Nitrogen and sulfur co-doped hierarchical graphene hydrogel for high-performance electrode materials

In this investigation, nitrogen and sulfur co-doped graphene hydrogel (N,S-GH) with well-connected hierarchical networks was prepared using a simple one-step process. The hierarchical structures provide electrically conductive channels for ion transfer, whereas N,S heteroatoms improve the chemical reactivity and pseudocapacitance of the electrode material. An optimized N,S-GH as a bind-free supercapacitor electrode demonstrates a large gravimetric capacitance (294.8 F g −1 at 1 A g −1 ), long lifetime (89.4% retention after 10,000 cycles), and excellent rate capability, twice as that of pure GH due to the synergistic effect of N and S doping. Therefore, a large capacitance of the optimized N,S-GH is ascribed to fast ion diffusion, large accessible area (hierarchical network), and pseudocapacitance (N and S co-doping). Furthermore, the optimized N,S-GH-based supercapacitor delivers a high energy density (8.6 Wh kg −1 ) at a high power density (2.4 kW kg −1 ). Overall, the obtained N,S-GH through this investigation presents a promising electrode material with outstanding electrochemical properties for energy storage applications. Graphic abstract