氢气在碳纳米管基材料上的吸附-脱附特性

利用高压容积法测定多壁碳纳米管(MWCNTs)及钾盐修饰的相应体系(K＋-MWCNTs)的储氢容量,并用程序升温脱附(TPD)方法表征研究氢气在MWCNTs基材料上的吸附-脱附特性.结果表明,在经纯化MWCNTs上,室温、9.0 MPa实验条件下氢的储量可达1.51％（质量分数）;K＋盐对MWCNTs的修饰对增加其储氢容量并无促进效应,但相应化学吸附氢物种的脱附温度有所升高;K＋的修饰也改变了MWCNTs表面原有的疏水性质.在低于723 K的温度下,H2/MWCNTs体系的脱附产物几乎全为氢气;773 K以上高温脱附产物不仅含H2,也含有CH4、C2H4、C2H2等C1/C2烃混合物;H2/K＋-MWCNTs储氢试样的脱附产物除占主体量的H2及少量C1/C2烃混合物外,还含水汽,其量与吸附质H2源水汽含量密切相关.H2在碳纳米管基材料上吸附兼具非解离 (即分子态) 和解离(即原子态)两种形式.

Characteristics of Adsorption and Desorption of Hydrogen on Multi-walled Carbon Nanotubes

Storage capacities of H2 in a kind of multi-walled carbon nanotubes (MWCNTs) and its corresponding system modified with K＋ salt were measured using volumetric method, and characteristics of adsorption and desorption of hydrogen on MWCNTs were studied by means of temperature-programmed desorption (TPD) method. The results showed that the storage capacities of H2 in the purified MWCNTs could reach 1.51％ (mass fraction) under condition of room temperature and 9.0 MPa, with adsorption of ～99％ of the H2 being reversible. A comparative study indicated that the modification of the K＋ salt to the MWCNTs did not improve its storage capacity of hydrogen, but led to elevating of desorption temperature of adsorbed hydrogen H2(a) to a certain extent; in addition, the K＋ modification resulted also in changing of surface property of the MWCNTs from original hydrophobicity to hydrophilicity. The products desorbed on H2/MWCNTs involved exclusively H2 at T≤ 723 K, and main part of H2 and small amount of CH4,C2H4,and C2H2 at T ≥ 773 K; whereas on H2/K＋-MWCNTs,H2O was also involved in the desorbed products, in addition to H2 and small amount of C1/C2-hydrocarbons.The adsorption of H2 on the MWCNTs-based materials is in the two models: associative (molecular state) and dissociative (atomic state).