Method for fabricating carbon nanotube aluminum foil electrode

Abstract

A method for fabricating a carbon nanotube aluminum foil electrode is used to increase the surface area of the electrode by growing the high-electric conductivity carbon nanotubes on an aluminum foil or an AAO (Anodic Aluminum Oxide)-containing aluminum template, whereby is greatly increased the capacitance of the aluminum electrolytic capacitor. The electrode fabricated via forming the carbon nanotubes on the AAO-containing aluminum template has a capacitance of 2158.6 μF/cm 2 and an operation voltage of 55.10 V. The electrode fabricated via directly forming the carbon nanotubes on the aluminum foil has a capacitance of 3425.78 μF/cm 2 and an operation voltage of 38.44 V. Therefore, the capacitance of the aluminum electrolytic capacitor is effectively increased. Further, the carbon nanotube aluminum foil electrode fabricated in different ways can meet the different requirements of operation voltages and capacitances.

1 . A method for fabricating a carbon nanotube aluminum foil electrode comprising steps:
 Step S 1 : pre-processing an aluminum foil to remove the grease and oxide layer on a surface thereof;   Step S 2 : electroplating a catalytic material on the aluminum foil;   Step S 3 : growing carbon nanotubes on the catalytic material-coated aluminum foil;   Step S 4 : sputtering aluminum on the carbon nanotube aluminum foil, wherein an aluminum target and a radio frequency power source are used to sputter aluminum on the aluminum foil where the carbon nanotubes have been grown, and wherein the sputtering is undertaken with a power of 50-95 W for 2-4 hours; and   Step S 5 : forming an aluminum oxide layer on the carbon nanotube aluminum foil after sputtering aluminum, the forming step is in an anodizing solution, and wherein the forming is undertaken at a temperature of 83-90° C. for 10 minutes, whereby is completed the carbon nanotube aluminum foil electrode.   
     
     
         2 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 1 , wherein after the Step S 1  comprises a Step S 1 A: electropolishing the aluminum foil which is placed in an electropolishing solution containing sulfuric acid, phosphoric acid and deionized water by a ratio of 2:2:3. 
     
     
         3 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 2 , wherein after the Step S 1 A comprises a Step S 1 B: performing a first anodizing process on the aluminum foil, wherein the electropolished aluminum foil is anodized in an oxalic acid solution to form an Anodic Aluminum Oxide layer. 
     
     
         4 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 3 , wherein after the Step S 1 B has a Step S 1 C: performing a second anodizing process on the aluminum foil, wherein an oxide-removing solution is used to remove the Anodic Aluminum Oxide layer formed in the first anodizing process, and then the aluminum foil is anodized in the oxalic acid solution to form a new Anodic Aluminum Oxide layer on the imprint left by the first anodizing process; the new Anodic Aluminum Oxide layer has a plurality of pores. 
     
     
         5 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 4 , wherein the oxide-removing solution contains 1.8 wt. % chromic acid and 6 wt. % phosphoric acid. 
     
     
         6 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 4 , wherein the first anodizing process and the second anodizing process are undertaken at a voltage of 30-40 V and a temperature of 5-15° C. for 12 minutes, and wherein the oxalic acid solution has a concentration of 0.3 M. 
     
     
         7 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 4 , wherein after the Step S 1 C has a Step S 1 D: after the second anodizing process, soaking the aluminum foil in a phosphoric acid solution containing 5 wt. % phosphoric acid at a temperature of 30° C. for 40 minutes to remove a barrier layer that is formed on the bottoms of the pores and contacts the aluminum foil. 
     
     
         8 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 1 , wherein the catalytic material is cobalt, and wherein the electroplating is undertaken in an electroplating solution containing 5 wt. % CoSO 4 .7H 2 O and 2 wt. % H 3 BO 3 , at an alternating voltage of 13.6 V and a frequency of 60 Hz, for 40 seconds. 
     
     
         9 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 1 , wherein in Step S 3 , the carbon nanotubes are grown with a Chemical Vapor Deposition method, and wherein argon is the carrier gas and acetylene is the carbon source, and wherein the growth is undertaken at a temperature of 575-610° C. for 15-90 minutes, and wherein the flow rate of argon is 100 sccm, and the flow rate of acetylene is 50 sccm. 
     
     
         10 . The method for fabricating a carbon nanotube aluminum foil electrode according to  claim 1 , wherein the anodizing solution is formed via mixing ammonium adipate and deionized water.