 The purified samples were then exposed to hydrogen gas at various high pressures, and their adsorption by weight percent was plotted.The data showed that hydrogen adsorption levels of up to 3.7% are possible with a very pure sample and under the proper conditions.It is thought that microwave digestion helps improve the hydrogen adsorption capacity of the CNTs by opening up the ends, allowing access to the inner cavities of the nanotubes.