Supramolecular-induced confining methylene blue in three-dimensional reduced graphene oxide for high-performance supercapacitors

Adding redox-active species into the electrolyte can supply extra capacitance to the carbon-based supercapacitors. However, the devices may suffer from serious self-discharge caused by the shuttling and intermixing of charged active species between the electrodes. Confining these active species in a solid-state electrode material is an effective strategy to avoid this. Inspired by this, we fabricate a three-dimensional reduced graphene oxide confined methylene blue composite via a supramolecular strategy, combined with a hydrothermal reduction and a freeze-drying process. Benefited from the porous and conductive structure of the product, the fast-reversible electrochemical reaction of methylene blue, and the spatial confinement effect of the methylene blue confined in reduced graphene oxide, the as-prepared product exhibits a high-rate capability (311 and 262 F g−1 at 1 and 20 A g−1, respectively) and an excellent cycle stability (96% capacitance retention after 10000 cycles) in a three-electrode system. Moreover, a solid-state symmetric supercapacitor device based on the as-prepared product delivers the maximum energy density of 8.2 Wh kg−1 and outstanding cycle stability. This supramolecular-induced confining active species in reduced graphene oxide strategy provides insight into the fabrication of other high-performance graphene-based pseudocapacitors.