Structure-Designed Synthesis of CoP Microcubes from Metal-Organic Frameworks with Enhanced Supercapacitor Properties

Metal-organic framework-based supercapacitors have been widely recognized as the best energy storage devices for future portable electronic equipment. Herein, CoP- T ( T = 300, 350, and 400 °C) microcubes with a solid and hollow microstructure were successfully synthesized by low-temperature phosphorization of [CH₃NH₃][Co(HCOO)₃] precursor at desired temperatures. The morphology, structure, and composition of the prepared CoP-350 °C samples were analyzed by scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. Hollow CoP-350 °C microcube has a larger specific surface area (25.9 m² g^-1) than that of solid ones (16.1 m² g^-1). When the two samples were used as electrode raw materials for supercapacitors, the hollow CoP-350 °C electrode exhibits better electrochemical performance (560 F g^-1) than that of the solid one (427.6 F g^-1) at a current density of 1 A g^-1. The enhanced supercapacitor properties may be attributed to the large surface area and the unique hollow structure. Further, an asymmetric supercapacitor was prepared by employing the hollow CoP-350 °C microcubes as anode and N-doped graphene as cathode. It has a high rate capability (capacitance retention of 69% from 0.5 to 8 A g^-1), a high energy density (21.4 W h kg^-1 at a power density of 373 W kg^-1), and outstanding cycling stability (remained 81.2% after 6000 cycles).