Abstract:
The storage of hydrogen in carbon nanotubes has attracted much research interest throughout the world since hydrogen is the cleanest renewable energy and the discovery of carbon nanotubes in the last decade. According to the Department of Energy in the USA, the target for no-board hydrogen envergy density on a fuel cell vehicle is 6.5 w% H2 and 62 kgH2/m3 for 500 km/fill-up. High reported values of hydrogen sorption by many research groups have been controversial in terms of relibaility due to the different treatments and sources of carbon nanotubes, the distince measuring techniques and the lack of complete information on experimental methods used. To verify and study the potential of carbon nanotubes as a hydrogen adsorbent, this work studied the sorption of hydrogen on two types of carbon materials, i.e. 94% purity multi-wall carbon nanotubes (MWNTs) and commercial activated carbon (AC), in a constant volumetric isothermal adsorption apparatus at pressures ranging form 140 psia to 1040 psia at a constant temperature of 298 K. The obtained results are varying from less than 0.1 to 2 wt% hydrogen depending on the different in amout of adsorbent, experimental method and calculated equilibrium time. All these effects plus background leak must be taken into account in the analysis of the reported results.
