Electrodes Synthesized from Carbon Nanostructures Coated with a Smooth and Conformal Metal Adlayer

Abstract

High-surface-area carbon nanostructures coated with a smooth and conformal submonolayer-to-multilayer thin metal films and their method of manufacture are described. The preferred manufacturing process involves the initial oxidation of the carbon nanostructures followed by a surface preparation process involving immersion in a solution with the desired pH to create negative surface dipoles. The nanostructures are subsequently immersed in an alkaline solution containing a suitable quantity of non-noble metal ions which adsorb at surface reaction sites. The metal ions are then reduced via chemical or electrical means. The nanostructures are exposed to a solution containing a salt of one or more noble metals which replace adsorbed non-noble surface metal atoms by galvanic displacement. The process can be controlled and repeated to obtain a desired film coverage. The resulting coated nanostructures may be used, for example, as high-performance electrodes in supercapacitors, batteries, or other electric storage devices.

1 . A method of depositing a contiguous noble metal thin film on carbon nanostructures comprising:
 oxidizing a surface of the carbon nanostructures;   forming a dipole at the surface of the, carbon nanostructures;   adsorbing metal ions on the surface of the carbon nanostructures;   reducing the adsorbed metal ions; and   immersing the carbon nanostructures in a solution containing a salt of at least one noble metal to form thin film of the noble metal.   
     
     
         2 . The method of  claim 1  wherein the adsorbed metal ions are Pb 2+ . 
     
     
         3 . The method of  claim 1  wherein the carbon nanostructures are selected from the group consisting of fullerenes, single-Walled carbon nanotubes, multi-walled carbon nanotubes, and carbon nanohorns. 
     
     
         4 . The method of  claim 1  wherein the noble metal consists of ruthenium. 
     
     
         5 . The method of  claim 1 , wherein the metal thin film is one of a contiguous noble metal atom monolayer and a contiguous noble metal atom bilayer. 
     
     
         6 . The method of  claim 1 , wherein the metal thin film is one of a contiguous ruthenium atom monolayer and a contiguous ruthenium atom bilayer. 
     
     
         7 . The method of  claim 1 , wherein the oxidizing a surface of the carbon nanostructures comprises at least one of thermal oxidation, acid solution oxidation, electrochemical oxidation, and peroxide oxidation. 
     
     
         8 . The method of  claim 1 , wherein the adsorbed metal ions comprises at least one of Pb 2+ , Zn 2+ , Cu 2+ , Bi 3+ , Tl + , Cd 2+ , Ag + , Sn 2+ , Hg + , Sb 3+ , Se 4+ , and Te 4+ . 
     
     
         9 . The method of  claim 1 , wherein the reducing the adsorbed metal ions is performed by using a reducing agent. 
     
     
         10 . The method of  claim 9 , wherein the reducing agent is at least one of sodium borohydride, citric acid, hypophosphorous acid, or hydrazine. 
     
     
         11 . The method of  claim 1 , wherein the reducing the adsorbed metal ions is performed electrochemically.