Acid-free solution process for structurally intact carbon fiber paper with long-lasting hydrophilicity

Abstract

This disclosure provides methods that render hydrophobic carbon fiber paper (CFP) hydrophilic for extended periods without damaging the carbon fibers that compose the CFP or the architecture of the network of those carbon fibers. The disclosure further provides hydrophilic CFP made by the inventive methods. The methods include sonicating the CFP in an aqueous surfactant solution followed by electrooxidizing the CFP in an aqueous electrolyte.

1 . A method of providing hydrophilic carbon fiber paper (CFP) with undamaged carbon fibers, said method comprising, in the following order:
 (a) subjecting to sonication in an aqueous surfactant solution hydrophobic CFP comprising a plurality of carbon fibers in an arrangement, which fibers have exteriors; and,   (b) subjecting said sonicated CFP to electrooxidation in an aqueous electrolyte that does not damage said fibers or said arrangement of said fibers in the CFP;   
       thereby providing hydrophilic CFP with carbon fibers that are undamaged. 
     
     
         2 . (canceled) 
     
     
         3 . The method of  claim 1 , in which said electrooxidation in said aqueous surfactant solution is for a time of 10 to 240 minutes. 
     
     
         4 . (canceled) 
     
     
         5 . The method of  claim 1 , in which said electrooxidation in said aqueous surfactant solution is for a time of 20±5 minutes. 
     
     
         6 . (canceled) 
     
     
         7 . The method of  claim 1 , in which said aqueous surfactant solution does not comprise organic solvents. 
     
     
         8 . The method of  claim 1 , further comprising step (c) storing said CFP in water following said electrooxidation. 
     
     
         9 - 12 . (canceled) 
     
     
         13 . The method of  claim 1 , wherein said aqueous surfactant is sodium dodecyl sulfate, cholamidopropyl)dimethyl-ammonio]-1-propane sulfonate, cetyltrimethylammonium bromide, citrate, or polyethylene glycol tert-octylphenyl ether, or a combination of two or more of these. 
     
     
         14 - 16 . (canceled) 
     
     
         17 . The method of  claim 1 , wherein said aqueous surfactant is present at a concentration of 0.5 M to 1.5 M. 
     
     
         18 - 20 . (canceled) 
     
     
         21 . The method of  claim 1 , wherein said aqueous electrolyte is potassium hydroxide, potassium nitrate, lithium perchlorate, or potassium bicarbonate, or a combination of any of these. 
     
     
         22 - 30 . (canceled) 
     
     
         31 . The method of  claim 1 , wherein said aqueous surfactant is sodium dodecyl sulfate and said aqueous electrolyte is potassium hydroxide. 
     
     
         32 . The method of  claim 31 , wherein said sodium dodecyl sulfate is present at a concentration of from 0.5 M to 1.5 M and said potassium hydroxide is present at a concentration of from 0.01M to 0.5 M. 
     
     
         33 . (canceled) 
     
     
         34 . Hydrophilic carbon fiber paper (CFP) that (a) remains hydrophilic when stored under water for 30 days and, (b) is composed of carbon fibers that are undamaged. 
     
     
         35 . The hydrophilic CFP of  claim 34 , wherein said carbon fibers are undamaged is determined by imaging said carbon fibers by scanning electron microscopy (SEM). 
     
     
         36 . The hydrophilic CFP of  claim 34 , wherein said CFP remains hydrophilic when stored under water for 60 days. 
     
     
         37 . The hydrophilic CFP of  claim 34 , wherein said CFP has both a high edge density and a high density of hydroxyl groups. 
     
     
         38 . The hydrophilic CFP of  claim 34 , wherein said CFP is not brittle. 
     
     
         39 . The hydrophilic CFP of  claim 34 , made by the process of subjecting hydrophobic CFP, which hydrophobic CFP is composed of a network of carbon fibers with an architecture, to sonication in an aqueous surfactant solution followed by electrooxidation in an aqueous electrolyte. 
     
     
         40 . (canceled) 
     
     
         41 . The hydrophilic CFP of  claim 39 , wherein whether said network of carbon fibers of said hydrophilic CFP is undamaged compared to said network of carbon fibers of said hydrophobic CFP is determined by SEM imaging said carbon fibers of said hydrophobic CFP, thereby creating a first SEM image, and SEM imaging said carbon fibers of said hydrophilic CFP, thereby creating a second SEM image, and comparing said first and said second SEM images for damage to said carbon fibers, wherein if there is no visible fraying of said carbon fibers of said second image compared to said carbon fibers in said first image, the carbon fibers are undamaged. 
     
     
         42 . A water purification system, capacitor, flow battery, aqueous electrolyzer, or sensor comprising hydrophilic carbon fiber paper that (a) remains hydrophilic when stored under water for 30 days and, (b) is composed of carbon fibers that are undamaged. 
     
     
         43 . The water purification system, capacitor, flow battery, aqueous electrolyzer, or sensor of  claim 42 , wherein said hydrophilic CFP is not brittle. 
     
     
         44 . The water purification system, capacitor, flow battery, aqueous electrolyzer, or sensor of  claim 42 , wherein said CFP has both a high edge density and a high density of hydroxyl groups.