石墨烯基雜化材料可控制備及其在超級電容器中的應(yīng)用
發(fā)布時(shí)間：2018-09-11 17:00
【摘要】：可持續(xù)能源的生產(chǎn)、存儲(chǔ)和消費(fèi)是當(dāng)今世界所面臨的重大挑戰(zhàn)。目前,核心目標(biāo)不僅是如何構(gòu)建可再生和可持續(xù)的新型能源,更重要的是如何有效地儲(chǔ)存和釋放能量以滿足實(shí)際應(yīng)用中的需求,比如新能源電動(dòng)汽車、便攜式電子產(chǎn)品、太陽能和風(fēng)力發(fā)電儲(chǔ)能系統(tǒng)等。超級電容器作為一種介于傳統(tǒng)電容器和電池之間的綠色新型儲(chǔ)能器件,由于具有高的功率密度、優(yōu)異的循環(huán)穩(wěn)定性、良好的可靠性和相對低廉的制作成本,已經(jīng)引起廣大科研者的關(guān)注和重視。石墨烯是近年來發(fā)現(xiàn)的只有一個(gè)碳原子厚度的二維材料,因其極大的比表面積、超高的導(dǎo)電性和良好的化學(xué)穩(wěn)定性,在儲(chǔ)能材料領(lǐng)域顯示出巨大的應(yīng)用前景。本論文主要以高性能、低成本石墨烯基雜化材料的可控制備和在超級電容器領(lǐng)域中的應(yīng)用為主題,利用石墨烯為導(dǎo)電網(wǎng)絡(luò)和機(jī)械支撐設(shè)計(jì)合成了多種無機(jī)化合物與石墨烯的高性能雜化電極材料,并探索了雜化材料的形成機(jī)理和其微觀結(jié)構(gòu)對其電化學(xué)性能的影響,有望促進(jìn)新型高性能超級電容器電極材料的發(fā)展。主要研究內(nèi)容和取得的進(jìn)展如下:(1)合成了具有獨(dú)特介晶多孔結(jié)構(gòu)、大比表面積、高導(dǎo)電性的石墨烯/自組裝三氧化二鐵納米介晶雜化材料。探索了石墨烯/自組裝三氧化二鐵納米介晶雜化材料的生長過程和形成機(jī)理并提出了自組裝成型機(jī)理。研究顯示,石墨烯表面棒狀α-Fe_2O_3介晶是由初始形成的FeOOH納米棒通過自組裝和同時(shí)伴隨的相轉(zhuǎn)變而形成的。恒電流充/放電曲線顯示出,石墨烯/自組裝三氧化二鐵納米介晶雜化材料具有優(yōu)越的比電容性能,在1MNa_2SO_4中性水溶液中,在3Ag~(-1)電流密度下,其比容量高達(dá)306.9Fg~(-1)。即使在10Ag~(-1)的高放電電流密度下,由于該雜化材料增強(qiáng)的離子和電荷傳輸效率仍然顯示了較高的比電容(98.2Fg~(-1))。石墨烯/自組裝三氧化二鐵納米介晶雜化材料也展示了優(yōu)良的循環(huán)性能,并優(yōu)于先前報(bào)道的石墨烯/三氧化二鐵復(fù)合電極材料。(2)雖然多孔三氧化二鐵納米介晶在石墨烯表面已經(jīng)成功合成,但其孔隙大小和結(jié)晶度是不可控的。為了進(jìn)一步提高其電化學(xué)性能,通過水熱法和隨后的煅燒過程制備了孔隙大小和結(jié)晶度均可控的石墨烯/熱誘導(dǎo)多孔三氧化二鐵雜化材料。在雜化材料中,多孔α-Fe_2O_3的孔徑大小和結(jié)晶度可以通過改變加熱速率進(jìn)行有效調(diào)控。其中,在1°Cmin~(-1)的緩慢升溫速率下所獲得雜化材料(S-PIGCs),由于優(yōu)化的結(jié)構(gòu)、窄的孔徑分布、合適的微晶尺寸和良好的導(dǎo)電性,作為超級電容器電極材料在3Ag~(-1)的電流密度下,表現(xiàn)出343.7Fg~(-1)的超高比電容,甚至在10Ag~(-1)的高電流密度下,仍保留182.1Fg~(-1)的比電容。另外,S-PIGCs也顯示了優(yōu)越的循環(huán)穩(wěn)定性,在50,000次循環(huán)充放電后,原始比容量仍可保留95.8%,同時(shí)其庫倫效率可達(dá)98.6%。(3)石墨烯由于大的比表面積、良好的化學(xué)穩(wěn)定性、高的機(jī)械柔韌性和優(yōu)異的導(dǎo)電性,可作為贗電容材料的良好載體。但是,目前所制備的石墨烯由于表面存在大量的含氧基團(tuán),從而表現(xiàn)出較差的導(dǎo)電性和較低的本質(zhì)電容容量。對石墨烯進(jìn)行摻氮處理可以有效提高石墨烯的電導(dǎo)率并增加其表面的電化學(xué)活性點(diǎn)。利用摻氮這一優(yōu)勢,本文采用原位一步法制備了多種摻氮石墨烯與錳的氧化物雜化材料。首先,采用低溫水熱法(120℃)利用尿素作為氮源一步合成摻氮石墨烯/超薄二氧化錳片雜化材料(NGMCs)。在水熱反應(yīng)過程中,石墨烯與超薄二氧化錳片的結(jié)合和氮原子在石墨烯中的摻雜是同步進(jìn)行的。研究表明,石墨烯與超薄二氧化錳片結(jié)合非常緊密,同時(shí)氮原子的摻雜不僅可以提高雜化材料的導(dǎo)電性,而且還可以有效抑制二氧化錳在石墨烯表面的團(tuán)聚,使得其均勻分布于石墨烯表面。由于高導(dǎo)電摻氮石墨烯與二維超薄二氧化錳片的優(yōu)化結(jié)合,NGMCs電極的電化學(xué)性能明顯優(yōu)于石墨烯/超薄二氧化錳片雜化材料(GMCs)電極。當(dāng)電流密度從0.2Ag~(-1)增加2Ag~(-1)時(shí),NGMCs電極的比電容仍保留初始電容的~74.9%,而GMCs電極僅保留有27%。此外,NGMCs電極也顯示了良好的循環(huán)穩(wěn)定性,在2000次循環(huán)充放電后,還保留有94.2%的原始比容量。其次,通過一步水熱法利用苯胺作為氮源合成褶皺摻氮石墨烯/超細(xì)四氧化三錳雜化材料(CNGMNs),并測試了其作為超級電容器電極材料的電化學(xué)性能。在CNGMNs制備過程中,由于苯胺的輔助作用,同時(shí)實(shí)現(xiàn)了超細(xì)四氧化三錳納米顆粒在石墨烯表面生長和氮原子在石墨烯中的摻雜。在所得CNGMNs中,氮原子在石墨烯中的摻雜以及褶皺摻氮石墨烯與超細(xì)四氧化三錳納米顆粒的優(yōu)化結(jié)合,可以有效提高其導(dǎo)電性、比表面積和電化學(xué)利用率,進(jìn)而增加了其電化學(xué)性能。CNGMNs電極的比電容大概是其對應(yīng)純四氧化三錳顆粒電極的5倍,在1Ag~(-1)的電流密度下,其比電容可達(dá)205.5Fg~(-1)。當(dāng)電流密度高達(dá)10Ag~(-1)時(shí),CNGMNs電極仍顯示了較高的比容量(110Fg~(-1)),表現(xiàn)出良好的倍率性能;在2000次循環(huán)測試后,比容量保持有98.7%,顯示了優(yōu)異的循環(huán)穩(wěn)定性。最后,在甲酰胺的作用下,開發(fā)了摻氮石墨烯/羥基氧化錳納米線雜化材料(MNGHNs),隨后將該雜化材料與熱處理氧化石墨烯(AGO)的水溶液進(jìn)行混合,并通過真空過濾獲得了AGO夾雜MNGHNs的三明治結(jié)構(gòu)柔性自支撐薄膜(MNGHNs/AGO)。所得柔性薄膜滿足了超級電容器電極所需的各種動(dòng)力學(xué)性能需求,如可與電解液充分接觸的大量多孔通道,可供電子高速傳遞的導(dǎo)電網(wǎng)絡(luò),可存儲(chǔ)更多電容量和更高能量密度的高含量MNGHNs(70wt%)以及可保持長期循環(huán)穩(wěn)定性所需的穩(wěn)定材料結(jié)構(gòu)和機(jī)械強(qiáng)度。由于以上的諸多優(yōu)點(diǎn),MNGHNs/AGO柔性自支撐薄膜顯示了優(yōu)異的電化學(xué)性能,其面電容在1mAcm~(-2)的電流密度下高達(dá)173.2mFcm~(-2)。最后,將該雜化薄膜組裝為柔性固態(tài)超級電容器,并系統(tǒng)研究了其電化學(xué)性能。研究結(jié)果顯示,MNGHNs/AGO固態(tài)超級電容器的體電容在0.1Acm~(-3)下達(dá)到了26.3Fcm~(-3),在功率密度為0.04Wcm~(-3)下獲得的最大能量密度是2.34mWhcm~(-3);在5Acm~(-3)的電流密度下,200,000次循環(huán)充放電后,初始容量仍保持91.5%。
[Abstract]:The production, storage and consumption of sustainable energy is a major challenge facing the world today. At present, the core objective is not only how to build renewable and sustainable new energy, but also how to effectively store and release energy to meet the needs of practical applications, such as new energy electric vehicles, portable electronic products, the sun. As a kind of green energy storage device between traditional capacitors and batteries, supercapacitors have attracted the attention of researchers for their high power density, excellent cycle stability, good reliability and relatively low manufacturing cost. Two-dimensional materials with only one carbon atom thickness have been found to have great potential applications in the field of energy storage materials due to their large specific surface area, ultra-high conductivity and good chemical stability. A variety of inorganic compounds and graphene hybrid electrode materials were designed and synthesized using graphene as conductive network and mechanical support. The formation mechanism of the hybrid materials and the effect of their microstructure on their electrochemical properties were explored. It is expected to promote the development of novel electrode materials for high performance supercapacitors. The results are as follows: (1) Graphene/self-assembled ferric oxide nano-mesomorphic hybrid materials with unique mesomorphic porous structure, large specific surface area and high conductivity were synthesized. The growth process and formation mechanism of graphene/self-assembled ferric oxide nano-mesomorphic hybrid materials were explored and the self-assembled forming mechanism was proposed. It is shown that the rod-like alpha-Fe_2O_3 mesomorphism on the graphene surface is formed by the self-assembly of the initially formed FeOOH nanorods and the accompanying phase transition. The constant current charge/discharge curves show that the graphene/self-assembled ferrous oxide nano-mesomorphism hybrid material has superior specific capacitance properties in 1MNa_2SO_4 neutral aqueous solution and 3Ag~(-1). The specific capacitance of the hybrid material is as high as 306.9Fg~(-1) at current density. Even at the high discharge current density of 10Ag~(-1), the enhanced ion and charge transfer efficiency of the hybrid material still shows a higher specific capacitance (98.2Fg~(-1). Graphene/self-assembled ferrous oxide nano-mesomorphic hybrid material also exhibits excellent cycling performance and is superior to that of 10Ag~(-1). Previous reports on graphene/ferric oxide composite electrode materials. (2) Although porous ferrous oxide nanocrystals have been successfully synthesized on graphene surface, their pore size and crystallinity are uncontrollable. In order to further improve their electrochemical performance, both pore size and crystallinity were prepared by hydrothermal method and subsequent calcination process. Controllable graphene/thermally induced porous ferric oxide hybrids. Pore size and crystallinity of porous alpha-Fe_2O_3 can be effectively controlled by varying heating rates in hybrids. Hybrids (S-PIGCs) obtained at a slow heating rate of 1 Cmin ~(-1) have narrow pore size distribution due to optimized structure and suitable crystallinity. Microcrystalline size and good conductivity, as a supercapacitor electrode material, show 343.7 Fg-1 supercapacitor at current density of 3Ag~(-1), even at high current density of 10Ag~(-1), retain 182.1 Fg~(-1) specific capacitor. In addition, S-PIGCs also show superior cyclic stability, after 50,000 cycles of charging and discharging, the original. Graphene can be used as a good carrier for pseudocapacitor materials because of its large specific surface area, good chemical stability, high mechanical flexibility and excellent conductivity. However, the graphene prepared at present has a large number of oxygen-containing groups on the surface, thus showing good performance. Nitrogen-doped graphene can effectively improve the conductivity of graphene and increase the electrochemical activity of graphene. Using the advantage of nitrogen-doped graphene, a variety of nitrogen-doped graphene and manganese oxide hybrid materials were prepared by in-situ one-step method. Nitrogen-doped graphene/ultrathin manganese dioxide hybrid materials (NGMCs) were synthesized by one-step synthesis using urea as nitrogen source at 120 C. The combination of graphene with ultrathin manganese dioxide sheets and the doping of nitrogen atoms in graphene were carried out synchronously during hydrothermal reaction. Atomic doping can not only improve the conductivity of hybrid materials, but also effectively inhibit the agglomeration of manganese dioxide on graphene surface and make it evenly distributed on graphene surface. When the current density increased from 0.2Ag~(-1) to 2Ag~(-1), the specific capacitance of the NGMCs electrode remained at ~74.9% of the initial capacitance, while that of the GMCs electrode remained at only 27%. Nitrogen-doped graphene/ultrafine manganese tetroxide hybrid materials (CNGMNs) were synthesized by one-step hydrothermal method using aniline as nitrogen source, and their electrochemical properties as electrode materials for supercapacitors were tested. In the obtained CNGMNs, the doping of nitrogen atoms in graphene and the optimum combination of folded nitrogen-doped graphene and ultrafine manganese tetroxide nanoparticles can effectively improve their conductivity, specific surface area and electrochemical utilization rate, thereby increasing their electrochemical performance. At the current density of 1Ag~(-1), the specific capacitance can reach 205.5Fg~(-1). When the current density is as high as 10Ag~(-1), the CNGMNs electrode still shows a high specific capacity (110Fg~(-1)), showing a good rate performance; after 2000 cycles, the specific capacitance maintains 98.7%, showing an excellent performance. Finally, nitrogen-doped graphene/hydroxy manganese oxide nanowire hybrid material (MNGHNs) was developed under the action of formamide. The hybrid material was then mixed with the aqueous solution of heat-treated graphene oxide (AGO), and the sandwich structure flexible self-supporting films (MNGHNs/AG) containing MNGHNs were obtained by vacuum filtration. O. The resulting flexible film meets the various dynamic requirements of the supercapacitor electrodes, such as a large number of porous channels in full contact with the electrolyte, a conducting network for high-speed transmission of electrons, a high content of MNGHNs (70wt%) with more capacitance and higher energy density, and the stability required to maintain long-term cycle stability. MNGHNs/AGO flexible self-supporting thin films exhibit excellent electrochemical properties, and their surface capacitance is as high as 173.2 mFcm~(-2) at the current density of 1 mAcm~(-2). Finally, the hybrid thin films are assembled into flexible solid-state supercapacitors and their electrochemical properties are systematically studied. The results show that the bulk capacitance of MNGHNs/AGO solid-state supercapacitor reaches 26.3 Fcm~(-3) at 0.1Acm~(-3), the maximum energy density at 0.04 Wcm~(-3) is 2.34 mWhcm~(-3), and the initial capacity remains 91.5% after 200,000 cycles of charging and discharging at 5 Acm~(-3).
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TM53;TB33
本文編號：2237295
[Abstract]:The production, storage and consumption of sustainable energy is a major challenge facing the world today. At present, the core objective is not only how to build renewable and sustainable new energy, but also how to effectively store and release energy to meet the needs of practical applications, such as new energy electric vehicles, portable electronic products, the sun. As a kind of green energy storage device between traditional capacitors and batteries, supercapacitors have attracted the attention of researchers for their high power density, excellent cycle stability, good reliability and relatively low manufacturing cost. Two-dimensional materials with only one carbon atom thickness have been found to have great potential applications in the field of energy storage materials due to their large specific surface area, ultra-high conductivity and good chemical stability. A variety of inorganic compounds and graphene hybrid electrode materials were designed and synthesized using graphene as conductive network and mechanical support. The formation mechanism of the hybrid materials and the effect of their microstructure on their electrochemical properties were explored. It is expected to promote the development of novel electrode materials for high performance supercapacitors. The results are as follows: (1) Graphene/self-assembled ferric oxide nano-mesomorphic hybrid materials with unique mesomorphic porous structure, large specific surface area and high conductivity were synthesized. The growth process and formation mechanism of graphene/self-assembled ferric oxide nano-mesomorphic hybrid materials were explored and the self-assembled forming mechanism was proposed. It is shown that the rod-like alpha-Fe_2O_3 mesomorphism on the graphene surface is formed by the self-assembly of the initially formed FeOOH nanorods and the accompanying phase transition. The constant current charge/discharge curves show that the graphene/self-assembled ferrous oxide nano-mesomorphism hybrid material has superior specific capacitance properties in 1MNa_2SO_4 neutral aqueous solution and 3Ag~(-1). The specific capacitance of the hybrid material is as high as 306.9Fg~(-1) at current density. Even at the high discharge current density of 10Ag~(-1), the enhanced ion and charge transfer efficiency of the hybrid material still shows a higher specific capacitance (98.2Fg~(-1). Graphene/self-assembled ferrous oxide nano-mesomorphic hybrid material also exhibits excellent cycling performance and is superior to that of 10Ag~(-1). Previous reports on graphene/ferric oxide composite electrode materials. (2) Although porous ferrous oxide nanocrystals have been successfully synthesized on graphene surface, their pore size and crystallinity are uncontrollable. In order to further improve their electrochemical performance, both pore size and crystallinity were prepared by hydrothermal method and subsequent calcination process. Controllable graphene/thermally induced porous ferric oxide hybrids. Pore size and crystallinity of porous alpha-Fe_2O_3 can be effectively controlled by varying heating rates in hybrids. Hybrids (S-PIGCs) obtained at a slow heating rate of 1 Cmin ~(-1) have narrow pore size distribution due to optimized structure and suitable crystallinity. Microcrystalline size and good conductivity, as a supercapacitor electrode material, show 343.7 Fg-1 supercapacitor at current density of 3Ag~(-1), even at high current density of 10Ag~(-1), retain 182.1 Fg~(-1) specific capacitor. In addition, S-PIGCs also show superior cyclic stability, after 50,000 cycles of charging and discharging, the original. Graphene can be used as a good carrier for pseudocapacitor materials because of its large specific surface area, good chemical stability, high mechanical flexibility and excellent conductivity. However, the graphene prepared at present has a large number of oxygen-containing groups on the surface, thus showing good performance. Nitrogen-doped graphene can effectively improve the conductivity of graphene and increase the electrochemical activity of graphene. Using the advantage of nitrogen-doped graphene, a variety of nitrogen-doped graphene and manganese oxide hybrid materials were prepared by in-situ one-step method. Nitrogen-doped graphene/ultrathin manganese dioxide hybrid materials (NGMCs) were synthesized by one-step synthesis using urea as nitrogen source at 120 C. The combination of graphene with ultrathin manganese dioxide sheets and the doping of nitrogen atoms in graphene were carried out synchronously during hydrothermal reaction. Atomic doping can not only improve the conductivity of hybrid materials, but also effectively inhibit the agglomeration of manganese dioxide on graphene surface and make it evenly distributed on graphene surface. When the current density increased from 0.2Ag~(-1) to 2Ag~(-1), the specific capacitance of the NGMCs electrode remained at ~74.9% of the initial capacitance, while that of the GMCs electrode remained at only 27%. Nitrogen-doped graphene/ultrafine manganese tetroxide hybrid materials (CNGMNs) were synthesized by one-step hydrothermal method using aniline as nitrogen source, and their electrochemical properties as electrode materials for supercapacitors were tested. In the obtained CNGMNs, the doping of nitrogen atoms in graphene and the optimum combination of folded nitrogen-doped graphene and ultrafine manganese tetroxide nanoparticles can effectively improve their conductivity, specific surface area and electrochemical utilization rate, thereby increasing their electrochemical performance. At the current density of 1Ag~(-1), the specific capacitance can reach 205.5Fg~(-1). When the current density is as high as 10Ag~(-1), the CNGMNs electrode still shows a high specific capacity (110Fg~(-1)), showing a good rate performance; after 2000 cycles, the specific capacitance maintains 98.7%, showing an excellent performance. Finally, nitrogen-doped graphene/hydroxy manganese oxide nanowire hybrid material (MNGHNs) was developed under the action of formamide. The hybrid material was then mixed with the aqueous solution of heat-treated graphene oxide (AGO), and the sandwich structure flexible self-supporting films (MNGHNs/AG) containing MNGHNs were obtained by vacuum filtration. O. The resulting flexible film meets the various dynamic requirements of the supercapacitor electrodes, such as a large number of porous channels in full contact with the electrolyte, a conducting network for high-speed transmission of electrons, a high content of MNGHNs (70wt%) with more capacitance and higher energy density, and the stability required to maintain long-term cycle stability. MNGHNs/AGO flexible self-supporting thin films exhibit excellent electrochemical properties, and their surface capacitance is as high as 173.2 mFcm~(-2) at the current density of 1 mAcm~(-2). Finally, the hybrid thin films are assembled into flexible solid-state supercapacitors and their electrochemical properties are systematically studied. The results show that the bulk capacitance of MNGHNs/AGO solid-state supercapacitor reaches 26.3 Fcm~(-3) at 0.1Acm~(-3), the maximum energy density at 0.04 Wcm~(-3) is 2.34 mWhcm~(-3), and the initial capacity remains 91.5% after 200,000 cycles of charging and discharging at 5 Acm~(-3).
【學(xué)位授予單位】：上海交通大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TM53;TB33
【參考文獻(xiàn)】
相關(guān)期刊論文 前1條
1 沈宸;陸云;;石墨烯/導(dǎo)電聚合物復(fù)合材料在超級電容器電極材料方面的研究進(jìn)展[J];高分子學(xué)報(bào);2014年10期
，本文編號：2237295
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