Acid treatment is an oxidation process to graphite felt. Usually using concentrated sulfuric acid, nitric acid, potassium dichromate to modify the graphite felt.put the graphite felt into concentrated sulfuric acid and under boiling situation for 5h,then make it as electrode material for vanadium redox flow battery,it could make the energy efficiency increase to about 90%.the result of testing shows that after the treatment of concentrated sulfuric acid,it can reduce the electric resistance of the electrode material,and the electrochemical property of the graphite felt can increase with the concentration of the sulfuric acid.the number of the active group on the surface of graphite felt have an obvious increase.
Some researchs showed that the graphite felt under the mixed acid and boiling situation can increase the hydrophily.make a comparison between the activation graphite felt and non activation graphite felt,the activation one can be soaked soon,but the non activation graphite felt can not be soaked lasting for many days.
After observation with the SEM,we could find that there are several little partical adhere the surface of the graphite felt,and after acid treatment,the partical disappeared,and the surface become smooth.
After the acid treatment to the carbon/graphite felt,the number of O atoms increase.the corrosion effect of the acid obviously increase the specific surface area.it found that,the graphite felt electric resistance of mixed acid is higher than only sulfuric acid.
There are a lot of ways to activate the graphite felt,but few articals to describe the difference and influence between the different ways.