Cross-linked graphene/carbon nanotube networks with polydopamine glue for flexible supercapacitors

Three-dimensional (3D) graphene-based composites can possess exceptional electrochemical performance owing to their unique structure and properties. Herein, a 3D cross-linked hierarchical porous polydopamine (PDA) modified reduced graphene oxide (rGO)/amino functionalized carbon nanotube (CNT-NH2) composites were synthesized via hydrothermal method. The hierarchical electrode incorporates the advantages of 1D nanotube for effective charge transport, 2D graphene nanosheet for fast ion transport and 3D cross-linked hierarchical porous substrate for mechanical stability and flexibility. Attributing to these characters, the obtained rGO/CNTNH 2/PDA (GCP) electrode presents a high capacitance (176.2 F g(-1) at 0.5 A g(-1)) in aqueous 6.0 M KOH electrolyte. Symmetric supercapacitor based on GCP-50 electrodes exhibits a high energy density of 4.22 Wh kg(-1) and excellent cycling stability with 98.9% capacitance retention after 10,000 cycles. Furthermore, the supercapacitors show superior flexibility and stability. The facile synthesis, promising electrochemical results and 3D hierarchical porous nanostructure of GCPs present potential for supercapacitor and other energy storage applications.