π-π stacked iron (II) phthalocyanine/graphene oxide composites: rational fabrication and excellent supercapacitor properties with superior rate performance

Using concentrated sulfuric acid as the solvent, nanocomposites of iron (II) phthalocyanine and graphene oxide (denoted as FePcGOn) are rationally and facilely fabricated by self-assembly via π-π interactions. The unique structure of FePcGO2 renders the nanocomposites greatly improved conductivity and accelerated rates of both charge transfer and electrolyte migration. The tightly π-π stacking between FePc and GO bestows the materials structural stability. The molecularly dispersive FePc contributes much pseudocapacitance to elevate the energy density of supercapacitor. Three-electrode test reveals a high specific capacitance of 514 F g⁻¹ for FePcGO2 at a current density of 1 A g⁻¹. A capacity of 90 F g⁻¹ sustains at an ultrahigh current density of 500 A g⁻¹. Symmetrical two-electrode supercapacitor also demonstrates excellent supercapacitive properties of FePcGO2 and delivers a capacitance of 235.5 F g⁻¹ at 1 A g⁻¹ over 1 V with an energy density of 8.2 Wh kg⁻¹. A steady capacity of 200.2 F g⁻¹ sustains at 5 A g⁻¹ after 60,000 cycles. Symmetrical FePcGO2 supercapacitor achieves high capacity of 308.6 F g⁻¹ and energy density of 21 Wh kg⁻¹ over 1.4 V at 1 A g⁻¹. The present work provides insights into high-performance supercapacitive materials.