for fabricating other conductive polymer.b)The network of PPy sheets can also be obtained by template-assisted electrochemical polymerization.It is worth mention that,the new type of functional PPy can be controled by chemical modification and phycial annealfor graded distribution of anions.It opens up a new research field of conductive polymer.i.The gradient 3D PPy?g-3D-PPy?was formed by electrolyte/electric field co-induced of anions doped into the 3D PPy framework.After freeze-drying treatment,the as-formed g-3D-PPy foam was then compressed into a tablet to enhance the gradient distribution of ClO4-,and facilitate the ion transport.It is intresting that,a high power density output of?6.9 mW m-2 is achieved under the moisture environment.ii.The moisture-induced power generation mechanism for g-3D-PPy can be explain as follows:With the accumulation of water molecules in g-3D-PPy,a regional solvation effect is enhanced,resulting in the broken of Li+-ClO4-and the release of free Li+.Owing to the concentration gradient of Li+induced by the gradient distribution of ClO4-in g-3D-PPy,the small Li+ion diffuses from high concentration side to the low side once ionized by water molecules,thus leading to generate a strong induced potential,vice versa.The chemical potential-electric energy conversion process depends on the water adsorption and desorption behaviorsiii.More interestingly,when changing the categray of gas molecule,it also activates the power generate of g-3D-PPy,the same as ethanol.Furthermore,both the voltage and current density output can be enhanced with the increasing of ethanol vapor concentration.So it can be used as self-power sensor.Impressively,the electric generation behavior of g-3D-PPy can also be inspired by other organic and inorganic solvent vapors in which the output of voltage and current trailed off as the polarity abate of the organic solvent.The actived gas can also be as aid or alkaline medium.Based on these above findings,this self-powered sensor can be widely applied for detecting the variation concentrate of gas molecule or identificating of gas molecule polarity.
Keywords/Search Tags:Carbon-based nano materials, Functional Assembly, Macro Structure Regulation, Supercapacitor, Actuator, Moisture-based power generation
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