Enrichment of pyrrolic nitrogen by hole defects in nitrogen and sulfur co-doped graphene hydrogel for flexible supercapacitors

The effect of the doping configuration and concentration of nitrogen (N) and sulfur (S) on the electrochemical performance of 3D N and S co-doped hole defect graphene hydrogel (NS-HGH) electrodes is investigated. Surprisingly, by introducing a hole defect on the graphene surface, the difference in the doping concentrations of N and S can be used to effectively modulate the electrochemical behavior of the NS-HGH. The hole defects provide a rapid ion diffusion path. Finally, we showed that the intriguing specific capacitance (536 Fg^-1) of the NS-HGH could enhance the overall performance of the pseudocapacitance and electric double layer capacitance. The rational design of the NS-HGH-based flexible solid state supercapacitor results in not only outstanding electrochemical performance with a maximum energy density of 14.8 Wh kg^-1 and power density of 5.2 KWkg^-1 but also in extraordinary mechanical flexibility and excellent cycle stability.