Apparatus for water electrolysis and methods of making and operating same

Abstract

Disclosed are devices, cells and stacks for water electrolysis in which the electrolyte and electrodes are separated in sealed compartments and separated from the water feedstock by a porous, non-wettable, gas and vapor permeable interface. Thus, an electrochemical reaction is fed by water vapor from a liquid water feed through the non-wettable interface and condensing in the sealed compartment. Hydrogen and oxygen generated by electrolysis move in opposite directions, across the non-wettable interface, and out of the sealed reaction compartment. There is no liquid flow contact between the sealed compartment and the environment, allowing the use of low mass water at neutral pH as feedstock.

Description

Technical Field

[0001] The present invention relates to the field of water electrolysis for generating hydrogen from water by an electrochemical method. Background Art

[0002] Hydrogen is a valuable industrial gas, widely used in the manufacture of nitrogen fertilizers, methanol and other useful chemicals, and in the petrochemical industry for the hydrogenation of heavy hydrocarbons. In recent years, hydrogen has increasingly been used as a fuel because it burns cleanly, with the only by-product being water and no emission of carbon dioxide or other greenhouse gases. Hydrogen-powered fuel cells are increasingly being used to generate electric mobility in vehicles and other applications.

[0003] Hydrogen can be generated from water using electricity in a process called electrolysis, which was first demonstrated in 1789 and the first industrial electrolyzer appeared in 1888. Water electrolysis is a conceptually simple process in which an electric current is applied between two electrodes and water is electrochemically split into hydrogen generated at the cathode and oxygen generated at the anode. Compensating ionic current flows between the electrodes in an electrolyte medium.

[0004] The most commonly used method for the electrolysis of liquid water is alkaline water electrolysis (AWE), which employs a strongly alkaline electrolyte and cost-effective electrodes made of non-noble metals such as nickel or nickel-iron alloys.

[0005] AWE uses a strongly alkaline electrolyte such as a high concentration of potassium hydroxide (KOH) or sodium hydroxide (NaOH) dissolved in high-purity deionized water. Although KOH and NaOH are inexpensive reagents, their solutions strongly absorb carbon dioxide from the atmosphere, resulting in the formation of carbonates, which reduces the electrolysis performance. In addition, KOH and NaOH solutions are highly corrosive, and their use requires the electrolyzer and support system to be made of high-quality corrosion-resistant materials and requires extra care to avoid contact of KOH with the environment and personnel.

[0006] The electrodes in some AWE systems must be separated by gaps that can be several millimeters in length to prevent the crossover of hydrogen and oxygen generated at the electrodes. The ionic resistance in the gaps between the electrodes causes polarization and significant IR losses during the process. More advanced AWE methods use solid spacers between the electrodes, such as spacers made of polysulfone and zirconia (such as Ziffron membranes), which eliminates the gaps but introduces additional costs and resistance. Generally, AWE cannot operate at high differential pressures because oxygen and hydrogen cross and mix between the electrodes, thus requiring compression of the hydrogen product after production.

[0007] Another common method for water electrolysis is proton exchange membrane water electrolysis (PEMWE), which is based on a proton-conducting solid electrolyte membrane. The PEMWE system is fed with ultrapure water, and its pH value can be neutral pH. However, during the oxidation of neutral water to gaseous oxygen at the anode, strong acids are generated, which are even more corrosive than KOH or NaOH. This strong acid will corrode the bipolar plates used to stack the PEMWE cells and degrade the performance of the system. Therefore, connecting the stacked PEMWE cells requires expensive acid-resistant bipolar plates made of titanium alloy or gold-plated steel to prevent acid corrosion. Summary of the Invention

[0008] In short, the present invention includes an apparatus, a cell, and a cell stack for water electrolysis, wherein the electrolyte and the electrodes are separated in a sealed compartment and are separated from the water feedstock by a porous, non-wettable gas and vapor permeable interface. Therefore, the electrochemical reaction is supplied by water vapor from the liquid feed water that passes through the non-wettable interface and condenses in the sealed compartment. The hydrogen and oxygen generated by electrolysis move in opposite directions, pass through the non-wettable interface, and leave the sealed reaction compartment.

[0009] The sealed compartment is under high pressure, thus promoting the escape of the generated gas from the sealed compartment and allowing the production of pressurized hydrogen.

[0010] The present invention also provides an integrated electrode structure and a method for manufacturing the same, as well as other methods for achieving electrical connection between the electrochemically active metal electrode located in the sealed compartment and the current-carrying structure (bipolar plate or pre-electrode) located outside the sealed compartment.

[0011] The apparatus of the present invention can be used for both AWE and PEMWE.

[0012] When used as an AWE system, the apparatus and method of the present invention use components commonly used in AWE - KOH or NaOH electrolyte and non-noble metal electrodes - while eliminating most of the disadvantages of AWE:

[0013] i. Allows the use of low-quality and low-purity water feedstock, including seawater (low-quality water), thus eliminating the need for high-purity water and associated demineralization systems and costs.

[0014] ii. Eliminates the disposal of highly corrosive alkaline hydroxides outside the sealed reaction compartment, thus allowing all feed, output, and other auxiliary systems to be made of inexpensive materials and reducing the health, safety, and environmental risks of concentrated KOH or NaOH solutions.

[0015] iii. Allows the direct production of high-purity and high-pressure hydrogen products in the electrolyzer, thus reducing the cost of post-treatment.

[0016] iv. Eliminates the contact of the KOH or NaOH solution with the atmosphere, resulting in reduced carbon dioxide absorption and improved performance.

[0017] v. Reduces the resistance of the inter-electrode spacer, thereby reducing the electrical IR loss and allowing operation at higher current densities.

[0018] When used as a PEMWE system, the apparatus and method of the present invention use the common components employed in PEMWE - a membrane, a catalyst electrode material, and a porous transport layer (PTL) - which are typically assembled into a membrane - electrode assembly (MEA) - while eliminating some of the PEMWE drawbacks:

[0019] i. Eliminates the leakage of the acid generated at the anode to the bipolar plate (BPP), thereby allowing the BPP to be constructed using inexpensive materials such as stainless steel.

[0020] ii. Allows the use of low - quality water feedstock, thereby eliminating the need for high - purity water and associated demineralization systems and costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In addition to the features that are apparent from this description, the claims, and the examples, certain details of the present disclosure are presented in the drawings and are clarified therein.

[0022] Throughout the various drawings, like reference numerals are used to denote like elements and are referred to accordingly in the detailed description.

[0023] Figure 1 is a schematic diagram of the layers in an electrolysis cell of the present invention having a sealed compartment 10. The cell includes a first pre - electrode 106, a second pre - electrode 107, and a sealed compartment 10 that includes a first electrode 102, a second electrode 103, an optional spacer 100, a seal or gasket 101, and two non - wettable interfaces 104. Electrodes 102 and 103 are in contact with pre - electrodes 106 and 107 over the entire perimeter using peripheral metal contacts 105, thereby ensuring electrical connectivity between them.

[0024] Figure 2 is a schematic diagram of the layers in a three - layer integrated electrode structure having conductive pins, the structure including a pre - electrode 111, a non - wettable interface 110, and an electrode 108, wherein the electrical contact between the electrode and the pre - electrode is achieved via conductive non - permeable pins 109.

[0025] Figure 3a is a schematic diagram of the layers in an integrated electrode structure having protrusions, the structure including a pre - electrode 111 and plating protrusions 113 that project from the pre - electrode through a non - wettable porous interface 112 into the sealed compartment. Figure 3bRepresents an integrated electrode structure 114 having a protrusion 113.

[0026] Figure 4 Is a schematic diagram of a single internal electrolytic cell in an AWE stack. The electrolytic cell includes a sealed compartment 11, which includes an integrated anode structure having a protrusion 115, an integrated cathode structure having a protrusion 116, an optional spacer 100, and a seal or gasket 101. The electrolytic cell with the sealed compartment is in series contact with adjacent electrolytic cells (not shown) through bipolar plates 117 and 118. The stacked arrangement of layers with gaskets and seals incorporates a feed line 117a for water and outlet lines 118a for brine and oxygen, which open into the space between the BPP 117 and the integrated anode structure 115; additional (optional) water feed line 118b and outlet line 117b for hydrogen, which open into the space between the BPP 118 and the integrated cathode structure 116; and electrolyte injection, replenishment, and exchange inlet line 117c and outlet line 118c, which open only within the sealed compartment 11. The BPP is characterized by having a protruding ridge 117d for electrical contact with the integrated electrode structure; and serrated valleys 117e as channels for water and gas flow.

[0027] Figure 5 Is a schematic diagram of a single internal electrolytic cell in an AWE stack. The electrolytic cell includes a sealed compartment 12 having a peripheral conductive contact 105. The numbered elements are described in Figure 1 and Figure 4 The description has been given.

[0028] Figure 6 Is a schematic diagram of a single internal electrolytic cell in a PEMWE stack. The electrolytic cell includes a sealed compartment 13, which includes a membrane - electrode assembly (MEA) 119, a porous transport layer (PTL) 120, a seal or gasket 101, and a non - wettable interface 104. The PTL 120 is connected to the BPPs 117 and 118 through a conductive peripheral contact 105 surrounding the sealed compartment. The stack incorporates feed and outlet lines similar to those of the AWE stack described in Figure 4 and Figure 5 One difference is that the inlet 117c and outlet 118c lines that open inside the sealed compartment 13 are used to wet the MEA 119 inside 13 with ultrapure water instead of an alkaline electrolyte solution. Detailed Description

[0029] The present invention includes an electrolytic cell or a stack of electrolytic cells having a sealed compartment separated from a water feed by a non - wettable, gas - and vapor - permeable interface.

[0030] AWE electrolyte cell with a sealed compartment

[0031] In Figure 1 the AWE electrolyte cell of the present invention as shown, the sealed compartment includes a first electrode (anode) 102, a second electrode (cathode) 103, a seal or gasket 101, and two porous, non-wettable interfaces 104, and may include an optional spacer 100 located between the anode and the cathode.

[0032] Throughout this disclosure, "non-wettable" means that generally liquid water and aqueous solutions are impermeable, but gases and vapors are permeable; "sealed compartment" means that the compartment has no liquid flow contact from or towards the external environment.

[0033] The sealed compartment is sealed with an alkaline electrolyte inside such that the electrolyte does not contact the external environment of the sealed compartment. Since the sealed compartment is delimited by non-wettable interfaces 104 on each side, the liquid electrolyte cannot wet the interphase and escape from the sealed compartment. At the same time, water vapor can enter, and the generated gas can leave the sealed compartment through the pores of the non-wettable interface.

[0034] In addition to the sealed compartment, the electrolyte cell further includes a first pre-electrode 106 and a second pre-electrode 107. The pre-electrodes are in electrical contact with the electrodes inside the sealed compartment 10 so that current can be transferred from the pre-electrodes to the electrodes, as described below. Although the electrodes and the pre-electrodes are electrically connected, they are separated by non-wettable interfaces, so only current can pass between them, while liquids such as water or electrolyte cannot pass through.

[0035] Electrodes and pre - electrodes

[0036] The electrodes 102 and 103 are compositions made of non-noble metals or metal alloys, and such materials are effective in alkaline water electrolysis and are well known in the art. Such metal and metal alloy materials include nickel, stainless steel, nickel-iron alloy, nickel-cobalt alloy, nickel-molybdenum alloy, etc. Certain metal or metal alloy electrode materials may incorporate non-metal atoms (heteroatoms), such as phosphorus.

[0037] The electrode materials generally have a high electrochemically active surface area (ECSA) to provide high electrochemical performance. Metal electrode materials with a high ECSA, such as Raney Nickel, are well known in the art. The electrode material structure is not monolithic, so liquids and gases can pass through it. Examples of non-monolithic structures for electrodes are metal mesh, metal paper, metal foam, metal felt, etc.

[0038] The pre - electrodes 106 and 107 are conductive structures having pores, holes or other openings that allow water and gas to pass through. In a preferred embodiment, the pre - electrodes are in the form of woven or non - woven stainless - steel meshes, grids or perforated stainless - steel sheets or expanded sheets. The function of the pre - electrodes is to distribute the current evenly, reduce the resistance and provide electrical contact with the bipolar plates in the electrolytic stack.

[0039] The electrodes and pre - electrodes must be electrically connected. In some embodiments, this is achieved through contact elements around their perimeters, as Figure 1 shown, where the conductive perimeter contact elements are denoted as element 105. These conductive contact elements 105 surround and enclose the sealed compartment 10 and are integrally connected to the solid, non - porous boundaries of the electrodes 102 and 103 and the pre - electrodes 106 and 107, respectively. For clarity, Figure 1 the 105 elements in are shown as separate layers, however, they can be integral raised portions of the electrodes 102 and 103 or the pre - electrodes 106 and 107.

[0040] In some other embodiments, the electrodes and pre - electrodes are in contact through a non - wettable phase interface to improve the conductivity between them and reduce resistive electrical losses. Figure 2 An example of such contact, called "contact with a conductive stud", is shown above. The contact with the conductive stud 109 is achieved by punching holes in the non - wettable interface 110 separating the electrode 108 from the pre - electrode 111 and applying a conductive coating inside and outside the perforations, where the conductive coating is applied for: (i) contacting and bonding the electrode to the pre - electrode through the perforations; and (ii) sealing the perforations so as to restore the non - wettable integrity of the non - wettable membrane. Conductive coatings or waxes are well - known in the art and typically comprise metal flakes or particles suspended in a polymer solution and are solidified by drying and / or curing after application.

[0041] Integrated electrode structure with protrusions

[0042] The subject of the present invention is an "integrated electrode structure" that includes projections from the pre - electrodes, through a non - wettable phase interface, as schematically shown in Figure 3. Figure 3a is a schematic view of a layer in an integrated electrode structure with projections, which includes a pre - electrode 111 and a plated projection 113 that projects from the pre - electrode through a non - wettable porous interface 112 into the sealed compartment. Figure 3b denotes an integrated electrode structure 114 with projections 113. The projections 113 are effective electrochemical electrodes responsible for electrochemically splitting water into hydrogen and oxygen inside the sealed compartment, and they represent a more economical alternative to separately manufactured independent electrodes such as Figure 1 the 102 and 103 in.

[0043] In a preferred embodiment, the protrusions are made of nickel or other metals plated onto a stainless steel pre-electrode through pores in a non-wettable phase interface.

[0044] The invention of these protrusions is based on the following understandings: (i) certain hydrophobic or porous membranes can be wetted by organic solvents (such as alcohols) and water-solvent mixtures, even though they cannot be penetrated by liquid water and liquid aqueous solutions; and (ii) electroplating of metals can be accomplished using organic solvents or water-solvent mixtures.

[0045] The production of the protrusions can be accomplished either by electroplating or by electroless methods.

[0046] In the electroplating method, the pre-electrode is used as the cathode and another material is used as the anode, and an electric current flows between the anode and the cathode through a solution of an electroplating bath containing a dissolved salt of the metal to be plated. The pre-electrode / cathode is covered with a non-wettable hydrophobic membrane, which is pressed tightly against the pre-electrode / cathode to ensure good contact between them. In addition to the dissolved salt, the electroplating bath also contains a solvent, which allows the hydrophobic membrane to be wetted.

[0047] In certain embodiments, the metal protrusions are made of electroplated nickel, and correspondingly, the electroplating bath contains a dissolved nickel salt, such as nickel chloride, nickel sulfate, nickel sulfamate, ammonium nickel sulfate, or other salts. In addition, the electroplating bath also contains an organic solvent to allow the membrane to be wetted, such as isopropyl alcohol, ethanol, methanol, ethylene glycol, glycerol, acetone, or another organic solvent. In certain embodiments, the electroplating bath contains a surfactant as a wetting agent instead of an organic solvent.

[0048] In electroless plating, an anode is not required and the metal protrusions are plated from a bath containing a reducing agent. The pre-electrode is covered with a non-wettable hydrophobic membrane, which is pressed tightly against the pre-electrode to ensure good contact between them, and an electroless bath is applied to the membrane. The metal is plated onto the pre-electrode and protrudes through the membrane to form metal protrusions.

[0049] In certain other embodiments, the metal protrusions are made of electroless nickel, and correspondingly, the electroless bath contains a dissolved nickel salt (such as nickel chloride) and a reducing agent (such as sodium hypophosphite). In addition, the electroless bath contains an organic solvent to allow the membrane to be wetted, such as isopropyl alcohol, ethanol, methanol, ethylene glycol, glycerol, etc. In certain embodiments, the electroless bath contains a surfactant as a wetting agent instead of an organic solvent.

[0050] Non - wettable interface

[0051] The non-wetting interface of the present invention is a hydrophobic porous polymer membrane or coating, which is generally not wetted by water or aqueous solutions and is made of polypropylene (PP), polyethylene (PE), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polyetherimide (PEI), or one or more other hydrophobic polymers.

[0052] In certain embodiments, the non-wetting interface is a fabricated porous hydrophobic non-wetting membrane. Such membranes are well known in the art and can be produced by a variety of methods, such as: dry stretching of PP, expansion of PTFE, phase inversion techniques of fiber spinning techniques (such as TIPS (temperature-induced phase separation)). Some of these non-wetting membranes are sold under the brand names Celgard (dry stretched PP), Gore-Tex (expanded PTFE), or others.

[0053] The wettability of these membranes to a given liquid depends on several factors: the surface tension of the liquid, the liquid-membrane contact angle, and the size and geometry of the pores. Theoretical models have been developed to estimate the pressure at which a liquid will enter the membrane, called the liquid entry pressure (LEP). Membranes with pore sizes small enough (less than 100 nanometers) can withstand hydrostatic pressures of several atmospheres from aqueous solutions without wetting. Thus, the use of such hydrophobic membranes allows the electrolysis device of the present invention to operate in the presence of a pressure difference across the non-wetting membrane between the reaction compartment and the feed and product compartments.

[0054] In other embodiments, the non-wetting interface is achieved by directly coating a hydrophobic polymer on a porous electrode or a porous current collector to obtain a non-wetting porous coating, which has a pore structure and function similar to the above-mentioned prefabricated membranes.

[0055] Sealing, electrode separation and electrolyte

[0056] The sealing of the sealed compartment is achieved with a waterproof seal or gasket. The material of the seal or gasket can be selected from a variety of thermoplastic polymers (such as polyethylene, polypropylene, PEEK) or thermoplastic elastomers (such as isobutylene) or other elastomers or rubbers well known for their waterproof sealing properties in the art. The function of the seal or gasket is to prevent liquid contact between the edge of the sealed compartment and the external environment.

[0057] Another function of the seal or gasket is the separation between the cathode and the anode, which serves two purposes: (i) to prevent electrical contact and short circuit between the electrodes; and (ii) to prevent the crossover of the generated oxygen and hydrogen, which would result in either the loss of hydrogen product to the oxygen outlet or the contamination of the hydrogen product by oxygen.

[0058] In some embodiments, the separation between the anode and the cathode is provided only by the gap between them. In other embodiments, the separation between the anode and the cathode is provided or supplemented by a solid spacer. The spacer can be a macroporous spacer, such as a non-woven fabric or a woven polymer mesh or paper. In other embodiments, the spacer can be a microporous spacer. In other embodiments, the spacer can be an anion exchange membrane (AEM) spacer.

[0059] The separation gap is filled with an electrolyte, and when the separation is enhanced by a solid spacer, the spacer is also impregnated with the electrolyte. The electrolyte is a concentrated solution of a strong base, such as 30% KOH or 30% NaOH. Such alkaline electrolytes are well-known and used in the AWE field.

[0060] AWE cell stack

[0061] In a preferred embodiment, two or more of the electrolytic cells of the present invention can be connected in a stack using a conductive solid bipolar plate (BPP). The stacking of electrolyte cells is well-known in the art.

[0062] In a preferred embodiment, using a BPP, the cells are electrically connected in series to form a stack. In that configuration, the bipolar plate is made of a conductive material, such as stainless steel or other metals. The bipolar plate is positioned between the cells such that one side (the cathode side) of the bipolar plate contacts the cathode pre-electrode / electrode of the cell (cell 1), and the other side (the anode side) of the bipolar plate contacts the anode pre-electrode / electrode of the next cell (cell 2), and so on.

[0063] The sides of the bipolar plate are not flat but are machined to have extended ridges for electrical contact with the pre-electrodes, and serrated valleys to form channels for feeding the inflow of water and the outflow of the generated gas to the corresponding pipelines.

[0064] Figure 4 is a schematic diagram of a single internal electrolyte cell in an AWE stack, which electrolyte cell includes a sealed compartment 11, which sealed compartment includes an integrated anode structure having protrusions 115, an integrated cathode structure having protrusions 116, an optional spacer 100, and a seal or gasket 101. The electrolyte cell having the sealed compartment is in series contact with adjacent electrolyte cells (not shown) through bipolar plates 117 and 118.

[0065] The stacked arrangement of layers with gaskets and seals incorporates a feed line 117a for water and an outlet line 118a for brine and oxygen, which open into the space between the BPP 117 and the integrated anode structure 115; an outlet line 117b for hydrogen and an additional (optional) water feed line 118b, which open into the space between the BPP 118 and the integrated cathode structure 116. The BPP is characterized by having an extended ridge 117d for electrical contact with the integrated electrode structure; and serrated valleys 117e as channels for water and gas flow.

[0066] In some embodiments, the stack also includes electrolyte injection, replenishment, and exchange lines, and is shown in Figure 4 as inlet line 117c and outlet line 118c, which open only within the sealed compartment 11.

[0067] In some other embodiments of the AWE stack, separate prefabricated electrodes are employed instead of protrusions. Figure 5 is a schematic diagram of a single internal electrolyte cell in the AWE stack, which includes a sealed compartment 12, with peripheral conductive contacts 105 provided between the separate electrodes 102 and 103 and the pre - electrodes 106 and 107 respectively (see also Figure 1 ). The names for the inlet and outlet lines and the BPP are the same as in Figure 4 .

[0068] Whenever the cells are in a stack arrangement, the seals take into account the nature of the electrodes and pre - electrodes used. In the case of an integrated electrode structure with protrusions, a simple seal or gasket between two non - wettable membranes is sufficient ( Figure 4 ). In the case where the electrodes are separate, independent structures (metal mesh or metal grid or foam), an additional seal is applied to the electrodes on the inner circumference of the cell, inside the outer peripheral metal - to - metal electrical contacts ( Figure 5 ).

[0069] Differential pressure operation

[0070] The AWE device of the present invention can operate with a differential pressure between the water feed line and the hydrogen product line, allowing water to be fed into the device at a low pressure close to atmospheric pressure (only slightly over - pressured, sufficient to overcome the hydraulic resistance in the flow path), while producing high - pressure hydrogen product and reducing the requirement for post - production compression.

[0071] This ability is based on the following discovery: the sealed compartment that is the subject of the present invention becomes self-pressurized during operation. An exhaustive scientific explanation of this discovery is not required, but we believe it is based on the low vapor pressure above concentrated KOH and NaOH solutions, which absorb and condense water vapor from the feed water, resulting in an expansion of the liquid volume within the sealed compartment. Since the liquid cannot penetrate and escape through the non-wettable interface, this excess liquid volume causes a sharp increase in pressure within the sealed compartment.

[0072] The differential pressure operating method of the present invention is achieved through a pressure control valve in the product outlet line of the electrolyzer stack, which can be adjusted to the desired output pressure. For a given electrolyzer configuration with a specific inter-electrode separation, there is a maximum output pressure (breakthrough pressure) that allows operation without significant hydrogen product crossover and loss into the inlet line. For an electrolyzer with a solid ion exchange separator, the breakthrough pressure is higher, while for a liquid gap separation without a solid separator, the breakthrough pressure is lower.

[0073] PEMWE electrolyte cell and stack with a sealed compartment

[0074] The electrolyte cell with a sealed compartment of the present invention can be implemented as a PEMWE cell and cell stack, where the non-wettable interface prevents the leakage of corrosive acid from the anode and allows the electrolyzer to operate with a low-quality water feed.

[0075] Figure 6 is a schematic diagram of a single internal electrolyte cell in a PEMWE stack, which includes a sealed compartment 13 that includes a proton exchange membrane (PEM)-catalyst layer 119, a porous transport layer (PTL) 120, a seal or gasket 101, and a non-wettable interface 104. The PTL 120 is connected to the BPPs 117 and 118 through a conductive peripheral contact 105 that surrounds the sealed compartment. The PEM catalyst layer 119 and the PTL 120 are commonly referred to in the art as a membrane-electrode assembly (MEA).

[0076] The stack incorporates inlet and outlet lines that are similar to those of the AWE stack described in Figure 4 and Figure 5 and are identified with the same reference numerals. One difference is that the inlet line 117c and the outlet line 118c that open within the sealed compartment 13 are used to wet the MEA (119, 120) inside 13 with ultrapure water instead of an alkaline electrolyte solution.

[0077] MEA, PEM, and PTL are well-known in the field of PEMWE. PEM is an electrically insulating proton-conducting membrane, typically made of sulfonated fluoropolymer (brand name Nafion). The electrode catalyst material is usually platinum or another platinum group metal and is typically bonded to the PEM and GTL by an ionomer binder with a chemical composition similar to that of the PEM. PTL generally appears on both sides of the MEA, and its function is to deliver and distribute current to the catalyst. PTL is often made of carbon paper or carbon cloth.

[0078] Figure 6 The non-wettable phase interface 104 used in the PEMWE cell is substantially the same as the non-wettable phase interface of the above-mentioned AWE cell.

[0079] In a preferred embodiment, the non-wettable phase interface 104 for the PEMWE stack is positioned between the PTL 120 and the BPPs 117 and 118, as Figure 6 shown, and low-quality feed water is supplied between the BPPs and the sealing compartment 13. In this arrangement, the strong acid generated at the PEMWE anode stays within the sealing compartment and does not corrode the BPPs. Thus, the BPPs can be made of inexpensive materials such as stainless steel.

[0080] The electrical contact between the BPP and the PTL of the PEMWE stack is achieved in the same manner as the contact between the pre-electrode and the electrode in the AWE stack. More specifically, in some embodiments, the electrical contact member 105 is located on the outer periphery of the stack, outside the sealing compartment 13, as Figure 6 shown. In other embodiments, the electrical contact is achieved using conductive studs made of a non-permeable conductive coating between the BPP and the PTL and through the non-wettable interface (see Figure 2 ). In other embodiments, metal protrusions are plated onto the BPP ridges, passing through the non-wettable interface and contacting the PTL (see Figure 3).

[0081] A seal is required between the PTL and the non-wettable phase interface to prevent low-quality water from the water inlet line from flowing into the sealing compartment from the edge of the stack.

[0082] The separate inlet line 117c and outlet line 118c in the stack have openings only within the sealing compartment of the cell and are used to supply a small amount of high-purity water for initial wetting of the MEA within the sealing compartment. The seal of the stack is arranged such that there is no contact between the low-quality feed water and the high-purity water used for the wetting line.

[0083] Example: Electrolysis using a sealed compartment and tap water

[0084] A simple electrolysis device with an effective area of 4 square centimeters was assembled, using a nickel paper electrode with low ECSA (purchased from Dioxide Materials) and an anion exchange spacer (FAS-PK membrane purchased from FumaSep). In the test experiment, the electrode was sealed in a sealed compartment using a stretched polypropylene membrane (Celgard), while it was not used in the control experiment.

[0085] In the control experiment on the left, 0.1M KOH electrolyte was used as the feed (pH 13); in the KDI experiment on the right (utilizing a sealed compartment), the feed was tap water (pH 6). A constant current of 40 mA was applied, and the electrolysis voltage and gas generation were monitored.

[0086]

[0087] Both electrolysis reactions proceeded at the expected gas generation rate (coulombic efficiency > 99% within the measurement error). In the KOH experiment, the voltage stabilized at 2.078 V, while in the KDI experiment, the voltage stabilized at 2.098 V.

Claims

1. A water electrolysis cell having a sealed compartment, comprising: A liquid alkaline electrolyte solution; A first electrode and a second electrode in electrical contact with circuit elements external to the sealed compartment; A first porous non-wettable interface and a second porous non-wettable interface, constructed and arranged such that the sealed compartment is sealed with the electrodes and electrolyte inside, such that there is no liquid flow contact with the environment external to the sealed compartment.

2. The electrolysis cell according to claim 1, further comprising a spacer located between the first electrode and the second electrode inside the sealed compartment.

3. The electrolysis cell according to claim 1, further comprising a pre-electrode located external to the sealed compartment and in electrical contact with the first electrode and the second electrode.

4. The electrolysis cell according to claim 1, further comprising a pre-electrode located external to the sealed compartment and in electrical contact with the first electrode and the second electrode via a conductive stud.

5. A plurality of electrolysis cells according to claim 1, electrically connected via bipolar cells and arranged in an electrolysis stack.

6. An integrated electrode structure, comprising: a. A layer of conductive material having pores, holes or other openings; b. A porous non-wettable interface in contact with the conductive layer; c. Metal protrusions protruding from the conductive layer through the pores of the porous non-wettable interface.

7. The integrated electrode structure according to claim 5, wherein the protrusions are electroplated through the pores of the porous non-wettable interface.

8. The integrated electrode structure according to claim 5, wherein the protrusions are electroless plated through the pores of the porous non-wettable interface.

9. A water electrolysis cell having a sealed compartment, comprising: A liquid alkaline electrolyte solution; A first integrated electrode structure having protrusions and a second integrated electrode structure having protrusions.

10. The electrolysis cell according to claim 9, further comprising a spacer located between the first integrated electrode structure and the second integrated electrode structure.

11. A plurality of electrolysis cells according to claim 9, electrically connected via bipolar cells and arranged in an electrolysis stack.

12. A water electrolysis cell having a sealed compartment, comprising: A membrane electrode assembly having a proton exchange membrane, a catalyst and a porous transport layer; A first porous non-wettable interface and a second porous non-wettable interface, constructed and arranged such that the membrane electrode assembly is sealed inside the sealed compartment.

13. A plurality of electrolysis cells according to claim 12, electrically connected via bipolar cells and arranged in an electrolysis stack.

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