Bio-inspired functionalization and redox charge transfer of graphene oxide sponges for pseudocapacitive electrodes

Bio-inspired and environmentally friendly chemical functionalization method for reducing of graphene oxide (GO) sponge using dopamine derivatives is developed. The GO sponge is readily modified by poly(norepinephrine) (p(Nor)) through a simple wet chemistry, and mechanical properties of the GO sponge is improved with structural stability. The oxidative polymerization of norepinephrine can considerably remove oxygen-containing species from the GO sponge surface as well as provide redox active quinone moieties for pseudocapacitive electrodes. Furthermore, three-dimensional (3D) macroporous networks of the reduced GO (rGO) sponge provide a large surface area and continuous ion pathways. As a result, p(Nor)-functionalized rGO (p(Nor)@rGO) sponge exhibits enhanced capacitive performance. The p(Nor)@rGO sponge shows that a specific capacitance of 232.1 F g−1 (2.5 times higher than that of chemically converted rGO sponge) and good cyclic stability over 2000 charge/discharge cycling tests.