▎ 摘　　要

Symmetry of adsorption site is the key to control the graphene band gap. When the adsorption sites change from mirror-symmetry adsorption (MSA) to mirror antisymmetric adsorption (MAA) position, the bandgap change (BC) exhibits two opposite tendencies. Therefore, a standard was developed to determine the type of band gap modification of graphene. When BC is negative, the bonding state between the adsorbent and graphene was the dominant factor. When BC is positive, the built-in electric field becomes dominated. Continuous tuning of the band gap can be achieved by adsorbing the appropriate functional groups. Our findings set the standard for determining the type of band gap modification and open the way for controllable adjustment of graphene band gap.