低维多级结构过渡金属化合物的导向性设计及电催化水分解应用研究

发布时间：2018-05-08 17:58

  本文选题：析氢反应 + 析氧反应　； 参考：《山东师范大学》2017年硕士论文

【摘要】：随着能源危机和滥用化石燃料带来的空气污染和全球变暖等问题的加剧,发展高效清洁的可再生能源刻不容缓。在众多的可再生能源中,氢气以其环境友好性和高能量密度等优势被视为极具发展潜力的新型洁净能源。在现有的制氢途径中,将电能转化为氢能的电解水过程被认为是一种高效、经济和环保的方式。常温常压下,电解水所需的理论电压窗口为1.23 V。然而在实际操作中,为了降低电极反应所需的过电势,使用电催化剂作为电极材料是当前公认的效率提升策略。在现有的催化剂中,基于贵金属的催化剂具有最高的催化效率,但其元素稀缺性和昂贵的价格极大限制了其工业应用可能,因此,开发高效廉价的电催化剂势在必行。在本论文中,作者以高丰度的过渡金属化合物作为研究对象,通过缺陷工程、无序结构工程、元素掺杂以及与导电材料复合等方式对催化剂的活性位点和导电性进行了优化,实现了催化性能的显著提升。该论文对未来电催化剂的设计与发展提供了指导性作用。本论文包括以下两个内容:1.作者利用元素掺杂、无序结构工程以及材料复合等方法制备出了垂直生长在碳布上的氧掺杂二硫化钼电催化剂,实现了活性位点和导电性的协同优化,获得了显著提升的析氢反应活性。在该复合电催化剂中,高度无序的MoS2纳米片提供了丰富的催化活性位点,氧掺杂以及与碳材料的复合赋予了材料优越的导电性,使更多的活性位点能够实现电学连通,有效地参与到催化过程中,最终实现了析氢反应性能的协同优化提升。协同优化后的氧掺杂MoS2/碳布催化剂显示出超低的起始过电位、优越的催化电流密度以及良好的稳定性。在本工作中提出的协同优化策略为新型电催化剂的设计提供了可供借鉴的方法。2.作者利用三元NiFe Zn层状氢氧化物(ZnNiFe LDH)为前驱物,通过刻蚀—熟化的方法制备出了含有大量直径约为2~3 nm的纳米孔的NiFe LDH超薄纳米筛,实现了析氧反应性能的显著提高。三元前驱物中两性的Zn离子可以通过强碱处理的方式被选择性刻蚀,实现了片内的初步成孔,而随后的熟化过程使纳米孔的孔径实现均匀化。纳米孔的引入能够促进具有催化活性的高价态物质的产生,提供更多的位点用于析氧反应。此外,纳米孔提供的空隙能够有效避免反复的氧化还原过程中的结构破坏,赋予材料优越的电化学稳定性,使其有望用于工业水分解。这个工作为析氧反应性能的优化提供了有效的策略,并为今后电催化剂的设计提供了启发。
[Abstract]:With the problems of energy crisis, air pollution caused by fossil fuel abuse and global warming, it is urgent to develop efficient and clean renewable energy. Among the many renewable energy sources, hydrogen is regarded as a new clean energy with great potential due to its environmental friendliness and high energy density. In the existing hydrogen production process, the process of converting electric energy into hydrogen energy is considered to be an efficient, economical and environmentally friendly way. At room temperature and atmospheric pressure, the theoretical voltage window for electrolytic water is 1.23 V. In practice, however, in order to reduce the overpotential of electrode reaction, it is widely accepted that the electrocatalyst is used as electrode material. Among the existing catalysts, the catalysts based on noble metals have the highest catalytic efficiency, but their rare elements and expensive prices greatly limit their industrial applications. Therefore, it is imperative to develop efficient and cheap electrocatalysts. In this thesis, the transition metal compounds with high abundance were used to optimize the active sites and conductivity of the catalysts by defect engineering, disordered structure engineering, element doping and composite with conductive materials. The catalytic performance was improved remarkably. This paper provides guidance for the design and development of electrocatalysts in the future. This thesis includes two parts as follows: 1. The oxygen doped molybdenum disulfide electrocatalysts grown vertically on carbon cloth were prepared by elemental doping, disordered structure engineering and material recombination. The cooperative optimization of active sites and conductivity was achieved. The activity of hydrogen evolution reaction was improved significantly. In the composite electrocatalyst, the highly disordered MoS2 nanoparticles provide abundant catalytic active sites, and oxygen doping and the compounding with carbon materials give the materials superior electrical conductivity, so that more active sites can be electrically connected. It can effectively participate in the catalytic process and finally realize the synergistic optimization of the hydrogen evolution reaction performance. Co-optimized oxygen doped MoS2/ carbon cloth catalysts show ultra-low initial overpotential, superior catalytic current density and good stability. The cooperative optimization strategy proposed in this work provides a reference method for the design of new electrocatalysts. Using ternary NiFe Zn layered hydroxide (ZnNiFe LDH) as precursor, NiFe LDH ultrathin nano-sieve containing a large number of nano-pores (about 2nm in diameter) was prepared by etching and ripening method, and the oxygen evolution reaction performance was improved remarkably. The amphoteric Zn ion in the ternary precursor can be selectively etched by strong alkali treatment, and the initial pore formation is realized, and the pore size is homogenized by subsequent ripening process. The introduction of nano-pores can promote the production of high-valence compounds with catalytic activity and provide more sites for oxygen evolution. In addition, the pores provided by the nano-pores can effectively avoid the structural damage during the repeated redox process, and give the material excellent electrochemical stability, which is expected to be used in the decomposition of industrial water. This work provides an effective strategy for the optimization of oxygen evolution reaction performance and provides inspiration for the design of electrocatalysts in the future.
【学位授予单位】：山东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36;TQ116.21
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本文编号：1862415