Band gap engineering in armchair-edged graphene nanoribbons by edge dihydrogenation

► The order of the three families in the gap is altered by different hydrogenations. ► The band structures and gaps of (n) H:H, (n + 1) H:H2 and (n + 2) H2:H2 ZGNRs are similar. ► It arises from the dihydrogenation-induced decrease of the effective ribbon width. ► The formation energy also shows distinct family behaviors.