Three-dimensional N- and S-codoped graphene hydrogel with in-plane pores for high performance supercapacitor

Abstract

Rationally designed electrodes with a high specific surface area, conductivity, and ion diffusion rate are essential for high performance supercapacitors. Hereby, we report the construction of a three-dimensional (3D) N- and S-codoped graphene hydrogel with abundant in-plane pores (NS-HGH). In NS-HGH, its highly interconnected network structure largely restrains the restacking of the graphene sheets, offering a specific surface area of as high as 317 m2 g−1. The abundant intimate graphene sheet-sheet contacts and in-plane pores created provide efficient electron transport pathways and ion transport pathways, respectively. The dopants of N and S heteroatoms further improve the porosity and conductivity of the resultant NS-HGH. With these characteristics, the NS-HGH electrode exhibits a high specific capacitance of 320.0 F g−1 at 1 A g−1 and retains 96.4% of the initial capacitance upon 10000 potential cycles at 10 A g−1. Whiles, the supercapacitors made from the NS-HGH electrodes deliver an impressive gravimetic energy density of 24.7 Wh kg−1 at 1 A g−1. To understand the high capacitive performance of the NS-HGH, we further performed first-principle simulations. It is revealed that heteroatom doping offers additional capacitance to NS-HGH because its density of states (DOS) near the Fermi energy level can be largely increased as a result of abundant polarized sites produced. These results suggest that NS-HGH shows great potential for practical application.