Polyoxometalate Archetype-Boosted Stability and Charge Storage of 2D Graphene Nanosheets

Abstract

In this study, the potential of impregnation of phosphotungstic acid (PTA), a polyoxometalate, in enhancing specific capacitance (Csp) and diminishing the well-known restacking phenomenon of graphene nanosheets was explored. Graphene nanosheets were prepared chemically from graphite powder through the formation of graphene oxide (GO) and then the subsequent reduction of GO to the reduced GO (rGO). Impregnation of PTA in rGO-PTA (rGP) composites was carried out by simply dispersing rGO and PTA derived from tungstic acid. Scanning electron microscopy, X-ray diffraction analysis, UV-vis reflectance spectroscopy, and Fourier-transform infrared spectroscopy were used to analyze the elemental composition, microstates, and morphology of the composites. The charge-storing capacity and stability of the prepared rGP composites casted on a graphite electrode were examined with cyclic voltammetric, chronopotentiometric, and electrochemical impedance techniques. The effect of ions on the charging capacity of the electrodes was verified using electrolytes with different ion sizes. About 100% enhancement of Csp of rGO was achieved by impregnating rGP composites with only 1% PTA and ca. 87% capacitance retention for 2000 charging-discharging cycles were observed.