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.

WO 93/16001 discloses an ozone generator having an electrode formed of a mass of helical windings.

KR 20010091796 discloses a system for treating dyeing wastewater using plasma and ozone. A fluid treatment device is shown and described in US 2009/0038944.

WO 2005/075357 discloses a water treatment apparatus using a voltaic cell circuit. An ozone generator is disclosed in US 4,035,657.

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 arrangement could provide an efficient operation in the electrolysis of a stream of water to produce ozone and ozonate the water. It would also be advantageous if the arrangement could also be simple to assemble and require a low number of parts.

According to the present invention, in a first aspect there is provided an assembly for use in the production of ozone from water, the assembly comprising: an electrochemical cell assembly;

a support assembly supporting the electrochemical cell assembly, the support assembly comprising:

an outer support member having a cavity therein;

a first inner support member extending inwards from the outer support member within the cavity, the first inner support member having a portion; and

a second inner support member extending inwards from the outer support member within the cavity, the second inner support member having a portion;

wherein the portion of the first inner support member opposes the portion of the second inner support member;

wherein the electrochemical cell assembly is held between the opposing portions of the first and second inner support members; and wherein the electrochemical cell assembly comprises a first electrode, a second electrode, and a semi-permeable membrane disposed between the first and second electrodes.

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.

The assembly of the present invention is easy to assemble and requires only a small number of components. The assembly of the present invention comprises a support assembly comprising an outer support member. The outer support member has or defines a cavity therein. An electrochemical cell assembly is supported within the cavity, as described in more detail hereinafter. In use, water to be ozonated is caused to pass through the cavity in the outer support member and to contact the electrochemical cell assembly therein.

The outer support member may have any suitable form that defines a cavity therein and allows an electrochemical cell assembly to be supported within the cavity. In one preferred embodiment, the outer support member is arranged to be disposed within a conduit through which water to be treated is to be passed in use. The assembly is preferably held within the conduit in use by the action of friction between the outer surface of the outer support member and the inner surface of the conduit. In particular, the outer support member is preferably arranged such that at least two portions of the outer surface of the outer support member contact the inner surface of the conduit, preferably at least two substantially opposing portions. In one preferred arrangement, the outer surface of the outer support member comprises a circumferential portion that contacts a circumferential band of the inner surface of the conduit. To provide additional support within the conduit, all or substantially all of the outer surface of the outer support member is arranged to contact the inner surface of the conduit in which the assembly is to be installed.

As many conduits are tubular having a circular cross-section, the outer support member is preferably formed to fit within a conduit having a circular cross- section and retain the entire assembly within the conduit. In one preferred embodiment, the outer surface of the outer support member has one or more curved portions having a radius of curvature equal to that of the inner surface of the conduit in which the assembly is to be installed. In one particular preferred embodiment, the outer support member has a cylindrical outer surface. More preferably, the outer support member is tubular, especially tubular having a circular cross-section.

The outer support member is preferably elongate, that is has a ratio of its length to its width of greater than 1.0. A ratio of greater than 1.5 is preferred, more preferably at least 2. The outer support member is preferably at least the same length as the length of the electrochemical assembly held therein. If two or more electrochemical cell assemblies are held within the same support assembly, the outer support member is preferably at least as long as the combined lengths of the electrochemical cell assemblies. In this way, the cell assemblies may be fully protected by the outer support member.

The support assembly further comprises a first inner support member and a second inner support member. The first inner support member has a portion. The second inner support member has a portion which opposes the portion of the first inner support member. The electrochemical cell assembly is held between the opposing portions of the first and second inner support members. The opposing portions of the first and second inner support members may be at any suitable position on the respective inner support member, provided that the electrochemical cell assembly can be held between the opposing portions.

Each of the first and second inner support members extends inwards from the outer support member within the cavity of the outer support member. In one preferred embodiment, the first inner support member extends from a first position on the outer support member and the second inner support member extends from a second position on the outer support member. The first and second positions on the outer support member are preferably opposite each other.

The opposing portions of the first and second inner support members are each preferably a portion at the end of the respective inner support member.

The first and second inner support members may have any suitable shape. In one preferred embodiment, one or both of the first and second inner support members have a stem, the or each stem being attached at its proximal end to the outer support member and having a distal end. The or each stem preferably extends inwards from the outer support member in the direction of the centre of the cavity. In one particularly preferred embodiment, the or each stem is provided with a support portion at its distal end. In one embodiment, the stem and its support portion together are generally T shaped. In a preferred embodiment, the stem and its support portion together are generally Ύ' shaped. In a particularly preferred embodiment, both the first and the second inner support members are provided with a stem as hereinbefore described, each stem having a support portion at its distal end, as also already described. The support portion of the first inner support member opposes the support portion of the second inner support member, with the electrochemical call assembly being held between the two opposing support portions.

To assist in assembling the assembly, in particular to assist in locating the electrochemical cell assembly between the opposing portions of the first and second inner support assemblies, the outer support member and/or one or both of the first and second inner support members may be resilient. The resilience of the outer support member and/or one or both of the inner support members preferably biases the opposing portions of the inner support members together, thereby holding the electrochemical cell assembly securely therebetween.

Preferably, at least the outer support member is resilient. More preferably, the outer support member is resilient and formed whereby two opposing forces may be applied to the outer surface of the outer support member, that is the outer support member may be squeezed, causing the outer support member to deform, in turn causing the inner support members to move relative to each other such that the opposing portions of the inner support members move apart. Releasing the outer support member causes the opposing portions of the inner support members to move towards each other. In this way, the opposing portions of the inner support members are urged towards each other by the resilient bias of the outer support member.

A further advantage of having the outer support member resilient is that its resilient bias can be used to hold the assembly more securely within the conduit, for example to resist high water flowrates in use and prevent the assembly from being dislodged. This in turn allows the assembly to be held more securely by the use of friction between the outer surface of the outer support member and the inner surface of the conduit. This helps to avoid the need to use other fixing means to hold the assembly within the conduit. Suitable forms for the outer support member are described above. In one preferred embodiment, at least one, more preferably both, of the first and second inner support members extend the full length of the outer support member. In this way, the inner support members provided additional protection for the electrochemical cells held in the support assembly.

The components of the support assembly may be formed as separate components, which act together as a unit. More preferably, the outer support member and the first and second inner support members are formed as a single piece. This allows the support assembly to be formed as a whole, for example by moulding or by extrusion.

The support assembly may be formed from any suitable material that is resistant to the components present in the water stream being treated and to the presence of ozone is significant concentrations. Preferred materials are polymers, in particular polyolefins, such as polyethylene and polypropylene, and polyvinyl chloride (PVC). Other materials such as fluorinated polymers, are particularly suitable for this application due to their enhanced resistance to oxidation from the ozone generated within the fitting. One particularly preferred material for the support assembly is polypropylene.

The support assembly holds an electrochemical cell assembly arranged in the cavity within the outer support member. In operation, a fluid, in particular water, is caused to flow through the housing and over the electrochemical cell assembly in the cavity, so as to contact the electrochemical cell, thereby to produce ozone, as described in more detail hereinafter. The assembly of the present invention may comprise a single electrochemical cell assembly within the outer support member. Alternatively, a plurality of electrochemical cell assemblies may be retained within the cavity of the support assembly. The number of cell assemblies may be selected 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 7 electrochemcial cell assemblies. Each electrochemical cell assembly 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 cavity within the outer support member, still more preferably substantially parallel to, in particular co-axial with, the longitudinal axis of the outer support member. In this way, each electrode extends substantially parallel to the direction of flow of water through the support assembly. In one embodiment, the assembly is oriented such that the outer housing has an inlet end and an outlet end, the cavity being open at both the inlet end and the outlet end, with the water being processed flowing through the cavity from the inlet end to the outlet end. Preferably, the electrochemical cell assembly is arranged whereby its elongate electrodes extend in a downstream direction, that is the direction of water flowing from the inlet end to the outlet end of the outer housing. In this way, the support assembly may be arranged to direct and distribute the flow of water past and over the electrochemical cell assembly.

The electrochemical cell assembly comprises a first electrode and a second electrode. A semi-permeable membrane is disposed and separates the two electrodes. Each electrode may have any suitable shape or form.

In some preferred embodiments, the electrodes are 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 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 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 preferably 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. In some preferred embodiments, 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 electrochemical cell assembly 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 electrodes in the assembly of 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.

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. Each electrode of the electrochemical cell assembly 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 chemical vapour deposition (CVD) to form the diamond material, 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, if employed. 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 of electrically conductive material as hereinbefore described, a layer of insulating material as hereinbefore described extending over the conductive 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 known in the art and 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 electrodes, 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 the surrounding 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

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. The semi-permeable membrane may terminate at the edges of the electrode bodies. However, it is preferred that the membrane extends beyond the electrode bodies 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 terminal. Again, this connection is preferably formed by soldering.

In a further aspect, the present invention provides an electrochemical assembly for the production of ozone from water, the electrochemical assembly comprising:

a housing;

an electrochemical cell assembly disposed within the housing;

a support assembly disposed within the housing and supporting the electrochemical cell assembly, the support assembly comprising:

an outer support member having a cavity therein; a first inner support member extending inwards from the outer support member within the cavity, the first inner support member having a portion; and

a second inner support member extending inwards from the outer support member within the cavity, the second inner support member having a portion;

wherein the portion of the first inner support member opposes the portion of the second inner support member;

wherein the electrochemical cell assembly is held between the opposing portions of the first and second inner support members; and wherein the electrochemical cell assembly comprises a first electrode, a second electrode, and a semi-permeable membrane disposed between the first and second electrodes. The housing of the electrochemical assembly may be any suitable housing or conduit through which water may be passed to contact the electrochemical cell assembly. In one preferred arrangement, the housing is a conduit, such as a pipe. In this way, the electrochemical cell assembly may be installed in pipework using known fittings, allowing water flowing through the pipework to pass through the housing and contact the electrochemical cell assembly. 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 sized in order to match the outer diameter of a standard pipe, for example 32 mm, 25 mm, 22 mm, 18 mm or 15 mm.

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.

As noted above, the electrochemical cell assembly is connected to a supply of electrical current using a suitable conductor. In one preferred arrangement, the housing is provided with a suitable port through which one or more conductors, such as one or more cables, extend from within the housing to the exterior, for connection to a suitable electrical supply. Other arrangements of a conductor assembly for allowing the electrochemical cell assembly within the housing to be connected to an external electrical supply may also be employed.

In a still further aspect, the present invention the present invention provides an assembly for use in the production of ozone from water, the assembly comprising: an electrochemical cell assembly comprising a first electrode, a second electrode, and a semi-permeable membrane disposed between the first and second electrodes;

a housing, the electrochemical cell assembly being disposed within the housing;

wherein the semi-permeable membrane extends beyond the edges of the first and second electrodes and bears upon an inner surface of the housing, thereby holding the electrochemical cell assembly within the housing.

The assembly of this aspect of the invention is particularly simple to construct and install. The assembly relies upon the membrane bearing upon the inner surface of the housing to hold the electrochemical cell assembly within the housing, most preferably centrally within the housing. In this respect, the material of the membrane is flexible and resilient and holds the electrochemical cell assembly in place, without the need for an additional support structure.

Details of the electrochemical cell assembly and the housing are as hereinbefore described.

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 assembly; 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, including disinfection 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 perspective side view of an electrochemical assembly for the production of ozone from water according to one embodiment of the present invention;

Figure 2 is a longitudinal cross-sectional view of the assembly of Figure 1 ;

Figure 3 is an end view of the assembly of Figure 1 viewed in the direction of arrow A;

Figure 4 is a perspective view of a support assembly for use in the assembly of Figure 1 ; Figure 5 is a perspective view of the support assembly of Figure 4 with an electrochemical cell assembly in position within the support assembly;

Figure 6 is a cross-sectional view of one embodiment of an electrochemical cell for use in the assembly of Figure 1 ; Figure 7 is a plan view of an electrode for use in the assembly of Figure 1 ;

Figure 8 is an end view of an embodiment of an assembly according to an alternative aspect of the present invention; and

Figure 9 is a cross-sectional view of the assembly of Figure 1 with a cable assembly in place.

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 in the form of a cylindrical pipe 4 having a first pipe end portion 6, a central pipe portion 8 and a second pipe end portion 10. The central pipe portion 8 has a port 12 opening into the interior of the pipe. The port 12 is threaded internally to receive a water-tight cap and provides a passage for electrical cables to extend into the housing.

The assembly 2 comprises a support assembly 14 disposed within the second pipe end portion 10. The support assembly 14 holds an electrochemical cell assembly 16, as shown more clearly in Figures 2 and 3.

As can be seen in Figure 3, the electrochemical cell assembly 16 comprises a first or upper electrode 18 and a second or lower electrode 20. The electrodes 18, 20 are separated by a semi-permeable membrane 22. The support assembly 14 is shown in Figure 4. The support assembly 14 comprises a cylindrical, tubular outer support member 30 having a cylindrical cavity 32 therein. The cavity 32 is open at each end of the outer support member 30. In operation, the fluid to be processed passes through the outer support member 30 along the cavity 32. A pair of opposing inner support members 34a and 34b extends inwards into the cavity 32 from opposing sides of the outer support member 30. Each of the inner support members 34a, 34b comprises a stem 36a, 36b extending generally radially inwards from the outer support member 30. The inner end of each stem 36a, 36b is provided with a support portion 38a, 38b. Each support portion 38a, 38b is generally V-shaped and together with the respective stem 36a, 36b forms a Y-shaped support member. As shown in Figure 5, the electrochemical cell assembly 16 is held between the opposing support portions 38a, 38b of the inner support members 34a, 34b. In the embodiment shown in the figures, the electrochemical cell assembly 16 is a friction fit between the two inner support members 34a, 34b. The support assembly 14 is formed from a resilient material. For example, the support assembly 14 may be moulded or extruded from a suitable polymer. The support assembly 14 may be compressed by applying a force to opposing sides of the outer support member 30 along a line perpendicular to the line extending through the first and second inner support members 34a, 34b. This compression force is indicated by the arrows F in Figure 5. This action causes the outer support member 30 to distort and the inner support members 34a, 34b to move apart. This action allows the electrochemical cell assembly 16 to be inserted into the support assembly 14 or removed therefrom. Turning to Figure 6, there is shown a cross-sectional view of an electrochemical cell according to one embodiment for use in the assembly of the present invention. The electrochemical cell, generally indicated as 102, comprises a first electrode assembly 104 having an electrode body 104a and a second electrode assembly 106 having an electrode body 106a.

Each electrode body 104a, 104b 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 108 extends between the first and second electrode assemblies 104, 106 and is in contact with a major surface of the electrode body 104a, 106a of each electrode assembly 104, 106. The membrane 108 preferably contacts the growth face of the electrode bodies 104a, 106a. The membrane 108 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 6, the membrane 108 extends beyond the edge of each electrode body 104a, 106a.

The major surface of each electrode body 104a, 106a not covered by the membrane 108, that is the nucleation face of the electrode body, is provided with a respective first layer 1 10a, 1 11 a of an electrically conductive material, in particular a layer of Titanium (Ti), and a second layer 110b, 1 11 b 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 6, an edge portion 114a, 114b of each electrode body is not covered by the electrically conductive layer 110a, 1 10b, 11 1a, 1 12b and is exposed. The layers of electrically conductive material 110, 11 1 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 1 16 is soldered to each layer 110b, 1 12b of the Copper-Silver electrically conductive material.

The exposed surface of each layer of electrically conductive material 110, 1 12 is coated in a layer of electrically insulating material 1 18, 120, in particular Silicon Nitride (S13N4). The layer of electrically insulating material 1 18, 120 is applied to the layer of electrically conductive material 1 10, 1 12 by sputter coating and has a thickness of up to 1000 nm. The layer of electrically insulating material overlaps the layers 110b, 112b of electrically conducting material, as shown in Figure 6. A layer of thermosetting hydrophobic resin 122, 124 is provided on each layer of electrically insulating material 118, 120. The resin is a polyester resin or an epoxy resin. The layer 122, 124 of resin material has a thickness between 1 mm and 3 mm. The layer of electrically insulating material 118, 120 may be omitted, in which case the layer of resin 122, 124 is provided directly onto the surface of the layer of electrically conductive material 110b, 112b.

Current feed cables 126 are connected to respective cable connector terminals 116 by soldering, to provide an electric current to the respective layers of electrically conductive material 110, 1 12 and to the electrode body 104a, 106a.

Turning to Figure 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 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 measured from the longitudinal axis X - X to the edge of the electrode body 202 perpendicular to the longitudinal axis, as indicated in Figure 7. 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 ² measured from the longitudinal axis X - X to the edge of the electrode body 202 perpendicular to the longitudinal axis, as indicated in Figure 3. 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 202 of Figure 7 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. The first and second body portions 204, 206 are shown in Figure 7 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.

Turning to Figure 8, there is shown an electrochemical cell assembly, generally indicated as 302. The assembly 302 comprises a housing in the form of a cylindrical pipe 304 having a port 306 opening into the interior of the pipe. The port 306 is threaded internally to receive a water-tight cap and provides a passage for electrical cables to extend into the housing.

The assembly 302 comprises an electrochemical cell assembly 310 comprising a first or upper electrode 312 and a second or lower electrode 314. The electrodes 312, 314 are separated by a semi-permeable membrane 316. The membrane 316 is formed from a flexible, resilient material, such as Nafion® type 1 17. The membrane 316 extends radially outwards from the sides of the electrodes 312, 314 to the pipe 304, where it contacts the inner wall of the pipe. The membrane acts to support the electrochemical cell assembly 310 and retain it within the pipe 304.

Turning to Figure 9, there is shown a cross-sectional view of the electrochemical cell assembly with a cable assembly in place for providing electrical power to the electrochemical cell assembly. As described above, the assembly 2 comprises a housing in the form of a cylindrical pipe 4 having a first pipe end portion 6, a central pipe portion 8 and a second pipe end portion 10. The central pipe portion 8 has a port 12 opening into the interior of the pipe. The port 12 is threaded internally to receive a water-tight cap 50. The cap 50 has a central bore 52 for receiving cables 54. The cables 54 extend through the central bore 52 in the cap 50 and into the interior of the housing, where they are connected to the electrochemical cell assembly 16, as described above. The cap 50 is provided with a seal 56 within the bore 52, to provide a water-tight seal around the cables 54.