Fabrication of iodine/nitrogen co-doped three-dimensional porous reduced graphene oxide for high energy density supercapacitors

As an electrode for supercapacitor, the gravimetric specific capacitance of two-dimensional layered graphene is theoretically superior to general porous carbon materials. However, the relatively low porosity and volumetric energy density of two-dimensional graphene-based electrode materials remain challenging for its practical application. Herein, iodine/nitrogen co-doped three-dimensional reduced graphene oxide (PGr) synthesized through the socking-drying process and subsequent calcination is reported. In the presence of NH4I and KI, the obtained PGr containing 2.9 wt.% of I element and 3.15 wt.% of N element possesses highly interconnected three-dimensional hierarchically porous network among the layered structure and possesses a high specific surface area of 622.5 m(2)center dot g(-1). Moreover, the synthesized PGr exhibits exceptional electrical conductivity and excellent capacitive characteristics, delivering 268 F center dot g(-1) of high gravimetric specific capacitance in a three-electrode system in KOH (6.0 mol center dot L-1). Furthermore, symmetric supercapacitor assembled from the synthesized PGr shows 9.46 Wh center dot kg(-1) of specific energy density when the power density is 600 W center dot kg(-1) and its initial capacitance retains 97.5% after 10 000 cycles of charging and discharging at 10 A center dot g(-1). In addition, the device utilizing ionic liquid as electrolyte delivers 32.9 and 46.2 Wh center dot kg(-1) of specific energy density under 1.35 kW center dot kg(-1) at 25 degrees C and 1.85 kW center dot kg(-1) at -50 degrees C, respectively.