Three-dimensional heterostructured nickel phosphide @ nickel cobalt phosphide nanocomposites with highly porous surface for high-performance supercapacitor

Nickel phosphide @ nickel cobalt phosphide heterostructure nanocomposites (NP@NCP) are prepared by phosphidization of metal-organic framework (MOF) precursors. The NP@NCP have similar morphology as MOF, but are highly porous. When used as the electrode material, the NP@NCP31/carbon cloth exhibits a specific capacity of 868.1 C g-1 at 1 A g-1 and 82.05% capacity is maintained after 5000 cycles in 4 M KOH. An asymmetric supercapacitor constructed with NP@NCP31 and activated carbon exhibits an energy density of 61.9 Wh kg-1 at a power density of 800.1 W kg-1 and a capacity retention rate of 94.17% after 5000 cycles. The high charge-storage performance of the NP@NCP is owing to the formation of heterointerface that causes charge redistribution, increases the electrochemically active sites, and facilitates the ion diffusion. The highly porous morphology also contributes to the high specific surface area and the increased active sites. Developing heterostructure materials based on transition metal phosphides is a viable approach to enhance the electrochemical capabilities of supercapacitors.