Design and Fabrication of Hierarchical NiCoP-MOF Heterostructure with Enhanced Pseudocapacitive Properties

Metal-organic framework (MOF)-derived heterostructures possessing the merits of each component are thought to display the enhanced energy storage performance due to their synergistic effect. Herein, a functional heterostructure (NiCoP-MOF) composed of nickel/cobalt-MOF (NiCo-MOF) and phosphide (NiCoP) is designed and fabricated via the localized phosphorization of unusual lamellar brick-stacked NiCo-MOF assemblies obtained by a hydrothermal method. The experimental and computational analyses reveal that such-fabricated heterostructures possess the modulated electronic structure, abundant active sites, and hybrid crystalline feature, which is kinetically beneficial for fast electron/ion transport to enhance the charge storage capability. Examined as the supercapacitor electrode, the obtained NiCoP-MOF compared to the NiCo-MOF delivers a high capacity of 728 C g^-1 (1.82 C cm^-2 ) at 1 A g^-1 with a high capacity retention of 430 C g^-1 (1.08 C cm^-2 ) when increasing the current density to 20 A g^-1 . Importantly, the assembled solid-state NiCoP-MOF-based hybrid supercapacitor displays superior properties regarding the capacity (226.3 C g^-1 ), energy density (50.3 Wh kg^-1 ), and durability (≈100% capacity retention over 10 000 cycles). This in situ heterogenization approach sheds light on the electronic structure modulation while maintaining the well-defined porosity and morphology, holding promise for designing MOF-based derivatives for high performance energy storage devices.