Al-decorated carbon nanotube as the molecular hydrogen storage medium

• Aluminum-decorated (8,0) CNT has been investigated for hydrogen storage application.
• The maximum storage capacity is 6.15 wt%.
• Adsorption binding energy lies between the desirable range (0.2–0.6 eV/H2).
• (8,0) CNT-8(Al + 4H2) is proposed as a high capacity hydrogen storage media.

Al-decorated, single-walled carbon nanotube has been investigated for hydrogen storage applications by using Density Functional Theory (DFT) based calculations. Single Al atom-decorated on (8,0) CNT adsorbs upto six H2 molecules with a binding energy of 0.201 eV/H2. Uniform decoration of Al atom is considered for hydrogen adsorption. The first Al atom has a binding energy of 1.98 eV on (8,0) CNT and it decreases to 1.33 eV/Al and 0.922 eV/Al respectively, when the number of Al atoms is increased to four and eight. Each Al atom in (8,0) CNT-8Al adsorbs four H2 molecules, without clustering of Al atoms, and the storage capacity reaches to 6.15 wt%. This gravimetric storage capacity is higher than the revised 2015 target of U.S Department of Energy (DOE). The average adsorption binding energy of H2 in (8,0) CNT-8(Al+4H2), i.e. 0.214 eV/H2, lies between 0.20 and 0.60 eV/H2 which is required for adsorbing and desorbing H2 molecules at near ambient conditions. Thus, Al-decorated (8,0) CNT is proposed as a good hydrogen storage medium which could be useful for onboard automobile applications, at near ambient conditions.