镁-镍/石墨烯复合物的储氢性能

Hydrogen Storage Properties of Mg-Ni/Graphene Composites

摘要:

分别通过物理法和化学法制备石墨烯载镍催化剂 (Ni/Graphene)，并采用球磨预处理或超声分散的方式与镁粉混匀，结合氢化燃烧合成和机械球磨复合技术制备镁-镍/石墨烯（Mg-Ni/Graphene）复合物储氢材料。采用X射线衍射仪、扫描电镜及气体反应控制器研究了材料的相组成、微观形貌和吸放氢性能。比较发现，添加化学法制备的Ni/Graphene并采用球磨预处理的Mg-Ni/Graphene复合物具有最佳的吸放氢性能，复合物的起始放氢温度降低，放氢速率加快。其在373 K温度下，100 s内就基本能达到饱和吸氢量6.21%（质量分数）；553 K，1800 s内完全放氢，且放氢量达到6.05%。球磨预处理使得Ni/Graphene更均匀的与Mg接触，利于发挥Ni的催化作用和石墨烯优异的导电导热性。化学法制备的Ni/Graphene原位还原出纳米晶Ni，有利于形成纳米级Mg2NiH4晶粒，促进复合物储氢性能的改善。

Abstract:

Graphene supported nickel catalysts (Ni/Graphene) were synthesized by physical method and chemical method, respectively. The as prepared Ni/Graphene was further mixed with Mg by ball milling pretreatment or ultrasonic dispersion. Then the well mixed powders were used to prepare Mg-Ni/Graphene composites by the combined process of hydriding combustion synthesis and mechanical milling (HCS+MM). The phase compositions, surface morphologies and hydriding/dehydriding properties of the samples were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) and gas reaction controller (GRC). Results show that the Mg-Ni/Graphene composite which mixed Ni/Graphene synthesized by chemical method and Mg through ball milling pretreatment exhibits the best hydriding/dehydriding properties. It has the lowest onset hydrogen desorption temperature and faster dehydrogenation rate. About 6.21 % hydrogen can be absorbed within 100 s at 373 K, and 6.05 % hydrogen can be desorbed within 1800 s at 553 K. Ball milling pretreatment makes Ni/Grapheme and Mg contact homogeneous, thus the excellent thermal?and?electrical conductivity of Grapheme and the catalytic effect of Ni are enhanced. In addition, nano-crystalline Ni with smaller grain size synthesized by chemical method is helpful to the formation of nanosized Mg2NiH4 grains, leading to the improvement in hydrogen storage properties of the composite.