GB2613360A

GB2613360A - Electrolyser

Info

Publication number: GB2613360A
Application number: GB2117306.7A
Authority: GB
Inventors: James Mason Thomas; Maier Maximilian
Original assignee: Bramble Energy Ltd
Current assignee: Bramble Energy Ltd
Priority date: 2021-11-30
Filing date: 2021-11-30
Publication date: 2023-06-07
Also published as: GB202117306D0

Abstract

An electrolyser 200 comprising: a cathode structure comprising a first PCB plate 202 and an electrically conductive substrate 220; an anode structure comprising a second PCB plate 204 and an electrically conductive substrate 220; a separator 218 located between the cathode structure 202 and the anode structure 204; two transport layers, 214, 216 one transport layer 216 disposed between the anode structure 204 and the separator 218 and one transport layer 214 disposed between the cathode structure 202 and the separator 218; and at least one fluid path to supply an electrolyte to the electrolyser 200. The PCB plates may also comprise copper plated layers with subsequent nickel overlayers. The transport layer 214,216 may also comprise a catalyst and porous material such as felt or metal mesh.

Description

Electrol ser The present invention relates to electrolysers, alkaline electrolysers, alkaline electrolyser apparatus for the production of hydrogen, electrolyser stacks, the use of an electrolysers and electrolyser stacks for the production or generation of hydrogen, methods of generating hydrogen, methods of manufacture of electrolysers and use of PCB plates in electrolysers and electrolyser systems.

The present inventions have particular application to the generation of hydrogen, particularly green hydrogen production.

BACKGROUND

An electrolyser is a device in which electrolysis occurs, where an electrolyte is decomposed as part of a chemical reaction at electrodes, driven by an electric current passed through the electrolyte via the electrodes. Without the current the reaction would be non-spontaneous.

The electrolyte decomposes due to ionization. An electrolyte is a chemical substance which contains some free ions and carries electric current (e.g. an ion-conducting polymer, solution, or a ionic liquid compound). Due to the need for the free flow of ions, electrolysis cannot occur in solid state materials, so an electrolyte can be i) melted or in a molten state, H) an aqueous solution created by solvation or reaction of an ionic compound with a solvent (such as water) to produce the necessary mobile ions, or iii) pure water. For example, in electrolysis of molten NaCI, chlorine gas forms at the anode, and deposits of metal sodium form at the cathode. For example, in electrolysis of pure water, at the cathode hydrogen bubbles are formed and at the anode oxygen bubbles form.

Electrodes are connected to a power source and immersed in the electrolyte. Each electrode will attract ions of the opposite charge, effectively electrons are introduced at the cathode as a reactant and removed at the anode as a product. Electrodes are typically graphite, metal or semiconductor materials, and choice will vary based on cost, supply and level of reaction with the electrolyte of choice. Non or low reactivity materials such as graphite and platinum are typically chosen.

Alkaline electrolysis is a specific type of electrolysis, where electrodes operate in a liquid alkaline electrolyte solution, typically potassium hydroxide (KOH), sodium hydroxide (NaOH) or water (H20). The electrodes are typically separated by a thin, porous, non-conductive foil (a diaphragm or separator), which prevents electrical shorting between electrodes, but allows for small distances between the electrodes for compact electrolysers. The separator prevents mixing of gases generated at the anode and cathodes, hydrogen at the cathode and oxygen at the anode. The ions in the aqueous alkaline solution can pass through the separator.

In alkaline water electrolysis (AWE) an alkaline solution is the electrolyte. Power is supplied by an external circuit which creates an electrical potential difference at the interface of the electrolyte and the electrode. Water reacts at the cathode, in 10 the hydrogen evolution reaction (HER) by means of electron (e-) transfer (e.g. 4H20 + 4e- 40H-+ 2H2). Hydroxide ions OH-produced in the HER are able to pass through the separator and react at the anode. There the hydroxide ions are consumed by the oxygen evolution reaction (OER): 40H--> 2H20 + 02 + 4e-.

Figure 1 shows a system 100 set up for and around an alkaline electrolyser 102.

System 100 comprises alkaline electrolyser 102. The electrolyser 102 comprises a cathode half 104 and an anode half 106. The electrolyser 102 is powered by power supply 108, providing the electrical power necessary to drive an electrolysis reaction. Heater 110 heats the electrolyser 102 to increase electrolysis speed, whilst heat exchanger 112 can recover heat from the various fluids to optimise performance of the electrolyser 102. Diaphragm pump 114 moves the fluids around the system 100 and can act to pressurise the gases produced from the electrolyser 102. Liquid-gas separator 116 separates the produced gases from the liquid electrolyte/water, separating the hydrogen 122 and oxygen 124. The produced gases hydrogen 122 and oxygen 124 are passed through pressure regulator valves 120 to regulate their pressure. Pressure relief valves 118 are also present, if necessary. From the liquid-gas separator 116, hydrogen can be stored, pressurised, and/or transported to where it is needed.

Alkaline electrolysis has shown promise in the renewable energy sector for enabling efficient energy conversion and storage. An alkaline environment is suitable for a large range of materials with good chemical stability under the operating conditions such processes occur. Green hydrogen can be produced through electrolysis, separating water into hydrogen and oxygen, possibly using electricity generated from renewable sources. Alkaline electrolysers could generate hydrogen for fuel cells to utilise.

Known alkaline electrolysers suffer from manufacturing scale issues. They are large bulky pieces of industrial equipment which do not lend to scaled manufacture. They are also expensive to produce, particularly on scale. As such, in a time where green hydrogen is in high demand an efficient and scalable technology in this space could be very valuable.

In view of the foregoing, it is desirable to provide improved alkaline electrolysers, improved methods of generating hydrogen and improved manufacture of alkaline electrolysers.

SUMMARY

According to a first aspect, there is provided an electrolyser. The electrolyser comprises: a cathode structure comprising a first PCB plate and an electrically conductive substrate; an anode structure comprising a second PCB plate and an electrically conductive substrate; a separator located between the cathode structure and the anode structure; two transport layers, one transport layer disposed between the anode structure and the separator and one transport layer disposed between the cathode structure and the separator; and at least one fluid path to supply an electrolyte to the electrolyser. Preferably, the electrolyser is an alkaline water electrolyser, for the production of hydrogen.

Surprisingly the inventors have found that PCBs can be utilised to produce high performing electrolysers. The construction of the present alkaline electrolysers is unique being a PCB structure. This has a clear manufacturing advantage from a supply perspective. The manufacture cost per cm3 will be significantly lower than electrolysers of the art, for example metal electrolysers. These electrolysers can be manufactured on a PCB line with no modification to materials or manufacturing equipment required. These can operate at typical operating temperatures of alkaline electrolysers, for example between 60 and 80 °C.

Further, electrolysers of the art are bulky metal constrictions with mechanical sealing. The use of PCB plates in the manufacture of alkaline electrolysers allows for an inherently sealed design, using compression sealing.

Preferably, the first PCB plate and/or the second PCB plate comprise a copper plated layer disposed on the PCB plate and comprise a nickel plated layer disposed on top of the copper plated layer. This may be referred to as a 'current collector' layer, as it must be conductive to allow an electric current to flow. Rather than copper, an additional layer, coating, deposit or current collector layer could be added which functions to replace the copper. As described in the Examples later, nickel was found by the inventors to have increased stability in KOH.

Preferably, the electrically conductive substrate of the cathode structure and the anode structure comprises metal. Preferably, copper and/or nickel or an alloy of copper and/or nickel, preferably nickel coated copper, ENIG coated copper, conductive epoxy coated copper, HASL coated copper, nickel-phosphorus coated copper or carbon coated copper.

Preferably, at least one of the first PCB plate and the second PCB plate are routed to comprise a fluid flow path for the electrolyte. This routing may be depth routed is in a PCB plate, preferably at least one fluid flow path is formed within at least one PCB layer such that the fluid flow path is routed or grooved within the PCB layer without the routing or groove extending all the way through the PCB plate. This ensures that the electrolyte has a flow path or a channel to the desired reaction areas (in contact with the transport layers), but does not flow out of the electrolyser or in any unwanted directions/areas. The ability to manufacture and customise PCB plates to have desired and customisable depth routed flow paths is an advantage of this PCB technology, it is harder and more expensive to achieve on metal plates and less customisable. Preferably, the fluid flow path directs the electrolyte to the nickel plated layer disposed on top of the copper plated layer on the first PCB plate and the second PCB plate.

Preferably, the first PCB plate and second PCB plate have at least one fluid inlet and at least one fluid outlet drilled extending all the way through the PCB plate. Preferably, the outlet is larger than the inlet. Because gases are generated at the cathodes and the electrodes, a larger outlet 206, 208 allows separation of the liquids and gases generated. The liquid will sink to the bottom and the gas will rise to the top, a large outlet 206, 208 relative to the inlet 208, 212 aids separation of this after the gas/electrolyte has passed through the electrolyser 200. This is advantageous allowing improved separation of the gas and liquid.

Preferably, the electrolyte comprises KOH and/or NaOH.

Preferably, the transport layers are porous transport layers. Preferably, the transport layers comprise a catalyst. Preferably, the transport layers comprise nickel as a Felt, nickel as a mesh or nickel foam, or alloys of nickel, or Zirconium.

Preferably, the transport layer comprises PCB or layered PCB, preferably also comprising nickel and/or a catalyst. Preferably the PCB has multiple holes through the whole body of the PCB.

Preferably, the anode transport layer and cathode transport layer are located adjacent the current collector area of the PCB plate.

Preferably, the separator comprises NiO or Zirfon (zirconia and polysulfonate).

Preferably, the electrolyser further comprises end plates and/or current collection plates/current collectors. These may be disposed either side of the anode and cathode plates to encase or house the electrolyser.

Preferably, the electrolyser further comprises housing. Housing may contain the herein described components, other components, or means to link the electrolyser to other electrolysers or wider system components. The housing may be or may comprise end plates or current collectors.

Preferably, the electrolyser further comprises an anode chamber and a cathode chamber suitable for fluid flow of the electrolyte. These chambers may be formed by the depth routing of the PCB plates as described herein, optionally in combination with the other components and the sealing described herein, enclosing the chamber.

Preferably, the electrolyser is up to 10 kW.

Preferably, the electrolyser is laminated together, preferably by heat bonding layers of sealing between the PCB plates under an increase temperature. This ensures the electrolyser is sealed Use of lamination with for example an epoxy resin prepreg also maintains compression of the layers, which can be an important component in maintaining electrolyser performance, without compromising distribution of reactant fluids.

According to a further aspect, there is provided an electrolyser apparatus for the production of hydrogen, the electrolyser apparatus comprising an electrolyser as described in the above preferably described electrolysers, or other electrolysers described herein or above.

According to a further aspect, there is provided an electrolyser apparatus for the production of hydrogen, the electrolyser apparatus comprising multiple electrolysers as described in the above preferably described electrolysers, or other electrolysers described herein or above.

This may be an electrolyser stack, which may comprise multiple electrolyser cells as describe herein arranged as a stack, in order to produce a greater rate of hydrogen production. Such a stack may include between two cells and two hundred cells, more typically between eight cells and one hundred cells. Such a stack may comprise housing. Such a stack may comprise end plates and/or current collectors. The stack may comprise electronic means to control operation of the stack, or other such electrical or control modules and/or components.

According to a further aspect, there is provided the use of an electrolyser of any one of the electrolysers described herein or above, or the electrolyser apparatus or stacks described herein or above, to generate hydrogen.

According to a further aspect, there is provided a method of generating hydrogen, the method comprising using an electrolyser of any one of the electrolysers described herein or above, or the electrolyser apparatus or stacks described herein 20 or above, to generate hydrogen.

According to a further aspect, there is provided a method of manufacture of an electrolyser, the method comprising laminating two or more PCB boards to make an electrolyser.

Preferably, plates and electrolyser components may be sealed together to form the electrolyser. Plates may be sealed together using known PCB sealing methods, for example PCB layers may be sealed with an epoxy resin prepreg (herein 'prepreg'). In construction of an electrolyser the components may be sealed with layers of prepreg between the different layers, with layers then laminated together.

Use of a sealing materials such as prepreg, and the use of PCB materials, ensures that the electrolyser is sealed from anything not deliberately directed to the components of the electrolyser by the inlets/channels/flow fields in the PCB boards (e.g. anode and cathode plates) directly adjacent to the internal electrolyser components. This is an advantage of the PCB technology, it allows quick, simple and cheap construction of such structures. Use of lamination with for example an epoxy resin prepreg also maintains compression of the layers, which can be an important component in maintaining electrolyser performance, without compromising distribution of reactant fluids.

Preferably, the method may involve involving careful pre-cutting and alignment of materials, along with bespoke heating, cooling, pressure and washing cycles.

Preferably, Mechanical seals could be used additionally to seal the electrolysers, particularly for electrolysers which will operate a higher pressures.

Preferably, before sealing, plated through holes can be drilled into the plates, along with inlet and outlet holes or other holes for bolting could be drilled or routed.

Preferably, may be due to the elevated pressures and/or temperatures at which alkaline electrolysers may be operated at, alternative sealants to prepreg may be used, for example Ethylene Propylene Diene Rubber Monomer (EPDM), polyvinylidene fluoride (PVDF) or fluoroelastomers can be used.

According to a further aspect, there is provided the use of PCB plates as electrodes in an electrolyser.

According to a further aspect, there is provided the use of PCB plates in an electrolyser.

According to a further aspect, there is provided an electrolyser system comprising an electrolyser of any one of the electrolysers described herein or above, or the electrolyser apparatus or stacks described herein or above. The system may comprise a power supply, providing the electrical power necessary to drive an electrolysis reaction. The system may comprise a heater to heat the electrolyser, e.g. to increase electrolysis speed. The system may comprise a heat exchanger to recover heat from the various fluids, e.g. to optimise performance of the electrolyser. The system may comprise a pump for example a diaphragm pump to move fluids around the system, and/or to pressurise the gases produced from the electrolyser. The system may comprise a liquid-gas separator to separates the produced gases from the liquid electrolyte/water, e.g. separating the hydrogen and oxygen. The system may comprise pressure regulator valves, where the produced gases hydrogen and oxygen are passed through pressure regulator valves to regulate their pressure. The system may comprise also pressure relief valves. From a liquid-gas separator, hydrogen can be stored, pressurised, and/or transported to where it is needed. The system may comprise a dryer to absorb water. The system may comprise means to store hydrogen or other gases.

Any the preferably components of the first electrolyser aspect described may be applied to the other aspects described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

Specific embodiments of the invention will now be described by reference to the accompanying drawings, in which: Figure 1 shows a schematic of an electrolyser system; Figure 2 shows a schematic exemplary embodiment of an electrolyser; Figure 3a shows an exemplary PCB plate; Figure 3b shows an exemplary PCB plate; Figure 4 shows an electrolyser with end plates and current collectors; Figure 5 shows an electrolyser as part of an electrolyser system; Figure 6a shows a 2 V hold over 200 hours with an embodiment of an electrolyser; Figure 6b shows the Polarisation curve for the PCB Alkaline Electrolyser at °C in 1 M KOH; Figure 6c shows a potentiostatic hold of a PCB Alkaline Electrolyser showing change in performance due to gas accumulation in nickel foam electrode; and Figure 7 shows polarisation curves of prior art electrolyser technologies for comparison.

DETAILED DESCRIPTION

Embodiments will now be described in detail with reference to the accompanying drawings. The same reference signs indicate the same or similar features in different figures and embodiment of the invention, although this is only for reference and is not limiting on the invention. In the following detailed description numerous specific details are set forth by way of examples, in order to provide a thorough understanding of the relevant teachings. However, it will be apparent to one of ordinary skill in the art that the present teachings may be practiced without these specific details.

FIG. 2 shows an electrolyser 200 or electrolyser cell 200 according to an embodiment. This is a 50 cm2 PCB alkaline electrolyser. Electrolyser 200 is a stackable PCB electrolyser comprising nickel coated PCB plates for use in a KOH electrolyte solution, as described herein.

Electrolyser 200 comprises two PCB plates 202, 204, which are cathode plate 202 and anode plate 204. These PCB plates 202, 204 sandwich the other components of the electrolyser 200. These plates 202, 204 act as the cathode and the anode in the electrolyser.

In this and other embodiments described herein, PCB plates may be produced in the known way. Insulating core layers may be made of dielectric substrates such as FR-1, FR-2, FR-3, FR-4, FR-5, FR-6, CEM-1, CEM-2, CEM-3, CEM-4, CEM-5, polytetrafluoroethylene, and G-10, preferably core layers are be made of or comprise FR-4. Layers may be laminated together with an epoxy resin prepreg.

In order to yield conductive areas, or conduction between PCB layers, a thin layer of copper may either be applied to the whole insulating substrate and etched away using a mask to retain the desired conductive pattern, or applied by electroplating. The PCB plates may have plated through holes (PTHs), copper through holes which allow conduction of electrical current from one face of the plate to another.

In embodiments, PCB materials may benefit from a coating to improve stability in the alkaline conditions that alkaline electrolysers operate in. Copper, the most commonly used metal in PCB manufacturing is often used for conducting current across different layers in the PCB, but will corrode in alkaline solutions, particularly at high potentials. Thus, the copper benefits from protection in some way. The PCB components or specifically the exposed copper areas may be coated or plated with a further layer on top of the copper. This may be referred to as a 'current collector' layer, as it must be conductive to allow an electric current to flow. Rather than copper, an additional layer, coating, deposit or current collector layer could be added which functions to replace the copper. As described in the Examples later, nickel was found by the inventors to have increased stability in KOH. The cathode current collector layer 220 used in electrolyser 200 is nickel and the anode current collector layer 220 used in electrolyser 200 is nickel.

For an anode this additional layer, coating, deposit or current collector layer could be or comprise nickel, a nickel alloy, nickel coated copper, Electroless nickel immersion in gold (ENIG) coated copper, conductive epoxy coated copper, and hot air solder levelling (HASL) coated copper or nickel-phosphorus coated copper.

For a cathode this additional layer, coating, deposit or current collector layer could be or comprise nickel, a nickel alloy, nickel coated copper, Electroless nickel immersion in gold (ENIG) coated copper, conductive epoxy coated copper, hot air solder levelling (HASL) coated copper, nickel-phosphorus coated copper or carbon coated copper.

ENIG has the advantage of using relatively cheap (relative to gold) nickel as a bulk conductor that also has relatively low contact resistance with a thin layer of gold over the top which prevents oxide layer formation (and thus maintains a low contact resistance with time) between cells and to electrical terminals.

HASL is a layer of molten solder which coats all the copper surfaces and enables electrical contacts to be easily made. Relative to ENIG HASL has a lower planarity zo but is cheaper relative to ENIG.

There may additionally or instead be a non-metallic conductive (protective) layer added, e.g. screen printed, (i.e. a carbon based ink, or conductive epoxy resin).

The current collector layer 220 is located in the region central of the anode plate 204 and cathode plate 202, adjacent where the anode transport layer 216 and cathode transport layer 214 are located, so that the current collector layers are adjacent to the anode transport layer 216 and cathode transport 214 layer. In the embodiment seen in FIG. 2 this is a circular shaped current collection area 220, but the shape could change based on ensuring an equivalent surface area to the anode transport layer 216 and cathode transport layer 214, as well as the separator 218. In FIG. 2 circular shaped current collection area 220 is visible only on anode plate 204. An identical current collection area is also found on cathode plate 202, but is not visible in FIG. 2 because of the angle of the plate. Under the nickel current collection area 220 is the copper plating of the PCB plates 202, 204. These plates 202, 204 are FR4 sheet sheets with copper either side, then nickel is added on a side (or both sides) in a plating process to create the current collector layer 220.

Due to the plating on these plates 202, 204, when an electrical current is directed to a plate, a plate can act to transport current to the electrolyser, specifically electrons to the cathode. The copper on the outer face of 202 is electrically connected via PTHs in the PCB to the inner surface of the plate which is coated in nickel. Due to the choice of coating, these PCB plates 202, 204 are non-reactive so do not degrade over time. This current collection area is the "reaction" site for the alkaline electrolyser, as all components necessary for the reactions are present.

The PCB plates 202, 204 may have copper, copper plated nickel or some other conductive material deposited on the edge of the plates, in order to test the voltage on the plate or for a connection to an external power source to power the electrolyser reactions. The plates may additionally or instead have a tab or exposed point which has copper, copper plated nickel or some other conductive material deposited on the edge of the plates, in order to test the voltage on the plate or for a connection to an external power source to power the electrolyser zo reactions.

The PCB plates 202, 204 shown here, but also for all embodiments, have holes 206, 208, 210, 212, 222 drilled or routed through the whole body of the plates. In FIG. 2, cathode outlet 206, cathode inlet 208, anode outlet 210 and anode inlet 212 are all labelled. Further holes 222 are also labelled, only 2 of the 8 of these holes on both the cathode plate 202 and the anode plate 204 are labelled. Using routed or drilled holes mean that the plates are easily, quickly and cheaply manufacturable. The plates are drilled for two primary reasons: i) inlet 208, 212 and outlet 206, 210 holes to distribute reactants and products through each cathode plate 202 and anode plate 204 in an electrolyser cell 200 to the enclosed layers e.g. the electrodes and the catalysts, as well as to and from end plates (not shown in Fig. 2), where end plates can have fittings that distribute the fluids/gas into and out of the wider system; and ii) to provide holes 222 where locations where bolts or other such holding means can hold electrolyser cells 200 together for sealing and compression purposes. These holes 222 can be for alignment and/or compression, and/or ultimately fixing, of end plates.

Generally, there are multiple designs of this PCB plates that are appropriate, the drilling or routing through the whole body of the PCB plate to create the flow fields or channels could be in any pattern or design which ensures correct passage of fluids and/or fixation or bolt locations.

Here outlets 206, 210 are larger than inlets 208, 212. Because gases are generated at the cathodes and the electrodes, a larger outlet 206, 208 allows separation of the liquids and gases generated. The liquid will sink to the bottom and the gas will rise to the top, a large outlet 206, 208 relative to the inlet 208, 212 aids separation of this after the gas/electrolyte has passed through the electrolyser 200.

The electrolyser could further comprise a separate outlet, for outlet of gas alone. Positioned in a spot, for example top centre, to ensure gases could be vented off from the electrolyser.

Electrolyser 200 comprises a cathode transport layer 214 and an anode transport layer 216. These are porous so are sometimes known as porous transport layers (PTLs). The cathode transport layers 214 and anode transport layer 216 in electrolyser 200 are nickel foam.

Generally, the transport layers act to allow transport ions generated at the electrodes across the separator to the other side of the electrolyser. They also allow thermal conduction through the electrolyser. Variations in their material properties can affect the electrolysis reaction rate and efficiency.

In this and other embodiments described herein, the cathode transport layer and the anode transport layer may comprise or be made from other materials. The anode transport layer may comprise or be made from nickel as a Felt, nickel as a mesh or nickel foam, or alloys of nickel, or Zirconium. The cathode transport layer may comprise or be made from Nickel as a Felt, nickel as a mesh or nickel foam, or alloys of nickel. Preferably transport layers are high surface area materials and made from a material such as nickel which can act as a catalyst for the reaction to take place at the electrodes. A high surface area ensures a higher reaction rate. When transport layers are made of materials such as nickel form or mesh they provide a high surface to volume ratio. Transport layers act to facilitate transport of water, gas, electrolyte and electrical current. Current and water/electrolyte is needed at any reaction site on the PTL as it drives the reaction. A suitably porous PTL will also facilitate the effective removal of produced gas such that more electrolyte can react at the reaction site once a product gas bubble is formed.

Further, transport layers made be made from or comprise a PCB. Complex 3D geometries can be achieved with PCB materials, due to their controllable manufacture techniques. For example, a nickel PCB plate with hole geometries could be utilised as transport layers, or for example, stacked PCB layers of nickel coated plates with hole geometries could be utilised as transport layers. These could act like a nickel mesh with FR4, optionally also with copper plating, as an intermediate layer.

The transport layers 214, 216 can be coated/loaded with a catalyst (not visible in FIG. 2). The cathode catalyst used in electrolyser 200 is nickel foam and the anode catalyst used in electrolyser 200 is nickel foam. An advantage of the present PCB technology for an alkaline electrolyser is that the catalyst can be manufactured in such a way that also enables effective fluid and electron transport, due to the utilisation of the PCB plates as the anode and the cathodes.

In this and other embodiments described herein, the catalysts may comprise or be made from other materials. The cathode catalysts may be MoCa (typical loading 4 mg cm-2), Pt black, Pt/C, Ni-Mo, or alloys of these metals. The anode catalysts may be NiFe (typical loading 4 mg cm-2), Iridium oxide, Copper cobalt oxides or Nickel cobalt oxides, or alloys of these metals.

The type of catalyst chosen may determine which side of the electrolyser will react as the anode and which side will act as the cathode. All other components may be identical, such as plate geometry, transport layer material etc., whilst the catalysts may differ to determine which reaction is that of the anode and which is that of the cathode. Other factors may also alter symmetry of the two halves of the electrolyser, such as the materials chosen for the transport layers, to determine which side acts as an anode and which side acts as a cathode.

Because the transport layers 214, 216 are typically made of a material such as nickel which can act as a catalyst for the reaction to take place at the electrodes, a catalyst is not essential for the alkaline electrolyser to function. A high surface area metal such as nickel transport layer may ensure a reaction of a sufficient rate can take place at the electrodes.

Electrolyser 200 comprises a separator 218. The separator used in electrolyser 200 is Zirfon. The separator, in this and other embodiments described herein, is thin, porous and non-conductive material, for example a foil, which prevents electrical shorting between electrodes. It ensures there is only a small distance between the electrodes, allowing for the manufacture of a compact electrolysers. The separator prevents mixing of gases generated at the anode and cathodes, for example hydrogen at the cathode and oxygen at the anode. The electrolyte, the aqueous alkaline solution (for example KOH), contains ions and can penetrate the pores of the separator.

In this and other embodiments described herein, the separator may comprise or be made from other materials, for example the separator may be NiO or Zirfon (zirconia and polysulfonate).

The liquid electrolyte utilised with the electrolyser 200 is Potassium hydroxide (KOH) solution in water. Potassium hydroxide is typically 30 to 50 wt%, but may also be usable at lower concentrations, e.g. 1 mol/L. Any strongly basic or alkaline solution known in the art may be utilised with the presently described electrolysers, for example KOH or NaOH in a concentration between 1M and 10M.

Figure 3a shows an exemplary PCB plate of an embodiment, the same plate as cathode plate 202 and anode plate 204 in electrolyser 200 in FIG. 2. This plate could be an anode plate 204 or a cathode plate 202. This is a 50 cm2 PCB alkaline electrolyser plate. Current collection layer 220 is circular and central to the plate. Holes 206, 208, 222 are drilled or routed through the whole body of the plate.

zs Plate outlet 206, and plate inlet 208 are all labelled. Further holes 222 are also labelled, only 2 of the 8 of these holes on the plate 202/204 are labelled.

Depth routed areas 224 are also visible in the plate 202/204 which is the fluid flow field, fluid flow path or fluid flow channel (terms interchangeable) of this plate 202/204. This is where the electrolyte will flow from the fluid inlet 208 to the reaction area, at the current collection layer 220 adjacent the transport layers 214, 216. The electrolyte will then flow out of the outlet 206. Here the reaction area adjacent is the nickel plated area, here circular, due to the fact it is adjacent to the transport layer, which may comprise the catalyst.

The same plate is used for both the cathode plate 202 and anode plate 204, but the plate is flipped for opposing electrodes. This includes all depth routed areas 224 of the plate, and which side is plated with the current collection means 220. When the plates 202/204 are facing each other, one diagonal of a depth routed area 224 serves the anode inlet & outlet of one plate 202, and the opposite diagonal of depth routed areas 224 serves the cathode inlet & outlet 206/208 of the other plate 204. A "cross" of the depth routed areas is formed. Where there is no depth routed area from a hole (two holes not labelled 206/208), the hole only acts as a manifold to other flow fields. This is advantageous for manufacture because the same plates can be manufactured for anode and cathode plates, making manufacture more efficient.

Electrolysers of this embodiment, and other embodiments described herein, comprise at least one first fluid path to supply an electrolyte to the electrolyser. There can be a first fluid path to supply the cathode structure and/or a second fluid path to supply an electrolyte to the anode structure, e.g. a first fluid path and a second fluid path, one for the anode plate and one to the cathode plate. These fluid paths can be the routed area on the cathode or the anode plate, which runs from the inlet, over the reaction area and to the outlet, so fluid can flow in and out of the reaction area of the plate.

PCB plates of all embodiments can be routed to comprise one or more fluid flow paths, for the electrolyte. These fluid flow paths can be formed PCB layers or plates such that the fluid flow path is routed or grooved within the PCB layer without the routing or groove extending all the way through the PCB plate. This creates a channel or routed area rather than a hole through the body of the plate.

This means that other than the inlets and outlets to the plates, the electrolysers internally are sealed to fluids. The two halves of the electrolyser are also fluidically sealed from each other, because of the presence of the separator and the sealed PCB structure. Routing flow paths into the PCB structures allows control of fluid flow, particularly electrolyte fluid. This means that in this embodiment the fluid flow paths can direct the electrolyte to the nickel plated layer disposed on top of the copper plated layer on the first PCB plate and the second PCB plate. This is adjacent to the transport layer, which may comprise the catalyst, so here the electrolysis will take place.

This could also be structured, or described, as there being an electrolyte chamber at each electrode -one at the anode and one at the cathode. These are fluidically sealed, other than the presence of the inlet(s) and the outlet(s). This chamber can be created due to the depth routing on the PCB plates. The electrolyte will be in contact with the transport layer and the anode/cathode plate, enabling the electrolyser reactions to take place within the chamber. Ions generated can then transport across the separator.

Figure 3b show further exemplary PCB plate 302 of an alternative embodiment. This plate 302 could be an anode plate or a cathode plate. This is a 9 cm2 PCB alkaline electrolyser plate. This whole plate is nickel coated so technically all has a current collection area. This ensures the whole plate is not likely to corrode as it is nickel coated. Plate outlet 206, and plate inlet 208 are labelled, where electrolyte is introduced to the plate flow field 320. Further holes 322 are also labelled, only 2 of the 4 of these holes on the plate 302 are labelled. Electrical connection point 306 is also labelled.

The four larger holes visible are for compression and alignment, as described herein. The smaller holes are plated through holes. These may be utilised to transport current from one face of the plate to another if necessary, or they may be capped with resin if necessary, for example they may be capped in an electrolyte stack to prevent leaks between adjacent plates in a stack.

The plate 302 is depth routed a flow field 320 to ensure that the liquid electrolyte introduced to the plate is able to be evenly distributed to the internal components of the electrolyser. In FIG. 3 a serpentine flow field 320 is visible only on plate 302. An identical flow field is also found on cathode plate 202, but is not visible in FIG. 2 because the field is not drilled or routed through the whole depth of the plate, it is only to partial depth (hence "depth routed"). The flow field is a channel through which liquid flows from the plate inlet to the plate outlet. Gas generated at the electrodes may also flow out of the plates via these flow fields to the outlets.

For this embodiment, the serpentine pattern of the flow field 320 is only exemplary. Other patterns could be used for the flow fields in this or other embodiments herein. The flow field pattern could be used on anode or cathode plates and could be identical or different depending on flow need.

Figure 4 shows an electrolyser plate with further end plates and further current collectors, with all relevant components from FIG. 2 re-labelled. Further shown in this figure are end plates 402 and current collectors 404. Current collector layers serve to distribute current from a power supply across the entirety of a plate -their desirable properties are to be highly conductive, resistance to corrosion, and to interfere as minimally as possible with the manifolding of the reactant and product fluids. The end plates provide compression for sealing and contact resistance between layers of the electrolyte. The endplates also provide places where pressurised fluid connectors can be mounted to and distribute into the stack.

Multiple electrolysers could be stacked together with such end plates 402 to compress the electrolysers. Endplates can act to compress electrolysers described herein to seal them, to preventing any unwanted any fluid leakage in operation. Electrolysers can be bolted together to ensure compression. The compression also reduces contact resistance.

Plates and electrolyser components may be sealed together to form the electrolyser. Plates may be sealed together using known PCB sealing methods, for example PCB layers may be sealed with an epoxy resin prepreg (herein prepreg'). In construction of an electrolyser the components may be sealed with layers of zo prepreg between the different layers, with layers then laminated together.

Boards which are laminated with a specific lamination process, involving careful pre-cutting and alignment of materials, along with bespoke heating, cooling, pressure and washing cycles.

Mechanical seals could be used instead of or additionally to seal the electrolysers, particularly for electrolysers which will operate a higher pressures.

Before sealing, plated through holes can be drilled into the plates, along with inlet and outlet holes or other holes for bolting could be drilled or routed.

Due to the elevated pressures and/or temperatures at which alkaline electrolysers may be operated at, alternative sealants to prepreg may be used, for example Ethylene Propylene Diene Rubber Monomer (EPDM), polyvinylidene fluoride (PVDF) or fluoroelastomers can be used.

In operation or use, the electrolysers described herein can be connected to a power source. An electrolyte can be supplied to the electrolyser, along with or comprising water. The electrolyser will then generate hydrogen gas which can be collected or stored. The energy supplied can be renewable energy and the electrolysers can be part of a green energy system. Multiple electrolysers can be stacked together to increase power density.

Hydrogen generated in the electrolyser is a very pure gas, saturated with water, and its oxygen content doesn't exceed 0.2%. If higher purity is required, the last molecules of oxygen can be removed by catalytic reaction for example in a deoxidizer.

The electrolysers described herein may be up to 1 kW, but the modularity of the 20 design enables stacking of electrolysers around 1 kW up to for example 10 kW. However, more electrolysers could be stacked to over 10 kW in total.

Figure 5 -shows a PCB alkaline Electrolyser system. The heat exchanger 502 is a coil of metallic pipes in a heated water bath. Present is a pump 504. The alkaline electrolyser 506 has heating cartridges to control the temperature. The liquid-gas separator 508 consists of sealed tanks with a common liquid reservoir. Not pictured is a power supply, which is typically a potentiostat.

Reference herein to 'flow' or 'flows' refers to fluids being allowed to flow, or being substantially directed, either with or without assistance, along fluid flow paths, channels or the like.

EXAMPLES Durability

Nickel and carbon coated tabs (comprising a corrosion protection inhibitor and a commercial ink) have been tested in 1M KOH. The carbon coated tabs showed dissolution of the resin into the solution after 48 hours and exhibited a high corrosion current (>40 mA cm-2 at 2 V, where a more typical value of <1 pA cm-2 is expected).

The Nickel coated tabs showed stability in 1 M KOH for several months. The corrosion current of these samples was approximately 100 nA cm-2 at 2 V for 24 hours.

Performance FIG. 6a shows no drop in performance over the course of a 200 hour test. Any performance loss was caused by gas accumulation in the nickel mesh electrode, which was reversible through agitation.

Polarisation curves of the electrolyser were generated using an Ivium XP40 as a power supply. On the cathode, the hydrogen evolution reaction (HER) was enabled with a Ni foam electrode. The same material was used on the anode for the oxygen evolution reaction (OER). 1 M KOH was used at 40 °C. The flowrate to each electrode was 50 mL min-1, supplied by a Verderflex Vantage 3000 B EZ pump.

FIG. 6b shows the Polarisation curve for the PCB Alkaline Electrolyser at 40 °C in 1 M KOH (top). FIG. 7 shows polarisation curves of competing technologies for comparison.

FIG. 6a and 6b were generated using PCB end plates as shown in FIG. 3b in electrolysers. A nickel mesh was used as the PTL on both anode and cathode with a Zirfon separator between them. The cell was run under both circumstances at 40 °C. The system shown in Figure 5 was used to generate this data. Electrical current/potential was applied and recorded with a potentiostat The polarisation curves are comparable to the prior art electrolyser technologies, however the PCB electrolysers described herein are able to run at elevated temperatures, which will allow for better cell performance than the prior art 30 technologies The electrolysers were successfully demonstrated and showed expected performance for an electrolyser running below the typical operating temperatures of alkaline electrolysers between 60 and 80 °C.

FIG. 6c shows a potentiostatic hold of a PCB Alkaline Electrolyser showing change in performance due to gas accumulation in nickel foam electrode. A potentiostatic hold of this system at 2 V demonstrated no irreversible loss in performance over a 30 hour period, with gas accumulation, which is easily removed with agitation, the only contributing factor to a loss in current, as shown in FIG. 6b. Arrow 601 shows a loss of current density with time due to gas accumulation. After agitation the current density was shown to increase (see arrow 602) back to above where it was originally, before slow degradation begins again. This would be accounted for in designs of electrolysers not just being used for benchtop testing experiments. FIG. 7 shows polarisation curves of prior art electrolyser technologies for comparison.

Thus, improved alkaline electrolysers have been demonstrated.

It will be clear to one skilled in the art that many improvements and modifications can be made to the foregoing exemplary embodiments without departing from the scope of the present disclosure.

Claims

CLAIMSWhat is claimed is: 1. An electrolyser, the electrolyser comprising: a cathode structure comprising a first PCB plate and an electrically conductive substrate; an anode structure comprising a second PCB plate and an electrically conductive substrate; a separator located between the cathode structure and the anode structure; two transport layers, one transport layer disposed between the anode 10 structure and the separator and one transport layer disposed between the cathode structure and the separator; and at least one fluid path to supply an electrolyte to the electrolyser.
2. The electrolyser of claim 2, wherein the first PCB plate and/or the second PCB plate comprise a copper plated layer disposed on the PCB plate and comprise a nickel plated layer disposed on top of the copper plated layer.
3. The electrolyser of claim 3, wherein the electrically conductive substrate of the cathode structure and the anode structure comprises copper and/or nickel or an alloy of copper and/or nickel, preferably nickel coated copper, ENIG coated copper, conductive epoxy coated copper, HASL coated copper, nickel-phosphorus coated copper or carbon coated copper.
4. The electrolyser of any preceding claim, wherein at least one of the first PCB plate and the second PCB plate are routed to comprise a fluid flow path for the electrolyte.
5. The electrolyser of claim 4, wherein at least one fluid flow path is formed within at least one PCB layer such that the fluid flow path is routed or grooved within the PCB layer without the routing or groove extending all the way through the PCB plate.
6. The electrolyser of claim 4 or claim 5, wherein the fluid flow path directs the electrolyte to the nickel plated layer disposed on top of the copper plated layer on the first PCB plate and the second PCB plate.
7. The electrolyser of any preceding claim, wherein the first PCB plate and second PCB plate have at least one fluid inlet and at least one fluid outlet drilled extending all the way through the PCB plate.
8. The electrolyser of claim 7, wherein the outlet is larger than the inlet.
9. The electrolyser of any preceding claim, wherein the electrolyte comprises KOH 15 and/or NaOH.
10. The electrolyser of any preceding claim, wherein the electrolyser is an alkaline water electrolyser.
11. The electrolyser of any preceding claim, wherein the transport layers are porous transport layers.
12. The electrolyser of any preceding claim, wherein the transport layers comprise a catalyst.
13. The electrolyser of any preceding claim, wherein the transport layers comprise nickel as a Felt, nickel as a mesh or nickel foam, or alloys of nickel, or Zirconium.
14. The electrolyser of any preceding claim, wherein the separator comprises NiO or Zirfon (zirconia and polysulfonate).
15. The electrolyser of any preceding claim, wherein the electrolyser further S comprises end plates and/or current collection plates.
16. The electrolyser of any preceding claim, wherein the electrolyser further comprises housing.
17. The electrolyser of any preceding claim, wherein the electrolyser further comprises an anode chamber and a cathode chamber suitable for fluid flow of the electrolyte.
18. The electrolyser of any preceding claim, wherein the electrolyser is laminated 15 together, preferably by heat bonding layers of sealing between the PCB plates under an increase temperature.
19. An electrolyser apparatus for the production of hydrogen, the electrolyser apparatus comprising an electrolyser of any one of claim 1 to 18.
20. An electrolyser apparatus for the production of hydrogen, the electrolyser apparatus comprising multiple electrolysers of any one of claim 1 to 18 stacked together.
21. The use of an electrolyser of any one of claims 1 to 18, or the electrolyser apparatus of claim 19 or claim 20, to generate hydrogen.
22. A method of generating hydrogen, the method comprising using an electrolyser of any one of claims 1 to 18, or the electrolyser apparatus of claim 19 or claim 20, to generate hydrogen.s
23. A method of manufacture of an electrolyser, the method comprising laminating two or more PCB boards to make an electrolyser.
24. Use of PCB plates as electrodes in an electrolyser.