【作者】 杨颖；

【导师】 陈玉安；

【作者基本信息】 重庆大学 ， 材料与化工（专业学位）， 2024， 硕士

【摘要】 氢能不仅来源广泛、清洁无污染,而且能量密度高,被认为是最具有发展潜力的新型能源形式之一。然而,如何安全、高效地储存氢气成为了当前氢能产业发展的主要瓶颈。在诸多储氢方式当中,基于镁基材料的固态储氢技术由于储氢容量大（Mg H₂的理论储氢密度高达7.6 wt.%）、资源丰富、环境友好等优点受到了广泛关注。但Mg基材料固有的高热力学稳定性和缓慢的吸放氢动力学等缺点阻碍了其在固态储氢领域的规模化应用。目前,通过引入催化剂来优化成分和调控微观组织结构能够显著改善Mg基材料的储氢性能。为此,本文以Mg-20Ni基储氢合金为研究对象,合成了TiV固溶体合金和YVO₄双金属氧化物两种催化剂,分别探究了其对Mg-20Ni和Mg-20Ni-5TiV吸放氢行为的影响规律及其作用机制。首先,利用湿化学球磨法制备一种具有面心立方结构的TiV固溶体合金催化剂,并进一步通过高能球磨将其与Mg-20Ni合金复合。结果表明,添加5 wt.%TiV可使Mg-20Ni合金具有较好活化性能和吸放氢动力学性能。在150℃下,Mg-20Ni-5wt.%TiV（Mg-20Ni-5TiV）复合体系在50 min内能够吸氢3.2 wt.%。在250℃下,可以在12 min内完成5.0 wt.%的放氢量。即使在200℃和225℃下,Mg-20Ni-5 wt.%TiV也能够在60 min和50 min内分别实现3.4 wt.%和4.7 wt.%的放氢量。此外,样品在经历了20次循环后储氢容量基本保持不变,展现出了优异的稳定性。通过结构演变分析发现,TiV合金在吸氢过程中发生了原位分解并析出Ti H₂与V₂H金属氢化物,放氢时该物质再还原为TiV。添加的TiV固溶体合金协同Mg₂Ni/Mg₂Ni H₄为复合体系构建了一个丰富的多相、多活性位点的催化环境,加速了吸放氢过程中氢的解离和扩散。随后,本文通过简易水热合成法制备了一种具有纳米结构的YVO₄双金属氧化物催化剂,并对上述的Mg-20Ni-5TiV储氢合金进行改性。结果表明,YVO₄催化剂的添加进一步改善了Mg-20Ni-5TiV的低温动力学性能。Mg-20Ni-5TiV+6 wt.%YVO₄复合储氢材料在50℃下60 min内吸氢量达到2.5 wt.%。对于脱氢过程,在225℃下也可达到4.5 wt.%的放氢量。此外,Mg-20Ni-5TiV+6 wt.%YVO₄复合材料还具有稳定的循环储氢性能,其在50次吸放氢循环后储氢容量基本保持不变。Mg-20Ni-5TiV+6 wt.%YVO₄复合体系明显改善的储氢性能主要得益于YVO₄催化剂在吸放氢过程中原位生成了V₂O₅与Y₂O₃两种金属氧化物,原位构筑了更加丰富的催化环境,不仅有利于氢的解离,还提供了大量的形核位点和氢扩散通道。更多还原

【Abstract】 Hydrogen energy not only comes from a wide range of sources,clean and pollution-free,but also has a high energy density,which is considered to be one of the most promising new forms of energy.However,how to store hydrogen safely and efficiently has become the main bottleneck of the current development of hydrogen energy industry.Among many hydrogen storage methods,solid hydrogen storage technology based on magnesium materials has attracted wide attention due to its advantages such as large hydrogen storage capacity（the theoretical hydrogen storage density of Mg H₂is as high as 7.6 wt.%）,abundant resources and environmental friendliness.However,the inherent high thermodynamic stability and slow hydrogen absorption and desorption kinetics of Mg-based materials hinder their large-scale application in solid state hydrogen storage.At present,the hydrogen storage properties of Mg-based materials can be significantly improved by introducing catalysts to optimize the composition and regulate the microstructure.In this paper,two catalysts,TiV solid solution alloy and YVO₄bimetallic oxide,were synthesized with Mg-20Ni hydrogen storage alloy as the research object,and their effects on the hydrogen absorption and desorption behavior of Mg-20Ni and Mg-20Ni-5TiV were investigated.First,a TiV solid solution alloy catalyst with face-centered cubic structure was prepared by wet chemical ball milling method,and further compounded with Mg-20Ni alloy by high energy ball milling.The results show that the addition of 5 wt.%TiV can make the Mg-20Ni alloy have better activation and hydrogen absorption and desorption kinetic properties.At 150℃,the Mg-20Ni-5 wt.%TiV（Mg-20Ni-5TiV）composite system can absorb 3.2 wt.%hydrogen within 50 min.At 250℃,5.0 wt.%of hydrogen can be dehydrogenated in 12 minutes.Even at 200℃and 225℃,Mg-20Ni-5 wt.%TiV can achieve 3.4 wt.%and 4.7 wt.%hydrogen emission in 60 min and 50 min,respectively.In addition,the hydrogen storage capacity of the sample remained basically unchanged after 20 cycles,showing excellent stability.The structure evolution analysis showed that TiV alloy decomposed in situ and precipitated Ti H₂and V₂H metal hydrides during hydrogen absorption,which were reduced to TiV during hydrogen dehydrogenation.The addition of TiV solid solution alloy in collaboration with Mg₂Ni/Mg₂Ni H₄established a rich multi-phase and multi-active site catalytic environment for the composite system,which accelerated the dissociation and diffusion of hydrogen in the process of hydrogen absorption and removal.Subsequently,a YVO₄bimetallic oxide catalyst with nano structure was prepared by a simple hydrothermal synthesis method,and the above Mg-20Ni-5TiV hydrogen storage alloy was modified.The results showed that the low temperature kinetic properties of Mg-20Ni-5TiV were further improved by adding YVO₄catalyst.The hydrogen absorption capacity of Mg-20Ni-5TiV+6 wt.%YVO₄composite hydrogen storage material reached 2.5 wt.%within 60 min at 50℃.For the dehydrogenation process,4.5 wt.%of hydrogen can be dehydrogenated at 225℃.In addition,Mg-20Ni-5TiV+6 wt.%YVO₄composite also has stable cyclic hydrogen storage performance,and its hydrogen storage capacity remains basically unchanged after 50cycles of hydrogen absorption and discharge.The significantly improved hydrogen storage performance of Mg-20Ni-5TiV+6 wt.%YVO₄composite system is mainly due to the formation of two metal oxides,V₂O₅and Y₂O₃,in situ by YVO₄catalyst in the process of hydrogen absorption and dehydrogenation,and a more abundant catalytic environment is constructed in situ,which is not only conducive to hydrogen dissociation,but also conducive to hydrogen dissociation.It also provides a large number of nucleation sites and hydrogen diffusion channels.更多还原