Hierarchical nanocomposite of carbon-fiber-supported NiCo-based layered double-hydroxide nanosheets decorated with (NiCo)Se2 nanoparticles for high performance energy storage

Exploring novel structures consisting of multiple highly active components is a crucial challenge for supercapacitor applications. Using an in-situ self-templated method, we demonstrate the controlled fabrication of a fibrous hierarchical nanocomposite made of carbon microfibers covered with a layer of metal-organic framework (MOF) derived from nickel-cobalt layered double-hydroxide (NiCo-LDH) nanosheets decorated with (NiCo)Se2 nanoparticles. The (NiCo)Se2 nanoparticles attached tightly onto the surface of the two-dimensional NiCo-LDH, both of which were generated by the decomposition of the NiCo-based MOF, and exhibited multiple active sites that contributed to improved electrical conductivity, high capacity, and structural stability. Density functional theory calculations revealed that the density of states near the Fermi level was significantly enhanced, favoured OH- adsorption, and promoted the kinetics of the electrochemical reaction. Benefiting from the intrinsic synergetic contributions from the hierarchical nanoscale structure, the electrode made from the nanocomposite delivered an impressive capacity of 1394.2 F g-1 (702.7 C g-1) at 1 A g-1. Furthermore, a hybrid supercapacitor based on the developed nanocomposite demonstrated an energy density of 50.6 W h kg-1 and a power density of 800 W kg-1 with high cyclic stability. Our results suggest that the hierarchical nanocomposite can be a powerful electrode for advanced next-generation supercapacitors.