High-Performance Supercapacitors Based on a Zwitterionic Network of Covalently Functionalized Graphene with Iron Tetraaminophthalocyanine

Graphene derivatives are promising candidates as electrode materials in supercapacitor cells, therefore, functionalization strategies are pursued to improve their performance. A scalable approach is reported for preparing a covalently and homogenously functionalized graphene with iron tetraaminophthalocyanine (FePc-NH2) with a high degree of functionalization. This is achieved by exploiting fluorographene’s reactivity with the diethyl bromomalonate, producing graphene-dicarboxylic acid after hydrolysis, which is conjugated with FePc-NH2. The material exhibits an ultrahigh gravimetric specific capacitance of 960 F g−1 at 1 A g−1 and zero losses upon charging–discharging cycling. The energy density of 59 Wh kg−1 is eminent among supercapacitors operating in aqueous electrolytes with graphene-based electrode materials. This is attributed to the structural and functional synergy of the covalently bound components, giving rise to a zwitterionic surface with extensive π–π stacking, but not graphene restacking, all being very beneficial for charge and ionic transport. The safety of the proposed system, owing to the benign Na2SO4 aqueous electrolyte, the high capacitance, energy density, and potential of preparing the electrode material on a large-scale and at low cost make the reported strategy very attractive for development of supercapacitors based on the covalent attachment of suitable molecules onto graphene toward high synergy hybrids.