Kinetic insights into the integration of polyoxometalate clusters on reduced graphene oxide for enhanced electrochemical performance in energy storage applications

Abstract

This article explores the electrochemical reactions in the hybrid material phosphotungstic acid (PW₁₂)/reduced graphene oxide (rGO), resulting from the integration of polyoxometalate (POM) clusters into rGO sheets, aiming for its application in supercapacitors. The synthesis process employs a direct chemical approach, leveraging the anchoring capability of rGO. Morphological analyses confirm the open porous structure of rGO sheets, increasing the number of electroactive sites per geometric area unit and facilitating ion transport to maintain the electrolytic connection between electroactive sites and the solution. The observed low irreversibility is crucial for achieving high power density. A frequency-domain kinetic model is proposed to better understand the electrochemical processes, enabling the extraction of kinetic parameters and the estimation of the amount of accessible and accessed active sites as a function of electric potential, aiding in the selection of active and support materials to increase charge storage capacity and energy density.