Asymmetric polyoxometalate-polypyrrole composite electrode material for electrochemical energy storage supercapacitors

Abstract

Nowadays, metal-oxides impregnated conducting polymers as electrode materials are attracted much attention due to their higher stability. Here, the metal-oxide cluster, polyoxometalate (K<inf>5</inf>H<inf>2</inf>[PV<inf>4</inf>W<inf>8</inf>O<inf>40</inf>]·11H<inf>2</inf>O, PV<inf>4</inf>W<inf>8</inf>), was introduced into the polypyrrole (PPy) matrix to overcome the polymers stability issues, and thus, the resulting novel PV<inf>4</inf>W<inf>8</inf>/PPy (symmetric) composite electrode has been reported. XPS confirmed the presence of all atoms on the polymer backbone with respective oxidation states. Nevertheless, doping of PV<inf>4</inf>W<inf>8</inf> on the conductive PPy matrix's surface can affectively improve the ion's transfer. Finally, the asymmetric PV<inf>4</inf>W<inf>8</inf>-PPy/PPy composite exhibits a prodigious specific capacitance of 291 F g−1, larger than the PPy (90.01 F g−1) and PV<inf>4</inf>W<inf>8</inf> (39.03 F g−1) at 0.4 A g−1 current density. The PV<inf>4</inf>W<inf>8</inf>-PPy/PPy (asymmetric) electrode showed excellent cycle stability. However, a symmetric supercapacitor device based on PV<inf>4</inf>W<inf>8</inf>/PPy composite possesses a specific capacitance of 195.27 F g−1 and an energy density of 8.94 Wh kg−1 at the same current density as PV<inf>4</inf>W<inf>8</inf>-PPy/PPy (asymmetric) electrode with remarkable cycle stability. © 2021 Elsevier B.V.