Abstract
An electrode assembly for use in an electrochemical cell for the production of ozone from water is provided, the electrode assembly comprising an electrode body formed from a polycrystalline diamond, the electrode body comprising first and second opposing contact surfaces, the first contact surface for contacting a semi-permeable membrane; wherein the electrode assembly further comprises a first layer comprising an electrically conductive material, the first layer extending across at least a portion of the second contact surface of the electrode body. An electrochemical cell comprising the electrode assembly and its use in the production of ozone by the electrolysis of water is also provided.
Claims
1. An electrode assembly for use in an electrochemical cell for the production of ozone from water, the electrode assembly comprising: an electrode body formed from a polycrystalline diamond, wherein the electrode body is cut from a diamond wafer, the electrode body comprising first and second opposing contact surfaces, the first contact surface for contacting a semi-permeable membrane; wherein the electrode assembly further comprises a first layer comprising an electrically conductive material, the first layer extending across at least a portion of the second contact surface of the electrode body; and wherein the electrode body is provided with at least one layer of insulating material over the at least one layer of electrically conducting material, wherein the insulating material comprises a metal nitride or silicon nitride.
2. The electrode assembly according to claim 1, wherein the diamond is boron-doped diamond (BDD).
3. The electrode assembly according to claim 1, wherein the electrically conductive material comprises a metal selected from the group consisting of titanium, platinum, tungsten, tantalum, niobium, copper, silver, gold and mixtures thereof.
4. The electrode assembly according to claim 1, wherein the second contact surface of the electrode body is provided with a first layer of a first electrically conductive material and a second layer of a second electrically conductive material.
5. The electrode assembly according to claim 4, wherein the first electrically conductive material is selected from titanium, platinum, tungsten, tantalum, niobium and mixtures thereof.
6. The electrode assembly according to claim 4, wherein the second electrically conductive material is selected from copper, gold, silver and mixtures thereof.
7. The electrode assembly according to claim 1, wherein the layer of electrically conductive material is applied by sputter deposition.
8. The electrode assembly according to claim 1, wherein the electrode body is cut from a diamond wafer having a growth surface and a nucleation surface, the electrically conductive material being provided on the nucleation surface.
9. The electrode assembly according to claim 1, wherein the electrically conductive material extends over a major portion of the surface of the electrode body, with an edge portion not being covered in the electrically conductive material.
10. The electrode assembly according to claim 1, wherein the insulating material comprises a nitride of hafnium, titanium or zirconium.
11. The electrode assembly according to claim 1, wherein the electrode body is provided with a layer of resin.
12. The electrode assembly according to claim 1, wherein the electrode body is an elongate electrode body having first and second opposing edge surfaces and opposing first and second major faces extending between the first and second opposing edge surfaces; wherein the electrode body has an elongate longitudinal axis; wherein the electrode body comprises: a first body portion having a first width measured in a direction perpendicular to the longitudinal axis and between the longitudinal axis and the first edge surface across the first and second opposing major surfaces; and a second body portion having a second width measured in a direction perpendicular to the longitudinal axis and between the longitudinal axis and the first edge surface across the first and second opposing major surfaces; wherein the second width is greater than the first width.
13. The electrode assembly according to claim 12, wherein the electrode body comprises a plurality of first body portions and a plurality of second body portions.
14. The electrode assembly according to claim 12, wherein the first and/or the second body portions are rectangular in shape.
Description
(1) Embodiments of the present invention will now be described, by way of example of only, having reference to the accompanying drawings, in which:
(2) FIG. 1 is a cross-sectional view of an electrochemical cell comprising an electrode assembly according to one embodiment of the present invention;
(3) FIG. 2 is a plan view of an electrode assembly according to one embodiment of the present invention;
(4) FIG. 3 is a plan view of an electrode assembly according to a further embodiment of the present invention;
(5) FIG. 4 is a plan view of an electrode assembly according to a further embodiment of the present invention;
(6) FIG. 5 is a plan view of the electrode assembly of FIG. 4 with a layer of electrically conductive material applied to the electrode body;
(7) FIG. 6 is a plan view of an electrode assembly according to a still further embodiment of the present invention; and
(8) FIG. 7 is a plan view of an electrode assembly according to a yet further embodiment of the present invention.
(9) Turning first to FIG. 1, there is shown a cross-sectional view of an electrochemical cell according to one embodiment of the present invention. The electrochemical cell, generally indicated as 2, comprises a first electrode assembly 4 having an electrode body 4a and a second electrode assembly 6 having an electrode body 6a.
(10) Each electrode body 4a, 4b is formed from a polycrystalline Boron-doped diamond (BDD), in particular cut from a wafer of the diamond material by a laser. The BDD material may be formed using any suitable technique, in particular CVD. Diamond material of this kind is available commercially. When prepared using a technique such as CVD, the diamond material has a growth face and a nucleation face, which form the major surfaces of the electrode body.
(11) A semi-permeable proton exchange membrane 8 extends between the first and second electrode assemblies 4, 6 and is in contact with a major surface of the electrode body 4a, 6a of each electrode assembly 4, 6. The membrane 8 preferably contacts the growth face of the electrode bodies 4a, 6a. The membrane 8 is formed from a material that allows for the polarity of the cell to be reversed, in particular Nafion® type N117. As shown in FIG. 1, the membrane 8 extends beyond the edge of each electrode body 4a, 6a.
(12) The major surface of each electrode body 4a, 6a not covered by the membrane 8, that is the nucleation face of the electrode body, is provided with a respective first layer 10a, 12a of an electrically conductive material, in particular a layer of Titanium (Ti), and a second layer 10b, 12b of a second electrically conductive material, in particular a layer of an alloy of Copper (Cu) and Silver (Ag). The layers of electrically conductive material are applied to each electrode body by sputter coating. As shown in FIG. 1, an edge portion 14a, 14b of each electrode body is not covered by the electrically conductive layer 10a, 10b, 12a, 12b and is exposed. The layers of electrically conductive material 10, 12 total about 5000 nm in thickness. The layers of the alloy of Copper and Silver may be replaced with a layer consisting essentially of Copper having a thickness of about 300 μm.
(13) A Copper cable connector terminal 16 is soldered to each layer 10b, 12b of the Copper-Silver electrically conductive material.
(14) The exposed surface of each layer of electrically conductive material 10, 12 is coated in a layer of electrically insulating material 18, 20, in particular Silicon Nitride (Si.sub.3N.sub.4). The layer of electrically insulating material 18, 20 is applied to the layer of electrically conductive material 10, 12 by sputter coating and has a thickness of up to 1000 nm. The layer of electrically insulating material overlaps the layers 10b, 12b of electrically conducting material, as shown in FIG. 1.
(15) A layer of thermosetting hydrophobic resin 22, 24 is provided on each layer of electrically insulating material 18, 20. The resin is most preferably a polyimide resin, with alternatives being a polyester resin or an epoxy resin. The layer 22, 24 of resin material has a thickness between 1 mm and 3 mm.
(16) The layer of electrically insulating material 18, 20 may be omitted, in which case the layer of resin 22, 24 is provided directly onto the surface of the layer of electrically conductive material 10b, 12b.
(17) It has been found that the resin adheres more readily to the metallised surfaces 10b, 12b after the Copper cable connector terminals 16 have been soldered in position.
(18) Current feed cables 26 are connected to respective cable connector terminals 16 by soldering, to provide an electric current to the respective layers of electrically conductive material 10, 12 and to the electrode body 4a, 6a.
(19) The electrochemical cell 2 of FIG. 1 is particularly suitable for use in the electrolysis of water to produce ozone. In use of the electrochemical cell 2, water is caused to flow over the assembly in the direction indicated by the arrow A in FIG. 1. When an electrical current is applied by way of the current feed cables 26 from a suitable source of electrical power, one of the electrode assemblies 4, 6 operates as the anode and the other assembly 6, 4 as the cathode, depending upon the polarity of the supplied current. Ozone is produced at the edges of the electrode body 4a, 6a of the anode at the interface between the electrode body 4a, 6a, the membrane 8 and the surrounding water. In operation, the polarity of the cell is periodically reversed, to prevent the accumulation of deposits on the electrode bodies.
(20) Turning to FIG. 2, there is shown a plan view of an electrode body according to one embodiment of the present invention. The electrode body, generally indicated as 102, is as described above with respect to FIG. 1. The electrode body 102 is elongate, having a length at least six times its width. The electrode body 102 has a longitudinal axis X-X and comprises a plurality of first body portions 104. Each of the first body portions 104 has a first width w.sup.1 measured from the longitudinal axis X-X to the edge of the electrode body 102 perpendicular to the longitudinal axis, as indicated in FIG. 2. The electrode body 102 further comprises a plurality of second body portions 106. Each of the second body portions 106 has a second width w.sup.2 measured from the longitudinal axis X-X to the edge of the electrode body 102 perpendicular to the longitudinal axis, as indicated in FIG. 2. The second width w.sup.2 is greater than the first width w.sup.1. For example, for an electrode body having a total length of 40 mm, the width w.sup.2 may be 3 mm and the width w.sup.1 1.5 mm.
(21) The first and second body portions 104, 106 are shown in FIG. 2 to have generally rectangular configurations, with the edges of the body portions being straight. Alternatively, the edges of the body portions 104, 106 may be curved. The corners of the body portions 104, 106 may be rounded.
(22) The electrode body 102 of FIG. 2 has the first body portions 104 and the second body portions 106 arranged in an alternating pattern along the length of the electrode body on side of the longitudinal axis X-X. The electrode body is asymmetrical about the longitudinal axis X-X.
(23) Turning to FIG. 3, there is a shown a plan view of an electrode body of an alternative embodiment of the present invention. The electrode body, generally indicated as 202, is as described above with respect to FIG. 1. The electrode body 202 is elongate, having a length at least six times its width. The electrode body 202 has a longitudinal axis X-X and comprises a plurality of first body portions 204. Each of the first body portions 204 has a first width w.sup.1 measured from the longitudinal axis X-X to the edge of the electrode body 202 perpendicular to the longitudinal axis, as indicated in FIG. 3. The electrode body 202 further comprises a plurality of second body portions 206. Each of the second body portions 206 has a second width w.sup.2 measured from the longitudinal axis X-X to the edge of the electrode body 202 perpendicular to the longitudinal axis, as indicated in FIG. 3. The second width w.sup.2 is greater than the first width w.sup.1. For example, for an electrode body having a total length of 40 mm, the width w.sup.2 may be 3 mm and the width w.sup.1 1.5 mm.
(24) The electrode body 202 of FIG. 3 has the first body portions 204 and the second body portions 206 arranged in an alternating pattern along the length of the electrode body on both sides of the longitudinal axis X-X. The first and second body portions 204, 206 on one side of the longitudinal axis X-X are staggered with respect to the first and second body portions 204, 206 on the opposite side of the longitudinal axis, that is a first portion 204 on one side of the axis is opposite a second portion 206 on the other side of the axis. The electrode body 202 is asymmetrical about the longitudinal axis X-X.
(25) The first and second body portions 204, 206 are shown in FIG. 3 to have generally rectangular configurations, with the edges of the body portions being straight. Alternatively, the edges of the body portions 204, 206 may be curved. The corners of the body portions 204, 206 may be rounded.
(26) Turning to FIG. 4, there is a shown a plan view of an electrode body of an alternative embodiment of the present invention. The electrode body, generally indicated as 302, is as described above with respect to FIG. 1. The electrode body 302 is elongate, having a length at least six times its width. The electrode body 302 has a longitudinal axis X-X and comprises a plurality of first body portions 304. Each of the first body portions 304 has a first width w.sup.1 measured from the longitudinal axis X-X to the edge of the electrode body 302 perpendicular to the longitudinal axis, as indicated in FIG. 4. The electrode body 302 further comprises a plurality of second body portions 306. Each of the second body portions 306 has a second width w.sup.2 measured from the longitudinal axis X-X to the edge of the electrode body 302 perpendicular to the longitudinal axis, as indicated in FIG. 4. The second width w.sup.2 is greater than the first width w.sup.1. For example, for an electrode body having a total length of 40 mm, the width w.sup.2 may be 3 mm and the width w.sup.1 1.5 mm.
(27) The electrode body 302 of FIG. 4 has the first body portions 304 and the second body portions 306 arranged in an alternating pattern along the length of the electrode body on both sides of the longitudinal axis X-X. The first and second body portions 304, 306 on one side of the longitudinal axis X-X are positioned along the length of the electrode body the same as the first and second body portions 304, 306 on the opposite side of the longitudinal axis, that the first and second portions 304, 306 on one side of the axis are opposite respective first and second portions 304, 306 on the other side of the axis. The electrode body 302 is symmetrical about the longitudinal axis X-X.
(28) The first and second body portions 304, 306 are shown in FIG. 4 to have generally rectangular configurations, with the edges of the body portions being straight. Alternatively, the edges of the body portions 304, 306 may be curved. The corners of the body portions 304, 306 may be rounded.
(29) Referring now to FIG. 5, there is shown a plan view of the electrode body 302 of FIG. 4, bearing a layer of electrically conductive material 310. The layer of electrically conductive material 310 is as described above with respect to FIG. 1. As shown in FIG. 5, the layer 310 extends over a major surface of the electrode body 302 and covers a major portion of the surface. An edge portion 312 of the surface of the electrode body 302 is left uncovered, such that the BDD diamond material of the electrode body 302 is exposed at the edge portion.
(30) Turning to FIG. 6, there is a shown a plan view of an electrode body of an alternative embodiment of the present invention. The electrode body, generally indicated as 402, is as described above with respect to FIG. 1. The electrode body 402 is elongate, having a length at least six times its width. The electrode body 402 has a longitudinal axis X-X and comprises a plurality of first body portions 404. Each of the first body portions 404 has a first width w.sup.1 measured from the longitudinal axis X-X to the edge of the electrode body 402 perpendicular to the longitudinal axis, as indicated in FIG. 6. The electrode body 402 further comprises a plurality of second body portions 406. Each of the second body portions 406 has a second width w.sup.2 measured from the longitudinal axis X-X to the edge of the electrode body 402 perpendicular to the longitudinal axis, as indicated in FIG. 6. The second width w.sup.2 is greater than the first width w.sup.1. For example, for an electrode body having a total length of 40 mm, the width w.sup.2 may be 3 mm and the width w.sup.1 1.5 mm.
(31) The electrode body 402 of FIG. 6 has the first body portions 404 and the second body portions 406 arranged in an alternating pattern along the length of the electrode body on both sides of the longitudinal axis X-X. The first and second body portions 404, 406 on one side of the longitudinal axis X-X are positioned along the length of the electrode body the same as the first and second body portions 404, 406 on the opposite side of the longitudinal axis, that the first and second portions 404, 406 on one side of the axis are opposite respective first and second portions 404, 406 on the other side of the axis. The electrode body 402 is symmetrical about the longitudinal axis X-X.
(32) The first and second body portions 404, 406 are shown in FIG. 6 to form a generally triangular configuration, with the edges of the body portions being straight. Alternatively, the edges of the body portions 404, 406 may be curved. The corners of the body portions 404, 406 may be rounded.
(33) Finally, turning to FIG. 7, there is a shown a plan view of an electrode body of an alternative embodiment of the present invention. The electrode body, generally indicated as 502, is as described above with respect to FIG. 1. The electrode body 502 is elongate, having a length at least six times its width. The electrode body 502 has a longitudinal axis X-X and comprises a plurality of first body portions 504. Each of the first body portions 504 has a first width w.sup.1 measured from the longitudinal axis X-X to the edge of the electrode body 502 perpendicular to the longitudinal axis, as indicated in FIG. 7. The electrode body 502 further comprises a plurality of second body portions 506. Each of the second body portions 506 has a second width w.sup.2 measured from the longitudinal axis X-X to the edge of the electrode body 502 perpendicular to the longitudinal axis, as indicated in FIG. 7. The second width w.sup.2 is greater than the first width w.sup.1. For example, for an electrode body having a total length of 40 mm, the width w.sup.2 may be 3 mm and the width w.sup.1 1.5 mm.
(34) The electrode body 502 of FIG. 7 has the first body portions 504 and the second body portions 506 arranged in an alternating pattern along the length of the electrode body on both sides of the longitudinal axis X-X. The first and second body portions 504, 506 on one side of the longitudinal axis X-X are positioned along the length of the electrode body the same as the first and second body portions 504, 506 on the opposite side of the longitudinal axis, that the first and second portions 504, 506 on one side of the axis are opposite respective first and second portions 504, 506 on the other side of the axis. The electrode body 502 is symmetrical about the longitudinal axis X-X.
(35) The first and second body portions 504, 506 are shown in FIG. 7 to be generally curved and to form a generally sinusoidal pattern extending along each side of the longitudinal axis.
