Electrolyser cell adapted for electrolyzing water into hydrogen and oxygen and a method for preparing an electrolyser cell adapted for electrolyzing water into hydrogen and oxygen

Abstract

An electrolyser cell comprises a diaphragm which partitions the cell into a cathode chamber and an anode chamber and wherein an oxygen evolving anode electrode arranged at the anode chamber side of the diaphragm and a hydrogen evolving cathode electrode arranged at the cathode chamber side of the diaphragm is provided. A spacer is provided between the cathode electrode and the diaphragm, and / or between the anode electrode and the diaphragm which spacer is adapted to ensure contact between electrolyte fluid elements in the cathode and / or in the anode chamber and the diaphragm, and adapted to ensure a pre-determined non-zero distance D between the cathode electrode and / or the anode electrode and the diaphragm.

Description

[0001] Electrolyser cell adapted for electrolyzing water into hydrogen and oxygen and a method for preparing an electrolyser cell adapted for electrolyzing water into hydrogen and oxygen.

[0002] Background of the invention

[0003] In both Proton Exchange Membrane (PEM) and Alkaline Water Electrolysis (AWE) electrolysis of water into hydrogen and oxygen, electrically charged particles are to travel from one electrolytic chamber through a partition diaphragm and into an adjacent chamber, and this requires the diaphragm to be as transparent as possible to the electrically charged particles such that ohmic losses in the diaphragm are avoided. Keeping ohmic losses low has a tendency to increase the so-named cross over gasses, whereby hydrogen produced at the cathode side travels through the diaphragm to the anode side, and here pollutes the produced oxygen, and likewise oxygen produced at the anode side of the diaphragm travels through the diaphragm to the cathode side and here pollutes the produced hydrogen.

[0004] Experiments and theories within the field attribute the rate of the cross over gasses to diffusion in the liquid phase at the two sides and notably inside the diaphragm.

[0005] It has been experimentally validated in the below reference that supersaturation is a major driver of crossover of the gasses, and especially supersaturation in the vicinity of the membrane surface is critical in driving crossover. Rodrigo Lira Garcia Barros, Joost T. Kraakman, Carlijn Sebregts, John van der Schaaf, Matheus T. de Groot; International Journal of Hydrogen, Volume 49, Part C, 2 January 2024, Pages 886- 896; “Impact of an electrode-diaphragm gap on diffusive hydrogen crossover in alkaline water electrolysis”.

[0006] Summary of the invention

[0007] It is therefore an object of the invention to reduce crossover and more specifically to do so by reducing super saturation at or near the membrane surface or surfaces.

[0008] This is achieved by an electrolyser cell adapted for electrolyzing water into hydrogen and oxygen and comprising a diaphragm which partitions the cell into a cathode chamber at a cathode side of the diaphragm and an anode chamber at an opposed anode side of the diaphragm and an oxygen evolving anode electrode arranged at the anode chamber side of the diaphragm and a hydrogen evolving cathode electrode arranged at the cathode chamber side of the diaphragm.

[0009] According to the invention a spacer is provided between the cathode electrode and the diaphragm, or between the anode electrode and the diaphragm, or between both of anode and cathode electrodes and diaphragm, which spacer is adapted to ensure contact between electrolyte fluid elements in the chamber in which it resides and the diaphragm and further adapted to ensure a pre-determined distance between the cathode electrode and the diaphragm.

[0010] With the spacer in place, a predefined minimum distance between the electrode and the diaphragm will be secured throughout operation and this will lead to less super saturation at the diaphragm surface. One reason for this is that the diaphragm surface naturally comprises a population of bubble nucleation points, which ensures a low saturation, as a bubble is a natural sink for gas dissolved in the electrolyte, however at points where the electrode touches, protrudes into or is very close to the diaphragm, even possible tendency of the diaphragm surface to generate bobbles, does not suffice in keeping supersaturation low. Especially points of touch and areas where the electrode is pressed into the surface of the relatively soft diaphragm, there will not be sufficient bubble formation and supersaturation may reach high levels, leading to spots of high cross over. With a spacer in place between the diaphragm and the electrode, it will be ensured that no such areas with no or even negative distance between the electrode and the diaphragm will exist even over a wide area electrode-diaphragm pair.

[0011] In an embodiment, the spacer comprise a coherent screen element adapted to extend flatly in a layer between opposed and facing surfaces of an electrode and the diaphragm.

[0012] Coherent screen elements are commercially available in many shapes and mesh sizes, and also are easy to manufacture in new sizes in case this is required. Meshes of this nature are also easy to handle and may be easily cut into shape and added to the cell during manufacture.

[0013] In an embodiment the spacer is adapted to extend along a substantially geometric plane and comprise a multitude of openings transversely to the geometric plane.

[0014] Screen elements are often characterised by their so-named mesh, which defines the number of single strands over 10 mm of screen element. It is assumed that the number of single strands per unit length are the same in two perpendicular directions, and that the screen comprises only such two interwoven or interwelded arrays of strands. The strands themselves thus comprise a solid substance forming a grid like structure. Such screens or meshes are usually manufactured to not comprise any internal stresses in the strands, and thus are ideally adapted to extend generally along a geometric plane when left un- affected by external forces. This allows the spacer to extend between the diaphragm and the electrode along a substantially plane geometric plane. A geometric plane in this connection is a mathematically defined plane surface, however the surface between an electrode and a diaphragm will deviate slightly from such a geometric plane, given manufacturing tolerances and the like for the engineering parts in use and especially a polymer mesh will easily adapt to any such manufacturing tolerance driven deviations from an ideal geometric plane.

[0015] In an embodiment the screen element has a mesh identical to the mesh of a screen element embedded in the diaphragm, and is aligned with this embedded mesh, such that in a projection perpendicular to the plane between diaphragm and electrode the embedded and the added mesh or meshes are aligned on top of each other. The embedded screen or mesh and the added screen element in like proportion hampers diaphragm cross section throughput of ions, however aligning the two with each other will ensure that the diaphragm cross section through-going flow channels blocked by the added screen are the very same diaphragm through-going flow channels blocked by the embedded screen, and thus in this case the added screen will not subtract from ion cross flow capacity of the diaphragm. In an embodiment, the solid substance of the spacer is adapted to be resistant to alkaline water and oxygen, and resistant to alkaline water and hydrogen and resistant to alkaline water and a combination of oxygen and hydrogen all at alkaline concentrations up to 45% by mass, and temperatures up to 150 degrees Celsius or up to 120 degrees Celsius or up to 110 degrees Celsius.

[0016] In alkaline water electrolysis, a heavy concentration of an alkaline substance such as potassium hydroxide in water is used as electrolyte as this will ensure a better performance in terms of gas production rate over used electric effect and usually a concentration around 30% - 45% by mass is used, and this is a demanding challenge for any of the substances exposed thereto, and in electrolyser cells there will further be a concentration of either oxygen or hydrogen present. Further, temperatures up to and including 150 degrees Celsius may exist within the cell. This is most challenging, and not many products will survive un-disturbed here as only few materials will sustain integrity under these conditions.

[0017] In an embodiment of the invention, the solid substance of the screen element covers a percentage of the area of the diaphragm area when projected perpendicular onto the diaphragm, whereby this percentage is between 1% and 25% or preferred between 2% and 12% or most preferred between 4% and 6% of the diaphragm area.

[0018] The solid substance forming the spacer will be pressed towards the surface of the diaphragm and will thereby obstruct at least some of the passages accounting for the function of the diaphragm as a conductive path for ions between the chambers residing on each their side thereof. It is desired to limit the effect of this functional blocking of the diaphragm, while securing a non-zero and predefined gab between electrode and diaphragm.

[0019] In an embodiment, the solid substance comprises at least one of the following materials:

[0020] Polypropylene

[0021] ETFE

[0022] Polyphenylene sulfide Polysulfone group polymers (PSU, PESLI or PPSLI) Polyetheretherketone (PEEK)

[0023] The here mentioned materials will survive the harsh environment inside an alkaline electrolyser cell for a long period of time and are also capable of being manufactured into a screen material.

[0024] In an embodiment a distributed spacer is provided at least between any of the electrodes and the diaphragm, which spacer comprises singular or coherent 3D- printed polymer spacer elements printed onto the electrode, which polymer spacer elements at proximal parts adhere to electrode surface parts facing the diaphragm and at distal ends are terminated a predetermined distance from the electrode surface.

[0025] 3D printing techniques have improved a lot over the years and today it would be possible to print onto expanded metal sheets, and with precision add polymer dots, strands or the like to the metal strands of such expanded sheets and avoid printing onto the orifices of such expanded sheets. Such spacer elements would thus ensure, that no part of the electrode itself is in contact with the diaphragm, and that a minimum distance between the surface of the diaphragm and the electrode is maintained. Further, it is noticed that with the distributed dots or other shapes of distance elements, there will be less disturbance of the fluid flow between the diaphragm and the electrode. The distance between any two neighboring dots should be in the order of any distance between any to neighboring strands of the abovementioned meshes. If dots, lines, strands or other polymer protrusions are used on electrodes on the two opposed sides of a diaphragm, it is preferred that the protrusions are aligned on the two sides of the diaphragm, such that a protrusion on a cathode is aligned with a similar dot on the anode on the opposed sided of the diaphragm. The 3D printed elements may be elongate, such as in a preferred flow direction and thus also be instrumental in in ensuring uniform flow with no eddies or dead-zones with reduced or no electrolyte flows.

[0026] In an embodiment at least one of the cathode electrode and the anode electrode is subjected to a pressure force towards the diaphragm, in order to ensure contact between the spacer and adjacent diaphragm and between the distributed spacer and the adjacent electrode surface.

[0027] A pressure force is advantageous to ensure that the distance element is in constant contact with the diaphragm and the corresponding adjacent electrode to thereby ensure a well-defined non-zero gab structure and ensure low super-saturation at the surface of the diaphragm. It is also in this connection mentioned, that certain types of electrodes are prone to wear and may during their service life loose surface material. This process may result in a widening of the non-zero distance over time, which is not desirous, and here the pressure force will ensure, that the non-zero distance remains uniform, even if ither or both of electrode and diaphragm thins down during use.

[0028] In an embodiment, the pressure force originates from elements such as springs arranged between the electrode and a cell partition wall also named bipolar plate to thereby ensure that the electrode and diaphragm are pressed towards each other with a predefined pressure force.

[0029] Spring elements are known in the art and are easy to manufacture to both give rise to the required pressurization force and to electric conductivity between bipolar plate and electrode. Also, spring elements may be made as close to ideal springs over a long deformation range, and thus better accommodate both manufacturing tolerances and possible wear of electrode and / or diaphragm. Also because of the possible thinning down of cell-internal elements such as electrodes, the diaphragm and even the spacer or spacers, it may be advantageous to have springs on each side of the bipolar plate, even if in theory the pressurization force between the electrodes is maintainable with springs only at one side of the bipolar plate. Alternatively, a woven, matted, knitted or similarly made mesh made by a corrosionresistant metal is inserted in a space between the bipolar plate and the electrode to thereby ensure a pressurization force between electrodes in a cell.

[0030] In an aspect, the invention relates to a method for preparing an electrolyser cell adapted for electrolyzing water into hydrogen and oxygen where a diaphragm which partitions the cell into a cathode chamber and an anode chamber at respective sides of the diaphragm is provided and an oxygen evolving anode electrode is arranged at the anode chamber side of the diaphragm and a hydrogen evolving cathode electrode is arranged at the cathode chamber side of the diaphragm and whereby a spacer is provided between the diaphragm and the one or the other of the electrodes placed adjacent to the diaphragm or a spacer is provided between the diaphragm and the one electrode and a further spacer is provided between the other of the electrodes and the diaphragm.

[0031] The spacer will inevitably increase the distance between the two electrodes and ohmic losses will increase, however the spacer or spacers will also decrease the cross over due to decreased amount of dissolved gas close to the diaphragm. This last effect may allow much thinner diaphragms to be used, and the net effect is thus an increase in efficiency of the cell.

[0032] In an embodiment the spacer comprise a coherent screen element adapted to extend flatly between opposed and facing surfaces of an electrode and diaphragm in one or in both the cathode and the anode chambers.

[0033] A coherent element allows handling, such as during cell stack building, and the element may easily be made using well known manufacturing techniques.

[0034] In a further embodiment the coherent spacer is at least partially submerged into and fused with the diaphragm material prior to an assembly of a cell.

[0035] A fusion between the diaphragm and the spacer will allow the spacer and diaphragm to be handled in joint operations, and this is much appreciated, as it saves production time.

[0036] In a further embodiment the spacer in a step prior to the assembly of electrode and diaphragm is adhered to the electrode.

[0037] It is possible to adhere the spacer to the electrode, and similarly, a productivity increase is gained especially during assembly of a cell stack. In a further embodiment, a spacer having an average distance between strands from 250 |im and to 5000 |im and comprising one or more of the following materials: a. Polypropylene b. ETFE c. Polyphenylene sulfide d. Polysulfon group (e.g. PSU, PESLI and PPSLI) e. Polyetheretherketone (PEEK) is chosen.

[0038] In the above description, ionic flow through the diaphragm is referred to, however such flows are not necessarily constituted by ions moving physically through the diaphragm but may also arise due to electrons moving from one side of the diaphragm to the other. Both mechanisms of ion transfer across the diaphragm is thus referred to, when ionic flows are mentioned.

[0039] It should be emphasized that the term "comprises / comprising / comprised of' when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

[0040] Brief description of the drawings

[0041] In the following, the invention will be described in greater detail with reference to embodiments shown by the enclosed figures. It should be emphasized that the embodiments shown are used for example purposes only and should not be used to limit the scope of the invention.

[0042] Figure 1 shows schematically a sectional view of a diaphragm part 1 having an electrode 2, 3 arranged on either side thereof and a spacer 4 arranged between the electrode 2,3 and diaphragm 1,

[0043] Figure 2 is a sectional view of a diaphragm as in Fig. 1, however having spacers 4 arranged on each side thereof,

[0044] Figure 3 shows schematically a sectional view of a diaphragm part 1 having an electrode 2; 3 arranged on either side thereof and a spacer 4 in the shape of diaphragm protrusions 8, 8.1 arranged between each electrode 2,3 and the diaphragm 1 and

[0045] Figure 4 shows schematically a sectional view of a diaphragm 1 having a partially embedded spacer 9 on each side thereof.

[0046] Detailed description of the embodiments

[0047] It is to be noted that the figures and the above description have shown the example embodiments in a simple and schematic manner. Many of the specific mechanical details have not been shown since the person skilled in the art should be familiar with these details and they would just unnecessarily complicate this description. For example, the specific materials used, and the specific spacer unit have not been described in detail since it is maintained that the person skilled in the art would be able to find suitable materials and suitable processes of manufacture for the spacer unit according to the current invention.

[0048] The sectional vies of Figures 1 - 4 corresponds to a small part of a cell in an electrolyser stack, such as a stack adapted for use in alkaline water electrolyses for generating the gasses oxygen and hydrogen. The shown cell parts are also usable in PEM style electrolysers.

[0049] In Fig. 1 a sectional view of a diaphragm 1 with a cathode electrode 2 at one side thereof and an anode electrode 3 at an opposed side thereof is disclosed. Between the cathode electrode 2 and the diaphragm 1 , the spacer 4 is arranged and here shaped as a mesh having strands running perpendicular to the view plane as well as strands running in parallel to the view plane and shown in dashed line. At intersections between perpendicular sets of strands, they may be welded to each other, and / or at welding points the strands may possibly be slightly flattened to not have increase thickness at such points.

[0050] In Fig. 2 a sectional view of a diaphragm 1 , and again a cathode electrode 2 at one side thereof and an anode electrode 3 at an opposed side thereof are shown. In Fig.

[0051] 2 spacers 4; 4.1 are shown both between the diaphragm 1 and anode electrode 3 and between the diaphragm 1 and the cathode electrode 2. The spacers 4; 4.1 in both of Figs. 1 and 2 are comprised of a polymer-based mesh, and in the shown embodiment the mesh strands running in parallel with the plane of view are shown in dashed line in a vertical direction on the drawing, where the strands running perpendicular to the view plane are shown with a hatching of the section.

[0052] The diaphragm is a polymer-based diaphragm of the fluid-permeable kind, comprising a multitude of small fluid flow channels which connects the two sides of the diaphragm, and allows ions to pass between the two sides thereof, with only a small resistance, but at the same time the flow channels are so small, that they prevent the passage of gas bobbles from the one to the other side of the diaphragm 1.

[0053] Inside of the disclosed diaphragm, 1 a diaphragm support mesh 5 is shown. This mesh 5 keeps together the otherwise somewhat spongy and not strong and not very coherent material of the diaphragm 1 and is provided to secure the integrity of the diaphragm during production and handling thereof. This internal support mesh 5 comprise strands running perpendicular to the view plane (shown with hatching) and strands running parallel to the view plane and their existence is schematically indicated in dashed lines.

[0054] The spacer 4; 4.1 is adapted to ensure that fluid components or electrolyte in the process chamber wherein the spacer 4; 4.1 is provided are allowed to contact the surface of the diaphragm 1. The same is the case with fluid parts contacting the electrode surface, where the spacer will prevent blockage of electrode surface parts, which in cells with no spacer are pressed against the diaphragm which leads to such surface parts of the electrode being starved off electrolyte with consequently reduced efficiency of the cell. The spacer 4; 4.1 shall ensure that a minimum distance D, between the diaphragm surface and the corresponding electrode is maintained under all conditions and thus fluid flow is maintained around the widest possible area of both diaphragm and electrode. To this end the spacers 4; 4.1 in the embodiments of Figs. 1 and 2 are shaped as perpendicularly arranged threads or strands of material, possibly welded together at intersection points to form a coherent, or even linen-like mesh. The electrodes 2, 3 may also comprise soft and yieldable materials such as foamy nickel or fibrous matted or woven materials (not shown in the figures). In such cases, the thickness of individual strands of the spacer should include both a yielding of material to the diaphragm side whereby the strands sink into the material of the diaphragm and do the same at the electrode side. The thickness of a strand can be as much as 50% above the desired minimum distance D between the surface of the electrode and the surface of the diaphragm facing each other so as to ensure, that even if diaphragm and electrodes responds to pressurizations against the strands of the spacer 4; 4.1 by being locally compressed, this does not impede their respective functions as diaphragm 1 and electrode 2; 3.

[0055] Each electrode 2; 3 is connected to a bipolar plate 6 (shown in Fig. 1) and flexible elements 7, also seen in Fig. 1, are provided to maintain an electrically conducting and a mechanical connection between electrode 2;3 and accompanying bipolar plate 6. The bipolar plates shown in Fig. 1 have the same reference number and are also identical in shape and function.

[0056] An electrolyser cell is usually considered to extend in a cell stack direction from an outer surface of a bipolar plate facing the cell and through a first (eg cathodic) chamber and further through a diaphragm 1 and through a second (eg anodic) chamber, and through the material of a further bipolar plate 6 and to the surface thereof facing the next cell in a row of such cells.

[0057] All bipolar plates 6 in the shown example of a cell in Fig. 1 are arranged with flexible elements 7 on each side, and on one side, the flexible elements 7 connects to a cathode 2, and on the opposed side they connect the bipolar plate 6 to an anode 3. The flexible elements 7 may comprise individual spring like elements as disclosed in Fig. 1, or may comprise woven, matted or similar types of flexible material all designed to ensure a limited but positive pressure on the electrode to which they are connected as well as an electrical connection between the bipolar plate and that electrode. Thus, even some deviations in manufacturing tolerances of bipolar plate, electrode and diaphragm shall not exclude a positive pressure on parts of the spacer 4 from the diaphragm 1 and an electrode 2;3 surface. Having springs or flexible elements on both sides of a diaphragm 1 allows for a wider range of movability of the diaphragm between the bipolar plates, and also in case some setting or wearing down of diaphragm and / or electrodes takes place over time, this can be accommodated by spring expansion while maintaining a positive pressurization force towards the diaphragm from the two bipolar plates.

[0058] It should further be noticed that the spacer is adapted to extend along a geometric plane, when left un-affected by any outer forces, and will thus sit between the electrode and adjacent diaphragm and not by itself contribute to any force between these two elements but will work simply to transfer such a force from the one to the other element.

[0059] The spacer disclosed in the embodiments shown in Figs. 1 and 2 is comprised of a multitude of openings transversely to the geometric plane, such as the plane between adjacent electrode 2;3 and diaphragm 1, and each such opening will be surrounded by a solid substance formed by the strands extending along the plane. The cathode and anode electrodes are made from a somewhat opens structure, such as a plate with a multitude of holes, a stretch metal plate, a woven metal fibre element or a sponge metal element or combinations of such elements or the like open structure element, all of which allows the electrolyte to flow transversely thereof and thus reach the membrane facing each of the mentioned multitude of openings. In a water electrolyser cell, there is going to be a flow of electrolyte and possible released gasses in a preferred direction, and an electrolyte and gas flow is thus going to be present in all the available space between a bipolar plate 6 and the diaphragm 1. Due to the spacer 4; 4.1 , the diaphragm surface and the electrode surface facing the diaphragm are going to be flushed by the electrolyte flow in the half-cell on all surface parts not being blocked by the presence of strands of spacer material and no build-up of super-saturation caused by stagnant flow between electrode 2;3 and diaphragm 1 is present.

[0060] In Fig. 1 the strands of the spacer 4 are placed independently of the diaphragm support mesh 5, and the spacing between spacer strands and their orientation in the plane is also not related to the diaphragm support mesh 5. In Fig. 2 the spacer 4 has a mesh number (number of strands per centimetre) which is the same as the mesh number of the diaphragm support mesh 5. And the spacer strands are arranged to be co- aligned with the strands of the support mesh 5 in a direction transversely of the diaphragm 1. The diaphragm support mesh 5 will in some measure block passage of ions through the diaphragm, at least in the transverse area occupied by the diaphragm support mesh 5. Adding the strands of the spacer 4 on top of this area and possibly compress the diaphragm material between the strands of the spacer 4 and the strands of the support mesh 5 may thus all in all have a lesser adverse effect on the conductivity (ionic conductivity) of the diaphragm than would be the case in the arrangement of the spacer disclosed in Fig. 1.

[0061] Possibly the spacer seen in Fig. 2 is made with a lower mesh number (fewer strands per cm) than the diaphragm support mesh 5, however keeping an alignment option between diaphragm support mesh 5 and the strands of the spacer 4. Thus the distance between strands in the spacer shall remain an integer multitude of the distance between strands in the support mesh 5.

[0062] It is also possible to align the strands of the spacer mesh with the flow in the individual cell, such as having a flow perpendicular to the strands in the mesh in one direction, such as in an upward direction. It is alternatively possible to have the flow moving in a diagonal direction and be aligned with a diagonal of square openings in the mesh such as by arranging the spacer accordingly with diagonals in a vertical direction and aligned with an upward moving cell internal flow.

[0063] In the above description, it has been taken for granted, that the mesh number of the spacer 4 is the same in the two orthogonal directions of the strands therein, however, it is an option to have strands closer to each other transversely to a flow direction, and then have a wider spacing between strands aligned with a flow direction within a cell or vice versa.

[0064] In Fig. 2, there are spacers 4; 4.1 at each side of the diaphragm 1 , and the spacers ensure like-size non-zero gaps D. However differently sized spacers may be used, giving rise to different non-zero gaps between the cathode and anode sides of the diaphragm and / or different mesh numbers on the two sides.

[0065] In Fig. 3, a further embodiment of a spacer is shown, where the spacer 8 itself is a part of the diaphragm 1. As seen, protrusions 8; 8.1 are provided as spacers in one or two opposed directions away from the diaphragm surface or surfaces. The protrusions 8 and further protrusion 8.1 making up the spacer may be oblong (not disclosed) to advance electrolyte and gas flow in a particular direction or may have a circular circumference in any plane parallel to the diaphragm surface plane and thus keep interference with the flow low.

[0066] As seen in the anode electrode 3 side of Fig. 3, the further protrusions 8.1 are shown in alignment with the strands 5 of the diaphragm support mesh.

[0067] When looking at the distance between the diaphragm surface and the top of the protrusions, or surface of spacer it is reckoned that if total thickness is defined as distance between electrodes, this value comprises the following contributors: diaphragm thickness + hight of protrusions 8; 81 , on one or both sides depending on embodiment, or diaphragm thickness + distance between diaphragm surface and surface points of the spacer 4; 4.1 ; 9; 9.1 most distanced from the diaphragm, (on one or both sides depending on embodiment.

[0068] Preferably the total thickness should be constrained by: Total thickness < 1500 |im (2)

[0069] Here it is assumed that the total thickness should preferably not exceed 1500 |im, to both ensure low ohmic losses and prevent overly long total length of the stack and stay above 50 |im to keep the risk of short circuits between the electrodes low.

[0070] It is assumed, that the presence of the protrusions or presence of the mesh- like spacer will ensure less super-saturation of dissolved gasses near the diaphragm surface, and thus a somewhat thinner diaphragm than the presently commercially available thin diaphragm of around 220|im could be employed without increasing cross over.

[0071] In Fig. 4, a further embodiment of a spacer is shown. Here a partially embedded spacer 9; 9.1 is shown, whereby spacer strands are partially embedded in the diaphragm material. As also seen in Fig. 4, there is no diaphragm support mesh inside of the diaphragm as the partially embedded strands of the embedded spacer 9; 9.1 will serve as a sufficient support means for the diaphragm. In Fig. 4, the embedded spacer 9 is disclosed at a cathode electrode 2 side of the diaphragm 1, and on the anode electrode 3 side, a further embedded spacer 9.1 is seen, however the embedded spacer 9, 9.1 may be provided at only the cathode electrode 2 or only at the anode electrode 3 side. The embedded spacer 9; 9.1 may be produced as a usual mesh, and then added to an also finalized diaphragm to give the shown embodiment. Alternatively, the embedded spacer 9, 9.1 is added to the diaphragm 1 during its manufacture. If an embedded spacer 9; 9.1 is provided on both sides of the diaphragm, it is preferred that the two meshes of the two embedded spacers 9, 9.1 are aligned with respect to each other in a direction perpendicular to the surface of the diaphragm 1.

[0072] Whether the spacer is an embedded spacer 9; 9.1 , which also supplants the diaphragm support mesh 5, or the spacer 4; 4.1 is provided along with a diaphragm support mesh 5, it is suggested to attach the spacer by one of the following processes:

[0073] -Brush the spacer mesh with solvent, apply the spacer mesh to the diaphragm 1 and partly dissolve the polymer in the surface of the diaphragm 1 and then wash the solvent away and re-solidify the polymer,

[0074] -Heat weld the embedded spacer 9, 9.1 to the surface of the diaphragm 1.

[0075] List of parts

[0076] 1 Diaphragm

[0077] 2 Cathode electrode 3 Anode electrode

[0078] 4 Spacer

[0079] 4.1 Further spacer

[0080] 5 Diaphragm support mesh 6 Bipolar plate

[0081] 7 Flexible element

[0082] 8 Diaphragm protrusions

[0083] 8.1 Furtehr diaphragm protrusion

[0084] 8.1 Further diaphragm protrusions 9 Embedded spacer

[0085] 9.1 Further embedded spacer D non-zero distance

Claims

Claims1. An electrolyser cell adapted for electrolyzing water into hydrogen and oxygen and comprising a diaphragm (1) which partitions the cell into a cathode chamber at a cathode side of the diaphragm and an anode chamber at an opposed anode side of the diaphragm (1) and an oxygen evolving anode electrode (3) arranged at the anode chamber side of the diaphragm (1) and a hydrogen evolving cathode electrode (2) arranged at the cathode chamber side of the diaphragm (1), characterised in that, a spacer (4; 4.1 ; 8; 8.1 ; 9;9.1) is provided between the cathode electrode (2) and the diaphragm (1), or between the anode electrode (3) and the diaphragm (1), or between both of anode and cathode electrodes and diaphragm (1), which spacer (4; 4.1 ; 8; 8.1; 9; 9.1) is adapted to ensure contact between electrolyte fluid elements in the cathode and / or in the anode chamber and the diaphragm (1), and adapted to ensure a pre-determined non-zero distance (D) between the cathode electrode (2) and / or the anode electrode (3) and the diaphragm (1).

2. An electrolyser cell as claimed in claim 1, characterised in that, the spacer (4; 4.1; 9; 9.1) comprise a coherent screen element adapted to extend flatly in a layer between opposed and facing surfaces of an electrode (2; 3) and the diaphragm (1).

3. An electrolyser cell as claimed in claim 2, characterised in that, the spacer (4; 4.1; 9; 9.1) is adapted to extend along a substantially geometric plane and comprise a multitude of openings transversely to the geometric plane.

4. An electrolyser cell as claimed in claim 3, characterised in that, the solid substance of the spacer (4; 4.1 ; 9; 9.1) is adapted to be resistant to alkaline water and oxygen, and resistant to alkaline water and hydrogen and resistant to alkaline water and a combination of oxygen and hydrogen all at concentrations up to about 30% - 45% by weight of potassium hydroxide in water, and temperatures up to 150 degrees Celsius or up to 120 degrees Celsius or up to 110 degrees Celsius.

5. An electrolyser cell as claimed in claim 4, characterised in that, the solid substance of the spacer (4; 4.1 ; 9; 9.1) covers a percentage of the area of the diaphragm area when projected perpendicular onto the diaphragm, whereby this percentage is between 1 % and 25% or preferred between 2% and 12% or most preferred between 4% and 6% of the diaphragm area.

6. An electrolyser cell as claimed in claim 5, characterised in that, the solid substance comprises at least one of the following materials a. Polypropylene b. ETFE c. Polyphenylene sulfide d. Polysulfon group (e.g. PSU, PESLI and PPSLI) e. Polyetheretherketone (PEEK)7. An electrolyser cell as claimed in claim 1 , characterised in that, a spacer (4; 4.1) is provided at least between any of the electrodes (2; 3) and the diaphragm (1), which spacer comprises singular or coherent 3D-printed polymer spacer elements printed onto the electrode, which polymer spacer elements at proximal parts adhere to electrode surface parts facing the diaphragm (1) and at distal ends are terminated a predetermined distance from the electrode surface.

8. An electrolyser cell as claimed in any of the above claims, charactrerised in that, at least one of the cathode electrode (2) and the anode electrode (3) is subjected to a pressure force towards the diaphragm (1), to ensure contact between the spacer (4; 4.1 ; 8; 8.1 ; 9; 9.1) and adjacent diaphragm (1) and between the spacer (4; 4.1 ; 8; 8.1 ; 9; 9.1) and the adjacent electrode surface.

9. An electrolyser as claimed in claim 8, characterised in that, the pressure force originates from elements (7) such as at least one spring arranged between the electrode (2; 3) and a bipolar plate (6) to thereby ensure that the electrode (2; 3) and diaphragm (1) are pressed towards each other with a predefined pressure force.1910. Method for preparing an electrolyser cell adapted for electrolyzing water into hydrogen and oxygen where a diaphragm (1) which partitions the cell into a cathode chamber and an anode chamber at respective sides of the diaphragm is provided and an oxygen evolving anode electrode (3) is arranged at the anode chamber side of the diaphragm (1) and a hydrogen evolving cathode electrode (2) is arranged at the cathode chamber side of the diaphragm (1) and whereby a spacer (4; 8; 9;) is provided between the diaphragm (1) and the one or the other of the electrodes (2; 3) placed adjacent to the diaphragm (1) or a spacer (4; 8; 9; ) is provided between the diaphragm (1 ) and the one electrode and a further spacer (4.1 ; 8.1 ; 9.1 ) is provided between the other of the electrodes and the diaphragm (1) and placed adjacent to the diaphragm (1).

11. Method as claimed in claim 10, where the spacer (4; 4.1 ; 9; 9.1 ) comprise a coherent screen element adapted to extend flatly between opposed and facing surfaces of an electrode (2; 3) and diaphragm (1) in one or in both of the cathode and the anode chambers.

12. Method as claimed in claim 11 , whereby the spacer (9; 9.1) is at least partially submerged into and fused with the material of the diaphragm (1) prior to an assembly of a cell.

13. Method as claimed in any one of claims 10 - 12, whereby the spacer (4; 4.1) in a step prior to the assembly of electrode and diaphragm is adhered to the respective electrode or electrodes.

14. Method as claimed in any one of claims 11 - 13 whereby a spacer (4; 4.1; 9; 9.1) having an average distance between strands of no less than 250 |im and no more than 5000 |im and comprising one or more of the following materials: a. Polypropylene b. ETFE c. Polyphenylene sulfide20 d. Polysulfon group (e.g. PSU, PESLI and PPSLI) e. Polyetheretherketone (PEEK) osen.

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