Co2P-Co3(PO4)2 nanoparticles immobilized on kelp-derived 3D honeycomb-like P-doped porous carbon as cathode electrode for high-performance asymmetrical supercapacitor

To improve the overall electrochemical performance of supercapacitors, we proposed a novel and low-cost strategy to prepare biomass-based carbon electrode materials with abundant electroactive sites. In this work, the kelp-derived 3D honeycomb-like P-doped porous carbon decorated with Co2P and Co3(PO4)2 nanoparticles (Co2P-Co3(PO4)2@KPC) was successfully constructed through impregnation and high-temperature phosphorization. The well-developed porous structure of kelp can provide abundant effective adsorption sites for Co2P and Co3(PO4)2 nanoparticles, reducing their shedding and volume expansion changes during electrochemical testing. This combination provides the electrode materials with high specific capacitance, good rate capability, and excellent cycling stability. The resulting Co2P-Co3(PO4)2@KPC composite displays an ultrahigh specific capacitance of 3024.5 F g−1 at 0.5 A g−1, and its specific capacitance still retains 2182.7 F g−1 at 10 A g−1. An asymmetric supercapacitor (ASC) composed of a Co2P-Co3(PO4)2 @KPC cathode and an activated carbon (AC) anode shows a maximum energy density of 74.5 W h kg−1 at a power density of 372.5 W kg−1. As novel biomass-derived electrode materials, this as-fabricated composite has promising applications in energy storage systems.