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A catalyst composition and method of use of the catalyst composition for producing single-walled carbon nanotubes (SWNTs). The catalyst is cobalt (Co) and molybdenum (Mo) on a silica support. The Mo occurs primarily as dispersed Mo oxide clusters on the support while the Co is primarily in an octahe

A catalyst composition and method of use of the catalyst composition for producing single-walled carbon nanotubes (SWNTs). The catalyst is cobalt (Co) and molybdenum (Mo) on a silica support. The Mo occurs primarily as dispersed Mo oxide clusters on the support while the Co is primarily in an octahedral configuration in a CoMoO4-like phase disposed on the Mo oxide clusters. In the method, the catalyst is used and the process conditions manipulated in such a manner as to enable the diameters of the SWNTs to be substantially controlled.

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What is claim is: 1. A method of preferentially forming single walled carbon nanotubes having a particular diameter, comprising: providing a catalyst comprising: Co and Mo disposed on a support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co

What is claim is: 1. A method of preferentially forming single walled carbon nanotubes having a particular diameter, comprising: providing a catalyst comprising: Co and Mo disposed on a support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co occurs as CoMoO4 with the Co therein primarily in an octahedral configuration, and wherein the CoMoO4 occurs substantially disposed upon the dispersed Mo oxide clusters; and exposing the catalyst in a reactor to a carbon-containing gas at a temperature between about 700�� C. and about 800�� C. and maintaining a CO2 concentration in the reactor below a threshold CO2 concentration above which the conversion of ionic Co to metallic Co is inhibited, wherein the majority of the single walled carbon nanotubes thus formed have a diameter between about 0.7 nm to about 0.9 nm. 2. The method of claim 1 wherein in the step of providing a catalyst, the support material is silica. 3. The method of claim 1 wherein in the step of exposing the catalyst to a carbon-containing gas, the reactor has a pressure therein between about 1 atm and 7 atm. 4. The method of claim 1 wherein in the step of exposing the catalyst to a carbon-containing gas, the threshold CO2 concentration in the reactor is 1%. 5. The method of claim 1 wherein in the step of exposing the catalyst to a carbon-containing gas, the carbon-containing gas is CO. 6. The method of claim 1 comprising the additional step of reducing the catalyst by exposing the catalyst to a heated hydrogen gas. 7. The method of claim 1 wherein in the step of providing the catalyst, the Mo oxide clusters comprise Mo oxide clusters having a domain size between that of MoO3 and heptamolybdate. 8. The method of claim 1 wherein in the step of providing the catalyst, the catalyst has a molar ratio of Co:Mo of less than 3:4. 9. A method of preferentially forming single walled carbon nanotubes having a particular diameter, comprising: providing a catalyst comprising: Co and Mo disposed on a support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co occurs as CoMoO4 with the Co therein primarily in an octahedral configuration, and wherein the CoMoO4 occurs substantially disposed upon the dispersed Mo oxide clusters; and exposing the catalyst in a reactor to a carbon-containing gas at a temperature between about 800�� C. and about 900�� C. and maintaining a CO2 concentration in the reactor below a threshold CO2 concentration above which the conversion of ionic Co to metallic Co is inhibited, wherein the majority of the single walled carbon nanotubes thus formed have a diameter between about 0.9 nm to about 1.2 nm. 10. The method of claim 9 wherein in the step of providing a catalyst, the support material is silica. 11. The method of claim 9 wherein in the step of exposing the catalyst to a carbon-containing gas, the reactor has a pressure therein between about 1 atm and 7 atm. 12. The method of claim 9 wherein in the step of exposing the catalyst to a carbon-containing gas, the threshold CO2 concentration in the reactor is 1%. 13. The method of claim 9 wherein in the step of exposing the catalyst to a carbon-containing gas, the carbon containing gas is CO. 14. The method of claim 9 comprising the additional step of reducing the catalyst by exposing the catalyst to a heated hydrogen gas. 15. The method of claim 9 wherein in the step of providing the catalyst, the Mo oxide clusters comprise Mo oxide clusters having a domain size between that of MoO3 and heptamolybdate. 16. The method of claim 9 wherein in the step of providing the catalyst, the catalyst has a molar ratio of Co:Mo of less than 3:4. 17. A method of preferentially forming single walled carbon nanotubes having a particular diameter, comprising: providing a catalyst comprising: Co and Mo disposed on a support material wherein the majority of the Mo occurs as dispersed Mo oxide clusters and the majority of the Co occurs as CoMoO4 with the Co therein primarily in an octahedral configuration, and wherein the CoMoO4 occurs substantially disposed upon the dispersed Mo oxide clusters; and exposing the catalyst in a reactor to a carbon-containing gas at a temperature between about 900�� C. and about 1,000�� C. and maintaining a CO2 concentration in the reactor below a threshold CO2 concentration above which the conversion of ionic Co to metallic Co is inhibited, wherein the majority of the single walled carbon nanotubes thus formed have a diameter between about 1.3 nm to about 1.7 nm. 18. The method of claim 17 wherein in the step of providing a catalyst, the support material is silica. 19. The method of claim 17 wherein in the step of exposing the catalyst to a carbon-containing gas, the reactor has a pressure therein between about 1 atm and 7 atm. 20. The method of claim 17 wherein in the step of exposing the catalyst to a carbon-containing gas, the threshold CO2 concentration in the reactor is 1%. 21. The method of claim 17 wherein in the step of exposing the catalyst to a carbon-containing gas, the carbon-containing gas is Co. 22. The method of claim 17 comprising the additional step of reducing the catalyst by exposing the catalyst to a heated hydrogen gas. 23. The method of claim 17 wherein in the step of providing the catalyst, the Mo oxide clusters comprise Mo oxide clusters having a domain size between that of MoO3 and heptamolybdate. 24. The method of claim 17 wherein in the step of providing the catalyst, the catalyst has a molar ratio of Co:Mo of less than 3:4.