Phosphorus Doping\nin Co<sub>9</sub>S<sub>8</sub>/Ni<sub>3</sub>S<sub>2</sub> Hollow\nNanorods for Supercapacitors

Metal sulfides, characterized by high crystalline stability\nand\nnarrowed band gap, are recognized as effective electrode materials\nfor energy storage in alkaline environments. This study enhances the\nsurface activity in Co<sub>9</sub>S<sub>8</sub>/Ni<sub>3</sub>S<sub>2</sub> hollow nanorod arrays by incorporating phosphorus (P) doping.\nIn situ Raman spectroscopy confirms that P doping facilitates rapid\nsurface reconstruction in alkaline media, resulting in substantial\namounts of oxyhydroxides that significantly enhance the energy density\nof supercapacitors. The optimized P–Co<sub>9</sub>S<sub>8</sub>/Ni<sub>3</sub>S<sub>2</sub> (1 h) electrode demonstrates a 4.56-fold\nincrease in performance over the original Co<sub>9</sub>S<sub>8</sub>/Ni<sub>3</sub>S<sub>2</sub>, achieving a capacitance of 20.5 F·cm<sup>–2</sup> at 3 mA·cm<sup>–2</sup> in 2 M KOH. The\nhybrid supercapacitor device assembled with activated carbon achieves\nan energy density of 1.73 mWh cm<sup>–2</sup> at a power density\nof 4.95 mW cm<sup>–2</sup>, showcasing a high cycling life\nwith 84.6% capacity retention after 10,000 cycles. This work effectively\nreconstructs the activity of oxyhydroxide species on Co<sub>9</sub>S<sub>8</sub>/Ni<sub>3</sub>S<sub>2</sub> electrodes in alkaline\nenvironments through P doping engineering, providing valuable guidance\nfor the design of in situ reconstructions of metal sulfide electrodes\nusing P atom doping engineering.