Abstract: 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).

Key words: Multi-walled carbon nanotubes, MWCNTs-based H₂-storage material, Adsorption-desorption characteristics of H₂, H₂-TPD