Polyoxometalate/Metal-Organic-Framework Hybrid Materials As Electrodes for Electrochemical Capacitors

Abstract

Tremendous effort has been focused on developing electrochemical capacitors with various applications such as portable electronics, heavy hybrid vehicles, load leveling, and uninterruptible power supplies.Electrochemical capacitors have the advantage of providing high power density which enable faster charge/discharge rates than batteries, as well as long cycle life. Polyoxometalates (POMs) are transition metal oxide clusters, and they possess fast and reversible multi-electron redox reactions.Several POMs have been studied in supercapacitors, such as H3[PMo12O40], H3[PW12O40],H4[SiMo12O40], H4[SiW12O40]. However, most of POMs can be dissolved in aqueous electrolyte. Therefore, some of them were combined with carbon materials or conducting polymers.In this study, we synthesized a vanadium-based POM combined with a metal-organic-framework (MOF) as electrode material in electrochemical capacitors. The electrochemical properties of this V-POM/MOF electrodes are studied by electrochemical measurements such as galvanostatic charge/discharge and cyclic voltammetry. Furthermore, a hybrid energy storage device which combines V-POM/MOF as negative electrode and activated carbon as positive electrode was assembled to demonstrate the potential for electrochemical capacitor applications.