钴基金属氧化物—还原氧化石墨烯复合材料的制备、表征及性能研究

发布时间：2018-03-17 23:07

  本文选题：石墨烯　切入点：纳米晶　出处：《郑州大学》2017年硕士论文　论文类型：学位论文

【摘要】：氢氧燃料电池作为一种清洁的能源体系引发了越来越多的关注,氢能的储存是该技术取得突破的关键问题。由于快速充放电、可靠的稳定性和长的循环寿命等优势,可充电锂离子电池(LIBs)一直是便携设备的主要动力来源。各种各样的过渡金属氧化物由于其具有较高的催化活性和大于商业碳质阳极的高理论比容量,而得到研究者的广泛青睐,同时结合石墨烯优异的物理化学性能,应用在催化和电极材料方面将会取得满意的效果。本文以石墨烯为载体,合成了一系列基于石墨烯的二维材料用于硼氢化钠水解制氢以及石墨烯包覆的三维材料用于锂离子电池负极材料。采用紫外可见光谱、X射线衍射仪、透射电子显微镜、比表面及孔径分析仪、X射线光电子能谱等技术对其形貌和结构进行表征,并对其催化产氢性能和电化学性质做了详细的测试和讨论。以油胺为保护剂,采用溶剂热的方法合成了小尺寸、分散性较好的Co_3O_4纳米晶,以此为前驱体与不同氧化程度的石墨烯进行复合,经过高温煅烧过程分别得到了负载钴氧化物纳米晶的多孔石墨烯和生长有碳纤维的石墨烯材料CoO_x-PG和CoO_x-GCNFs。在煅烧过程中,Co_3O_4纳米晶作为蚀刻剂与石墨烯之间发生碳热反应而得到还原,在石墨烯上蚀刻出均匀的孔,以及催化碳纤维在石墨烯表面的生长,这也是本文的创新所在。CoO_x-PG和CoO_x-GCNFs用于催化硼氢化钠(NaBH4)水解产氢,在30℃产氢速率分别达到1472 m L·min-1·gCo-1和2696 mL·min-1·gCo-1,这种显著的催化活性归因于CoO_x和PG/GCNFs之间的协同作用,小尺寸的CoO_x纳米晶具有较高的催化活性,PG/GCNFs作为二维的基底,可以阻止纳米晶的团聚和提供更多的催化位点。另外,这两种催化剂在催化过程中产生的磁性,一方面利于催化剂回收重复利用,另一方面可以利用磁性传动作用控制催化剂与NaBH4溶液的接触来控制产氢反应的发生和停止。综上,这两种催化剂可以作为廉价、高效的催化剂。以四水乙酸钴为前驱体,通过溶剂热法得到了花状结构的四氧化三钴微球(Co_3O_4-MS),然后与石墨烯进行复合包覆,并以水合肼对石墨烯进行还原,得到了氮掺杂-石墨烯包覆的四氧化三钴微球(Co_3O_4-MS@NG)。得到的Co_3O_4-MS,尺寸均一,是有许多超薄的纳米片自组装而成,具有介孔结构。将Co_3O_4-MS和Co_3O_4-MS@NG用作LIBs阳极材料,在0.2 C下100次循环后,容量分别达到342.4 m A·h·g-1和407.5 mA·h·g-1,同时库伦效率接近100%,高倍率充放电后,仍能回到较高的容量值,电化学阻抗较小,满足LIBs阳极材料的性能要求。这种优越性能归因于独特的带有孔隙的三维结构以及外层包覆的氮掺杂还原氧化石墨烯为电子的快速传输提供通道。
[Abstract]:As a clean energy system, hydrogen-oxygen fuel cell (HFC) has attracted more and more attention. Hydrogen energy storage is a key problem in this technology. Due to the advantages of rapid charge and discharge, reliable stability and long cycle life, Rechargeable lithium-ion battery (Libs) has been the main power source of portable devices. Various transition metal oxides have been widely used by researchers because of their high catalytic activity and high theoretical specific capacity larger than commercial carbon anodes. In combination with the excellent physical and chemical properties of graphene, satisfactory results will be obtained in catalysis and electrode materials. A series of graphene based two-dimensional materials were synthesized for hydrolysis of sodium borohydride to produce hydrogen and three dimensional materials coated with graphene for negative electrode materials of lithium ion batteries. The morphology and structure of the catalyst were characterized by X-ray photoelectron spectroscopy (XPS), and the catalytic and electrochemical properties of the catalyst were tested and discussed in detail. Co_3O_4 nanocrystals with small size and good dispersion were synthesized by solvothermal method. The porous graphene loaded with cobalt oxide nanocrystals and the graphene materials CoO_x-PG and CoOx-GCNFsgrown with carbon fiber were obtained by high temperature calcination. The homogeneous pores etched on graphene and the catalytic growth of carbon fibers on graphene surface are also the innovations of this paper. CoOx-PG and CoO_x-GCNFs are used to catalyze the hydrolysis of NaBH4 to produce hydrogen. The hydrogen production rate at 30 鈩，

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