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

Abstract

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.