本文選題：石墨烯 + 氣凝膠��； 參考：《北京化工大學》2017年博士論文

【摘要】：石墨烯作為一種典型的二維納米材料,因其高比表面積、優(yōu)異電導率和熱導率、突出力學性能和化學穩(wěn)定性等,在能源存儲領域具有廣闊的應用前景。以氧化石墨烯(GO)為前驅體材料,通過化學還原來制備石墨烯是一種有較大發(fā)展?jié)摿Φ募夹g路線,可以實現石墨烯的宏量制備。然而,這種方法得到的石墨烯片層容易發(fā)生團聚,影響了石墨烯性能的充分發(fā)揮,限制了其更為廣泛的應用。本論文以GO為前驅體制備了三維的石墨烯材料,預先形成三維石墨烯傳導網絡,保證了石墨烯優(yōu)異傳導性能的充分發(fā)揮。主要創(chuàng)新性研究結果如下:1、泡沫鎳還原氧化石墨烯用作超級電容器電極材料:針對目前三維石墨烯構筑過程中需要大量還原劑和能源消耗的問題,我們提出了一種簡便方法制備可直接用作超級電容器電極材料的三維還原氧化石墨烯/泡沫鎳(RGO/Nifoam)復合材料。在pH=2的室溫條件下,直接利用泡沫鎳對GO進行還原,無需添加其它化學還原劑。得到的RGO在泡沫鎳骨架上組裝,制得RGO/Nifoam復合材料,直接用作超級電容器電極材料,無需添加高分子粘結劑,表現出優(yōu)異的電化學性能。通過調節(jié)還原時間可調控RGO/Ni foam中的RGO含量,達到調控復合電極材料的單位面積比電容的目的。當還原時間從3天提高到15天,在0.5 mA·Cm-2的電流密度下,其面積比電容從26 mF·Cm-2增加到了 136.8 mF·Cm-2。此外,溫度是影響還原速率的重要因素。當提高還原溫度至70℃時,反應5小時后得到的5-hour RGO/Ni foam復合材料比室溫下反應15天得到的15-day RGO/Ni foam復合材料呈現出更為優(yōu)異的電化學性能。5-hour RGO/Ni foam復合材料的面積比電容高達206.7 mF·cm-2,并且兼具優(yōu)異的倍率性能和循環(huán)穩(wěn)定性,充放電循環(huán)10000次,容量保留率高達97.4%。在70℃延長反應時間至9小時,得到的9-hour RGO/Ni foam復合材料表現出了更高的面積比電容,達到323 mF·Cm-2,并且仍然兼具突出的倍率性能和優(yōu)異的循環(huán)穩(wěn)定性。2、多級孔道結構的石墨烯/胞沫鎳復合材料用作電極材料:成功制備一個兼具高導電、含大量含氧官能團、以及多孔道結構的三維石墨烯復合材料,并用作高性能超級電容器電極材料。連續(xù)高效的三維網絡結構為復合材料提供了優(yōu)異的倍率性能,而三維網絡中豐富的含氧官能團則為復合材料提供較高的贗電容。通過將GO/Ni foam復合材料暴露在打火機外焰下,幾秒鐘內就可得到具有多級孔道結構的RGO/Ni foam復合材料。這是因為泡沫鎳中的GO瞬間受熱釋放出大量的氣體導致片層間膨脹與剝離。當用作電化學儲能電極時,這種多級孔道可以為離子擴散和電子傳輸提供快速的通道,而石墨烯片層表面殘留的大量含氧官能團可提供大的贗電容。直接用作超級電容器電極時,RGO/Ni foam復合材料在0.5和30 A·g-1的電流密度下,其比電容分別高達407.2和285.5 F·g-1。當組裝成兩電極的超級電容器體系時,其穩(wěn)定電壓窗口高達1.8 V,可以得到比較可觀的能量密度和功率密度。當用作鋰離子電池的負極材料時,在100 mA·g-1的電流密度下,RGO/Ni foam復合材料的首圈可逆放電和充電容量分別高達 2194 和 1372 mA·h·g-1。3、室溫干燥的石墨烯復合氣凝膠用作高導熱相變儲能復合材料:為了構筑連續(xù)的傳導網絡和三維骨架,解決相變儲能材料熱導率低和尺寸穩(wěn)定性差的問題,我們制備了可以室溫干燥的三維石墨烯凝膠。GO和高品質石墨烯(GNPs)在水中進行自組裝,隨后在空氣中室溫干燥,即獲得高導熱和高壓縮性能的高密度石墨烯(RGO/GNP)復合氣凝膠。RGO片層搭接成一個三維骨架,而GNPs作為增強相可以避免室溫干燥過程中RGO/GNP水凝膠的體積過度收縮。利用真空浸漬方法將常用的相變儲能材料十八醇填充到多孔的RGO/GNP復合氣凝膠中,制得具有優(yōu)異導熱性能的十八醇/RGO/GNP(ORG)復合材料。在12 wt%石墨烯添加量下,ORG復合材料熱導率高達～5.92 W·m-1·K-1,相比于純的十八醇提高了 26倍,其相變焓也高達～202.8 J·g-1。即使在～70 ℃施加1 kg載荷,ORG復合材料仍然能保持良好尺寸穩(wěn)定性,且未見明顯的十八醇熔體漏流。4、高品質的石墨烯氣凝膠用于相變儲能復合材料:以GO為原料制備的三維石墨烯因其片層上含有殘留的含氧官能團和缺陷,嚴重影響了三維網絡的傳導性,且這種三維石墨烯材料的尺寸及形狀高度依賴于反應器的尺寸和形狀。我們以GO為前軀體,通過低溫濃縮GO水分散液獲得具有優(yōu)秀加工性能的GO組裝物;通過冷凍干燥獲得形狀固定的GO氣凝膠;對上述GO氣凝膠進行高溫石墨化處理,以去除石墨烯片上殘留的含氧官能團并修復缺陷,最終制得兼具高效導熱網絡和質輕特點的高品質石墨烯氣凝膠(HGA)。通過簡單地真空浸漬,即可將熔融的十八醇填充到HGAs的三維網絡中得到十八醇/HGA (OHGA)相變儲能復合材料,在較低石墨烯含量下獲得高熱導率。在石墨烯填充量僅僅為～5.0 wt%時,OHGA復合材料的熱導率高達～4.28 W·m-1·K-1,比純的十八醇提高了 18倍多;其相變熔融焓也高達225.3 J·g-1。
[Abstract]:Graphene is a typical two-dimensional nanomaterial. Because of its high specific surface area, excellent conductivity, thermal conductivity, outstanding mechanical properties and chemical stability, graphene has a broad application prospect in the field of energy storage. Graphene oxide (GO) is a precursor material, and the preparation of graphene by chemical reduction is of great potential. The technical route can be used to make the macro preparation of graphene. However, the graphene lamellae obtained by this method are easy to be reunion, affecting the full play of the properties of graphene and limiting its more extensive application. In this paper, a three-dimensional graphene material was prepared by GO as a precursor, and a three-dimensional graphene conduction network was formed in advance to guarantee the stone. The main innovative research results are as follows: 1, nickel foam is used as a supercapacitor electrode material for the reduction of graphene oxide by nickel foam reduction. In view of the problem that a large number of reducing agents and energy consumption are needed in the construction of three-dimensional graphene, a simple method is proposed to be used directly as a supercapacitor. The three-dimensional reduction of graphene oxide / nickel foam (RGO/Nifoam) composite material in the electrode material. At room temperature of pH=2, the GO is reduced directly with nickel foam, and no other chemical reductants need to be added. The obtained RGO is assembled on the foamed nickel skeleton to produce RGO/Nifoam composites directly as the electrode material of the supercapacitor, without the need to add. The polymer binder shows excellent electrochemical performance. By regulating the reduction time, the RGO content in RGO/Ni foam can be regulated to achieve the purpose of regulating the unit area of the composite electrode material. When the reduction time is increased from 3 days to 15 days, the area is increased to 136.8 from 26 mF Cm-2 under the current density of 0.5 mA. Cm-2. In addition, mF Cm-2., temperature is an important factor affecting the reduction rate. When the reduction temperature is increased to 70, the 5-hour RGO/Ni foam composite obtained after 5 hours reacts more than the room temperature for 15 days, and the 15-day RGO/Ni foam composite presents a more excellent electrochemical performance of the.5-hour RGO/Ni foam composite material. Up to 206.7 mF. Cm-2, with excellent multiplication and cycle stability, charge discharge cycle 10000 times, the capacity retention rate is up to 97.4%. at 70 C to 9 hours. The obtained 9-hour RGO/Ni foam composite shows a higher area specific capacitance, up to 323 mF. Cm-2, and still has outstanding multiplier performance and performance. Excellent cyclic stability.2, multistage channel structure of graphene / foam nickel composite material used as electrode material: a successful preparation of a high conductivity, a large number of oxygen functional groups, and porous structure of the three-dimensional graphene composite material, and used as a high-performance supercapacitor electric pole material. Continuous and efficient three-dimensional network structure composite The material provides excellent multiplier performance, while the rich oxygen functional groups in the three-dimensional network provide high pseudopotential for the composite. By exposing the GO/Ni foam composite to the flame of the lighter, the RGO/Ni foam composite with multistage channel structure can be obtained in a few seconds. This is due to the instant heat of the GO in the foam nickel. The release of a large number of gases leads to interlaminar expansion and stripping. When used as an electrochemical energy storage electrode, this multistage channel can provide a fast channel for ion diffusion and electron transport. A large number of oxygen functional groups remaining on the surface of the graphene layer can provide large pseudo capacitors. The RGO/Ni foam composite is used directly as the electrode of the supercapacitor. Under the current density of 0.5 and 30 A. G-1, when the specific capacitance is up to 407.2 and 285.5 F. G-1. respectively, when the supercapacitor system is assembled into two electrodes, the stable voltage window is up to 1.8 V, and a considerable energy density and power density can be obtained. When used as a anode material for lithium ion batteries, the current density at 100 mA. G-1 The first ring reversible discharge and charge capacity of RGO/Ni foam composites are as high as 2194 and 1372 mA. H. G-1.3. The dry graphene composite aerogel at room temperature is used as a high thermal conductivity phase change energy storage composite material. We have prepared a three-dimensional graphene gel.GO and high quality graphene (GNPs), which can be dry at room temperature, and then dry in the air at room temperature. The high density and high density graphene (RGO/GNP) composite aerogel.RGO lamellae of high thermal conductivity and high compressibility are lap into a three-dimensional skeleton, and GNPs can be avoided as an enhanced phase. The volume of RGO/GNP hydrogel is overcontracted during the process of warm drying. Using the vacuum impregnation method, the commonly used phase change energy storage material eighteen alcohol is filled into the porous RGO/GNP composite aerogel. The excellent thermal conductivity of the eighteen alcohol /RGO/GNP (ORG) composite is prepared. The thermal conductivity of the ORG composite is up to 5.92 under the addition of 12 wt% graphene. W. M-1. K-1 is 26 times higher than pure eighteen alcohol, and its phase transition enthalpy is up to 202.8 J. G-1., even at 1 kg loading at 70 C, ORG composites still maintain good dimensional stability, and no obvious eighteen alcohol melt leakage.4 is found. High quality graphene gas condensate is used in phase change energy storage composite material: GO as raw material The three dimensional graphene, which contains residual oxygen functional groups and defects, seriously affects the conductivity of the three-dimensional network, and the size and shape of this three-dimensional graphene material depends highly on the size and shape of the reactor. We use GO as a precursor to obtain excellent processability GO by condensing GO water solution at low temperature. The GO aerogels are obtained by freeze-drying. The above GO aerogels are graphitized at high temperature to remove the residual oxygen functional groups on the graphene sheets and repair the defects. Finally, high quality graphene aerogels (HGA), which have high thermal conductivity network and light quality, can be obtained by simple vacuum impregnation. Eighteen alcohol OHGA (OHGA) phase change energy storage composite was obtained by filling the fused eighteen alcohol into the three-dimensional network of HGAs. The high thermal conductivity was obtained under the lower graphene content. The thermal conductivity of OHGA composites reached to 4.28 W. M-1. K-1 when the filling amount of graphene was only 5 wt%, and the enthalpy of the phase change melting enthalpy was more than that of the pure eighteen alcohol. Also up to 225.3 J. G-1.
【學位授予單位】：北京化工大學
【學位級別】：博士
【學位授予年份】：2017
【分類號】：TB332;TQ127.11

【參考文獻】

相關期刊論文 前1條

1 任文才;高力波;馬來鵬;成會明;;石墨烯的化學氣相沉積法制備[J];新型炭材料;2011年01期

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本文編號：2027087