Impact of the degree of functionalization of graphene oxide on the electrochemical charge storage property and metal ion adsorption

Graphene oxide (GO) samples were prepared at room temperature using a modified Hummer's method. The quantitative variation of oxidizing agent for the oxidation of graphene sheets resulted in increase of the oxygen functionalities on the GO samples. The qualitative analysis of functional groups and surface charge variation were studied using Fourier transform infra-red (FTIR) spectroscopy and zeta potential, respectively. Different oxidation degrees of GO were investigated by X-ray diffraction (XRD), Raman and X-ray photoelectron spectroscopy (XPS). The electrochemical charge storage properties of the GO samples were studied using a two electrode supercapacitor cell. The fabricated supercapacitor demonstrates linear enhancement in the specific charge storage with an increase in the oxidation of the GO samples. A maximum charge storage of 71 F g(-1) has been obtained with the highly oxidized GO sample at room temperature. The adsorption of metal ions from aqueous solution has also been studied with the variation in the degree of functionalization of the GO samples. It was observed that increasing oxygen functionalities from GO-1 to GO-5 amplifies the uptake of metal ions [Cd(II) and Cu(II)]. The experimental data fits well with the Langmuir adsorption model, indicating monolayer adsorption of metal ion on the GO samples.