Hydrogen Sorption by Single-Walled Carbon Nanotubes with Metallic Species of Intended Distribution

在含Ni-Y催化剂的石墨棒之间电弧放电合成的单壁碳纳米管（SWCNTs）经硝酸声化学处理后，在室温和0.1 MPa氢气条件下，其氢容量小于0.1 wt.%，即基本为零。通过非电解镀或有机金属化合物的热分解进行金属改性，并在氘形成后通过程序升温解吸（TPD）评估氢容量。当钯、铁、镍等或它们的组合分布在SWCNTs上时，可以观察到较高的氢容量。然而，金属原位合成修饰（PVD）的SWCNTs的氢容量比湿法修饰的SWCNTs大。铁族元素修饰的SWCNTs燃烧时的热量明显超过碳族元素修饰的SWCNTs，这表明SWCNTs与金属之间形成了吸热键。通常适用于金属氢化物的反稳定性规律，因此预测铁族元素修饰的SWCNTs足够不稳定，可以形成稳定的氢化物，上述结果也证实了这一点。由于低比表面积为200 m2/g的SWCNTs已获得接近1 wt%的氢容量，因此将通过将比表面积增加到2000 m2/g来开发实用的储氢材料。另一种原位改性包括化学气相沉积（CVD），当Mg-Ni或Mg-Fe粉末存在时，得到了有希望的纳米碳。TPD分析表明，CVD样品的氢容量似乎比PVD样品高。目前正在进行大规模合成，以评估等温测量的定性能力。通过类似的金属修饰，具有层状结构的B-C-N化合物的氢容量也被赋予。少

Hydrogen capacities of single-walled carbon nanotubes (SWCNTs), which were synthesized by arc-discharge between graphite rods having Ni-Y catalysts and were sono-chemically treated in nitric acid to be free of bundle-like structures and free from metallic species contaminated on arc-discharge, were less than 0.1 wt.% at room temperature and 0.1 MPa of hydrogen, that is, essentially zero.Metal modification was carried out by non-electrolytic plating or by thermal decomposition of organometallic compounds and hydrogen capacities were evaluated by Temperature Programmed Desorption (TPD) after deuterium was formed. High hydrogen capacities were observed when palladium, iron, nickel etc. or combinations of them were distributed on SWCNTs. Howeve4 hydrogen capacities of those SWCNTs which were in situ modified with metals on synthesis (PVD) were larger than the ones modified by the wet methods.Heats on combustion of SWCNTs modified with iron group elements significantly exceeded those of c … More arbons, which suggested that endothermic bonding was formed between SWCNTs and metals. The rule of reversed stability, which generally holds for metal hydrides, thus gives a prediction that SWCNTs modified with iron group elements were unstable enough to form stable hydrides, and that has been verified by the above-mentioned results. Since hydrogen capacities close to 1 wt% have been obtained for SWCNTs with low specific surface areas of 200 m2/g, practical hydrogen storage materials will be developed by increasing specific surface areas to 2,000 m2/g.Another in situ modification comprising chemical vapor deposition (CVD) gave promising nanocarbons when Mg-Ni or Mg-Fe powders were present The TPD analysis showed plausible higher hydrogen capacities for CVD samples than for PVD samples. Large scale synthesis is now under progress to evaluate the qualitative capacities by isothermal measurements.Hydrogen capacities were also imparted to B-C-N compounds with layered structures by similar metal modifications. Less