Polyoxometalate/MOF-derived MoSe2/(Ni, Co)Se2 for battery-type electrodes of high-performance supercapacitors

Abstract

Polyoxometalates (POMs), as multinuclear metal oxide clusters, possess natural multi-electron redox properties and high electrical conductivity. However, their susceptibility to leaching and agglomeration limits their application in energy storage. MOF materials provide a solution to the limitation of POMs due to their controllable pore sizes, big surface areas and strong adsorption properties. The synergistic effect between the two components greatly improves the electrochemical properties of the composites. In view of this, PMo12 is encapsulated in ZIF-67 to form PMo12@ZIF-67 by in situ self-assembly, and benefitted from this unique precursor, MoSe2/(Ni, Co)Se2 hollow structures assembled by nanoparticles are synthesized though Ni2+ etching and selenization process. At the same time, the PMo12 content is optimized to get the best performance of 60-MoSe2/(Ni, Co)Se2. In the three-electrode test, the developed 60-MoSe2/(Ni, Co)Se2 electrode material exhibits an excellent specific capacity of 359.9 mA h g−1 at a current density of 1 A g−1, and a capacitance retention rate of 83.7 % after 10,000 cycles. In addition, the asymmetric supercapacitor (ASC) assembled with a positive electrode of 60-MoSe2/(Ni, Co)Se2 and a negative electrode of activated carbon exhibits an excellent energy density of 40.3 W h kg−1 at a power density of 800.9 W kg−1. These superior electrochemical properties are attributed to the unique electronic structure of PMo12, which further demonstrates the feasibility of constructing hollow multicomponent selenides as energy storage materials using PMo12-ZIF-67 as a precursor.