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

► The carbonyl pair and carbonyl-hydroxyl pair are formed on ribbon surface. ► Stabilities of these pairs relative to the initial structures strongly depend on the sites. ► The O-CH bond belonging to the carbonyl-hydroxyl pair was highly dissociative. ► Magnetic and electronic properties of ribbons were well tuned by oxidized groups.