Investigation of the effect of oxygen-containing groups on the hydrogen adsorption behavior of CSCNTs using density functional theory

The hydrogen adsorption behavior of cup-stacked carbon nanotubes (CSCNTs) decorated by –CO, –OH and –COOH at the edge of conical graphene layer (CGL) is investigated using density functional theory (DFT). The results reveal that the edge of pristine CGL hardly adsorbs hydrogen molecule due to the positive potential. When oxygen-containing group is decorated, the negative potential of O atom adsorbs hydrogen molecule strongly and the adsorption energy increases from 5.19 to 5.58, 6.25 and 6.53 kJ/mol following the order of –COOH > –OH > –CO. When two –COOH are decorated next to each other, the equilibrium position of hydrogen molecule deviates from the extended surface of CGL in an angle of 38°. When they are decorated next but one, the deviation angle of hydrogen molecule is reduced to 12°, so that the adsorption surface is expanded and the steric hindrance is avoided.