Comparative study of electrosorption performance of solar reduced graphene oxide in flow-between and flow-through capacitive deionization architectures

There are a large number of capacitive deionization (CDI) cell architectures developed with different levels of complexities associated. Here, we compare flow-between (FB-CDI) and flow-through (FTE-CDI) capacitive deionization setups with respect to electrosorption performances by using solar reduced graphene oxide (SRGO) as an electrode material. SRGO is synthesised using solar irradiation and characterized for crystallinity, structure and morphology using x-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The electrode material is studied for charge storage using cyclic voltammetry and galvanostatic charge-discharge in aqueous sodium chloride and potassium chloride solutions. To compare the two capacitive deionization architectures with respect to electrosorption performance, we use two different cations, i.e sodium and potassium to study its effect on hydrated radius and hydration ratio of these cations. The electrosorption performance is estimated by varying the voltage between two electrodes and concentrations of salt solutions. The electrosorption capacity obtained is high 46.1 mg/g for FTE-CDI, whereas electrosorption rate is high i.e 0.026 mg/g/s for FB-CDI for potassium chloride solution. Further the obtained values of electrosorption capacities are validated by Langmuir and Freundlich adsorption isotherms. We confirm that the data fits well with Langmuir adsorption isotherm for both the cations. We further validate the electrosorption data by modified Donnan (mD) model.