Ozonolysis of carbon nanotubes

Abstract

Methods of treating single walled and multiwalled carbon nanotubes with ozone are provided. The carbon nanotubes are treated by contacting the carbon nanotubes with ozone at a temperature range between 0° C. and 100° C. to yield functionalized nanotubes which are greater in weight than the untreated carbon nanotubes. The carbon nanotubes treated according to methods of the invention can be used to prepare complex structures such as three dimensional networks or rigid porous structures which can be utilized to form electrodes for fabrication of improved electrochemical capacitors. Useful catalyst supports are prepared by contacting carbon nanotube structures such as carbon nanotube aggregates, three dimensional networks or rigid porous structures with ozone in the temperature range between 0° C. and 100° C.

1 . A method of functionalizing carbon nanotubes comprising the step of:
 contacting carbon nanotubes with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form functionalized nanotubes which are greater in weight than said carbon nanotubes.   
     
     
         2 . The method of  claim 1 , wherein said temperature range is between 0° C. to 60° C. 
     
     
         3 . The method of  claim 1 , wherein said temperature range is between 20° C. to 50° C. 
     
     
         4 . The method of  claim 1 , wherein said carbon nanotubes are multiwalled carbon nanotubes having a diameter of less than 0.1 micron. 
     
     
         5 . The method of  claim 1 , wherein said carbon nanotubes are single walled nanotubes having a diameter less than 5 nanometer. 
     
     
         6 . The method of  claim 1 , wherein the surface of said functionalized nanotubes have an oxygen content greater than 4 percent. 
     
     
         7 . The method of  claim 1 , wherein the surface of said functionalized nanotubes have an oxygen content greater than 6 percent. 
     
     
         8 . The method of  claim 1 , wherein said functionalized nanotubes exhibit upon titration an acid titer greater than 2 meq/g. 
     
     
         9 . The method of  claim 1 , wherein said functionalized nanotubes exhibit upon titration an acid titer from 1.6 to 2.2 meq/g. 
     
     
         10 . The method of  claim 1 , wherein said functionalized nanotubes exhibit upon titration an acid titer from 2.5 to 3.5 meq/g. 
     
     
         11 . The method of  claim 1 , wherein said functionalized nanotubes exhibit upon titration an acid titer which is at least 1.5 meq/g greater than the acid titer of said carbon nanotubes. 
     
     
         12 . The method of  claim 1 , wherein said functionalized nanotubes exhibit upon titration an acid titer which is at least 2 meq/g greater than the acid titer of said carbon nanotubes. 
     
     
         13 . The method of  claim 1 , wherein said functionalized nanotubes exhibit upon titration an acid titer which is 1.5 meq/g to 3 meq/g greater than said carbon nanotubes. 
     
     
         14 . The method of  claim 1 , wherein said functionalized carbon nanotubes exhibit a weight gain greater than 5% by comparison to said carbon nanotubes. 
     
     
         15 . The method of  claim 1 , wherein said functionalized carbon nanotubes exhibit a weight gain from 5% to 20% by comparison with said carbon nanotube. 
     
     
         16 . The method of  claim 1 , wherein said functionalized carbon nanotubes exhibit a weight gain from 10% to 15% by comparison with said said carbon nanotube. 
     
     
         17 . The method of  claim 1 , further comprising treating said functionalized carbon nanotubes with a reactant suitable to react with moieties of said functionalized carbon nanotubes thereby adding at least a secondary group onto the surface of said functionalized nanotubes. 
     
     
         18 . The method of  claim 17 , wherein said additional secondary group is selected from the group consisting of an alkyl or aryl silane wherein said alkyl has C 1  to C 18 , said aryl has C 1  to C 18 , an alkyl of C 1  to C 18  or an aralkyl group of C 1  to C 18 , a hydroxyl group of C 1  to C 18  and an amine group of C 1  to C 18 . 
     
     
         19 . The method of  claim 17 , wherein said additional secondary group is a fluorocarbon. 
     
     
         20 . The method of  claim 1  further comprising
 dispersing said functionalized carbon nanotubes into a liquid medium to form a mixture;   filtering said medium to collect a residue of functionalized carbon nanotubes; and   drying said residue to form a mat.   
     
     
         21 . The method of  claim 20 , further comprising heating said mat to a temperature range of 200° C. to 900° C. 
     
     
         22 . The method of  claim 20 , further comprising forming said mat into an electrode. 
     
     
         23 . The method of  claim 1 , wherein said carbon nanotubes are in the form of aggregates having a macromorphology resembling a shape selected from the group consisting of cotton candy, bird nests, combed yarn and open net aggregates. 
     
     
         24 . The method of  claim 23 , wherein said aggregates have an average diameter of less than 50 microns. 
     
     
         25 . A method for producing a network of carbon nanotubes comprising the steps of:
 (a) contacting carbon nanotubes with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form functionalized nanotubes which are greater in weight than said carbon nanotubes;   (b) subjecting said functionalized nanotubes to conditions sufficient to cause crosslinking.   
     
     
         26 . The method of  claim 25 , wherein said temperature range is between 0° C. to 60° C. 
     
     
         27 . The method of  claim 25 , wherein said temperature range is between 20° C. to 50° C. 
     
     
         28 . The method of  claim 25 , wherein said conditions sufficient to cause crosslinking include heating said functionalized nanotubes in air in a temperature range from 200° C. to 600° C. 
     
     
         29 . The method of  claim 25 , wherein said conditions sufficient to cause crosslinking include heating said functionalized nanotubes in an inert atmosphere in a temperature range from 200° C. to 2000° C. 
     
     
         30 . A method for producing a network of functionalized carbon nanotubes comprising the steps of
 (a) contacting carbon nanotubes with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form functionalized nanotubes which are greater in weight than said carbon nanotubes;   (b) treating said functionalized nanotubes with a reactant suitable to react with moieties of said functionalized nanotubes thereby adding at least a secondary group onto the surface of said functionalized nanotubes;   (c) further contacting said nanotubes bearing secondary groups with an effective amount of crosslinking agent.   
     
     
         31 . The method of  claim 30 , wherein said temperature range is between 0° C. to 60° C. 
     
     
         32 . The method of  claim 30 , wherein said temperature range is between 20° C. to 50° C. 
     
     
         33 . The method of  claim 30 , wherein said crosslinking agent is selected from the group consisting of a polyol or polyamine. 
     
     
         34 . The method of  claim 30 , wherein said polyol is a diol and said polyamine is a diamine. 
     
     
         35 . A method for preparing a rigid porous structure comprising the steps of:
 (a) contacting carbon nanotubes with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form functionalized nanotubes which are greater in weight than said carbon nanotubes;   (b) dispersing said functionalized nanotubes in a medium to form a suspension; and   (c) separating said medium from said suspension to form a porous structure of entangled functionalized nanotubes wherein said nanotubes are interconnected to form a rigid porous structure.   
     
     
         36 . The method of  claim 35 , wherein said temperature range is between 0° C. to 60° C. 
     
     
         37 . The method of  claim 35 , wherein said temperature range is between 20° C. to 50° C. 
     
     
         38 . The method of  claim 35 , wherein said carbon nanotubes are in the form of aggregates having a macromorphology resembling a shape selected from the group consisting of cotton candy, bird nests, combed yarn and open net aggregates. 
     
     
         39 . The method of  claim 35 , further comprising heating said suspension in air to a temperature in a range from about 200° C. to about 600° C. thereby forming said rigid porous structure. 
     
     
         40 . The method of  claim 35 , further comprising heating said suspension in an inert gas to a temperature in a range from about 200° C. to about 2000° C. thereby forming said rigid porous structure. 
     
     
         41 . The method of  claim 35 , wherein said medium is water or organic solvents. 
     
     
         42 . The method of  claim 35 , wherein said medium comprises a dispersant selected from the group consisting of alcohols, glycerin, surfactants, polyethylene glycol, polyethylene imines and polypropylene glycol. 
     
     
         43 . The method of  claim 35 , wherein said suspension further comprises gluing agents selected from the group consisting of cellulose, carbohydrate, polyethylene, polystyrene, nylon, polyurethane, polyester, polyamides and phenolic resins. 
     
     
         44 . The method of  claim 35 , further comprising the steps of:
 (a) forming said rigid porous structure into a mat; and   (b) forming said mat into an electrode.   
     
     
         45 . An electrochemical capacitor having at least one electrode comprising the functionalized carbon nanotubes prepared by the method of  claim 1 . 
     
     
         46 . An electrochemical capacitor having at least one electrode prepared by a method which comprises the following steps:
 (a) contacting aggregates of carbon nanotubes with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form aggregates of functionalized nanotubes which are greater in weight than said carbon nanotubes;   (b) dispersing said aggregates of functionalized nanotubes prepared in step (a) in a liquid medium to form a slurry;   (c) filtering and drying said slurry to form a mat of functionalized carbon nanotubes; and   (d) subjecting said mat to conditions sufficient to cause the crosslinking of said functionalized carbon nanotubes.   
     
     
         47 . The method of  claim 46 , wherein said temperature range in step (a) is between 0° C. to 60° C. 
     
     
         48 . The method of  claim 46 , wherein said temperature range in step (a) is between 20° C. to 50° C. 
     
     
         49 . The electrochemical capacitor of  claim 46 , wherein said conditions of step (d) include heating said mat to a temperature in the range of from 180° C. to 350° C. 
     
     
         50 . An electrochemical capacitor having at least one electrode formed by a method comprising the following steps:
 (a) dispersing aggregates of carbon nanotubes in a liquid medium to form a slurry;   (b) filtering and drying said slurry to form a mat of carbon nanotubes;   (c) treating said mat with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form a mat of functionalized carbon nanotubes which are greater in weight than said mat of carbon nanotubes.   
     
     
         51 . Ozone treated carbon nanotubes which exhibit upon titration an acid titer greater than 2 meq/g. 
     
     
         52 . Ozone treated carbon nanotubes which exhibit upon titration an acid titer between 1.6 and 2.2 meq/g. 
     
     
         53 . Ozone treated carbon nanotubes which exhibit upon titration an acid titer between 2.5 and 3.5 meq/g. 
     
     
         54 . An ozone treated carbon nanotube structure which exhibits upon titration an acid titer greater than 1 meq/g, said ozone treated carbon nanotube structure comprising a multiplicity of carbon nanotubes entangled with one another. 
     
     
         55 . The ozone treated carbon nanotube structure of  claim 54 , wherein said structure is in the form of aggregate of carbon nanotubes having a macromorphology resembling a shape selected from the group from the group consisting of cotton candy, bird nests, combed yam and open net aggregates. 
     
     
         56 . The ozone treated carbon nanotube structure of  claim 54  which substantially retains the original untreated carbon nanotube structure. 
     
     
         57 . The ozone treated carbon nanotube structure of  claim 54  which exhibits upon titration an acid titer between 1 and 2 meq/g. 
     
     
         58 . A method for forming catalyst support comprising the steps of:
 forming an aggregate of carbon nanotubes, and   contacting said aggregate with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form a functionalized aggregate which is greater in weight than said aggregate.   
     
     
         59 . The method of  claim 58 , wherein said temperature range is between 0° C. to 60° C. 
     
     
         60 . The method of  claim 58 , wherein said temperature range is between 20° C. to 50° C. 
     
     
         61 . The method of  claim 58 , wherein said carbon nanotubes are multiwalled carbon nanotubes having a diameter of less than 0.1 micron. 
     
     
         62 . The method of  claim 58 , wherein said carbon nanotubes are single walled nanotubes having a diameter less than 5 nanometer. 
     
     
         63 . The method of  claim 58 , wherein the surface of said functionalized aggregate have an oxygen content greater than 4 percent. 
     
     
         64 . The method of  claim 58 , wherein the surface of said functionalized aggregate have an oxygen content greater than 6 percent. 
     
     
         65 . The method of  claim 58 , wherein said functionalized aggregate exhibits upon titration an acid titer from 1 to 2 meq/g and retains the structure of said aggregate. 
     
     
         66 . The method of  claim 58 , wherein said functionalized aggregate exhibits upon titration an acid titer from 1 to 2 meq/g. 
     
     
         67 . The method of  claim 58 , wherein said functionalized aggregate exhibits a weight gain greater than 5% by comparison to said aggregate. 
     
     
         68 . The method of  claim 58 , wherein said functionalized aggregate exhibits a weight gain from 5% to 20% by comparison with said aggregate. 
     
     
         69 . The method of  claim 58 , wherein said functionalized aggregate exhibits a weight gain from 10% to 15% by comparison with said aggregate. 
     
     
         70 . A catalyst support formed by the method of  claim 58 . 
     
     
         71 . A catalyst support formed by the method of  claim 58  wherein the functionalized aggregate exhibits upon titration an acid titer between 1 to 2 meq/g. 
     
     
         72 . A catalyst support formed by the method of  claim 58  wherein the functionalized aggregate exhibits upon titration an acid titer greater than 1 meq/g and retains the structure of said aggregate. 
     
     
         73 . A method for forming a catalyst support comprising the steps of:
 forming a network of carbon nanotubes, and   contacting said network with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form a functionalized network which is greater in weight than said network.   
     
     
         74 . The method of  claim 73 , wherein said temperature range is between 0° C. to 60° C. 
     
     
         75 . The method of  claim 73 , wherein said temperature range is between 20° C. to 50° C. 
     
     
         76 . The method of  claim 73 , wherein said carbon nanotubes are multiwalled carbon nanotubes having a diameter of less than 0.1 micron. 
     
     
         77 . The method of  claim 73 , wherein said carbon nanotubes are single walled nanotubes having a diameter less than 5 nanometer. 
     
     
         78 . The method of  claim 73 , wherein the surface of said functionalized network have an oxygen content greater than 4 percent. 
     
     
         79 . The method of  claim 73 , wherein the surface of said functionalized network have an oxygen content greater than 6 percent. 
     
     
         80 . The method of  claim 73 , wherein said functionalized network exhibits upon titration an acid titer greater than 1 meq/g and retains the structure of said network. 
     
     
         81 . The method of  claim 73 , wherein said functionalized network exhibits upon titration an acid titer from 1 to 2 meq/g. 
     
     
         82 . The method of  claim 73 , wherein said functionalized network exhibits a weight gain greater than 5% by comparison to said network. 
     
     
         83 . The method of  claim 73 , wherein said functionalized network exhibits a weight gain from 5% to 20% by comparison with said network. 
     
     
         84 . The method of  claim 73 , wherein said functionalized network exhibits a weight gain from 10% to 15% by comparison with said network. 
     
     
         85 . A catalyst support formed by the method of  claim 73 . 
     
     
         86 . A catalyst support formed by the method of  claim 73  wherein the functionalized network exhibits upon titration an acid titer between 1 to 2 meq/g. 
     
     
         87 . A catalyst support formed by the method of  claim 73  wherein the functionalized network exhibits upon titration an acid titer greater than 1 meq/g and retains the structure of said network. 
     
     
         88 . A method for forming a catalyst support comprising the steps of:
 forming a rigid porous structure comprising carbon nanotubes, and   contacting said rigid porous structure with ozone at a temperature range between 0° C. to 100° C. under conditions sufficient to form a functionalized rigid porous structure which is greater in weight than said rigid porous structure.   
     
     
         89 . The method of  claim 88 , wherein said temperature range is between 0° C. to 60° C. 
     
     
         90 . The method of  claim 88 , wherein said temperature range is between 20° C. to 50° C. 
     
     
         91 . The method of  claim 88 , wherein said carbon nanotubes are multiwalled carbon nanotubes having a diameter of less than 0.1 micron. 
     
     
         92 . The method of  claim 88 , wherein said carbon nanotubes are single walled nanotubes having a diameter less than 5 nanometer. 
     
     
         93 . The method of  claim 88 , wherein the surface of said functionalized rigid porous structure have an oxygen content greater than 4 percent. 
     
     
         94 . The method of  claim 88 , wherein the surface of said functionalized rigid porous structure have an oxygen content greater than 6 percent. 
     
     
         95 . The method of  claim 88 , wherein said functionalized rigid porous structure exhibits upon titration an acid titer greater than 1 meq/g and retains the structure of said rigid porous structure. 
     
     
         96 . The method of  claim 88 , wherein said functionalized rigid porous structure exhibit upon titration an acid titer from 1 to 2 meq/g. 
     
     
         97 . The method of  claim 88 , wherein said functionalized rigid porous structure exhibit a weight gain greater than 5% by comparison to said rigid porous structure. 
     
     
         98 . The method of  claim 88 , wherein said functionalized rigid porous structure exhibit a weight gain from 5% to 20% by comparison with said rigid porous structure. 
     
     
         99 . The method of  claim 88 , wherein said functionalized rigid porous structure exhibit a weight gain from 10% to 15% by comparison with said rigid porous structure. 
     
     
         100 . A catalyst support formed by the method of  claim 88 . 
     
     
         101 . A catalyst support formed by the method of  claim 88  wherein the functionalized rigid porous structure exhibit upon titration an acid titer between 1 to 2 meq/g. 
     
     
         102 . A catalyst support formed by the method of  claim 88  wherein the functionalized rigid porous structure exhibits upon titration an acid titer greater than 1 meq/g and retains the structure of said rigid porous structure.