Adsorption of epoxy and hydroxyl groups on zigzag graphene nanoribbons: Insights from density functional calculations

Density functional theory calculations have been used to investigate the adsorption of epoxy and hydroxyl groups on zigzag graphene nanoribbons. Our calculations show that the adsorbed epoxy groups and both the epoxy and hydroxyl groups on a ribbon surface can be transformed to a carbonyl pair and a carbonyl-hydroxyl pair. The energy barriers of these processes are 1.13 and 0.37 eV, respectively. In contrast to the reduced GO sheets, the stabilities of the carbonyl-hydroxyl pair and the carbonyl pair, with respect to the corresponding initial configuration, strongly depend on the adsorbed sites of groups. The vacancy defect improves the adsorptions of oxygen-containing groups on the surface. Because of the adsorption of new hydroxyl groups, the O-H bond belonging to the carbonyl-hydroxyl pair was highly dissociative and led to the formation of a highly stable carbonyl group with the release of water. The magnetic and electronic properties of the zigzag graphene nanoribbons were well tuned by different oxidized groups.