Two-dimensional nitrogen and oxygen Co-doping porous carbon nanosheets for high volumetric performance supercapacitors

Two-dimensional (2D) porous carbon nanosheets possess large open flat layer with high surface area, short ion diffusion route and small diffusion resistance have attracted greatly attention as electrode materials for supercapacitors. However, developing a simple and widely available preparation method remains a major challenge. Herein, we demonstrate a new, widely available way to rationally design the nitrogen and oxygen co-doping porous carbon nanosheets (PCN) utilizing graphene oxide as template by an electrostatic self-assembly process with cationic polyacrylamide and subsequent KOH activation. Benefiting from the open and accessible surface, short ion diffusion route and rich nitrogen and oxygen functional groups, the optimized PCN-3 electrode shows a high volumetric specific capacitance of 325.7 F cm−3 at 0.5 A g −1 with a high capacitance retention of 66% at 50 A g−1 (215.3 F cm−3). Moreover, the PCN-3//PCN-3 symmetric supercapacitor shows a high volumetric energy density of 22.1 Wh L−1 and outstanding cycling stability in 1 M Na2SO4 aqueous elec1trolyte. Consequently, the work highlights a convenient and widely available preparation way to prepare heteroatom doped porous carbon nanosheets for supercapacitors.