Reduced Graphene Oxide Hydrogel for High Energy Density Symmetric Supercapacitor with High Operation Potential in Aqueous Electrolyte

Abstract

Abstract Reduced graphene oxide hydrogels (rGOHs) with tunable surface functionalities were prepared through a hydrothermal treatment. The self‐standing hydrogels were directly used as electrode materials without any binder or conducting agent in aqueous electrolyte. Electrochemical measurements show that the hydrogels can endure high potential up to 1.7 V in acid (H 2 SO 4 ) and KI‐additive (H 2 SO 4 +KI) electrolyte. With the introduction of extra pseudocapacitance through KI, rGOH possesses a high specific capacitance of 539 F g −1 , which is much larger than that (141 F g −1 ) in acid electrolyte. The energy density for rGOHs‐based supercapacitor with can reach up to 54 Wh kg −1 and the value can maintain at 28.8 Wh kg −1 even a high power density of 8500 W kg −1 . Such a good supercapacitive performance can be attributed to the open porous and interconnected structure, together with surface functionalities.