Nickel-iron sulfide nanoparticles supported on biomass-derived N-doped hierarchical porous carbon as a robust electrode for supercapacitors

Biomass-based carbon electrode material with hierarchical porous structure is considered as a promising candidate for supercapacitor applications, which could enhance the electron transfer and shorten the ion diffusion pathways. However, the low energy density of carbon-based materials seriously affects their wide applications. Herein, 3D N-doped hierarchical porous carbon coupled with nickel-iron sulfide nanoparticles (Fe5Ni4S8/FeS@N-HPC) is fabricated by a simple pyrolysis process. The 3D N-doped interconnected porous structure with large specific surface area provides more channels for ion transport and electron transfer. The nickel-iron sulfide nanoparticles in the porous carbon offer numerous sites for reduction and oxidation occurring to improve the charge storage for supercapacitors. Consequently, the synthesized Fe5Ni4S8/FeS@N-HPC electrode exhibits excellent electrochemical properties. The optimized Fe5Ni4S8/FeS@N-HPC composite fabricated under 800 °C displays an excellent capacitance of 2812.4 F g−1 (734.56 C g−1) at a current density of 0.5 A g−1. Beside, the Fe5Ni4S8/FeS@N-HPC-800//active carbon asymmetric supercapacitor shows an energy density of 76.8 W h kg−1 at a power density of 395.03 W kg−1 and superior cycling stability of 93.24% over 10,000 charge-discharge cycles. Our work presents a novel approach to the construction of high-performance electrode materials for supercapacitors.