Optimized supercapacitive performance of graphene-hydrogel by porous texture controlling

Porous texture of graphene-hydrogel electrode material is critical for the performance of supercapacitors. In this work, the pore channels are controlled by two aspects, including the graphene oxide concentration and the pressure for fabricating hydrogel electrodes. It is found that the sample starting from 3 mg ml −1 graphene oxide shows the largest specific capacitance of 297 F g −1 at a current density of 0.5 A g −1 in 2 M KOH solution after the hydrothermal process. By increasing the pressure to 10 MPa, the electrochemical performance can be further improved to 330 F g −1 . This good performance is mainly attributed to the preferable specific surface area (2110 m 2 g −1 ) and the dense laminated structure under the optimizing preparation conditions. Besides, the cycle measurement demonstrates the excellent cycling stability of the samples, while 88% of its initial capacitance can be retained after 10,000 cycles.