Hydrogen Storage Behaviors by Adsorption on Multi-Walled Carbon Nanotubes

In the present study, MWCNTs were synthesized through CVD method, employing CH4 as carbon source over Co-Mo/MgO nanocatalyst at a temperature of 1000 A degrees C and then treated by two methods. First by KOH activation (A-MWCNTs), with a weight ratio of KOH: MWCNTs = 3:1 at 900 A degrees C in He atmosphere and second treated by H2SO4: HNO3 = 3:1 (F-MWCNTs). MWCNT samples were characterized by FE-SEM, TEM, XRD, FT-IR, BET and Raman spectroscopy. The adsorption of H-2 gas was performed using volumetric method. Various parameters on adsorption of H-2 including surface defects, surface areas, pore characteristics and functional groups have been investigated. Furthermore, it was found that the hydrogen adsorption of P-MWCNTs, A-MWCNTs and F-MWCNTs were 0.67, 1.24 and 0.40 wt%, respectively at room temperature (298 K) while the pressure varied from 0 to 34 bar. The results indicated a considerable rise in the H-2 adsorption capacity of A-MWCNTs (85%), due possibly to the high surface area and enhanced micro-pore volume and the defects formed on the surface sites of MWCNTs by KOH activation. In this case, hydrogen molecules adsorption on the defective cavities could have a significant role through van der walls forces. Therefore, it can be concluded that KOH-modified MWCNTs is one of the most significant ways of developing the textural characteristic and improving hydrogen storage properly.