Abstract: Halogenated graphene nanoplatelets that are characterized by having, except for the carbon atoms forming the perimeters of the graphene layers of the nanoplatelets, (i) graphene layers that are free from any element or component other than sp2 carbon, and (ii) substantially defect-free graphene layers; the total content of halogen in the nanoplatelets is about 5 wt % or less calculated as bromine and based on the total weight of the nanoplatelets. Processes for producing such nanoplatelets and various end uses for such nanoplatelets are also described. Halogenated exfoliated graphite having a total content of halogen of about 5 wt % or less calculated as bromine and based on the total weight of the halogenated exfoliated graphite and processes for producing the halogenated exfoliated graphite are also provided.