Cactus-Like NiCoP/NiCo-OH 3D Architecture with Tunable Composition for High-Performance Electrochemical Capacitors

To effectively enhance the energy density and overall performance of electrochemical capacitors (ECs), a new strategy is demonstrated to increase both the intrinsic activity of the reaction sites and their density. Herein, nickel cobalt phosphides (NiCoP) with high activity and nickel cobalt hydroxides (NiCo-OH) with good stability are purposely combined in a hierarchical cactus-like structure. The hierarchical electrode integrates the advantages of 1D nanospines for effective charge transport, 2D nanoflakes for mechanical stability, and 3D carbon cloth substrate for flexibility. The NiCoP/NiCo-OH 3D electrode delivers a high specific capacitance of ≈1100 F g⁻¹, which is around seven times higher than that of bare NiCo-OH. It also possesses ≈90% capacitance retention after 1000 charge–discharge cycles. An asymmetric supercapacitor composed of NiCoP/NiCo-OH cathode and metal–organic framework-derived porous carbon anode achieves a specific capacitance of ≈100 F g⁻¹, high energy density of ≈34 Wh kg⁻¹, and excellent cycling stability. The cactus-like NiCoP/NiCo-OH 3D electrode presents a great potential for ECs and is promising for other functional applications such as catalysts and batteries.