Study On Reaction Of Mechanism Of The Modified Graphite Felt Electrode In All Vanadium Redox Flow Battery

The electrode material in all-vanadium flow battery is one of the key components of all-vanadium flow battery.Graphite felt is suitable as electrode materials because of its large specific surface area and good stability.However,graphite felt has poor wetting ability in an aqueous solution,and therefore must be subjected to surface treatment before use.There are three methods of potassium permanganate liquid phase oxidation,heat treatment,and electrochemical oxidation treatment for graphite felt,the conclusions were as follows:After liquid-phase oxidation treatment with potassium permanganate,SEM and FT-IR tests show the increase of electrode activity is attributed to the increase of oxygen-containing functional groups on the electrode and the increase of gully on the electrode surface;the voltammetric curve test results show that the redox activity of the treated graphite felt is significantly enhanced;the analysis of the tafel curve show that the corrosion resistance of the graphite felt oxidized by KMn O₄ has been improved;The test results in the all-vanadium flow battery show that the graphite felt oxidized by KMn O₄ has lower over potential,it is difficult to discharge,and the energy efficiency increased from 75.43%to 81.00%.After the heat treatment,the graphite felt has significantly enhanced hydrophilicity,the specific surface area and the activation was increased,which provides a favorable place for the adhesion of vanadium ions.The FT-IR test show that the infrared spectrum peak increased and the peak shape became broader after the heat treatment,which indicated that the heat treatment enhanced the activity of functional groups on the graphite felt;AC impedance and cyclic voltammetry tests show that the graphite felt after the heat treatment,the electrochemical resistance decreases,and the charge conduction performance gradually increases.The graphite felt electrode after heat treatment at 600?has a smaller redox peak potential difference;charge and discharge test show that the discharge potential platform increased from 1.28-1.35V to1.32-1.36V,and the energy efficiency increased from 75.43%to80.30%The grooves on the carbon fiber are deepened after electrochemical oxidation treatment,in the process of carbon fiber,the unsaturated carbon atoms at the edge of carbon lattice are oxidized,some oxygen-containing functional groups are oxidized to CO₂,the graphite microcrystals are etched;FT-IR results show that the number of oxygen-containing functional groups of graphite felt electrode increased after electrochemical oxidation treatment,the peak enhanced and the peak shape broadened;The AC impedance and cyclic voltammetry tests show that the effect of current density on the electrochemical activity of graphite felt is greater than that of electrochemical oxidation time.The charge and discharge test show that when the current density of electrochemical oxidation treatment is 50m A/cm²?150m A/cm²?250m A/cm²,the energy efficiency is 77.41%,79.28%,82.37%?...