Electrically conductive polycrystalline diamond and particulate metal based electrodes

Abstract

An electrically conducting and dimensionally stable diamond ( 12, 14 ) and metal particle ( 13 ) electrode produced by electrodepositing the metal on the diamond is described. The electrode is particularly useful in harsh chemical environments and at high current densities and potentials. The electrode is particularly useful for generating hydrogen, and for reducing oxygen and oxidizing methanol in reactions which are of importance in fuel cells.

1 - 12 . (canceled)  
   
   
       13 . A diamond electrode which comprises: 
 (a) a first polycrystalline diamond support, doped with at least one element so as to be electrically conductive;    (b) particles of a conductive metal which have been electrodeposited as a coating on the diamond support; and    (c) a polycrystalline diamond film deposited on the diamond support and around the particles of the conductive metal to surround and anchor the particles to thereby provide the conductive electrode.    
   
   
       14 . The electrode of  claim 13  wherein the element is boron.  
   
   
       15 . The electrode of  claim 13  wherein the first and second diamond films are deposited by chemical vapor deposition.  
   
   
       16 . The electrode of claim  12  wherein the chemical vapor deposition is microwave-assisted in the presence of methane and hydrogen at reduced pressures.  
   
   
       17 . A diamond electrode which comprises: 
 (a) a first polycrystalline diamond film doped with at least one element so as to be electrically conductive;    (b) particles of a conductive metal which have been electrodeposited as a coating on the first diamond film; and    (c) a second polycrystalline diamond film deposited on the first diamond film and around the particles of the conductive metal to surround and anchor the particles to thereby provide the conductive electrode.    
   
   
       18 . The electrode of  claim 17  wherein the element is boron.  
   
   
       19 . The electrode of  claim 17  wherein the first and second diamond films are deposited by chemical vapor deposition.  
   
   
       20 . The electrode of  claim 19  wherein the chemical vapor deposition is microwave-assisted in the presence of methane and hydrogen at reduced pressures.  
   
   
       21 . The electrode of any one of  claim 17 ,  18 ,  19  or  20  wherein the metal has been electrodeposited by electrolyzing a metal halide salt which is reduced to the metal.  
   
   
       22 . The process of any one of claims  17 ,  18 ,  19  or  20  wherein the second polycrystalline diamond film is also doped.  
   
   
       23 . The electrode of any one of claims  17 ,  18 ,  19  or  20  wherein the second polycrystalline film is also doped.  
   
   
       24 . The electrode of any one of claims  17 ,  18 ,  19  or  20  wherein the conductive metal particles are irregularly spherical in shape.  
   
   
       25 . The electrode of any one of claims  17 ,  18 ,  19  or  20  wherein the metal has been electrodeposited by electrolyzing a platinum halide salt in the presence of perchloric acid.