Preparation And Electrochemical Properties Of Graphene Modified Electrode In A MV/4-HO-TEMPO Flow Battery

The electrode material is an important component of the battery,which affects the overall performance of the battery.At present,the common problems of the flow battery electrode material include:electrochemical polarization,ohmic polarization and concentration polarization cause voltage loss,resulting in battery power reduction,Therefore,it is a goal of this experiment to modify electrode materials,reduce losses,and improve battery performance.In the experiment,graphene oxide was prepared according to the modified Hummer method,and the carbon paper and graphite felt electrodes were respectively modified by coating or self-assembly method.The surface morphology,crystal structure,surface structure,element content,surface state and functional group of the modified electrode were characterized by physical testing methods of SEM,XRD,XPS,Raman and FT-IR and other tests.At the same time,the electrochemical methods of cyclic voltammetry and impedance were used to study the effects of the type of binder,the content of three-dimensional graphene,the pretreatment method and the post-treatment temperature.The final assembled single cell was tested for charge and discharge performance in a methyl viologen（MV）/4-hydroxy-2,2,6,6-tetramethylpiperidine oxide（4-HO-TEMPO）flow battery system.Experimental results show that Nitrogen-doped three-dimensional reduced graphene oxide is used on the surface of the carbon paper electrode as a catalyst to construct a multi-layered porous structure,and the durability and hydrophilicity of the electrode are improved by the binder,thereby increasing the reaction area of the electrode and reducing the concentration polarization.The experimental results show that PTFE,compared with the other two modified electrodes,the electrode as a binder and loaded with three-dimensional reduced graphene oxide has higher catalytic performance.In the study of graphene/graphite felt modified electrode It was found that microwave pretreatment is more suitable for graphene self-assembly process,and its modified electrode has higher loading and better catalytic performance.After post-treatment of the graphene/graphite felt composite electrode,it was found that the oxygen-containing functional group has an important influence on the conductivity and hydrophilicity of the electrode.In the experiment,the microwave-treated graphene/graphite felt composite electrode,at a current density of 60 m A·cm^-2,the capacity retention rate increased by 17.03%,rising to 90.21%,far exceeding the original reported 57%,There is a significant improvement in the charging and discharging of large currents for the modified electrode.