  The interaction between hydrogen molecules and platinum (Pt)-decorated carbon
nanotubes (CNTs) with boron (B)-, nitrogen (N)-dopants or sidewall vacancies is
discussed from first-principle calculations. The adsorption patterns of
hydrogen molecules on four types of Pt-decorated CNTs are investigated, and the
partial density of states projected on the Pt atom is computed to reveal the
response to the number of hydrogen molecules, dopants or vacancies. It is found
that the B-, N-dopants or sidewall vacancies can adjust the binding energy
between the hydrogen molecules and the Pt atom deposited on the defective CNT,
while not reducing the maximum number of hydrogen molecules that are chemically
adsorbed on the Pt atom. It is demonstrated that the binding energy of the
first H2 and the Pt atom on the pristine CNT or the CNT with the B-, N-dopants
is quite strong, so each Pt atom in these three cases can only release the
second H2 under ambient conditions. However, when the Pt atom is deposited on
the CNT with sidewall vacancies, it can adsorb and desorb two hydrogen
molecules under ambient conditions.

Mesoscale and Nanoscale Physics