Nano ZIF-67/PBA derived core-shell sulfides or phosphides for enhanced electrochemical performance of supercapacitors

Abstract

Metal-organic frameworks (MOFs) possess large specific surface area, high porosity, and adjustable pore size, exhibiting a broad prospect in the field of supercapacitors. However, the poor stability and conductivity of MOFs limited their application in energy storage. The structure of MOF composites and their derivatives are beneficial for storing electric charge and boosting the diffusion of electrolyte ions. In this study, we prepared heterostructured ZIF-67/Prussian blue analogues (PBA) derived sulfides and phosphides using the hydrothermal and solid-phase phosphating method, respectively. The ZIF-67/PBA composites with an average particle size of approximately 1100 nm, retained the rhombic dodecahedral shape of ZIF-67. Compared with MOF-derived phosphides, MOF-derived sulfides more completely retained the rhombic dodecahedron morphology of ZIF-67/PBA and demonstrated good electrochemical performance, especially ZPS-3. The unique core-shell nanostructure provides more active sites and suitable ion transport paths for reversible oxidation-reduction reactions. In three-electrode system, the ZPS-3 electrode exhibited a specific capacity of 603.9 F g−1 at a current density of 0.5 A g−1, superior rate performance, and excellent cycle stability. This study established a new synthesis paradigm for the development of MOF derivatives as a potential class of electrode materials for supercapacitors.