Double redox-active quinone molecules functionalized a three-dimensional graphene network for high-performance supercapacitor

As a well-known two-dimensional material, graphene is widely used as an electrode material in energy storage devices. However, the tendency of the agglomeration or restacking of graphene sheets limit the properties. To overcome this issue, redox-active molecules can be introduced that inhibit the stacking of graphene sheets and impart excellent pseudocapacitance properties. In this study, we design a three-dimensional (3D) graphene network anchored with redox-active 2,5-(di-p-phenylenediamine)-1,4-benzoquinone (DBP) and hydroquinone (HQ) (DFGN) using a facile one-step hydrothermal process. The covalent binding and absorption between redox-active molecules and graphene sheets reduce restacking and enable promising pseudocapacitance through reversible faradic reactions of quinone and aniline structures. Among all the samples, DFGN-1 shows the best specific capacitance (667.3 F/g at 1 A/g), high-rate capability (89.2 % even up to 50 A/g), and good cycling stability. Furthermore, DFGN-1 is also employed as an electrode material to construct flexible solid-state supercapacitors (FSSCs), which exhibit great specific capacitance (441 F/g at 0.5 A/g), excellent cycling stability (90.6 % after 10,000 cycles at 10 A/g) and high-energy density of 9.29 Wh/kg at a power density of 96.22 W/kg. Interestingly, FSSCs also display great mechanical flexibility in bending and twisting states and extraordinary mechanical durability even after being bent 5000 times. Overall, double redox-active quinone molecules functionalized 3D graphene network provides a novel tactic to construct promising potential electrodes in energy storage applications.