Electrolysis: processes – compositions used therein – and methods – Electrolytic synthesis – Preparing organic compound
Reexamination Certificate
1999-10-14
2001-07-31
Bell, Bruce F. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic synthesis
Preparing organic compound
C205S453000, C205S456000, C205S463000, C205S465000, C205S440000
Reexamination Certificate
active
06267866
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electrode for electrochemical uses and, more particularly, to an electrode made of metal mesh coated with boron-doped diamond.
2. Description of the Related Art
In recent years, there has been an increasing interest in the electrochemical properties of diamond and boron-doped diamond coated substrates, primarily due to the excellent resistance of material to chemical degradation and, as a result, its dimensional stability. The physical and electrochemical properties of boron-doped diamond have been described in the following patents and publications incorporated herein by reference: U.S. Pat. No. 5,399,247 to Carey; U.S. Pat. No. 5,900,127 to Iida et al; Swain, “The Electrochemical Activity of Boron-Doped Polyciystallinc Diamond Thin Film Electrodes” Anal. Chem 1993, 65 pp 345-351; DeClements and Swain, “The Formation and Electrochemical Activity of Microporous Diamond Thin Film Electrodes in Concentrated KOH”, J. Electrochem. Soc., Vol 144, No. 3 March 1997, pp 856-866; Swain “The Susceptibility to Surface Corrosion in Acidic Fluoride Media: A Comparison of Diamond, HOPG, and Glassy Carbon Electrodes”, J. Electrochem. Soc., Vol 141, No. 12, December 1994, pp 3382-3393; Tenne et al, “Efficient Electrochemical Reduction of Nitrate to Ammonia Using Conductive Diamond Film Electrodes” J. Electroanal. Chem 347 (1993) pp 409-415; Awada, “Electrodeposition of Metal Adlayers on Boron-Doped Diamond Thin-Film Electrodes” J. Electrochem Soc., Vol.142, No.3 March 1995, pp L42-L45; Martin et al, “Hydrogen and Oxygen Evolution on Boron-Doped Diamond Electrodes” J. Electrochem. Soc., Vol 143, No. 6, June 1996, pp L133-L136, and Glesener et al “Fabrication of High Surface Area Boron-Doped Diamond Coated Tungsten Mesh for Electrochemical Applications” Material Letters 37 (1998), pp 138-142.
SUMMARY OF THE INVENTION
It has now been discovered that boron-doped diamond can be used in the fabrication of a high surface area flow electrode. This is done by forming a coating of boron-doped diamond on a conductive metal mesh substrate. The mesh structure allows for enhanced mass transport of reactants when used as an electrode in an electrochemical cell. The use of conducting metal as the material that makes up the of the mesh substrate improves the conductivity and energy efficiency of the electrode. The boron-doped diamond coating provides for enhanced dimensional stability and corrosion resistance for the mesh structure.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The present invention relates to the use of a boron-doped diamond coated metal mesh as an electrode in electrochemical applications.
The conductive metal mesh of the present invention can be made of any conductive metal or alloy, including, but not limited to tungsten, titanium, tantalum, copper and alloys of these metals.
As used herein, the term “mesh” refers to a structure comprised of a grid or of interwoven conductive metal filaments. The mesh morphology provides for a porous structure having a high surface area, thereby maximizing the contact of the electrode with the solution of the electrolytic cell in which the electrode is used. Preferably, the grid segments or filaments are about 0.5 mm to about 10 mm in diameter. The spacing between grid segments or filaments can range from very fine to coarse.
The conductive metal mesh may be coated with a boron-doped diamond coating by any method known in the art for creating a doped diamond coating on a substrate. Preferably, the coating is formed by filament assisted chemical vapor deposition (FACVD), a method that is described, for example in the following patents and publications, incorporated herein by reference: U.S. Pat. No. 5,075,094 to Morrish et al.; U.S. Pat. No. 5,374,414 to Morrish et al; and Natishan and Morris “The Electrochemical Behavior of Diamond Coated Molybdenum”, Materials Letters, Vol. 8 No. 8, August 1989, pp 269-272.
The electrode of the present invention has a wide potential window and therefore may be used in an electrochemical cell either as an anode to oxidize reactants or as a cathode to reduce reactants. Examples of reactants that can be treated include chlorides, bromides, organic materials and water. The electrode may be used for decomposition reactions or other reactions that cannot normally be run on metal electrodes because of the high hydrogen overvoltage on the diamond surface. One example of would be the dehalogenation of organic materials as a reduction reaction at the cathode. The electrode may also be used with an aerated solution to produce peroxide, peroxide radicals and hydroxy radicals that, in turn, act as a reactant in the decomposition of organic materials not in contact with the diamond electrodes. Oxygen may be added at the cathode side to increase the amount of peroxide that is produced. Because of the dimensional stability of the electrode, it may be used with an alternating current to function cyclically as both an anode and a cathode. An ac signal may be desirable for some applications where a prolonged dc current could produce undesirable reactions such as a polymerization reaction.
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patent: 5374414 (1994-12-01), Morrish et al.
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patent: 5900127 (1999-05-01), Iida et al.
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patent: 5935392 (1999-08-01), Lubin et al.
Glesener, et al., Fabrication of high surface area boron-doped diamond coated tungsten mesh for electrochemical applications, Materials Letters 37, Oct. 1998, pp. 138-142.
Martin, et al., Hydrogen and Oxygen Evolution on Boron-Doped Diamond Electrodes, J. Electrochem. Soc., vol. 143, No. 6, Jun. 1996, pp. L133-L136.
Awada, et al., Electrondeposition of Metal Adlayers on Boron-Doped Diamond Thin-Film Electrodes, J. Electrochem. Soc., vol. 142, No. 3, Mar. 1995, pp. L42-L45.
Swain, The Susceptibility to Surface Corrosion in Acidic Fluoride Media: A comparison of Diamond, HOPG, and Glassy Carbon Electrodes, J. Electrochem. Soc., vol. 141, No. 12, Dec. 1994, pp. 3382-3393.
DeClements, et al., The Formation and Electrochemical Activity of Microporous Diamond Thin Film Electrodes in Concentrated KOH, J. Electrochem. Soc., vol. 144, No. 3, Mar. 1997, pp. 856-n 866.
Swain, et al., The Electrochemical Activity of Boron-Doped Polycrystalline Diamond Thin Film Electrodes, Anal. Chem., 1993, 65, pp. 345-351 No month available.
Tenne, et al., Efficient electrochemical reduction of nitrate to ammonia using conductive diamond film electrodes, J. Electroanal. Chem., 347 (1993) pp. 409-415 No month available.
Morrish, et al., Effects of surface pretreatments on nucleation and growth of diamond films on a variety of substrates, Appl. Phys. Lett. 59 (4), Jul. 22, 1991, pp. 417-419.
Morrish, et al., Diamond tubes and fibers, Diamond and Related Materials, 3 (1993), pp. 173-176 No month available.
Mort, et al., Chapter 4, Carbon Thin Films, Plasma Deposited Thin Films, CRC Press, Inc., Boca Raton, FL, pp. 89-127 No month/year available.
Angus, et al., Chemical Vapour deposition of diamond, Phil. Trans. R. Soc. Lond. A (1993) 342, pp. 195-208 No month available.
Letterinton, Applications of Diamond-like carbon thin films, Phil. Trans. R. Soc. Lond. A (1993) 342, pp. 287-296 No month available.
Robertson, Deposition of diamond-like carbon, Phil. Trans. R. Soc. Lond. A (1993) 342, pp. 277-286 No month available.
Natishan, et al., The Electrochemical Behavior of Diamond Coated Molybdenum, Materials Newsletter, vol. 8, No. 8, Aug. 1989, pp. 296-27.
Hagans et al., Electrochemical Oxidation of Phenol on CVD-Carbon Electrodes, ECS Meeting Abstracts, vol. MA99-1, 1999, p. 835 No month available.
Glesener John W.
Hagans Patrick L.
Morrish Arthur A.
Natishan Paul M.
O'Grady William E.
Bell Bruce F.
Karasek John J.
Ressing Amy L.
The United States of America as represented by the Secretary of
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