Electrochemical Exfoliation of Graphite to Fluorographene: An Effect of Degree of Functionalization on 2Br−/Br2 Redox Reaction

Abstract

AbstractIn this work, we employed the electrochemical exfoliation (EE) to synthesize and tune the degree of functionalization in fluorinated graphene (FG) and studied its (degree of functionalization) effect on bromine redox reaction. The degree of functionalization was tuned by varying the concentration of the electrolyte. Physical characterization of as‐synthesized FG reveals that fluorine and oxygen content varies from 2.32 to 3.92 atomic % and from 10.46 to 21.16 atomic % respectively. The concentration of fluoride to hydroxide ion ratio should be at an optimum level in the electrolyte to get maximum degree of fluorination, which shows a sizeable effect on bromine redox reaction. The bromine redox reaction is more reversible on highly FG and less reversible on less FG and Oxygen functionalities has no effect on the reaction. The kinetic parameters such as rate constant (k) (varying from 1.45 x 10−3 to 52.43 x 10−3 mA/cm2) and exchange current density (io) (varying from 2.61 x 10−4 to 9.92 x 10−4 cm/s) suggest that nature and degree of functionalization play a vital role to improve the kinetics of redox reaction of bromine. This investigation can pave paths to design new and sustainable electrode materials for bromine‐based redox flow batteries.