多壁碳纳米管载镍对镁基合金储氢性能影响

Effect of Multi-Wall Carbon Nanotubes Supported Nickel on Hydrogen Storage Properties of Mg-Based Alloy

摘要:

采用化学法制备多壁碳纳米管载镍催化剂(Ni/MWNTs)，并将其加入到镁粉中，结合氢化燃烧合成(Hydriding Combustion Synthesis, HCS)和机械球磨(Mechanical Milling, MM)，即HCS+MM复合技术制备Mg85-Nix/MWNTs15-x (x代表质量百分数, x=3, 6, 9, 12)合金。通过X射线衍射仪、透射电子显微镜、扫描电镜以及气体反应控制器研究了材料的晶体结构、微观形貌和吸放氢性能。结果表明：Mg85-Ni9/MWNTs6合金具有最佳综合吸放氢性能，其在373 K，吸氢量达到5.68%(质量分数, 下同)，且在100 s内就基本达到饱和吸氢量；在523 K，1800 s内的放氢量达到4.31%。Ni/MWNTs催化剂的添加，不但起到催化的作用，而且MWNTs具有优异的纳米限制作用，使得催化剂的粒径限制在纳米级，有利于限制产物中Mg2NiH4颗粒的长大。另外Ni与MWNTs存在协同催化作用，当它们达到一定比例时，对合金的吸放氢促进作用达到最优化，明显改善了合金的吸放氢性能

Abstract:

Mg85-Nix/MWNTs15-x (x=3, 6, 9, 12, mass fraction) alloys were prepared from Mg and multi-wall carbon nanotubes supported nickel (Ni/MWNTs) by the combined methods of hydriding combustion synthesis (HCS) and mechanical milling (MM). The crystal structures, surface morphologies and hydriding/dehydriding properties of the products were investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and gas reaction controller (GRC), respectively. The results show that the Mg85-Ni9/MWNTs6 alloy possesses the best hydriding/dehydriding properties, which absorbs nearly the saturated hydrogen capacity of 5.68 wt% within 100 s at 373 K, and desorbs 4.31 wt% hydrogen within 1800 s at 523 K. The addition of Ni/MWNTs plays a catalytic role, and it takes the effect on nano-confinement of the Mg2NiH4 particles in the product. There is synergic catalysis between Ni and MWNTs, and when the mass ratio of Ni/MWNTs = 3/2, the hydriding/dehydriding properties of the Mg-Ni/MWNTs system reach the best