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

• Published in: Advanced functional materials 2018-05, Vol.28 (20), p.n/a
• Main Authors: Li, Xin, Wu, Haijun, Elshahawy, Abdelnaby M., Wang, Ling, Pennycook, Stephen J., Guan, Cao, Wang, John
• Format: Article
• Language: English
• Subjects: Batteries; cactus‐like nanostructures; Capacitance; Capacitors; Carbon; Charge transport; Cloth; Cobalt; Density; electrochemical capacitors; Electrodes; energy density; Flux density; Hydroxides; Materials science; Nickel; NiCoP/NiCo‐OH electrodes; Phosphides; Structural hierarchy; Substrates
• ISSN: 1616-301X; 1616-3028
• DOI: 10.1002/adfm.201800036

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. A self‐supported NiCoP/NiCo‐OH nanoarray electrode with 3D cactus‐like architecture is grown on a carbon cloth substrate. The metal hydroxide matrix stabilizes the overall structure and the uniform embedded metal phosphide nanocrystals lead to higher capacitance. This smart electrode design provides great potential for electrochemical capacitors and it may also be useful for other energy harvesting and storage applications.