Facile Synthesis of Nitrogen/Sulfur Co-doped Three-Dimensional Holey Graphene Hydrogels for High Supercapacitive Performance

Abstract

Heteroatom-doped holey graphene hydrogels (HGHs) have attracted great interest owing to their remarkable porous structure, superior electrochemical performances, and prospective applications for supercapacitors. Herein, a simple and scalable approach to synthesize nitrogen, sulfur co-doped three-dimensional HGHs is developed using (NH4)2S2O8 as the pore-making agent and N, S sources by a one-step hydrothermal reaction. In a 6 M KOH electrolyte, the optimized HGH-based asymmetric supercapacitor exhibits an exceptionally high specific capacitance of 354 F g-1 at 1 A g-1, an excellent rate capability of 299 F g-1 at 100 A g-1, and outstanding cycle stability (104% of initial capacity retention at 5 A g-1 after 10,000 cycles). Additionally, the assembled HGH electrode supercapacitor possesses a high energy density of 21.14 Wh kg-1 (449.95 W kg-1) in a 1 M Na2SO4 electrolyte. The N, S heteroatom doping and hierarchical pore structure are ascribed to the superior electrochemical performance of HGHs. Therefore, the convenient and efficient method in the present work provides new ways into the preparation of heteroatomdoped HGHs for high-performance supercapacitors.