Free-standing amorphous nanoporous nickel cobalt phosphide prepared by electrochemically delloying process as a high performance energy storage electrode material

Energy storage system based on supercapacitors has recently received lots of attention as a complementary technology to batteries to meet the different requirement for energy usage in practice. Herein we demonstrate a new battery-type electrode material for supercapacitors which is based on free-standing amorphous nanoporous nickel-cobalt-phosphide (np-Ni-Co-P) prepared by electrochemical dealloying of Ni-Co-P precursor. Benefiting from the semi-metallic properties of Ni-Co-P in the bulk and the fast kinetics of Faraday charge transfer of the active material in the porous structure, the as-prepared amorphous material exhibited excellent specific capacitance of 1236 F cm⁻³ (171.4 mAh cm⁻³ at 1 A cm⁻³), high retention rate (782 F cm⁻³, 108.5 mAh cm⁻³ at 100 A cm⁻³) and outstanding stability (85.3% capacity retention after 20,000 cycles). Hybrid supercapacitors based on the synthesized materials and a carbon electrode delivered an impressive energy density of 31.7 mWh cm⁻³ (power density = 0.7 W cm⁻³) and robust stability with capacity retention of 79.0% after 20,000 charging/discharging cycles.