新型纳米结构的合成及其在电化学储锂和电分解水制备氢气领域的应用研究

发布时间：2018-03-06 22:22

  本文选题：水热法　切入点：二硫化钼　出处：《青岛科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：近些年来,能源问题是全球都一直关注的重点问题,随着对能源的需求越来急切,也就急需探索和研究新型绿色能源来解决这个问题。纳米材料的出现和日渐成熟有望在能源问题上有很大的应用,尤其是新型过渡金属硫化物纳米材料以及其复合材料,这些纳米材料来源广泛,价格便宜,对环境友好,而且具有高的比表面积以及好的化学稳定性,在锂离子二次电池和电化学催化析氢反应中有广泛的应用。但是,过渡金属硫化物本身导电性很差,锂离子扩散速率较低,析氢过电位较高,而且在锂离子的嵌入-脱出过程中体积变化较大,导致其应用在锂离子电池上时倍率性能和循环性能较差;在作为电催化析氢反应的催化剂时,过电位又较高,能量损失严重,这些缺点都限制了它在实际生活中的应用。为了克服以上缺陷,研究人员尝试将过渡金属硫化物制备成特殊的形貌或将其与碳材料结合制成复合纳米材料,特殊形貌的纳米材料具有大的比表面积,因此扩大了电解液和活性物质的接触面积;过渡金属硫化物与碳材料复合,增加了材料的导电性,缓解了体积效应。所以改进后的过渡金属硫化物拥有更好的电化学性能,在锂离子电池和电化学催化析氢反应中有更好的应用。本论文主要研究了片状的MoS_2-CoMo_2S_4/G、3D结构的MoS_2-G、SnS_2-G和PB-MoS_2-G的制备及其电化学性能,包括储锂性能和电化学析氢性能。1)我们采用一步水热法在石墨烯基体上原位生长二维结构的二硫化钼纳米片和CoMo_2S_4纳米片,作为新型的电化学析氢反应催化剂。由于石墨烯结构的良好导电性和MoS_2和CoMo_2S_4之间的电化学协同作用和2D的结构优势,MoS_2-CoMo_2S_4/graphene复合催化剂显示出很好的析氢性能,起始电位低至110mV,在η=300 mV时,阴极电流密度高达85 mA cm-2,塔菲尔斜率为42 mV dec-1,第1000圈的催化曲线跟第1圈的比较,析氢效率并没有衰减,显示了良好的耐久性。2)此次工作将亚铁氰化钾,二硫化钼和石墨烯通过一步水热的方法,合成MoS_2-PB-GO复合材料。复合材料中具有独特的PB立方体,与石墨烯紧密结合。合成的复合材料同时具有独特的结构和组成优势,在电化学析氢反应中显示出优异的催化性能。此种具有特殊3D结构的复合催化剂显示出低至160 mV的过电位,在过电压为300 mV时,对应的电流密度达到60 mA cm-2,而且经过测试,材料还具有较大的电化学活性表面积(ECSA),每个活性位点还具有较高的电催化活性,这对复合材料催化性能的提高都起到了很重要的促进作用。3)利用水热法合成了基于MoS_2-G混合纳米片自组装成的3D构造,片层的MoS_2纳米片和石墨烯基底紧密结合。特殊的3D架构以及复合材料的组分选择,有益于提高锂离子电池和HER的电化学性能。在电流密度为200 m A g~(-1)时,循环200圈后,容量仍然保持在904 mAh g~(-1),相比循环2圈后的容量910 mAh g~(-1),容量保持率为99%,说明其良好的循环性能。在1 Ag~(-1)和2 Ag~(-1)的高电流密度下循环,依然保持706 mAh g~(-1)和581 mAh g~(-1)的高容量,当电流密度再回到100mA g~(-1)时,容量恢复至898 mAh g~(-1),显示出好的结构稳定性和可逆性。在析氢反应中,MoS_2-G显示出低至110 mV的过电位,塔菲尔斜率为47 m V dec-1,而且在循环1000圈后,电化学析氢性能并没有衰减,显示出良好的循环稳定性。4)通过水热法合成由2D SnS_2纳米片和石墨烯复合组成的3D结构,由于SnS_2-G的结构优势,显示出良好的锂离子存储性能。2D的片状结构提供了大的比表面积和结构稳定性,同时也缓解了体积效应。SnS_2和石墨烯的紧密连接保证了快速的电子交换,所以该复合材料在作为负极材料时,容量高至933 mAh g~(-1),在500 mA g~(-1)的电流密度下循环200圈后,容量依然保持在826 mAh g~(-1),显示出良好的循环稳定性,在8 A g~(-1)的高电流密度下,容量为498 mAh g~(-1),表现出杰出的倍率性能。
[Abstract]:In recent years, the energy problem is the key problem in the world have been concerned, with the growing demand for energy is urgent, urgent need to explore and study new green energy to solve this problem. The emergence of nano materials and is expected to become more mature in terms of energy has great applications, especially the new Transition Metal Sulfide Nanomaterials and their composites these nano materials, wide material source, cheap, environmentally friendly, and has a high surface area and good chemical stability, is widely used in the reaction of lithium ion secondary battery two and the electrochemical hydrogen evolution. However, the conductivity of transition metal sulfides itself is very poor, the lithium ion diffusion is low. Hydrogen overpotential is higher, and the volume changes in lithium ion - intercalation process is large, when the application rate performance and cycle performance in lithium ion battery; In the catalyst as the electrocatalytic reaction when the potential is higher, the energy loss is serious, these disadvantages limit its application in real life. In order to overcome the above defects, researchers try to transition metal sulfide prepared into special shape or combine it with carbon materials made of composite nano materials, nano materials with special morphology with large surface area, thus expanding the contact area of the electrolyte and active material; composite transition metal sulfide and carbon materials, increasing the conductivity of the material, alleviate the volume effect. So the electrochemical properties of transition metal sulfides into the better, has a better application in lithium ion battery and the electrochemical hydrogen evolution reaction. This paper mainly studies the flake like MoS_2-CoMo_2S_4/G, 3D MoS_2-G and PB-MoS_2-G SnS_2-G structure, the preparation and electrochemical properties, including storage The properties of lithium and the electrochemical hydrogen evolution properties of molybdenum disulfide and.1) CoMo_2S_4 nanosheets we used one-step hydrothermal method in situ growth in two-dimensional structure of graphene substrate, as the electrochemical hydrogen evolution reaction catalyst model. Due to the structural advantages of electrochemical between graphene structure and good conductivity and MoS_2 and CoMo_2S_4 and 2D synergistic effect the MoS_2-CoMo_2S_4/graphene composite catalyst showed the hydrogen evolution of good performance, low initial potential to 110mV in =300 mV, ETA, the cathodic current density up to 85 mA cm-2, Tafel slope of 42 mV dec-1, compared with 1000th laps of the catalytic curve with first rings, the hydrogen evolution efficiency and no attenuation, shows a good the durability of.2) the work of potassium ferrocyanide, MoS2 and graphene by one-step hydrothermal method, synthesis of MoS_2-PB-GO composite materials. The composite has a unique PB cube, and stone Combination of graphene. The synthesis of composite materials with special structure and composition, showed excellent catalytic performance in the electrochemical hydrogen evolution reaction. The composite catalyst has a special 3D structure shows the potential is too low to 160 mV, the voltage is 300 mV, the current density should reach 60 mA cm-2, but after testing, material also has a larger electrochemical active surface area (ECSA), the electrocatalytic activity of each active site also has high, which increases the catalytic properties of the composite materials play a very important role in promoting.3 3D) to construct MoS_2-G mixed nano film based on self assembly was prepared by the hydrothermal method, combined with lamellar MoS_2 nanosheets and graphene substrate. The special 3D architecture and composite components, is beneficial to improve the electrochemical performance of lithium ion battery and HER. At a current density of 200 m A G ~(-1)鏃，

本文编号：1576755