Carbon nanotubes for improving dehydrogenation from NaAlH4

Abstract

Carbon nanotubes (CNTs) improve the dehydrogenation kinetics of NaAlH4. The present paper reports the effect of small diameter CNTs for lowering the dehydrogenation energy from NaAlH4 cluster using Density functional theory. Pristine carbon nanotubes (P-CNTs) with Zig-Zag (n,0) and Armchair (n,n) chirality with n=3, 4, 5; chemically B/N doped CNTs (C-CNTs) and CNTs with vacancy defect (V-CNTs) are considered systematically to study the interaction with NaAlH4 cluster. NaAlH4 interacts with P-CNTs, C-CNTs and V-CNTs with binding energy of the order 0.77–0.98eV, 0.60–1.01eV and 0.81–1.74eV respectively. The hydrogen release energy of NaAlH4 decreases from 3.95eV by 38%, 49% and 39% when interacting with P-CNTs, C-CNTs and V-CNTs respectively. Results can be explained on the basis of electronic charge transfer and redistribution between CNTs and NaAlH4 which weaken the bonds involved in cluster and enhance easy removal of hydrogen. The results are in agreement with the available experimental data.