The present invention relates to an electrode and to an electrochemical cell comprising the electrode. The electrode and the electrochemical cell are of advantage in the production of ozone by the electrolysis of water.

Electrochemical cells are well known and find use in a range of

electrochemical applications. Electrodes for use in the electrochemical cells are also known. One such application for electrochemical cells is in the production of ozone from water by electrolysis. Electrochemical cells for the production of ozone from water generally comprise an anode and a cathode, with the anode and cathode being separated by a semi-permeable membrane, also referred to as a proton exchange membrane. The electrochemical production of ozone from water may be

represented generally by the following formula:

3H ₂ 0 -> 0 ₃ + 3H ₂ ΔΗ°298 = 207.5 kcal

The reaction at the anode of the electrochemical cell may be represented by the following formula:

3H ₂ 0 -> 0 ₃ + 6H ⁺ + 6e-

An example of the electrochemical production of ozone from water and an electrochemical cell for such use is disclosed in US 5,972, 196 A.

Electrodes for use in electrochemical cells for the production of ozone from water are known in the art. For example, a perforated conductive diamond electrode for ozone generation by the electrolysis of water is disclosed in JP 2005-336607. One recent disclosure of an electrode assembly is US 2010/0006450. This document discloses a diamond electrode and an electrolysis cell. US 2010/0006450 discloses an electrode comprising an electrically conducting diamond plate comprising at least one elongate aperture, in which the aperture edge length per unit working area of the diamond plate is greater than about 4 mm/mm ² . The electrode may consist essentially of a diamond plate. The diamond plate is preferably CVD diamond, with a preference for CVD polycrystalline diamond being expressed in US 2010/0006450. The apertures in the diamond electrode may be formed by laser cutting. Other techniques for forming the apertures disclosed include ion beam milling and plasma etching. There is also disclosed an alternative to using a diamond plate electrode. In particular, it is disclosed that an electrode assembly may be formed by coating an electrically conductive substrate with a conductive diamond layer. The substrate is formed with at least one elongate aperture. This

arrangement is indicated to have the advantage of allowing a backing plate and flow channels to be incorporated into a single component. In addition, the use of a conductive diamond coating is stated to have cost advantages compared to a monolithic diamond plate.

EP 2418304 discloses a hydrogen generator.

US 2012/01 17789 discloses a method of making a cell stack for an electrical purification apparatus.

WO 98/42617 describes and shows an integrated ozone generator system.

A membrane with supported internal passages is disclosed in US 6,149,810.

US 4,416,747 discloses a process for the electrolytic production of ozone. As noted above, one application for an electrochemical cell is in the production of ozone by the electrolysis of water. There is a need for an improved electrochemical cell arrangement that is advantageous to use in the electrolysis of water to produce ozone. It would be advantageous if the improved electrochemical cell could provide an efficient operation in the electrolysis of a stream of water to produce ozone and ozonate the water.

According to the present invention, there is provided an assembly for use in the production of ozone from water, the assembly comprising:

a housing;

a support assembly disposed within the housing and supporting a plurality of electrochemical cell assemblies;

each electrochemical cell assembly comprising a first electrode, a second electrode, a semi-permeable membrane disposed between the first and second electrodes, and a conductor for providing an electrical current to the first and second electrodes; and

a conductor assembly, the conductor of each electrochemical cell being connected to the conductor assembly to receive an electrical current therefrom for delivery to the first and second electrodes of the electrochemical cell.

The assembly of the present invention provides a number of advantages. In particular, the assembly may be used to produce ozone from a stream of liquid, especially to ozonate water flowing in a conduit, such as pipe. This in turn allows the assembly to be employed to provide ozonated water to a wide range of facilities that consume or require a stream of water. The assembly is particularly efficient in the production of ozone. In addition, the assembly is modular and can have its capacity readily changed, in particular increased, to accommodate a wide range of different flow conditions and rates. This in turn renders the assembly very flexible in its application.

The assembly of the present invention comprises a housing. The housing may be of any suitable form to contain the plurality of electrochemical cell assemblies described hereinafter. In one preferred embodiment, the housing is generally cylindrical and has a circular cross-section. Other forms of housing may be employed.

As noted above, the electrochemical cell assembly is particular useful for the production of ozone from a stream of water, to thereby ozonate the water. In use, as will be described hereinafter, the assembly may be installed in a conduit, such as a pipe, through which the water to be ozonated is flowing. Accordingly, in one preferred embodiment, the housing is generally cylindrical and has the same nominal diameter as the conduit or pipe into which the assembly is to be installed.

For example, in one embodiment the housing of the assembly may have an outer diameter of 50 mm. The outer diameter of the housing may be reduced in order to match the outer diameter of a standard pipe, for example 32 mm, 25 mm, 22 mm, 18 mm or 15 mm. In general, fewer electrochemical cell assemblies will be accommodated within housings of smaller diameter.

Alternatively, the housing may be provided with reducing couplings at either end, that is a coupling having a connector at one end to match the diameter of the housing and a connector at the other end to match the diameter of the pipe. In this respect, the diameter of the housing may be larger or smaller than the pipe to which it is connected. Preferably, the housing is the same diameter or a larger diameter than the pipe to which it is connected. This ensures that a suitably high flowrate of water through the pipe or conduit can be maintained, with minimal loss of pressure across the assembly.

The housing may be formed from any suitable material. For example, the housing may be formed from a metal, such as copper or steel, in particular stainless steel. Stainless steel, especially 316 grade, is one particularly preferred metal. More preferably, the housing is formed from a polymer. Suitable polymers include polyolefins, such as polyethylene, in particular high density polyethylene (HDPE), polypropylene, polyvinyl chloride (PVC) and chlorinated polyvinyl chloride (CPVC). Preferred polymers for forming the housing are those that are resistant to water that has been chlorinated and/or ozonated. The housing contains a plurality of electrochemical cell assemblies arranged therein. In operation, a fluid, in particular water, is caused to flow through the housing and over the plurality of electrochemical cell assemblies within the housing, so as to contact each electrochemical cell, thereby to produce ozone, as described in more detail hereinafter. The assembly of the present invention may comprise any suitable number of electrochemical cells within the housing, so as to accommodate the required duty and meet the requirements for ozone production. For example, the assembly may comprise 2, 3, 4, 5, 6 or 7electrochemcial cell assemblies, each having its own electrochemical cell therein.

The electrochemical cell assemblies may each be contained within a conduit disposed within the housing. In this case, the flow of water through the housing is divided into separate sub-flows through each of the conduits, with the

electrochemical cell assembly in each conduit being exposed only to the water flowing through the respective conduit. The conduits within the housing may have any suitable shape. It is particularly preferred that the conduits are generally cylindrical and have a circular cross-section. However, the conduits may have a cross-section having another form, for example polygonal, such as a quadrilateral, preferably a regular polygon, in particular rectangular or square. If present, the conduits may be formed from any suitable material, such as the materials discussed above with respect to the housing.

More preferably, there are no conduits within the housing and each electrochemical cell assembly is exposed to the interior of the housing and to the flow of water through the housing. In this way, water within the housing may contact two or more electrochemical cells as it flows along the length of the housing.

In one preferred embodiment, the assembly comprises 7electrochemical cells. It has been found that a particularly compact assembly may be provided by having 7 electrochemical cells arranged in a symmetrical pattern having a first electrochemical cell arranged coaxially and centrally with the housing and 6 further electrochemical cells arranged equidistantly around the first electrochemical cell.

The assembly of the present invention comprises a plurality of

electrochemical cell assemblies disposed within the housing. Each electrochemical cell comprises a first electrode and a second electrode. A semi-permeable membrane extends between the first and second electrodes. In a preferred embodiment, each of the first and second electrodes is an elongate electrode, more preferably each elongate electrode having a longitudinal axis extending along the housing, still more preferably substantially parallel to the longitudinal axis of the housing. In this way, each electrode extends substantially parallel to the direction of flow of water through the housing. In one embodiment, the assembly is oriented such that the housing has an inlet end and an outlet end, with the water being processed flowing through the housing from the inlet end to the outlet end. Preferably, each electrochemical cell assembly is arranged whereby its elongate electrodes extend from the support assembly in a downstream direction, that is with the electrochemical cell extending from the support assembly towards the outlet of the housing. In this way, the support assembly may be arranged to direct and distribute the flow of water past and over the electrochemical cell assemblies.

Each electrochemical cell comprises a conductor for providing an electrical current to the first and second electrodes

Each electrode may have any suitable shape or form. As noted above, the electrodes are preferably elongate. In one preferred embodiment, each electrode comprises 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.

The electrode assembly of this embodiment comprises an electrode body. The electrode body is elongate and has a longitudinal axis. The longitudinal axis discussed herein is the central longitudinal axis of the elongate electrode body. In this respect, the term 'elongate' is a reference to the length of the electrode body being greater than the width of the electrode. In use, when the electrode assembly is incorporated into an electrochemical cell and the cell is operated, water is caused to flow over the electrode body. In use, the electrode body is arranged to extend with its longitudinal axis generally parallel to the general direction of flow of the water through the cell.

The ratio of the length of the electrode body to the width of the electrode body may be any suitable ratio. In this respect, the ratio of the length of the electrode body to its width is a reference to the ratio of the length to the width of the body at its widest point, measured across a major surface of the electrode body from one edge surface to the opposite edge surface perpendicular to the longitudinal axis. The ratio is preferably at least 2, more preferably at least 3, still more preferably at least 4. A ratio of at least 5 is preferred, still more preferably at least 6. In a preferred embodiment, the ratio of the length of the electrode body to the width of the electrode body is in the range of from 2 to 12, more preferably from 3 to 10, still more preferably from 4 to 8. A ratio of about 6 to 7 has been found to be particularly suitable for many embodiments.

As noted above, the electrode body has opposing major surfaces extending between opposing edge surfaces. The relative dimensions of the electrode body are such that the body is an elongate plate, that is the width of the major surfaces is significantly greater than the width of the edge surfaces. In this respect, the width of the edge surface can be considered to be the thickness of the electrode body.

Preferably, the ratio of the width of each major surface, that is the width of the major surface at its widest point measured across the major surface from one edge surface to the opposite edge surface perpendicular to the longitudinal axis, to the width of the edge surface is at least 2, preferably at least 4, more preferably at least 5, still more preferably at least 6, more preferably still at least 8. In a preferred embodiment, the ratio of the width of each major surface to the width of the edge surfaces is at least 10. In a preferred embodiment, the ratio is in the range of from 2 to 25, more preferably from 4 to 20, still more preferably from 6 to 18, more preferably still from 8 to 15. A ratio of about 12 has been found to be particularly suitable for many embodiments.

Similarly, the ratio of the length of the electrode body to the width of the edge surface is preferably at least 10, more preferably at least 20, still more preferably at least 30, more preferably still at least 40, in particular more preferably at least 50. In a preferred embodiment, the ratio of the width of each major surface to the width of the edge surfaces is at least 60. In a preferred embodiment, the ratio is in the range of from 10 to 150, more preferably from 30 to 130, still more preferably from 50 to 120, more preferably still from 60 to 100. A ratio of from 70 to 90, more particularly about 80, has been found to be particularly suitable for many embodiments.

The dimensions of the electrode body are selected according to the required duty of the electrode and the electrolytic cell in which it is used. In particular, the dimensions of the electrode may be selected to provide the required current efficiency. In the case of the electrode assembly of the present invention, the current efficiency is a function of the ratio of the length of the edges of the electrode body exposed to liquid being electrolysed, in particular water, to the surface area of the electrode body. In general, a higher ratio of edge length to surface area of the electrode body results in a higher current efficiency of the electrode assembly when in use.

Preferably, the ratio of the total length of the edges of the electrode body to the surface area of the electrode body is at least 0.1 , more preferably a least 0.2, still more preferably at least 0.25, more preferably still at least 0.3. A ratio of up to 2.5 can be provided, preferably up to 2.0, more preferably up to 1.5. A ratio in the range of from 0.1 to 2.5, preferably from 0.2 to 2.0, more preferably from 0.25 to 1.75, still more preferably from 0.3 to 1.6, especially from 0.3 to 1.5 is preferred. A ratio of from 0.35 to 1.4 is particularly suitable for many embodiments.

The ratio of the total length of the edges of the electrode body to the surface area of the electrode body may vary according to the size of the electrode.

Examples of the dimensions and ratio for different sizes of electrode are summarised in the following table. Electrode Edge Electrode Ratio

Dimensions Length Area EL/EA

(mm x mm) (mm) (mm ² ) (mm ¹ )

3 x 3 12 9 1.33

5 x 5 20 25 0.80

5 x 10 30 50 0.60

5 x 20 50 100 0.50

6 x 40 92 240 0.38

As noted above, the dimensions of the electrode body are selected according to the duty to be performed when in use. In addition, the dimensions of the electrode body may be determined by the construction of the electrode body and its method of manufacture. For many applications, the electrode body is preferably at least 3 mm in length, more preferably 5 mm in length, more preferably at least 10 mm, still more preferably at least 20 mm, more preferably still at least 30 mm. The maximum electrode body length may be limited by the construction and method of manufacture. Lengths of up to 200 mm may be employed, for example up to 150 mm. In the case of one preferred embodiment, in which the electrode body is cut from a wafer of solid diamond material prepared by chemical vapour deposition (CVD), the maximum length of the electrode body is up to about 140 mm. For many embodiments, a length of from 30 to 50 mm, in particular from 35 to 45 mm, for example about 40 mm, is particularly suitable. The width of the electrode body, that is the width of the major surfaces of the body between opposing edge surfaces at its widest point, is preferably at least 1 mm, more preferably at least 2 mm, still more preferably at least 3 mm. A width of up to 20 mm, preferably up to 15 mm, more preferably up to 10 mm is particularly suitable for many embodiments. For many embodiments, a length of from 2 to 12 mm, preferably from 3 to 10 mm, more preferably from 4 to 8 mm is particularly suitable, for example from 5 to 7 mm, such as about 6 mm. The width of the edge surfaces is preferably at least 0.1 mm, more preferably at least 0.2 mm, still more preferably at least 0.3 mm. A width of up to 2 mm may be employed, for example up to 1.5 mm or up to 1 mm. A width of from 0.1 to 1 mm has been found to be particularly suitable for many embodiments, preferably from 0.2 to 0.8 mm, more preferably from 0.3 to 0.7 mm, still more preferably from 0.4 to 0.6 mm, such as about 0.5 mm.

The first and second body portions of the electrode body may have any suitable cross-sectional shape. Preferably, the first and second body portions have the same general cross-sectional shape, with the dimensions of the portions differing, as noted above. A preferred cross-sectional shape is rectangular.

As noted above, the electrode body comprises first and second body portions, in which the first body portion has a first width and the second body portion has a second width, with the second width being greater than the first width. In this respect, the first and second widths are each 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. The first and second body portions may be asymmetrical about the longitudinal axis. For example, a first body portion on one side of the longitudinal axis may be opposite a second portion on the opposite side of the longitudinal axis. More preferably, at least one, more preferably both, of the first and second portions are arranged symmetrically about the longitudinal axis of the electrode body. More particularly, a first body portion on one side of the longitudinal axis is preferably opposite a first body portion on the opposite side of the axis and/or a second body portion one side of the longitudinal axis is preferably opposite a second body portion on the opposite side of the longitudinal axis. More preferably, each body portion on one side of the longitudinal axis is opposite a body portion of the same type on the other side of the longitudinal axis. The first body portion is preferably adjacent the second body portion.

As noted, the width of the second body portion is greater than the width of the first body portion. In this respect, the widths of the body portions are references to the width at the widest point of the said body portion. The ratio of the width of the second body portion to the width of the first body portion is preferably at least 1.1 , more preferably at least 1.2, still more preferably at least 1.3, more preferably still at least 1.4. A ratio of at least 1.5 is more preferred, more preferably at least 1.6, still more preferably at least 1.7, more preferably still at least 1.8, for example at least 1.9. A ratio of the width of the second body portion to the width of the first body portion is preferably 2.0 or greater.

The electrode body may comprise one or more first body portions and one or more second body portions. Preferably, the electrode body comprises a plurality of first body portions and a plurality of second body portions, more preferably with the first and second body portions arranged in an alternating pattern along the length of the electrode body.

The first and second body portions may have any suitable shape, that is the shape of the first and second major surfaces of the body portion. For example, the first and/or second body portions may have a rounded shape, that is with the edges of the first and second major surfaces extending in an arc. More preferably, the first and/or second body portions are angular in shape, that is the edges of the first and second major surfaces extend in a plurality of straight lines, each straight line extending at an angle to an adjacent straight line. For example, the first and/or second body portions may comprise an edge having two straight lines, forming a generally triangular form. More preferably, the first and/or second body portions have a generally rectangular shape. Preferably, the first and second body portions have the same general shape.

In embodiments in which the electrode body comprises a plurality of first and/or second body portions, the plurality of first body portions are preferably of the same shape and size and/or the plurality of second body portions are preferably of the same shape and size.

The electrode body may be asymmetrical about the longitudinal axis. More preferably, the electrode body is symmetrical about the longitudinal axis. The electrodes of the electrochemical cell may be formed from any suitable material. Preferably, each electrode comprises diamond, more preferably at least in the edge portions of the electrode. The electrode may comprise a substrate material bearing a layer or coating of diamond. The layer or coating of diamond may be applied to the substrate material by any suitable technique, as is known in the art.

Most preferably, the electrode comprises an electrode body formed from diamond. More particularly, the electrode is cut from a diamond wafer, for example by means of a laser. The diamond wafer may be formed using any suitable technique. A preferred technique for forming the diamond wafer is chemical vapour deposition (CVD). CVD techniques for forming diamond wafer are known in the art.

A particularly preferred diamond material is a doped diamond material, more preferably boron-doped diamond.

When forming the electrode body from a wafer formed by techniques, such as CVD, in which the wafer has a growth surface, the electrode body is preferably cut such that the growth surface forms one of the first or second major surfaces of the electrode body.

As noted hereinbefore, each electrode of each electrochemical cell is connected to a source of electrical current by a conductor assembly. To improve the distribution of electrical charge from the conductor assembly along and across the electrode and provide an even current density across the surface of the electrode, the body of the electrode is preferably provided with a layer of an electrically conductive material on a major surface of the electrode body. A preferred conductive material for the said layer is a metal, in particular Titanium. Titanium forms a Ti-C bond with the sp ³ carbon structure of the diamond material. Other metals that may be used include platinum (forming Pt-C bonds), tungsten (forming W-C bonds), tantalum (forming Ta-C bonds), niobium (forming Nb-C bonds), gold (forming Au-C bonds) and copper (forming Cu-C bonds). Other metals or mixtures of metals may be used, provided they are compatible with the physical properties of the boron doped diamond material, for example its thermal expansion properties. Alternatively, the layer of electrically conductive material comprises two or more metals. One preferred metal composition is a mixture of copper and silver or gold. The electrode body may be provided with a single layer of conductive material or a plurality of layers of conductive material. In one preferred embodiment, the electrode body is provided with a first layer of a first conductive material adjacent the surface of the electrode body and a second layer of a second conductive material adjacent the surface of the first layer. In one preferred embodiment, the first layer consists essentially of a single metal. Titanium is a particularly preferred metal for forming the first layer. In one preferred embodiment, the second layer comprises a mixture of metals. An amalgam of copper and silver is one particularly preferred material for forming the second layer. The layer of electrically conductive material may be applied to the electrode body using any suitable technique. One particularly preferred technique is sputter deposition or sputter coating. Different sputter deposition techniques may be employed, with radio frequency (RF) sputter coating being preferred. In embodiments in which the electrode body is cut from a diamond wafer having a growth surface, such as occurs when using CVD, the layer of electrically conductive material is preferably applied to the major surface of the electrode body that is the nucleation side, that is not the major surface corresponding to the growth side of the wafer.

The layer of electrically conductive material is preferably at least 200 nm in thickness, more preferably at least 300 nm, still more preferably at least 400 nm, more preferably still at least 500 nm. A thickness of at least 600 nm is particularly preferred, especially at least 1000 nm. The layer may have a thickness of up to 10000 nm, more preferably up to 7500 nm. A thickness of 5000 nm is particularly suitable for many embodiments and provides for an improved current distribution and an even current density across the surface of the electrode body. In general, increasing the thickness of the layer of conductive material increases the electrical conductivity of the layer. In embodiments comprising a plurality of layers of conductive material, the layer adjacent the surface of the electrode body is preferably relatively thin and the successive layer or layers relatively thick. In one preferred embodiment, the electrode body is provided with a first layer adjacent the surface of the electrode body and having a thickness of from 600 to 1000 nm, more preferably about 900 nm, and a second layer adjacent the surface of the first layer and having a thickness of from 2000 to 2500 nm, more preferably about 2400 nm. The layer of electrically conductive material may extend across all or part of a major surface of the electrode body. Preferably, the layer of electrically conductive material extends over a major portion of a major surface of the electrode body. More preferably, the layer of electrically conductive material extends over a major portion of the major surface of the electrode body, with a portion at an edge of the major surface, preferably all edges of the major surface, not being covered by the conductive material. This edge portion may be at least 0.5 mm in width, that is the distance from the edge of the major surface of the electrode body to the edge of the layer of conductive material measured perpendicular to the edge, preferably at least 1.0 mm. An edge portion having a width of 1.5 mm or greater is particularly preferred for many embodiments. An edge portion having a width of 2.0 mm or greater is also suitable for many embodiments.

In one preferred arrangement, the body of each electrode is provided on a major surface with a first layer of an electrical conductive material, as discussed above, and a second layer of an electrically insulating material. The first layer of electrically conductive material may comprise separate layers of one or more electrically conductive materials, as discussed above. The second layer extends over the first layer. In one embodiment, the second layer comprises a material that is both electrically insulating and exhibits hydrophobic properties. Suitable materials for forming the second layer include nitrides, for example of silicon, titanium, zirconium or hafnium. Preferred compounds for inclusion in the second layer are silicon nitride (S13N4), titanium nitride (TiN), zirconium nitride (ZrN) and hafnium nitride (HfN).

Anodised aluminium oxide may also be used as an electrically insulating material. The second layer may be applied using any suitable technique. A preferred embodiment employs a material for the second layer that can be applied by sputter coating, for example the silicon, titanium, zirconium and hafnium nitrides mentioned above.

The electrode assembly may comprise a single layer of an electrically insulating material. Alternatively, two or more different insulating materials may be employed in two or more layers. Alternatively, or in addition to the second layer, each electrode body may be coated in a resin, preferably a hydrophobic resin, more preferably a thermosetting hydrophobic resin. Examples of suitable resins include polyester resins and epoxy resins. The resin acts to seal the layers of conductive material and insulating material. The resin may also be employed to seal the conductor connection, discussed in more detail below.

It has been found that the adhesion of the resin is improved if the

aforementioned layer of insulating material is employed. Accordingly, it is particularly preferred to provide the electrode body with a layer electrically conductive material as hereinbefore described, a layer of insulating material as hereinbefore described extending over the condutive layer, and a layer of resin extending over the insulating layer.

Each electrochemical cell comprises a semi-permeable membrane extending between the first electrode and the second electrode. In embodiments in which the electrodes comprise a generally planar arrangement having two major surfaces, the semi-permeable membrane most preferably extends between opposing major surfaces of the first and second electrodes. The semi-permeable membrane functions as a cation exchange membrane and is also referred to as a proton exchange membrane (PEM) when the

electrochemical cell is in use, selectively allowing the passage of certain cations and protons (hydrogen ions) from one of the first and second electrodes to the other of the first and second electrodes, depending upon the polarity of operation of the cell, that is from the anode to the cathode, while preventing the passage of anions.

Suitable materials for forming the semi-permeable membrane are known in the art and are commercially available. Particularly preferred materials for forming the semi-permeable membrane are fluoropolymers, in particular chemically stabilized perfluorosulfonic acid/PTFE copolymers. Such materials are commercially available under the trade name Nafion ^® (ex. Du Pont), for example. The semi-permeable proton exchange membrane (PEM) extends between the first and the second electrode, in particular between a major surface of the first electrode and a major surface of the second electrode, and is in contact with both electrodes. During operation of the cell, in particular in the electrolysis of water to produce ozone, the production of ozone occurs along the edges of the electrodes at the interface between the electrode forming the anode, the semi-permeable membrane and water. It has been found that the electrode assembly exhibits a high efficiency in the production of ozone at the aforementioned interface. In addition, however, it has been found that the form of the electrode body as described hereinbefore promotes the mass transfer of ozone away from the electrode bodies, in turn further increasing the efficiency and productivity of the electrochemical cell.

It is preferred that the semi-permeable proton exchange membrane (PEM) extends across the entire opposing major surfaces of the electrode bodies of the first and second electrodes. More preferably, the semi-permeable proton exchange membrane both extends across the entire opposing major surfaces of the electrode bodies of the first and second electrodes and extends therebeyond at some, most preferably at all edges of the electrode body. Preferably, the semi-permeable proton exchange membrane extends beyond the edges of the electrode bodies by at least 1.0 mm, more preferably at least 2.0 mm, still more preferably at least 3.0 mm, more preferably still at least 5.0 mm.

As noted above, each electrode of each electrochemical cell is connected in use to a supply of electrical current by a suitable conductor. In embodiments in which the electrode body is provided with a layer of electrically conductive material, the conductor preferably comprises a conductor connector terminal connected to the said layer. The layer of electrically conductive material preferably has a composition that allows the terminal to be connected to the layer by soldering. Preferably, the terminal is coated in a resin, as described hereinbefore.

An electrical conductor, such as a cable, may be connected to the conductor connector terminal. Again, this connection is preferably formed by soldering.

The electrochemical cell assembly further comprises a conductor assembly. The conductor of each electrochemical cell is connected to the conductor assembly to receive an electrical current therefrom for delivery to the first and second electrodes of the electrochemical cell.

The conductor assembly may be of any suitable form and construction. In one embodiment, the conductor assembly comprises a bus formed from a suitable electrically conductive material, for example a metal, such as copper. The conductor of each electrochemical cell assembly is connected to the bus and receives electrical current therefrom. However, it has been found that this arrangement can lead to premature failure of the assembly, in particular in the case that one electrochemical cell fails and causes the remaining cells to overload and fail in a cascade manner.

Accordingly, it is preferred that the conductor assembly comprises a plurality of conductor elements, such as cables, with the conductor of each electrochemical cell assembly being connected to respective cables. In this way, the supply of electrical charge to each electrochemical cell may be individually controlled, for example by a suitable controller. In this arrangement, the failure of one

electrochemical cell assembly does not affect the operation of the remaining electrochemical cells. As noted above, the assembly of the present invention comprises a support assembly. The support assembly holds each electrochemical cell assembly within the housing. The support assembly may have any suitable form. The support assembly is arranged to allow the flow of water therethrough. In one embodiment, the support assembly comprises a plurality of support arms, with each arm

supporting a respective electrochemical cell assembly.

As indicated above, in one embodiment, the support assembly is upstream of the plurality of electrochemical cell assemblies, with each electrochemical cell assembly extending from the support assembly in the downstream direction, that is towards the outlet end of the housing. In this arrangement, the support assembly may be provided with guide surfaces to direct the flow of water within the housing, in particular to direct the flow of water onto the electrochemical cell assemblies.

The assembly of the present invention preferably comprises a control system including a controller and arranged to deliver a predetermined electrical current to each electrochemical cell assembly individually, depending upon the condition of the cell. In this respect, the voltage (potential) applied to each cell is allowed to float, that is increase or decrease, in order to maintain the electrical current supplied to the cell at the required level. The condition of each electrochemical cell, including the condition of the electrodes and the membrane, may be determined by measuring the voltage required to provide a given current. An increase in the required voltage over time indicates that the condition of the cell may be worsening, with a high voltage indicating a cell that requires maintenance or replacement.

The controller may be arranged to record data relating to the operation and performance of each cell and/or the assembly as a whole. The controller may be arranged to provide a signal alerting a user to a change in the condition of an electrochemical cell in the assembly, in particular when the condition of a cell is becoming worse, indicated by an increase in the voltage required to be applied to the said cell, as noted above. Other operating parameters of the assembly may also be monitored and stored, for example water flow rate, water volume, pH and operating time. The controller may communicate with a remote server, to allow the condition and operation of the assembly to be monitored.

In a further aspect, the present invention provides a method for the production of ozone by the electrolysis of water, the method comprising:

providing an assembly as hereinbefore described; supplying an electrical current to the first and second electrodes of each electrochemical cell; and

providing water to each electrochemical cell assembly of the assembly. In the method of the present invention, water is provided to the

electrochemical cell assembly in the housing. The water is ozonated, that is provided with a concentration of ozone, under the action of the electrochemical cell. Water ozonated in this way finds use in a range of applications, includingdisinfection and sanitisation.

In a still further aspect, the present invention provides the use of an assembly as hereinbefore described in the production of ozone by the electrolysis of water.

Embodiments of the present invention will now be described, by way of example of only, having reference to the accompanying drawings, in which: Figure 1 is a longitudinal cross-sectional view of an assembly according to one embodiment of the present invention;

Figure 2 is a cross-sectional view of the assembly of Figure 1 along the line II - II in Figure 1 ;

Figure 3 is a further cross-sectional view of the assembly of Figure 1 along the line III - III of Figure 1 ;

Figure 4 is a perspective exploded view of an electrochemical cell for use in the assembly of Figure 1 ; and

Figure 5 is a cross-sectional view of an alternative embodiment of an electrochemical cell for use in the assembly of Figure 1. The terms 'upper' and 'lower' as used herein are with reference to the orientation of the assembly as shown in the figures and do not necessarily indicate the particularly orientation of the components when in use.

Turning to Figure 1 , there is shown an electrochemical cell assembly, generally indicated as 2. The assembly 2 comprises a housing assembly 4 having an inlet end 4a and an outlet end 4b. The housing assembly 4 comprises a generally cylindrical central housing 6 and a first end housing portion 8 and a second end housing portion 10. Each end housing portion 8, 10 comprises a generally cylindrical portion 8a, 10a, which extends over the respective end region of the central housing portion 6 and provides a fluid-tight seal thereto. Each end housing portion 8, 10 further comprises a frusto-conical portion 8b, 10b extending from the respective cylindrical portion 8a, 10a, and from which a conduit 8c, 10c extends. In the arrangement shown in Figure 1 , the conduit 8c provides an inlet for fluid to be treated and the conduit 10c provides an outlet for ozonated fluid.

A support assembly 20 is disposed within the central housing 6 and located towards the inlet end 4a of the housing assembly 4. The support assembly 20 comprises two support members 22a, 22b arranged perpendicular to each other in the form of a cross. Each support member 22a, 22b is formed with a cross-sectional profile that tapers in the upstream direction, that is towards the inlet end 4a of the housing assembly 4. The support assembly 20 further comprises a plurality of support arms 24.

Each support arm extends from the support members 22a, 22b in the downstream direction, that is towards the outlet end 4b of the housing assembly 4. Each support arm is provided with an electrode cap 26 supporting the upstream end of a respective electrochemical cell assembly 100, as described in more detail below.

As shown in Figure 3, the assembly 2 comprises a total of seven

electrochemical cell assemblies 100, with one electrochemical cell assembly 100a being arranged centrally and extending along the central longitudinal axis of the housing assembly 4 and six electrochemical assemblies 100b being arranged equidistantly around the central cell assembly 100a in a circular pattern.

A conductor assembly 30 is contained within the support assembly 20 and comprises a plurality of cables 32 for supplying an electrical current to each electrochemical cell assembly 100. Each electrochemical cell assembly 100 has a respective conductor connected to the cables 32, as indicated by dotted lines in Figure 1. Each electrochemical cell assembly 100 is connected to a pair of cables 32 providing a feed and return path for the electrical supply to the cell. The cables 32 extend through the central housing 6 and terminate at an electrical socket 40 as shown in Figure 2, by which the assembly 2 may be connected to a suitable controller and an electrical supply. Turning to Figure 4, there is shown an exploded view of one embodiment of an electrochemical cell assembly for use in the assembly of Figures 1 to 3. The electrochemical cell assembly, generally indicated as 100, comprises a generally cylindrical, hollow support member 102, from which extend upper and lower support members 104 and 106. The support member 102 is mounted in the cap 26 of a respective support arm 24. The conductor connecting the electrochemical cell assembly 100 to the respective cables 32 extends through the hollow support member 102.

Each of the upper and lower support members comprises a support body 104a, 106a engaging with and extending within the open end of the support member 102, and an elongate, tapered electrode holder 104b, 106b extending in the downstream direction from the respective support body 104a, 106a. The tapered electrode holders 104b, 106b act to hold an electrode assembly 120 therebetween. The electrode assembly 120 comprises a first electrode body 122a and a second electrode body 122b (not visible in Figure 4). Each electrode body 122a, 122b 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. A semi-permeable or proton exchange membrane 124 extends between the first and second electrode bodies 122a, 122b and is in contact with a major surface of the electrode body. The membrane 124 preferably contacts the growth face of the electrode bodies 122a, 122b. The membrane 124 is formed from Nafion ^® Type N117. As shown in Figure 4, the membrane 8 extends beyond the edges of each electrode body 122a, 122b.

The major surface of each electrode body 122a, 122b not covered by the membrane 124, that is the nucleation face of the electrode body, is provided with a respective conductor having a conductor portion, in the form of a layer of an electrically conductive material, in particular a first layer of Titanium (Ti), and a second layer of an alloy of Copper (Cu) and Silver (Ag). Each layer extends along a major portion of the length of the electrode body 122a, 122b. An edge portion of each electrode body is preferably not covered by the electrically conductive layer and is exposed.

The layers of electrically conductive material are applied to each electrode body by sputter coating. The layer of electrically conductive material is

approximately 5000 nm in thickness. The conductor further comprises an elongate connector terminal 126 soldered to each layer of electrically conductive material on each electrode body 122a, 122b. A cable 128 is soldered to the upstream end of each connector terminal 126, to provide an electric current to the respective electrode body 122a, 122b. Each cable 128 extends through the hollow support member 102 and is connected to a respective cable 32 of the conductor assembly 30, as shown in Figure 1.

The exposed surface of each layer of electrically conductive material is coated in a layer of electrically insulating material, in particular Silicon Nitride (S13N4) . The layer of electrically insulating material is applied to the layer of electrically conductive material by sputter coating and is approximately 1000 nm in thickness.

A layer of thermosetting hydrophobic resin is provided on each layer of electrically insulating material. The resin is a polyester resin or an epoxy resin. The resin layer is from 1 to 3 mm thick.

The layer of electrically insulating material may be omitted, in which case the layer of resin is provided directly onto the surface of the layer of electrically conductive material. However, it has been found that the resin adheres more readily to the metallised coatings after the connector terminals have been soldered to the respective layer of conductive material.

A portion of resin 130 is applied to the soldered joint between the cable 128 and the conductor terminal 126.

In use of the electrochemical cell assembly 2, water is caused to flow through the housing from the inlet end 4a to the outlet end 4b in the direction indicated by the arrow A in Figure 1. The water flows through the support assembly 20 and over and around the electrochemical cell assemblies 100.

When an electrical current is applied by way of the conductor assembly from a suitable source of electrical power, one of the electrode bodies 122a, 122b operates as the anode and the other as the cathode, depending upon the polarity of the supplied current. Ozone is produced at the edges of the electrode body 122a, 122b of the anode at the interface between the electrode body 122a, 122b, the membrane 124 and the surrounding water. In operation, the polarity of the cell is periodically reversed to prevent the accumulation of deposits, such as calcium, on the electrode bodies.

Turning again to Figure 4, there is a preferred form of an electrode body for use in the electrode assembly of the present invention. The electrode body 122a, 122b is elongate, having a length at least twice its width. The electrode body 122a, 122b has a longitudinal axis X - X and comprises a plurality of first body portions 134. Each of the first body portions 134 has a first width w measured from the longitudinal axis X - X to the edge of the electrode body 122a, 122b perpendicular to the longitudinal axis, as indicated in Figure 4. The electrode body 122a, 122b further comprises a plurality of second body portions 136. Each of the second body portions 136 has a second width w ² measured from the longitudinal axis X - X to the edge of the electrode body 122a, 122b perpendicular to the longitudinal axis, as indicated in Figure 4. The second width w ² is greater than the first width w ¹ . For example, for an electrode body having a total length of 40 mm, the width w ² may be 3 mm and the width w 1.5 mm.

The electrode body 122a, 122b has the first body portions 134 and the second body portions 136 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 134, 136 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 134, 136 on the opposite side of the longitudinal axis, that the first and second portions 134, 136 on one side of the axis are opposite respective first and second portions 134, 136 on the other side of the axis. The electrode body 122a, 122b is symmetrical about the longitudinal axis X - X. This castellated form for the electrode bodies 122a, 122b has been found to be particularly efficient in the formation of ozone.

The first and second body portions 134, 136 are shown in Figure 4 to have generally rectangular configurations, with the edges of the body portions being straight. Alternatively, the edges of the body portions 134, 136 may be curved. The corners of the body portions 134, 136 may be rounded.

Turning to Figure 5, there is shown a cross-sectional view of an

electrochemical cell according to an alternative embodiment. The electrochemical cell, generally indicated as 202, comprises a first electrode assembly 204 having an electrode body 204a and a second electrode assembly 206 having an electrode body 206a. Each electrode body 204a, 204b 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.

A semi-permeable proton exchange membrane 208 extends between the first and second electrode assemblies 204, 206 and is in contact with a major surface of the electrode body 204a, 206a of each electrode assembly 204, 206. The membrane 208 preferably contacts the growth face of the electrode bodies 204a, 206a. The membrane 208 is formed from a material that allows for the polarity of the cell to be reversed, in particular Nafion ^® type N1 17. As shown in Figure 5, the membrane 208 extends beyond the edge of each electrode body 204a, 206a.

The major surface of each electrode body 204a, 206a not covered by the membrane 208, that is the nucleation face of the electrode body, is provided with a respective first layer 210a, 212a of an electrically conductive material, in particular a layer of Titanium (Ti), and a second layer 210b, 212b 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 Figure 5, an edge portion 214a, 214b of each electrode body is not covered by the electrically conductive layer 210a, 210b, 212a, 212b and is exposed. The layers of electrically conductive material 210, 212 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 μηι.

A Copper cable connector terminal 216 is soldered to each layer 210b, 212b of the Copper-Silver electrically conductive material.

The exposed surface of each layer of electrically conductive material 210, 212 is coated in a layer of electrically insulating material 218, 220, in particular Silicon Nitride (S13N4) . The layer of electrically insulating material 218, 220 is applied to the layer of electrically conductive material 210, 212 by sputter coating and has a thickness of up to 1000 nm. The layer of electrically insulating material overlaps the layers 210b, 212b of electrically conducting material, as shown in Figure 5.

A layer of thermosetting hydrophobic resin 222, 224 is provided on each layer of electrically insulating material 218, 220. The resin is a polyester resin or an epoxy resin. The layer 222, 224 of resin material has a thickness between 1 mm and 3 mm.

The layer of electrically insulating material 218, 220 may be omitted, in which case the layer of resin 222, 224 is provided directly onto the surface of the layer of electrically conductive material 210b, 212b.

Current feed cables 226 are connected to respective cable connector terminals 216 by soldering, to provide an electric current to the respective layers of electrically conductive material 210, 212 and to the electrode body 204a, 206a.