Simple preparation of two-dimensional lamellar ammonium cobalt phosphate materials derived from ZIF-L and its application in supercapacitors

Abstract

Supercapacitors have been widely concerned in various energy storage systems for high power density, extended life, and environmental friendliness. In this study, two-dimensional(2D) lamellar phosphate NH4CoPO4·H2O(NCP) materials were generated using Co-MOF as a template by (NH4)2HPO4 etching and stripping. The effect of etching stripping on supercapacitor morphology and energy storage performance was investigated. The two-dimensional lamellar structure, morphology, and electrochemical properties were analyzed by SEM, XRD, XPS, TEM and electrochemical characteristics. The results show that the 2D lamellar nanosheet structure of NH4CoPO4·H2O increases electroactive sites and facilitates complete connection between electrolyte and the active substances, considerably increasing the energy store ability of materials. When the time of phosphate etching is 8 h, the specific capacitance of NCP-8 h reaches 585.83 F·g−1/322.20 C·g−1 (0.6 A·g−1) and remains 457.63 F·g−1/251.69 C·g−1 (10 A·g−1). After 4000 times constant current charge-discharge cycle, the specific capacitance value is kept at 87.3% of the initial value with the current density of 10 A·g−1 under the three-electrode test system. The above demonstrated excellent energy storage performance as well as application possibilities.