A Theoretical Study on the Effect of Intercalating Sulfur Atom and Doping Boron Atom on the Adsorption of Hydrogen Molecule on (10,0) Single-Walled Carbon Nanotubes

Adsorption of molecular hydrogen on single-walled carbon nanotube (SWCNT), sulfur-intercalated SWCNT (S-SWCNT),and boron-doped SWCNT (BSWCNT), have been studied by means of density functional theory (DFT). Two methods KMLYP and local density approximation (LDA) were used to calculate the binding energies. The most stable configuration of H2 on the surface of pristine SWCNT was found to be on the top of a hexagonal at a distance of 3.54 Å in good agreement with the value of 3.44 Å reported by Han and Lee (Carbon, 2004, 42, 2169). KMLYP binding energies for the most stable configurations in cases of pristine SWCNT, S-SWCNT, and BSWCNT were found to be -2.2 kJ mol-1, -3.5 kJ mol-1, and -3.5 kJ mol-1, respectively, while LDA binding energies were found to be -8.8 kJ mol-1, -9.7 kJ mol-1, and -4.1 kJ mol-1, respectively. Increasing the polarizability of hydrogen molecule due to the presence of sulfur in sulfur intercalated SWCNT caused changes in the character of its bonding to sulfur atom and affected the binding energy. In H2-BSWCNT system, stronger charge transfer caused stronger interaction between H2 and BSWCNT to result a higher binding energy relative to the binding energy for H2-SWCNT