Metal-organic framework derived directional growth of ultrathin amorphous NiCo hydroxide nanosheets on NiCo₂O₄ nanowire arrays for enhanced electrochemical properties

The rational design of hierarchical nanostructured electrode materials is critical for achieving high electrochemical property for supercapacitor (SC) applications. Herein, we report a facile method for fabricating hierarchical NiCoO@NiCo–OH core-shell nanowire array (NiCoO@NiCo–OH NWA) on flexible carbon fiber clothes by using a cobalt-based metal organic framework (Co-MOF) as an intermediate. The growth mechanism study shows the formation process is completed by a localized dissolution of Co-MOF followed by a directional growth of NiCo–OH nanosheets on NiCo₂O₄ nanowires. The unique hierarchical nanostructure endows the material a high surface area, rich active sites, fast electron transport, and efficient electrolyte ion diffusion. Consequently, the as-prepared material exhibited an over 3 times’ higher specific capacity than the pristine NiCo₂O₄ nanowire arrays and an excellent rate capability at 40 A g⁻¹ for SCs. Moreover, the NiCoO@NiCo–OH NWA based hybrid supercapacitor (HSC) exhibited a considerably high energy density of 57.2 Wh kg⁻¹, a high power density of 17.6 kW kg⁻¹, and ultralong cycling stability of over 10 000 cycles (retention rate of 91.8%), outperforming most of the current state-of-the-art SCs. The directional growth strategy using MOFs as intermediates reported here provides a simple but effective way to fabricate hierarchical nanostructured electrode materials for advanced energy storage applications.