Graphene oxide/12 tungstophosphoric acid nanocomposites – achieving favorable properties with ion beams for electrochemical supercapacitors

Abstract

In recent years graphene oxide (GO)/12-tungstophosphoric acid (WPA) nanocomposites have demonstrated promising potential for electrochemical supercapacitors. However, to enhance their performance, it is necessary to modify the surface chemistry of GO to minimize the influence of basal plane oxygen groups, which hinder the material's conductivity. Additionally, some degree of structural modification of WPA is desired. In this regard, ion beam irradiation presents a promising method to simultaneously optimize surface chemistry of GO and structurally modify WPA. To accomplish this, ion beam irradiation is employed for modification of individual components as well as their nanocomposites with varying mass ratios. Different ion species, fluences and energies were utilized depending on the sample type, ranging from 10 keV C to 710 MeV Bi. Spectroscopy methods were employed to gain insight into the type and degree of structural modification in WPA. A direct correlation is observed between the parameters of the ion beams and the resulting structural changes. As the disordering increases, the structure transitions from partially modified to increased bond breaking, ultimately leading to reconnected bronze-like structures. By increasing the fluence, a gradual modification of the structure and surface chemistry of GO was possible. The effects of irradiation on GO and WPA are particularly pronounced in irradiated composites, where higher capacitance is measured.