Influence of Chemical, Electrochemical Exfoliation, Hydrophilic, and Hydrophobic Binder on the Sorption Capacity of Graphene in Capacitive Deionization

Abstract

Graphene is expected to play a significant role as a capacitive deionization (CDI) electrode due to its exceptional characteristics. However, difficulties in achieving high specific surface area (SSA) reduces the sorption capacity and limits its usage in CDI. Effort taken toward improving the SSA of graphene by adding composites and through surface modification resulted in significant SSA with lower sorption capacity. Thus, the present study investigated the effect of the synthesis method and materials used to prepare electrode slurry (binder material) on SSA and specific capacitance. Graphene was synthesized employing Hummers, modified Hummers, and electrochemical exfoliation, and its quality was characterized based on X-ray diffraction, scanning electron microscope, and ultraviolet spectra analysis. The influence of binder type on specific capacitance was assessed by fabricating the electrode with commonly used two hydrophobic and two hydrophilic binders. Sorption analysis was also carried out to study the effect of SSA and specific capacitance of graphene with selected binders. The results revealed that electrochemically exfoliated graphene yield SSA of 1,529.8 m2/g with a sorption capacity 64% and 52% greater than graphene synthesized using the Hummers and modified Hummers methods, respectively. Usage of polyvinylidene fluoride (PVdF) binder resulted in a specific capacitance of 974.45 F/g and a sorption capacity of 32.73 mg/g. Thus, graphene’s increased sorption capacity implies that the suitable method of synthesis and fabrication of electrodes with a suitable binder offers adequate SSA and specific capacitance by suppressing pseudocapacitance.