Electrolyser

Abstract

A core structure 1 for a capillary fed electrolyser comprising a first electrolyte chamber 9 having first 10 and second 12 opposing surfaces each with an array of pores, an inlet 3 and an outlet 17, a

Description

Field of the Invention The present invention relates to an electrolyser. The invention is particularly suitable, but by no means limited, for use during the electrolysis of carbon dioxide during a carbon dioxide recycling procedure. Background to the Invention There is now a broad global consensus that industry / governments ought to reduce carbon emissions, particularly so in the case of greenhouse gas emissions such as carbon dioxide, to meet ever more stringent sustainability and ecological goals. Many nations have agreed upon aiming for net-zero carbon emissions within the next thirty years in an attempt to limit global warming to 1.5 °C above pre-industrialised levels. Meeting such goals based on current technologies is proving challenging. For instance, the UK’s Department for Energy Security &Net Zero estimates that in 2022 the UK alone had total greenhouse gas emissions of around 417 million tonnes carbon dioxide equivalent (MtCO2e), with around 332 Mt of those emissions being carbon dioxide itself (these values are inclusive of removals of carbon dioxide from the atmosphere by carbon sinks). A current method to reduce carbon emissions is carbon capture and storage (CCS). CCS is a three-step process, which involves (1) capturing carbon dioxide produced by power generation or other industrial activities, such as steel or cement manufacturing; (2) transporting the captured carbon dioxide; and (3) storing the transported carbon dioxide in geological features, often deep underground. However, there are significant costs associated with CCS, both for industry in terms of the capital investment required, and well as for taxpayers (CCS schemes are often government subsidised in view of the high capital expenses associated with introduces CCS procedures). An alternative method to reduce carbon emissions is in carbon capture and utilisation (CCU) processes. CCU processes convert carbon dioxide captured during industrial processes into other useful products, such as feedstocks for use in subsequent procedures. One of the steps in a CCU process includes the electrochemical reduction of carbon dioxide into a reduced chemical species by electrolysis, such species (e.g., methanol and carbon monoxide) being feedstocks for use in subsequent procedures. For use in CCU processes or otherwise, current electrolysers, i.e., the apparatus used in an electrolysis process (sometimes referred to as an “electrolysis cell”), typically comprise an anode, a cathode, membrane components (e.g., for separating the anode and the cathode), means for supplying a direct current, an electrolyte through which the direct current is applied, and a reference electrode. However, such apparatus suffers from the use of expensive membrane components, and from the expense and inconvenience of using reference electrodes. Moreover, current electrolysers often have a poor conversion rate as, well as poor selectivity for carbon monoxide production. There is therefore a desire for an improved electrolyser which addresses at least some of the above problems. Summary of the Invention The present invention is set out in the appended independent claims. Optional features are set out in the appended dependent claims. According to a first example a core structure for forming a capillary electrolyser is provided. The core structure may comprise a first chamber for receiving an electrolyte containing a fluid to be electrolysed. The first chamber may comprise a first surface having a first array of pores therethrough, for interfacing with a first electrode external to the first chamber, against the first surface and extending across the first array of pores; and a second surface having a second array of pores therethrough, for interfacing with a second electrode external to the first chamber, against the second surface and extending across the second array of pores; wherein the first surface and the second surface are opposingly facing; and wherein the pores of the second array are larger than the pores of the first array. The core structure may further comprise an inlet in communication with the first chamber for supplying the fluid to be electrolysed; and an outlet in communication with the first chamber for outputting a species formed by electrolysis of said fluid. Beneficially, by virtue of the difference in pore sizes between the first and second arrays, the core structure is able to promote the formation of reduced species over oxidised species during an electrolysis procedure, thereby improving the efficiency of the electrolysis process. Optionally, a second chamber may be fluidically disposed between the inlet and the first chamber, for providing a reservoir for the electrolyte. In addition, a plurality of channels may extend from the second chamber to the first chamber, the plurality of channels being arranged substantially across a receiving side of the first chamber to promote laminar flow of electrolyte / fluid to be electrolysed into the first chamber. Optionally, to further promote the formation of reduced species during electrolysis, the pores of the second array may be greater in number than the pores of the first array. Optionally, a second outlet in communication with the first chamber may be provided for enabling a flow of the electrolyte through the first chamber. Optionally, the pores of the first array may have a first radius and the pores of the second array may have a second radius. A ratio of the second radius relative to the first radius may be in the range of 1.5:1 to 3:1. For example, the ratio of the second radius relative to the first radius may be 2:1. Optionally, the first radius may be in the range of 0.005 mm to 0.5 mm, and the second radius may be in the range of 0.01 mm to 1 mm. For example, the first radius may be in the range of 0.05 mm to 0.5 mm, and the second radius may be in the range of 0.1 mm to 1 mm. Optionally, the core structure may be formed as a unitary structure for mechanical robustness. Optionally, the core structure may also comprise at least one means for securing the core structure to another component. According to another example, an electrolyser may comprise: a core structure; a first electrode external to the first chamber, against the first surface of the core structure and extending across the first array of pores; and a second electrode external to the first chamber, against the second surface of the core structure and extending across the second array of pores. Beneficially, the electrolyser promotes the formation of reduced species over oxidised species during an electrolysis procedure. Optionally, the electrolyser may further comprise a first cover plate and a second cover plate; wherein the first cover plate may be arranged to cover the first surface of the core structure and the first electrode, and the second cover plate may be arranged to cover the second surface of the core structure and the second electrode. Optionally, the first cover plate may incorporate a first cover plate chamber surrounding the first electrode. Optionally, the second cover plate may incorporate a second cover plate chamber surrounding the second electrode. In one option, the first electrode may be an anode, and the second electrode may be a cathode. Optionally, the first cover plate may further comprise: an inlet in communication with the first cover plate chamber for receiving a further supply of the electrolyte; a first outlet in communication with the first cover plate chamber for outputting the further supply of the electrolyte; and a second outlet in communication with the first cover plate chamber for outputting an anode-formed species formed by electrolysis of said fluid. Optionally, the second cover plate may further comprise: a first outlet in communication with the second cover plate chamber for outputting overflow electrolyte from the first chamber of the core structure; and a second outlet in communication with the second cover plate chamber for outputting a cathode- formed species formed by electrolysis of said fluid. Optionally, the second cover plate chamber may define a serpentine path extending between the first outlet of the second cover plate chamber and the second outlet of the second cover plate chamber for supporting the cathode. According to another example, a stacked electrolyser may comprise: a first core structure; a first first-electrode external to the first chamber of the first core structure, against the first surface of the first core structure and extending across the first array of pores of the first core structure; a first second-electrode external to the first chamber of the first core structure, against the second surface of the first core structure and extending across the second array of pores of the first core structure; a second core structure; a second first-electrode external to the first chamber of the second core structure, against the first surface of the second core structure and extending across the first array of pores of the second core structure; a second second-electrode external to the first chamber of the second core structure, against the second surface of the second core structure and extending across the second array of pores of the second core structure; a first cover plate arranged to cover the first second-electrode; a second cover plate arranged to cover the second second-electrode; and a coupling cover plate is arranged to cover the first first-electrode and the second first-electrode and to couple the first core structure and the second core structure in a back-to-back configuration. Beneficially, the manufacture of the stacked electrolyser is simplified (and potentially made more compact) by virtue of the coupling cover plate being shared by the first and second core structures on either side. Optionally, the first first-electrode and the second first-electrode may be anodes, and the first second-electrode and the second second-electrode may be cathodes. Optionally, the first cover plate may incorporate a first cover plate chamber, and the second cover plate may incorporate a second cover plate chamber, each surrounding the respective second electrodes, and wherein the first cover plate chamber and the second cover plate chamber may each further comprise: a first outlet in communication with the respective first cover plate chamber for outputting overflow electrolyte from the first chamber of the respective core structure; and a second outlet in communication with the respective first cover plate chamber for outputting a cathode-formed species formed by electrolysis of said fluid. Optionally, the first cover plate chamber and the second cover plate chamber may each define a serpentine path extending between the first outlet and the second outlet of the respective first cover plate chamber and the second cover plate chamber. Optionally, the coupling cover plate may incorporate two cover plate chambers, each cover plate chamber surrounding the respective first electrodes, and wherein each cover plate chamber may further comprise: an inlet in communication with the respective cover plate chamber for receiving a further supply of the electrolyte; a first outlet in communication with the respective cover plate chamber for outputting the further supply of the electrolyte; and a second outlet in communication with the respective cover plate chamber for outputting an anode-formed species formed by electrolysis of said fluid. Advantageously, electrolysers according to preferred embodiments of the present invention have no membrane between the or each core structure and either of the electrodes adjacent to the or each core structure. Optionally, the electrolysers may further comprise a gas diffusion layer disposed against the or each second electrode to beneficially assist in the even distribution of gases which are produced during electrolysis procedures, as well as protect electrodes from corrosion. According to an example, a method for performing electrolysis upon a fluid contained within an electrolyte using the electrolyser may comprise supplying the fluid contained within the electrolyte to the electrolyser; applying a current to the electrodes; and collecting a species formed by electrolysis of said fluid. Optionally, the cathode may include a substrate having a material thereon, wherein the material is selected from a group which may comprise indium, tin, zinc, nickel, gallium, carbon, and a combination thereof, and wherein the substrate is selected from a group which may comprise copper, tin, indium, iron, nickel, cobalt, gold, platinum, titanium, niobium, tantalum, molybdenum, tungsten, zinc, gallium, carbon, and a combination thereof. Optionally, the material may include indium and the substrate may include indium. Optionally, the material may include indium and the substrate may include copper. Optionally, the substrate may be oxidised. Optionally, the material may be a nanoparticle. Optionally, the anode may include a nickel-based anode, a cobalt-based anodes, an iron-based anodes, or platinum-coated titanium anode. The anode may be mesh-like and / or porous. Each feature disclosed in this specification (which term includes the claims) and / or shown in the drawings may be incorporated in the invention independently (or in combination with) any other disclosed and / or illustrated features. In particular but without limitation the features of any of the claims dependent from a particular independent claim may be introduced into that independent claim in any combination or individually. Brief Description of the Drawings The invention will now be described by way of example only with reference to the attached figures in which: Figure 1a is a simplified schematic illustrating a core structure for forming a capillary electrolyser in a perspective view, showing a first surface having a first array of pores therethrough, for interfacing with a first electrode (e.g. an anode) of the electrolyser; Figure 1b illustrates an obverse perspective view of the core structure shown in Figure 1a, showing a second surface having a second array of pores therethrough, for interfacing with a second electrode (e.g. a cathode) of the electrolyser; Figure 1 c is a simplified schematic cross-section of the core structure of Figures 1a and 1b, across the surfaces shown in Figures 1a and 1b, showing that the pores of the second array are larger than the pores of the first array; Figure 2 is a schematic pseudo-transparent plan view of the core structure illustrated in Figure 1b showing both surfaces simultaneously; Figure 3a is a schematic plan view of the inside of a first cover plate for covering the first surface of the core structure and for containing the first electrode therein; Figure 3b is a schematic plan view of the outside of the first cover plate illustrated in Figure 3a; Figure 4a is a plan view of the inside of a second cover plate for covering the second surface of the core structure and for containing the second electrode therein; Figure 4b is a schematic plan view of the outside of the second cover plate illustrated in Figure 4a; Figure 5a is a simplified exploded side view of the components of an electrolyser according to a first example; Figure 5b is a simplified side view of the components of the electrolyser shown in Figure 5a when assembled; Figure 6 is a simplified cutaway of the first chamber showing an electrolysis procedure biased towards the second array relative to the first array; Figure 7 is a simplified exploded side view of the components of a stacked electrolyser according to a first example; Figure 8 is a simplified side view of the components of the stacked electrolyser shown in Figure 7 when assembled; and Figure 9 is a perspective view of a coupling cover plate for the stacked electrolyser. In the figures, like elements are indicated by like reference numerals throughout. Detailed Description of Preferred Embodiments The present embodiments represent the best ways known to the Applicant of putting the invention into practice. However, they are not the only ways in which this can be achieved. Electrolyser- Core Structure for Forming a Capillary Electrolyser To overcome disadvantages with current electrolysers, the present work discloses the use of a core structure for forming a capillary electrolyser, the core structure being sandwiched between an anode (and an associated anode cover plate) and a cathode (and an associated cathode cover plate). That is to say, in the present electrolyser, the anode and the cathode are each adjacent to a respective surface of the core structure. Before describing the complete electrolyser, an overview of the core structure will first be described with reference to Figures 1a, 1b and 1c. Figure 1a schematically illustrates, in perspective view, a core structure 1 for forming a capillary electrolyser according to one example, with Figure 1b schematically illustrating the core structure 1 from an obverse perspective view relative to Figure 1a (like reference signs are used across both Figures where appropriate). Figure 1c schematically illustrates core structure 1 projecting out of the plane of the page in cutaway view. The core structure 1 comprises a first chamber 9 for receiving an electrolyte (e.g. potassium hydroxide) containing a fluid (e.g. a gas such as carbon dioxide, or a liquid) to be electrolysed. The first chamber 9 comprises a first surface 10 having a first array of pores 11 therethrough, for interfacing with a first electrode (e.g. an anode, not shown) external to the first chamber 9, against the first surface 10 and extending across the first array of pores 11. The first chamber 9 also comprises a second surface 12 having a second array of pores 13 therethrough, for interfacing with a second electrode (e.g. a cathode, not shown) external to the first chamber 9, against the second surface 12 and extending across the second array of pores 13. The first and second arrays 11, 13 are each arranged over a two-dimensional area, for instance in a grid-like manner. As illustrated, the first surface 10 and the second surface 12 are opposingly facing. As will be described in more detail below, the electrolysis procedure takes place in the first chamber 9 against the first and second electrodes, via the first and second arrays of pores 11, 13. Notably, to bias the electrolysis process towards the second electrode, the pores of the second array 13 are larger than the pores of the first array 11. The core structure 1 also comprises an inlet 3 in communication with the first chamber 9 for supplying the fluid to be electrolysed, and an outlet 17 in communication with the first chamber 1 for outputting a species (e.g. carbon monoxide) formed by electrolysis of said fluid. It will appreciated that, with the exception of the arrays of pores 11,13 and the inlet(s) and outlet(s) as expressly described herein, the first chamber 9 is fluidically enclosed by walls on all sides. In the illustrated example shown in Figures 1a to 1c, the core structure 1 further comprises a second chamber 5 fluidically disposed between the inlet 3 and the first chamber 9, for providing a reservoir for the electrolyte. In such a configuration, a plurality of channels 7, sometimes referred to as “feeder capillaries”, may be arranged between the reservoir chamber 5 and the chamber 9 for conveying the electrolyte into chamber 9 to minimise any associated turbulence, and ideally achieve lam inar flow of the electrolyte (or the fluid to be electrolysed) through the first chamber 9. In the illustrated example, three channels 7-1, 7-2, 7-3 are arranged substantially across a receiving side of the first chamber 9 (i.e., the side of the first chamber 9 which is proximate to the inlet 3) to promote uniform distribution of the electrolyte into the chamber 9 with reduced turbulence, ideally in a laminar fashion. In one example, the feeder capillaries 7 may have a radius of 0.5 mm or 1 mm or values therebetween. In another example, the feeder capillaries 7 may have a diameter of 3 mm, and a length of 7 mm, although it will be appreciated that these dimensions may be adapted as appropriate. It may also be noted that the channels 7-1, 7-2, 7-3 may typically have a greater radius than those of the pores of the first and second arrays 11, 13 to allow for sufficient flow of the electrolyte (or the fluid to be electrolysed). In the illustrated example shown in Figures 1a to 1c, the core structure 1 further comprises a second outlet 15 in communication with the first chamber 9 for enabling a flow of the electrolyte through the first chamber 9. Figure 1c illustrates the “capillary” nature of the core structure 1, the capillary being formed by the inlet 3, the chamber 9, and the outlet 17 for outputting electrolysed species (and optionally also by the electrolyte reservoir 5, the channel(s) 7 fluidically interposed between reservoir 5 and chamber 9, and the outlet 15). According to one example, the electrolyte may contain the fluid to be electrolysed (for instance, carbon dioxide dissolved in potassium hydroxide electrolyte), and the electrolyte may be introduced into the first chamber 9 of the core structure 1 via the inlet 3 by use of a pump external to the core structure 1 (not shown), or by using other suitable apparatus. Alternatively, the electrolyte not containing the fluid to be electrolysed may be prefilled (e.g. a “static” quantity of electrolyte) within the first chamber 9 of the core structure 1 via the inlet 3, and the fluid to be electrolysed may be introduced into the core structure 1 via inlet 3 (for instance, carbon dioxide may be passed into the first chamber 9 via the inlet 3). Such introduction may also be achieved by use of an external pump (not shown), or by using other suitable apparatus. Also, the prefilled electrolyte may be refreshed by suppling fresh electrolyte via inlet 3. As mentioned above, and as illustrated in Figures 1a and 1b, the first chamber 9 has a first surface 10 having a first array 11 of pores extending therethrough and a second surface 12 having a second array of pores 13 extending therethrough, the respective arrays 11,13 being opposingly facing across a volume defined by the first chamber 9. In one example, e.g., when the core structure 1 is fabricated using a 3D printer (or die-casting), the distance D between the first array 11 and the second array 13 may be between 2 mm to 5 mm. In this case, the core structure 1 may be fabricated semi-transparently using a resin. In another example, e.g., when the core structure 1 is fabricated using a machine under Computer Numerical Control (CNC), the distance D between the first array 11 and the second array 13 may be between 0.5 mm to 5 mm. Moreover, the extent of the area occupied by each of the first and second arrays of pores 11,13 may, for example, be around 2.5 cm x 2.5 cm, although it will of course be appreciated that alternative areas of the arrays of pores 11, 13 may be used instead (e.g. around 5 cm x 5 cm, or larger). As described above, the first array of pores 11 is for interfacing with a first electrode (not shown) external to the first chamber 9, with the first array of pores 11 being arranged across the surface of the first electrode once assembled for use. Similarly, the second array of pores 13 is for interfacing with a second electrode (not shown) external to the first chamber 9, with the second array of pores 13 being arranged across the surface of the second electrode once assembled for use. Oxidation and reduction of fluid (e.g. carbon dioxide sequestered from industrial processes) within the electrolyte (e.g. aqueous potassium hydroxide) takes place via the pores 11, 13 of the first chamber 9 when an electric current is applied to the electrodes during the electrolysis procedure (the electrolysis procedure itself will be described in more detail later). Advantageously, the use of the core structure 1 obviates the need to use membranes to separate the electrodes, and hence the electrolyser described herein is simpler to produce and operate relative to current electrolysers. Specifically, with the present electrolyser, there is no membrane between the core structure 1 and either of the electrodes between which the core structure 1 is sandwiched (and hence the present electrolyser may be termed “membraneless”). As mentioned above and as illustrated in Figures 1a to 1c, the pores of the second array 13 are larger than the pores of the first array 11. In the illustrated configuration, the pores of the first array 11 are arranged to interface with an anode as the first electrode, and the pores of the second array 13 are arranged to interface with a cathode as the second electrode. When the fluid being electrolysed is carbon dioxide, the difference between the respective size of the pores of the first and second arrays 11, 13 biases the formation of carbon monoxide at the cathode, relative to the formation of oxygen at the anode, during the electrolysis procedure. To further bias the formation of carbon monoxide at the cathode during the electrolysis procedure, the pores of the second array 13 may also be greater in number relative to the number of pores of the first array 11. The pores of the first array 11 may have a first radius and the pores of the second array 13 may have a second radius. The ratio of the radii of the first and second arrays 11,13 (and hence physical sizes of the pores of these arrays) can be modified to bias the desired formation of carbon monoxide over other reduction products, thereby improving the efficiency of the electrolysis procedure overall. According to one example, such a biasing effect may be achieved in the case where the ratio of the second radius relative to the first radius is in the range of 1.5:1 to 3:1. Furthermore, notable efficiencies have been obtained in the case where the ratio of the second radius relative to the first radius is 2:1. Moreover, electrolysis process efficiencies have been observed when the first radius is in the range of 0.005 mm to 0.5 mm, and the second radius is in the range of 0.01 mm to 1 mm. Additionally, efficiencies have been obtained in the case where the first radius is in the range of 0.05 mm to 0.5 mm, and the second radius is in the range of 0.1 mm to 1 mm. Advantageously, the above-described core structure 1 may be formed as a unitary structure, e.g., by 3D printing, or by the use of a CNC machine. Using these techniques increases the mechanical robustness of the core structure 1, as well as aiding the straightforward, precise and rapid fabrication thereof. The electrolyte which has flowed through the first chamber 9 and past the pores of the first and second arrays 11, 13 may exit the first chamber 9 via electrolyte outlet 15. Meanwhile, the species formed at the pores of the arrays 11, 13 as the reaction products of the electrochemical process, such as carbon monoxide and oxygen (discussed in detail below), may exit the first chamber 9 via outlet 17. To facilitate the interconnection of the core structure 1 with other electrolyser components, at least one means for securing the core structure 1 to other electrolyser components may be provided on a peripheral interface region R. In the illustrated example, when viewed from the outside of either surface 10, 12, the peripheral interface region R and the respective surface 10, 12 are coplanar. In the illustrated example, the core structure 1 comprises several fastening holes 19 passing through the peripheral interface region R, which are configured for colocation with another respective electrolyser component (not shown). Once holes 19 are collocated with a corresponding feature on another electrolyser component, the respective components may be secured to one another, e.g., by using a fastener such as a nut and bolt. Figure 2 will now be described, which shows in two-dimensional plan view the core structure 1 illustrated in Figure 1b. In Figure 2, a pseudo-transparent rendering of the first chamber 9 has been employed to show the mutual arrangement of the first and second arrays 11,13 (essentially by overlaying the first and second arrays 11, 13). As illustrated in this example, the number of pores of the first array 11 are fewer in number than in the second array 13, whilst the pores of the second array 13 are larger than those of the first array 11. In this example, the first array 11 is formed of 19 x 12 pores, and the second array 13 is formed of 18 x 18 pores, although it will be appreciated that arrays of alternative sizes and numbers may be used instead. Beneficially, the relative features of the first array 11 and the second array 13 bias the formation of carbon monoxide at the second array 13, for reasons described later. Electrolyser- Anode and Anode Cover Plate The assembly of an electrolyser built around to the above-described core structure 1 will now be described. To begin with, an overview of the materials used for the electrolyser’s first electrode, which in the present example is an anode, as well as a first cover plate for covering that electrode, will be described with reference to Figures 3a and 3b. By way of example, a nickel-based anode, a cobalt-based anode, an iron-based anode, or a platinum-coated titanium anode, may be used as the electrolyser’s anode. The anode may, for example, be mesh-like and / or porous. In the present examples, the anode is positioned against the first surface 10 of the core structure 1 shown in Figures 1a, 1b and 1c, and extends across the first array of pores 11, to enable electrolysis of the fluid contained within the electrolyte during the electrolysis procedure. The inside of a first (anode-side) cover plate 20 is schematically illustrated in plan view in Figure 3a (the anode itself being omitted for clarity), with Figure 3b schematically illustrating the outside of the first cover plate 20 in a plan view obverse to that shown in Figure 3a. The anode is housed within the first cover plate 20 and is secured to the inside of the first cover plate 20 using a fastener 25. The anode is then held in position against the first array of pores 11 when the first cover plate 20 is attached to the core structure 1, for example by mutual alignment of the fastening holes 19 of the core structure 1 with the corresponding fastening holes 31 provided on a peripheral interface region R' of the first cover plate 20, and the attachment of fasteners (e.g. nuts and bolts) therethrough. More particularly, the first cover plate 20 incorporates a first cover plate chamber 23 that is arranged to cover the anode, and to define a void in the chamber 23 outward of the anode. The first cover plate 20 may also comprise an inlet 21 in communication with said void of the first cover plate chamber 23 for receiving an additional supply of electrolyte (i.e. the electrolyte which was provided to the core structure 1 via inlet 3), a first outlet 27 in communication with said void of the first cover plate chamber 23 for outputting the additional supply of electrolyte, and a second outlet 29 in communication with said void of the first cover plate chamber 23 for outputting an oxidised species (e.g. oxygen) formed by electrolysis of the fluid contained within the electrolyte (the oxidised species having passed through the anode and into the second outlet 29 via said void). The electrolyte may be introduced into the first cover plate chamber 23 via the inlet 21 by use of a pump external to the first cover plate 20 (not shown), or by using other suitable apparatus. Electrolyser- Cathode and Cathode Cover Plate An overview of the materials used for the electrolyser’s second electrode, which in the present example is a cathode, as well as a second cover plate for covering that electrode, will now be described with reference to Figures 4a and 4b. By way of example, a cathode can be used that includes a substrate having a material thereon. The substrate can be copper, tin, indium, iron, nickel, cobalt, gold, platinum, titanium, niobium, tantalum, molybdenum, tungsten, zinc, gallium, and carbon, and alloys, and oxidized forms thereof, and the material can be a metal, metal alloy, metal oxide, or a metal hydroxide. For instance, the material can be indium, tin, zinc, gallium, nickel and carbon and a combination thereof, or alloys (e.g. copper-indium or copper-tin), oxides (such as CU2O), mixed oxides, or hydroxides thereof. The material can be disposed on about 5 to 75 % of the surface of the substrate, and can be disposed on the substrate using a technique such as electrodeposition, electrophoretic deposition, or drop-casting. According to one example, the material can be one that has a high hydrogen overpotential (e.g., about 500 mV, at 25 °C, 1 atm). Moreover, the material may be prepared in the form of a sheet or foil disposed on the substrate. In another embodiment, the material can include particles of the material such as microparticles, nanoparticles, or a mixture thereof. Beneficially, and particularly in the case of using a copper-indium (Cu-ln) alloy as the cathode’s material, a selective conversion of carbon dioxide to carbon monoxide is observed with a low overpotential. This type of cathode is a highly selective electrocatalyst, energy efficient, and does not rely on the use of precious metals. Moreover, this cathode minimises the competitive reduction of protons to form hydrogen during aqueous carbon dioxide conversion into carbon monoxide. In one example, the cathode may be deposited onto a suitable gas diffusion layer (GDL), such as carbon paper (i.e., thin sheets of carbon fibres that are bonded together with a resin or other suitable binder). Alternative GDLs may instead be used, such as carbon plate, carbon cloth, or a metal mesh such as sintered titanium. Beneficially, the GDL assists in the even distribution of gases which are produced during the electrolysis procedure as well as protecting electrodes from corrosion, thereby optimising the electrolyser’s efficiency and performance. As those skilled in the art will appreciate, GDLs are not considered to be “membranes” (i.e. in the sense of membranes which are used to separate electrodes in standard electrolyser designs). The inside of a second (cathode-side) cover plate 40 is schematically illustrated in plan view in Figure 4a (the cathode itself being omitted for clarity), with Figure 4b schematically illustrating the outside of the second cover plate 40 in a plan view obverse to that shown in Figure 4a. The cathode is housed within the second cover plate 40 and is secured to the inside of the second cover plate 40 using a fastener 47. The cathode is then held in position against the second array of pores 13 when the second cover plate 40 is attached to the core structure 1, for example by mutual alignment of the fastening holes 19 of the core structure 1 with the corresponding fastening holes 51 on a peripheral interface region R" of the second cover plate 40 and the attachment of fasteners (e.g. nuts and bolts) therethrough. More particularly, the second cover plate 40 incorporates a second cover plate chamber 43 that is arranged to cover the cathode, and to define a void in the chamber 43 outward of the cathode. The second cover plate 40 may also comprise an outlet 41 in communication with the second cover plate chamber 43 for outputting overflow electrolyte from the first chamber 9 of the core structure 1, and a second outlet 49 in communication with the second cover plate chamber 43 for outputting a reduced species (e.g. carbon monoxide) formed by electrolysis of the fluid contained within the electrolyte (the reduced species having passed through the cathode and into the second outlet 49 via said void). According to the illustrated example, the second cover plate chamber 43 may define a serpentine path 45 which extends between the first and second outlets 41,49 of the second cover plate chamber 43. The serpentine path structure 45 provides a scaffold for receiving the cathode (or the GDL bearing the cathode), whilst also increasing the path length between the respective outlets 41, 49, thereby facilitating a straightforward egress of reduced species, such as carbon monoxide, and / or overflow electrolyte from the second cover plate chamber 43. Any overflow electrolyte can be recovered and used during subsequent electrolysis procedures. Assembled Electrolyser An assembled electrolyser will now be described which comprises the core structure 1, the first cover plate 20 comprising the anode, and the second cover plate 40 comprising the cathode. In this regard, reference is made to Figure 5a, which schematically illustrates an exploded view of components of the electrolyser, and to Figure 5b which schematically illustrates the assembled electrolyser 100. Specifically, Figures 5a and 5b illustrate a first electrode 22, external to the first chamber 9 of the core structure 1, which is positioned against the first surface 10 of the core structure 1 and which extends across the first array of pores 11. Figures 5a and 5b further illustrate a second electrode 42, external to the first chamber 9, which is positioned against the second surface 12 of the core structure 1 and which extends across the second array of pores 13. Also shown in Figure 5a between the second electrode 42 and the second cover plate 40 is a GDL 44 (the GDL 44 is omitted from Figure 5b for clarity), and in the case where the second electrode 42 is a cathode, the cathode may be formed on the GDL 44. Each of the first cover plate 20 and a second cover plate 40, as described above, respectively cover the first electrode 22 and the second electrode 42. It will be appreciated that the various inlets and outlets of the core structure 1, the first cover plate 20 and the second cover plate 40, as described above with reference to Figures 1 to 4, have been omitted for clarity from Figures 5a and 5b. Also omitted from Figures 5a and 5b is the external power supply which is used to provide a direct current to the first electrode 22 and the second electrode 42. It can be clearly seen from Figures 5a and 5b that the electrolyser 100 described herein is significantly simpler than current electrolysers, in that electrolyser 100 does not require membranes or reference electrodes. Beneficially, therefore, electrolyser 100 represents a significant reduction in production costs and operational complexities relative to current systems, in addition to further benefits described in more detail below. Electrolysis of Carbon Dioxide Now that the electrolyser 100 has been described, an example of its use in the electrolysis of carbon dioxide will be discussed, from which it will be appreciated that the electrolyser described herein may facilitate the recycling of this otherwise harmful greenhouse gas into useful downstream products, such as carbon monoxide. For example, and as noted above, carbon dioxide may be sequestered from industrial processes and dissolved in an electrolyte, such as aqueous potassium hydroxide (e.g. 1.0 M KOH), for treatment by electrolysis using the electrolyser 100 described above. Of course, it will be appreciated that a variety of other fluids may be electrolysed, and that these fluids may be contained within various other electrolytes. For instance, an electrolyte may be an aqueous medium containing an acidic electrolyte (e.g., citric acid, perchloric acid, hydroiodic acid, nitric acid, sulfuric acid, bromic acid, etc.) or a basic electrolyte (e.g., hydroxides such as NaOH, sodium amide, sodium hydride, etc.), simple salts, KCI, NaCI, KHCO3, and NaHCOs, whereas non-aqueous electrolytes may comprise nBuPFe (TBHP) in MeCN solution, and a combination thereof. In some examples, the simple salts can include an anion (e.g., chloride, fluoride, sulfate, nitrate, nitrite, phosphate, acetate, etc.) and a cation (e.g., sodium, potassium, magnesium, iron, calcium, ammonium, etc.) such as KHCO3, NaCI, KCI, LiCI, CaCh, or Na2SO4. The electrolytes may be employed at various pH levels depending upon the system, reactants, and products to be generated. To illustrate the electrolysis of carbon dioxide schematically, reference is now made to Figure 6, which shows a simplified side view of the first chamber 9 of the core structure 1, the core structure’s electrolyte inlet 3 and outlet 17, the first electrode 22 (in this example, an anode) covering the first array of pores 11, and the second electrode 42 (in this example, a cathode) deposited on GDL 44 covering the second array of pores 13. Other features of the assembled electrolyser 100, such as the first and second cover plates 20, 40, an external power source for supplying power to the electrodes, etc., have been omitted for clarity. Beneficially, utilisation of renewable energy at the power source ensures a sustainable and environmentally friendly CO2 recycling process. The electrolyte according to this example is supplied to the inlet 3 of core structure 1, e.g., by using a pump or another suitable apparatus (also, electrolyte may similarly be supplied to the inlet 21 of the first cover plate 20, not shown in Figure 6). The electrolyte then flows into the first chamber 9 and passes through the first array of pores 11 and the second array of pores 13, to reach the anode and cathode respectively. One of the reduction products obtained by the electrolysis of carbon dioxide is carbon monoxide, the reduction of which may proceed via equations 1 and 2, which are given below: CO2 + 2H+ + 2e_ -> CO + H2O (Equation 1, reduction potential - 0.53 V) CO2 + 2H2O + 2e_ -> CO + 2OH (Equation 2, reduction potential - 1.347 V) As described above, the second array of pores 13 of the core structure 1 are larger than the pores of the first array 11. Therefore, and without being bound by theory, it is believed that when electrolyte flows through the first chamber 9 an increased local pressure is produced at the pores of the second array 13 relative to the pores of the first array 11 (i.e. setting up a pressure gradient across the first chamber 9, as well as facilitating the intimate interaction / mixing of CO2 and electrolyte to promote efficient CO2 conversion). This increased pressure results in the carbon dioxide dissolved in the electrolyte having a greater degree of interaction with the cathode, relative to the anode, during the electrolysis procedure. Consequently, preferential reductions at the cathode are observed relative to oxidations at the anode, and therefore greater volumes of carbon monoxide are obtained during the electrolysis procedure relative to oxidised counterparts generated at the anode (e.g., oxygen). To further bias the formation of desirable reduction products, the first array of pores 11 may have fewer pores relative to the number of pores of the second array 13. Consequently, the interaction of the electrolyte with the cathode is yet further increased, relative to the electrolyte’s interaction with the anode, and hence carbon monoxide may be recovered with even greater efficiency. Moreover, electrolysis using the electrolyser 100 described herein may be performed at ambient temperatures and pressures, thereby reducing the energy required when performing electrolysis when compared to many current electrolysis procedures (which rely on relatively high temperatures, and hence are energy-intensive, thereby potentially reducing the environmental benefits associate with carbon dioxide recycling). As noted above, the carbon dioxide may be pumped into the electrolyser 100 via inlets 3, 21. According to one example, the pump’s flow rate may be set between 15 mL to 50 mL CO2 min-1, although other flow rates may be used instead. In the case where carbon dioxide has already been dissolved in the electrolyte, and fresh electrolyte is supplied to the electrolyser, the pump’s flow rate may be set between 10 mL to 25 mL electrolyte min-1. The pump’s flow rate may also be varied as a function of time. Advantageously, setting the pump’s flow rate in this way reduces the likelihood of the formation of precipitates, such as potassium bicarbonate. In summary, the electrolyser described herein may provide the following advantages: • The electrolyser described herein enhances CO2 saturation and reaction kinetics through increased pressure, resulting in higher current density and increased selectivity for CO production, specifically for use as chemical feedstock. • The capillary design of the electrolyser described herein enables higher CO2 saturation and more thorough reactions, resulting in a remarkable selectivity of CO production, reaching up to 90%. • The electrolyser described herein achieves a remarkable conversion rate of 150 mA cm-2 in a 1.0 M KOH solution as the electrolyte. • Unlike conventional electrolyser technologies, the present capillary electrolyser operates without the need for membranes and reference electrodes, making it a practical and scalable solution for carbon-emitting industries with e.g. 85% efficiency. • The incorporation of porous holes on the capillary separator wall allows for efficient mixing of CO2 and electrolyte, promoting optimal CO2 conversion and increasing overall electrolyser performance. • Adjusting pressure and mass flow rate parameters can enhance electrolysis efficiency, which is achievable using the present capillary electrolyser. • The present capillary electrolyser contributes to CO2 recycling processes, which enables the production of e-fuels and supports the circular economy. • The present capillary electrolyser offers straightforward scalability (for instance to a scale where the first and second arrays of pores are of the order of 100 cm2 or larger) and eliminates the need for extensive equipment and infrastructure, thus reducing implementation costs. • The present capillary electrolyser may be used by manufacturers and industries to significantly reduce production costs associated with generating chemical feedstock or e-methanol from waste gases. • The present capillary electrolyser may incorporate safety measures integrated into the capillary electrolyser unit, ensuring that production halts automatically in the event of a power supply interruption. Moreover, it is envisaged that the electrolyser 100 described herein may be used in the following additional application areas: • Renewable Energy Storage: The disclosed technology can be used for renewable energy storage by utilising excess electricity from renewable sources to produce CO through electrolysis. The produced CO can then be stored and used as a renewable fuel or feedstock for various industrial processes. • Synthetic Fuel Production: The disclosed electrolyser can be employed to assist in the production of synthetic fuels such as methanol or dimethyl ether (DME) from CO2 emissions. These fuels can be used as alternatives to conventional fossil fuels in the transportation and energy sectors. • Chemical Industry: The disclosed technology can find applications in the chemical industry for the production of various chemicals and intermediates. CO, produced through capillary electrolysis, can serve as a key building block for the synthesis of chemicals like formic acid, acetic acid, or higher hydrocarbons. • Carbon Capture and Utilization (CCU): The disclosed electrolyser can play a role in CCU technologies, which aim to capture CO2 emissions from industrial processes and convert them into valuable products. The disclosed electrolyser can contribute to the efficient and cost-effective conversion of CO2 into useful chemicals, reducing greenhouse gas emissions. • Waste-to-Energy Conversion: The disclosed technology can be integrated into waste treatment and landfill sites to convert landfill gas (LFG), which contains CO2 and methane, into CO through electrolysis. This allows for the utilisation of waste gases and the production of a valuable product simultaneously. Stacked Electrolyser An alternative electrolyser to the assembled electrolyser 100 shown in Figure 5b will now be described with reference to Figures 7 to 9. Specifically, Figure 7 illustrates in an exploded side view of a so-called “stacked” electrolyser (which demonstrates the modular nature in which an electrolyser can be assembled according to the present disclosure), and Figure 8 shows a simplified side view of the components of the stacked electrolyser 200 shown in Figure 7 when assembled. As illustrated, the stacked electrolyser 200 comprises a first core structure 1-1 as described in detail above. A first first-electrode 22-1 is shown external to the first chamber 9-1 of the first core structure 1 -1, against the first surface 10-1 of the first core structure 1-1 and extending across the first array of pores 11-1 of the first core structure 1-1. A first second-electrode 42-1 is shown external to the first chamber 9-1 of the first core structure 1-1, against the second surface 12-1 of the first core structure 1-1 and extending across the second array of pores 13-1 of the first core structure 1 -1. The stacked electrolyser 200 further comprises a second core structure 1-2 (i.e. another of the core structures described in detail above). The second core structure 1-2 comprises a second first-electrode 22-2 external to the first chamber 9-2 of the second core structure 1-2, against the first surface 10-2 of the second core structure 1-2 and extending across the first array of pores 11-2 of the second core structure 1-2. A second second-electrode 42-2 is shown external to the first chamber 9-2 of the second core structure 1-2, against the second surface 12-2 of the second core structure 1-2 and extending across the second array of pores 13-2 of the second core structure 1-2. Whilst not shown in Figures 7 or 8, it will be appreciated that a GDL may be disposed between the first second-electrode 42-1 and the first cover plate 40-1 and that a GDL may be disposed between the second second-electrode 42-2 and the second cover plate 40-2. A first cover plate 40-1 is arranged to cover the first second-electrode 42-1, whilst a second cover plate 40-2 is arranged to cover the second second-electrode 42-2. A coupling cover plate 20-1 is arranged to cover the first first-electrode 22-1 and the second first-electrode 22-2 and to couple the first core structure 1-1 and the second core structure 1-2 in a back-to-back configuration (i.e. in mirror symmetry about the centre of the coupling cover plate 20-1). Beneficially, the configuration of the stacked electrolyser 200 provides a higher throughput electrolyser relative to the “single cell” electrolyser 100 illustrated with reference to Figures 5a and 5b. The manufacture of the stacked electrolyser 200 is also simplified (and potentially made more compact) by virtue of the coupling cover plate 20-1 being shared by the first and second core structures 1-1, 1-2 on either side. According to one example of a stacked electrolyser 200, the first first-electrode 22-1 and the second first-electrode 22-2 are anodes, and the first second-electrode 42-1 and the second second-electrode 42-2 are cathodes. In this configuration, the first cover plate 40-1 incorporates a first cover plate chamber (not shown, but which is functionally equivalent to the chamber 43 described above with reference to Figure 4a), and the second cover plate 40-2 incorporates a second cover plate chamber (not shown, but which is functionally equivalent to the chamber 43 described above with reference to Figure 4a), each surrounding the respective second electrodes 42-1,42-2. The first cover plate chamber and the second cover plate chamber each further comprise a first outlet (not shown, but which are functionally equivalent to the outlet 41 described above with reference to Figures 4a and 4b) in communication with the respective first cover plate chamber for outputting overflow electrolyte from the first chamber of the respective core structure 1-1, 1 -2 and a second outlet (not shown, but which are functionally equivalent to the outlet 49 described above with reference to Figures 4a and 4b) in communication with the respective first cover plate chamber for outputting a cathode-formed species formed during electrolysis. Reference is now made to Figure 9, which illustrates a perspective view of the coupling cover plate 20-1 for the stacked electrolyser 200. The coupling cover plate incorporates two discrete cover plate chambers 23-1, 23-2, each cover plate chamber surrounding the respective anodes (anodes, not illustrated in Figure 9). Each cover plate chamber 23-1, 23-2 further comprises an inlet 21-1,21-2 in communication with the respective cover plate chamber for receiving a further supply of the electrolyte, a first outlet 27-1,27-2 in communication with the respective cover plate chamber for outputting the further supply of the electrolyte; and a second outlet 29-1,29-2 in communication with the respective cover plate chamber for outputting an anode-formed species formed by electrolysis of said fluid. The anodes are held in position against the first array of pores 11 of each respective core structure 1-1, 1-2 when the coupling cover plate 20-1 is attached to each respective core structure 1-1, 1-2, for example by mutual alignment of the fastening holes 19 of the core structure 1 with the corresponding fastening holes 31 of the coupling cover plate 20-1 and the attachment of fasteners (e.g. nuts and bolts) therethrough. Modifications and Alternatives Detailed examples have been described above. As those skilled in the art will appreciate, a number of modifications and alternatives can be made to the above examples whilst still benefiting from the inventions embodied therein. In the example core structure 1 illustrated with reference to Figures 1a to 1c, an electrolyte reservoir 5 and an associated plurality of channels 7 was shown. It will be appreciated that such a reservoir 5 and associated plurality of channels 7 are optional, and that electrolyte / fluid to be electrolysed may instead be provided directly into the first chamber 9 via inlet 3. The stacked electrode described with reference to Figures 7 and 8 illustrated that the central coupling cover plate covered and secured anodes, whereas the first and second cover plates covered and secured cathodes. Instead, the central coupling cover plate may cover and secure cathodes, and the first and second cover plates may cover and secure anodes, in which case the orientation of the first and second core structures 1 -1, 1-2 will be secured to the coupling cover plate after being rotated through 180° relative to their orientation in Figures 7 and 8. It will be further appreciated that the central coupling chamber (for covering anodes or cathodes) may be “shared” between the respective electrodes, and hence the central coupling chamber may comprise a common cover plate chamber instead of the two discrete cover plate chambers as described with reference to Figures 7 and 8. Whilst the electrolysis of carbon dioxide has been described, it will be appreciated that the electrolysers disclosed herein may be used in the electrolysis of other fluids to generate useful products, such as hydrogen or 5 ammonia. Various other modifications will be apparent to those skilled in the art and will not be described in further detail here.

Claims

1. A core structure for forming a capillary electrolyser, the core structure comprising:a first chamber for receiving an electrolyte containing a fluid to be electrolysed, the first chamber comprising:a first surface having a first array of pores therethrough, for interfacing with a first electrode external to the first chamber, against the first surface and extending across the first array of pores; anda second surface having a second array of pores therethrough, for interfacing with a second electrode external to the first chamber, against the second surface and extending across the second array of pores;wherein the first surface and the second surface are opposingly facing; andwherein the pores of the second array are larger than the pores of the first array;wherein the core structure further comprises:an inlet in communication with the first chamber for supplying the fluid to be electrolysed; andan outlet in communication with the first chamber for outputting a species formed by electrolysis of said fluid.

2. The core structure according to claim 1, further comprising a second chamber fluidically disposed between the inlet and the first chamber, for providing a reservoir for the electrolyte.

3. The core structure according to claim 2, further comprising a plurality of channels extending from the second chamber to the first chamber, the plurality of channels being arranged substantially across a receiving side of the first chamber.

4. The core structure according to any preceding claim, wherein the pores of the second array are greater in number than the pores of the first array.

5. The core structure according to any preceding claim, further comprising a second outlet in communication with the first chamber for enabling a flow of the electrolyte through the first chamber.

6. The core structure according to any preceding claim, wherein the pores of the first array have a first radius and the pores of the second array have a second radius.

7. The core structure according to claim 6, wherein a ratio of the second radius relative to the first radius is in the range of 1.5:1 to 3:1.

8. The core structure according to claim 7, wherein the ratio of the second radius relative to the first radius is 2:1.

9. The core structure according to any of claims 6 to 8, wherein the first radius is in the range of 0.005 mm to 0.5 mm, and the second radius is in the range of 0.01 mm to 1 mm.

10. The core structure according to claim 9, wherein the first radius is in the range of 0.05 mm to 0.5 mm, and the second radius is in the range of 0.1 mm to 1 mm.

11. The core structure according to any preceding claim, formed as a unitary structure.

12. The core structure according to any preceding claim, further comprising at least one means for securing the core structure to another component.

13. An electrolyser comprising:the core structure according to any preceding claim;a first electrode external to the first chamber, against the first surface of the core structure and extending across the first array of pores; anda second electrode external to the first chamber, against the secondsurface of the core structure and extending across the second array of pores.

14. The electrolyser according to claim 13, further comprising a first cover plate and a second cover plate;wherein the first cover plate is arranged to cover the first surface of the core structure and the first electrode, and the second cover plate is arranged to cover the second surface of the core structure and the second electrode.

15. The electrolyser according to claim 14, wherein the first cover plate incorporates a first cover plate chamber surrounding the first electrode.

16. The electrolyser according to claim 14 or claim 15, wherein the second cover plate incorporates a second cover plate chamber surrounding the second electrode.

17. The electrolyser according to any of claims 13 to 16, wherein the first electrode is an anode, and the second electrode is a cathode.

18. The electrolyser according to claim 17, wherein the first cover plate further comprises:an inlet in communication with the first cover plate chamber for receiving a further supply of the electrolyte;a first outlet in communication with the first cover plate chamber for outputting the further supply of the electrolyte; anda second outlet in communication with the first cover plate chamber for outputting an anode-formed species formed by electrolysis of said fluid.

19. The electrolyser according to claim 17 or claim 18, wherein the second cover plate further comprises:a first outlet in communication with the second cover plate chamber for outputting overflow electrolyte from the first chamber of the core structure; anda second outlet in communication with the second cover plate chamber for outputting a cathode-formed species formed by electrolysis of said fluid.

20. The electrolyser according to claim 19, wherein the second cover plate chamber defines a serpentine path extending between the first outlet of the second cover plate chamber and the second outlet of the second cover plate chamber.

21. A stacked electrolyser comprising:a first core structure according to any of claims 1 to 12;a first first-electrode external to the first chamber of the first core structure, against the first surface of the first core structure and extending across the first array of pores of the first core structure;a first second-electrode external to the first chamber of the first core structure, against the second surface of the first core structure and extending across the second array of pores of the first core structure;a second core structure according to any of claims 1 to 12;a second first-electrode external to the first chamber of the second core structure, against the first surface of the second core structure and extending across the first array of pores of the second core structure;a second second-electrode external to the first chamber of the second core structure, against the second surface of the second core structure and extending across the second array of pores of the second core structure;a first cover plate arranged to cover the first second-electrode;a second cover plate arranged to cover the second second-electrode; anda coupling cover plate is arranged to cover the first first-electrode and the second first-electrode and to couple the first core structure and the second core structure in a back-to-back configuration.

22. The stacked electrolyser according to claim 21, wherein the first first-electrode and the second first-electrode are anodes, and the first second-electrode and the second second-electrode are cathodes.

23. The stacked electrolyser according to claim 22, wherein the first cover plate incorporates a first cover plate chamber, and the second cover plate incorporates a second cover plate chamber, each surrounding the respectivesecond electrodes, and wherein the first cover plate chamber and the second cover plate chamber each further comprises:a first outlet in communication with the respective first cover plate chamber for outputting overflow electrolyte from the first chamber of the respective core structure; anda second outlet in communication with the respective first cover plate chamber for outputting a cathode-formed species formed by electrolysis of said fluid.

24. The stacked electrolyser according to claim 23, wherein the first cover plate chamber and the second cover plate chamber each define a serpentine path extending between the first outlet and the second outlet of the respective first cover plate chamber and the second cover plate chamber.

25. The stacked electrolyser according to any of claims 22 to 24, wherein the coupling cover plate incorporates two cover plate chambers, each cover plate chamber surrounding the respective first electrodes, and wherein each cover plate chamber further comprises:an inlet in communication with the respective cover plate chamber for receiving a further supply of the electrolyte;a first outlet in communication with the respective cover plate chamber for outputting the further supply of the electrolyte; anda second outlet in communication with the respective cover plate chamber for outputting an anode-formed species formed by electrolysis of said fluid.

26. The electrolyser according to any of claims 13 to 25, having no membrane between the or each core structure and either of the electrodes adjacent to the or each core structure.

27. The electrolyser according to any of claims 13 to 26, further comprising a gas diffusion layer disposed against the or each second electrode.

28. A method for performing electrolysis upon a fluid contained within anelectrolyte using the electrolyser of any of claims 13 to 27, the method comprising:supplying the fluid contained within the electrolyte to the electrolyser; applying a current to the electrodes; and5 collecting a species formed by electrolysis of said fluid.

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