多維摻雜碳材料的可控組裝及其氧還原性能的研究
發(fā)布時(shí)間：2018-11-18 13:24
【摘要】：電催化氧還原反應(yīng)是燃料電池陰極的一個(gè)重要的反應(yīng),由于其遲滯的動(dòng)力學(xué)過(guò)程,成為限制燃料電池性能提升的關(guān)鍵步驟。因而,開發(fā)高效氧還原催化劑具有重大意義。對(duì)于氧還原反應(yīng)來(lái)說(shuō),可以主要分為高效難發(fā)生的一步四電子反應(yīng)及低效易發(fā)生第一步反應(yīng)的兩步兩電子反應(yīng)。由于兩電子過(guò)程的第二步反應(yīng)更難發(fā)生,且中間產(chǎn)物H_2O_2具有極強(qiáng)的催化劑毒性,因而制備具有四電子反應(yīng)選擇性,高效、高穩(wěn)定性及低成本的氧還原催化劑是關(guān)鍵。本文致力開發(fā)具有優(yōu)異電催化氧還原性能的碳基催化材料,通過(guò)摻雜引入催化活性位點(diǎn)進(jìn)而控制四電子反應(yīng)過(guò)程;構(gòu)筑多維立體結(jié)構(gòu)提高電解液的傳輸及電流的體相導(dǎo)電性;通過(guò)催化劑表面造孔及形成褶皺等方式降低碳材料的表面能,增強(qiáng)對(duì)氧氣的吸附能力,同時(shí)增大了材料的比表面積。以呈不同電性的聚合物通過(guò)靜電作用可控的構(gòu)筑了一系列具有多維立體結(jié)構(gòu)的高效碳基氧還原催化劑,實(shí)現(xiàn)了高效的四電子氧還原進(jìn)程。在論文第一部分,我們通過(guò)使用聚對(duì)苯撐乙烯(PPV-precursor)作為前驅(qū)物,利用其水溶性及正電性通過(guò)插層修飾,水熱自組裝在石墨烯表面形成了聚合物球,最后經(jīng)氨氣氣氛下高溫焙燒,形成了薄層多褶皺的氮摻雜多孔石墨烯。研究發(fā)現(xiàn),該電極材料較高的氧還原催化活性及循環(huán)穩(wěn)定性。三維結(jié)構(gòu)碳納米催化劑由于結(jié)構(gòu)上的優(yōu)勢(shì)(更大的比表面積,更穩(wěn)定的催化劑材料結(jié)構(gòu))可以表現(xiàn)出比二維結(jié)構(gòu)催化劑更優(yōu)異的催化活性。在論文第二部分,我們研究了通過(guò)PPV-precursor的粘接作用,實(shí)現(xiàn)了三維N-RGO-PPV(c)-CNTs材料的構(gòu)筑,并得到了更為穩(wěn)固結(jié)構(gòu)和更大的比表面積,得到了具有更多反應(yīng)活性位點(diǎn)的氧還原催化劑。作為無(wú)鉑非金屬氧還原催化劑,N-RGO-PPV(c)-CNTs具有接近商業(yè)鉑碳的起始電位(0.92V)及高于商業(yè)鉑碳的極限電流密度(5.7m A*cm-2);此外,催化劑還具有優(yōu)良的抗甲醇能力及循環(huán)穩(wěn)定性,可以看出其具有大規(guī)模應(yīng)用的前景。在論文第三部分,我們用聚乙酰亞胺(PEI)修飾氧化石墨使其表面帶正電,通過(guò)靜電作用可以使石墨烯量子點(diǎn)(GQDs)與氧化石墨烯進(jìn)行有效的復(fù)合,進(jìn)而形成具有二維立體結(jié)構(gòu)的氧還原催化劑;GQDs的引入有效的阻止了石墨烯片層的聚集,提高了催化劑的比表面積;而小尺寸GQDs為催化劑提供了更多的活性位,進(jìn)而提高了催化劑表面對(duì)氧氣分子的吸附能。隨后,我們通過(guò)一步水熱法實(shí)現(xiàn)了硼氮雜原子的摻雜及氧化石墨的還原,制備了新型的具有氧還原催化潛質(zhì)的硼氮共摻雜GQDs/石墨烯二維碳材料。
[Abstract]:Electrocatalytic oxygen reduction is an important reaction of fuel cell cathode. Because of its hysteresis kinetic process, it becomes a key step to limit the performance of fuel cell. Therefore, it is of great significance to develop high-efficiency oxygen reduction catalyst. For the oxygen reduction reaction, it can be divided into one step and four electron reaction which is highly efficient and difficult to occur, and two step two electron reaction which is easy to take place in the first step reaction with low efficiency. Because the second step of the two-electron process is more difficult to take place and the intermediate product H_2O_2 is highly toxic to the catalyst, the preparation of oxygen reduction catalyst with four-electron reaction selectivity, high efficiency, high stability and low cost is the key. This paper is devoted to the development of carbon-based catalytic materials with excellent electrocatalytic oxygen reduction performance, which can control the four-electron reaction process by introducing catalytic active sites into the catalyst, and construct multi-dimensional structures to improve the transport of electrolyte and the bulk conductivity of the current. The surface energy of carbon materials was reduced by making pores and forming folds on the surface of catalysts, and the adsorption ability of oxygen was enhanced, and the specific surface area of the materials was increased. A series of highly efficient carbon-based oxygen reduction catalysts with multi-dimensional structure were constructed by electrostatics with different electrical properties, and the process of four-electron oxygen reduction was realized. In the first part of the thesis, polymer spheres were formed by hydrothermal self-assembly on the surface of graphene by using poly (p-phenylene) (PPV-precursor) as precursor and by using its water-solubility and positive electrical properties through intercalation modification. Finally, nitrogen doped porous graphene was formed by calcination in ammonia atmosphere at high temperature. It is found that the electrode material has high catalytic activity and cycle stability for oxygen reduction. Three-dimensional carbon nanocatalysts exhibit better catalytic activity than two-dimensional catalysts due to their structural advantages (larger specific surface area and more stable structure of catalyst materials). In the second part of the thesis, we study the construction of 3D N-RGO-PPV (c)-CNTs materials by bonding of PPV-precursor, and obtain more stable structure and larger specific surface area. Oxygen reduction catalysts with more reactive sites were obtained. As a non-platinum non-metallic oxygen reduction catalyst, N-RGO-PPV (c)-CNTs has the initial potential of commercial platinum carbon (0.92V) and the limit current density of commercial platinum carbon (5.7m A*cm-2). In addition, the catalyst also has excellent methanol resistance and cycle stability, it can be seen that it has the prospect of large-scale application. In the third part of the thesis, we modify graphite oxide with polyimide (PEI) to make it have positive charge on its surface. By electrostatic action, we can effectively compound graphene quantum dot (GQDs) with graphene oxide. Then the oxygen reduction catalyst with two-dimensional stereoscopic structure was formed. The introduction of GQDs can effectively prevent the agglomeration of graphene layers and increase the specific surface area of the catalyst, while the small size GQDs provides more active sites for the catalyst, and thus increases the adsorption energy of oxygen molecules on the surface of the catalyst. Subsequently, the boron nitrogen hetero-atom doping and graphite oxide reduction were realized by one-step hydrothermal method. A novel boron-nitrogen co-doped GQDs/ graphene two-dimensional carbon material with oxygen reduction potential was prepared.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ127.11;O643.36
[Abstract]:Electrocatalytic oxygen reduction is an important reaction of fuel cell cathode. Because of its hysteresis kinetic process, it becomes a key step to limit the performance of fuel cell. Therefore, it is of great significance to develop high-efficiency oxygen reduction catalyst. For the oxygen reduction reaction, it can be divided into one step and four electron reaction which is highly efficient and difficult to occur, and two step two electron reaction which is easy to take place in the first step reaction with low efficiency. Because the second step of the two-electron process is more difficult to take place and the intermediate product H_2O_2 is highly toxic to the catalyst, the preparation of oxygen reduction catalyst with four-electron reaction selectivity, high efficiency, high stability and low cost is the key. This paper is devoted to the development of carbon-based catalytic materials with excellent electrocatalytic oxygen reduction performance, which can control the four-electron reaction process by introducing catalytic active sites into the catalyst, and construct multi-dimensional structures to improve the transport of electrolyte and the bulk conductivity of the current. The surface energy of carbon materials was reduced by making pores and forming folds on the surface of catalysts, and the adsorption ability of oxygen was enhanced, and the specific surface area of the materials was increased. A series of highly efficient carbon-based oxygen reduction catalysts with multi-dimensional structure were constructed by electrostatics with different electrical properties, and the process of four-electron oxygen reduction was realized. In the first part of the thesis, polymer spheres were formed by hydrothermal self-assembly on the surface of graphene by using poly (p-phenylene) (PPV-precursor) as precursor and by using its water-solubility and positive electrical properties through intercalation modification. Finally, nitrogen doped porous graphene was formed by calcination in ammonia atmosphere at high temperature. It is found that the electrode material has high catalytic activity and cycle stability for oxygen reduction. Three-dimensional carbon nanocatalysts exhibit better catalytic activity than two-dimensional catalysts due to their structural advantages (larger specific surface area and more stable structure of catalyst materials). In the second part of the thesis, we study the construction of 3D N-RGO-PPV (c)-CNTs materials by bonding of PPV-precursor, and obtain more stable structure and larger specific surface area. Oxygen reduction catalysts with more reactive sites were obtained. As a non-platinum non-metallic oxygen reduction catalyst, N-RGO-PPV (c)-CNTs has the initial potential of commercial platinum carbon (0.92V) and the limit current density of commercial platinum carbon (5.7m A*cm-2). In addition, the catalyst also has excellent methanol resistance and cycle stability, it can be seen that it has the prospect of large-scale application. In the third part of the thesis, we modify graphite oxide with polyimide (PEI) to make it have positive charge on its surface. By electrostatic action, we can effectively compound graphene quantum dot (GQDs) with graphene oxide. Then the oxygen reduction catalyst with two-dimensional stereoscopic structure was formed. The introduction of GQDs can effectively prevent the agglomeration of graphene layers and increase the specific surface area of the catalyst, while the small size GQDs provides more active sites for the catalyst, and thus increases the adsorption energy of oxygen molecules on the surface of the catalyst. Subsequently, the boron nitrogen hetero-atom doping and graphite oxide reduction were realized by one-step hydrothermal method. A novel boron-nitrogen co-doped GQDs/ graphene two-dimensional carbon material with oxygen reduction potential was prepared.
【學(xué)位授予單位】：吉林大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類號(hào)】：TQ127.11;O643.36
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