Theoretical study of chemisorption of hydrogen atoms on (5,5) silicon carbide nanotubes with and without Stone-Wales defects

The adsorption of one hydrogen atom on the surface of (5, 5) single-walled silicon carbide nanotube (SiCNT) and (5, 5) SiCNTs with two types of Stone-Wales defects (labeled as SW1 and SW2) has been investigated employing density functional theory. The reaction energy values for the hydrogenation at various sites were obtained at the UB3LYP/6-31G* level. It is shown that hydrogen can chemically adsorb on carbon sites or silicon sites on pristine (5, 5) SiCNT, with the reaction energies ranging from -34.7 to -36.6 kcal/mol. The introduction of a SW defect on the (5, 5) SiCNT shows an enhanced interaction of hydrogen with the defective SiCNTs compared to that with the pristine SiCNT. The computed reaction energies range from -39.9 to -67.9 kcal/mol for (5, 5) SW1 and from -33.6 to -69.8 kcal/mol for (5, 5) SW2 SiCNTs. Furthermore, the adsorption of two hydrogen atoms has also been explored. It is found that the system is more energetically favorable for both perfect and SW defective (5, 5) SiCNTs. The electronic properties analysis indicates that single hydrogen atom chemisorption can reduce the HOMO-LUMO gap of corresponding nanotubes, but not for double hydrogen chemisorbed SW defective nanotube. (C) 2016 Elsevier B.V. All rights reserved.