N/O co-enriched amorphous carbon coated graphene with a sandwiched porous architecture as supercapacitor electrodes with high volumetric specific capacitance

High-performance electrode materials are one of critical factors that need to be considered for practical applications of supercapacitors with high power density. Herein, nitrogen/oxygen co-enriched amorphous carbon coated graphene with a sandwiched porous architecture was prepared by one-pot hydrothermal synthesis using soy protein as the nitrogen and carbon precursor, followed by carbonization in an argon atmosphere at medium temperatures. To improve the energy storage capability, the as-prepared carbon materials were further thermally oxidized at 350 °C in air. The resultant material demonstrates a high gravimetric (volumetric) specific capacitance of 221 F g −1 (330 F cm −3 ) at 0.2 A g −1 and 153 F g −1 (229 F cm −3 ) at 20 A g −1 in 6 M KOH aqueous electrolyte with a high retention rate of ca. 69%.