Phosphorus Doping in Co9S8/Ni3S2 Hollow Nanorods for Supercapacitors

Abstract

Metal sulfides, characterized by high crystalline stability and narrowed band gap, are recognized as effective electrode materials for energy storage in alkaline environments. This study enhances the surface activity in Co₉S₈/Ni₃S₂ hollow nanorod arrays by incorporating phosphorus (P) doping. In situ Raman spectroscopy confirms that P doping facilitates rapid surface reconstruction in alkaline media, resulting in substantial amounts of oxyhydroxides that significantly enhance the energy density of supercapacitors. The optimized P–Co₉S₈/Ni₃S₂ (1 h) electrode demonstrates a 4.56-fold increase in performance over the original Co₉S₈/Ni₃S₂, achieving a capacitance of 20.5 F·cm^–2 at 3 mA·cm^–2 in 2 M KOH. The hybrid supercapacitor device assembled with activated carbon achieves an energy density of 1.73 mWh cm^–2 at a power density of 4.95 mW cm^–2, showcasing a high cycling life with 84.6% capacity retention after 10,000 cycles. This work effectively reconstructs the activity of oxyhydroxide species on Co₉S₈/Ni₃S₂ electrodes in alkaline environments through P doping engineering, providing valuable guidance for the design of in situ reconstructions of metal sulfide electrodes using P atom doping engineering.