Water electrolysis device using anion exchange membrane

Abstract

The water electrolysis device includes an electrolyzer stack including at least two electrochemical cells, each cell including an anion exchange membrane, a base metal anode electrocatalyst, a base metal cathode electrocatalyst, and an ion conduction path long enough between adjacent cells such that shunt current is less than 1% of the total current supplied to the stack.

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application is related to and claims the benefit of priority to U.S. patent application Ser. No. 17 / 222,553, filed Apr. 5, 2021, entitled "Water Electrolysis Apparatus Using Anion Exchange Membranes." The '553 application is incorporated herein by reference in its entirety. The field of the invention is electrochemistry. The devices, systems and compositions described herein involve the electrolysis of water. [Background technology]

[0002] Water electrolysis is currently used as a source of hydrogen, for example in hydrogen filling stations and chemical plants, and as a method of storing surplus renewable energy using a technique called "power to gas".

[0003] There are two main types of low-temperature electrolysers: proton exchange membrane (PEM) electrolysers and alkaline water electrolysers. PEM electrolysers can deliver 1 A / cm at cell voltages below 2 V. 2 They can operate at current densities both forward and backward, and can be rapidly switched on and off. Unfortunately, PEM electrolysers typically require the use of precious metal catalysts such as platinum or iridium, which is a major economic constraint.

[0004] In contrast, the current generation of alkaline water electrolyzers do not require the use of precious metals and can instead use base metal catalysts. Unfortunately, the current generation of alkaline water electrolyzers typically operate at lower current densities than PEM electrolyzers, which increases capital equipment costs.

[0005] For example, Patent Document 1 discloses an alkaline water electrolysis device that operates at a cell potential of 1.8 to 2 V and a current of 200 to 300 mA / cm 2 (0.2~0.3A / cm 2 ) Patent Document 1 also points out that by increasing the cell temperature to 110°C, the cell can be operated at 1 A / cm 2However, as pointed out in Patent Document 2, excessive corrosion is observed in these high pH systems (typically 1 M KOH electrolyte) above 80-90°C, so the upper temperature limit for practical alkaline water electrolysis devices is 80-90°C. Recently, Patent Document 3 has reported that a current of 40 A / dm at 80°C and 1.9 V can be obtained. 2 (0.4A / cm 2 disclose an improved electrolyzer design that can achieve 100% CO2 emission at 1000 sq. m., which is a significant improvement but still falls short of the performance of the PEM electrolyzer.

[0006] Discussions in the literature surrounding anion exchange membrane (AEM) water electrolysis as an alternative to conventional alkaline water electrolysis have also begun. A recent review by Vincent and Bessarabov (Non-Patent Document 1) notes that "only a few research papers (less than 20) have been published on AEM water electrolysis."

[0007] Many additional papers have been published since 2018, but most have only examined single cell performance; electrolyzer stacks combining multiple cells are required, and stack design has not been extensively considered.

[0008] However, a small commercial AEM electrolyser that houses a small scale electrolyser stack is available from Enapter. The Enapter cell design is described in US Pat. No. 5,999,336. At the time the Enapter AEM electrolyser was designed, available AEMs were not stable at KOH concentrations above 1%. As a result, Enapter designed their electrolyser to operate by replenishing the cell with a 1 wt % KOH (0.17M) solution.

[0009] More recently, however, Masel's US Pat. Nos. 5,993,333 and 5,133,663 have demonstrated AEMs that are stable in 9M KOH at room temperature. This has allowed Masel and coworkers to develop AEM electrolyzers that operate at higher KOH concentrations, as described in US Pat. No. 5,993,333. Advantages of these AEM electrolyzers include: (a) the cell current is much higher and therefore the cell can produce much more hydrogen; (b) Base metals are stable at higher pH levels, thus avoiding the use of precious metal catalysts.

[0010] The use of higher KOH concentrations presents a major challenge: as the KOH concentration increases, shunt current increases, as described in U.S. Pat. Nos. 5,393,323 and 5,433,633. [Prior art documents] [Patent documents]

[0011] [Patent Document 1] U.S. Pat. No. 4,445,994 [Patent Document 2] U.S. Patent Application No. 15 / 029,952 (U.S. Patent Application Publication No. 2016 / 0237578) [Patent Document 3] U.S. Patent Application No. 15 / 103,924 (U.S. Patent Application Publication No. 2016 / 0312371) [Patent Document 4] U.S. Pat. No. 9,340,882 [Patent Document 5] U.S. Pat. No. 9,370,773 [Patent Document 6] U.S. Patent No. 9,580,824 [Patent Document 7] U.S. Pat. No. 10,647,652 [Patent Document 8] U.S. Pat. No. 4,371,433 [Patent Document 9] Dutch Patent Registration No. 1013630 [Non-patent literature]

[0012] [Non-Patent Document 1] Written by Vincent and Bessarabov (Renewable and Sustainable Energy Reviews, Vol. 81, p1690-1704 (2018)) Summary of the Invention [Problem to be solved by the invention]

[0013] The AEM electrolyzer design minimizes or at least reduces shunt current and provides a current of 1A / cm 2 It operates at a current of 100 mA or more. [Means for solving the problem]

[0014] A water electrolysis device for producing hydrogen gas can include an electrolyzer stack including at least two electrochemical cells, each of the cells comprising: (a) an anode containing an anode gas diffusion layer (GDL) and a quantity of anode electrocatalyst; (b) a cathode comprising a cathode GDL and a quantity of a cathode electrocatalyst; (c) a source of a solution comprising water directed to at least one of the anode and the cathode; (d) an anion exchange membrane interposed between the anode and the cathode; where: (i) the solution has a conductivity (σ) of at least 0.05 S / cm at 60° C. sol ) (ii) Each of the anion exchange membranes has an average thickness (t) and a conductivity (σ) at 60° C. in 1 M KOH. mem ) (iii) Here, the shortest ion conduction path (L) between any two anode GDLs of the cells and the anode GDL of any different cell in the stack GDLA)teeth: L GDLA >10 * t * σ sol / σ mem It is.

[0015] In some preferred embodiments, L GDLA teeth, L GDLA >50 * t * σ sol / σ mem It is.

[0016] In some more preferred embodiments, L GDLA is at least 1.5 cm, preferably at least 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm or 10 cm.

[0017] In some embodiments, the shortest ion conduction path (L) between the cathode GDLs of any two cells in the stack. GDLC )teeth: L GDLC >10 * t * σ sol / σ mem It is.

[0018] In some preferred embodiments, the solution has a pH greater than 8 at 25° C. In some more preferred embodiments, the solution has a pH greater than 10 at 25° C. In some even more preferred embodiments, the solution has a pH of 12 or greater at 25° C.

[0019] In some preferred embodiments, σ sol In some more preferred embodiments, σ sol >0.1S / cm.

[0020] In some preferred embodiments, the electrolysis device includes a conduit fluidly connecting the anode of one cell in the stack to the anode of a different cell in the stack, and a source of solution comprising water is conducted to the conduit.

[0021] In some preferred embodiments, the electrolyser includes an electrical connection between the anode of one cell in the stack and the cathode of a different cell in the stack.

[0022] In some preferred embodiments, the electrolyser includes a potential source between the cathode of one cell in the stack and the anode of a different cell in the stack.

[0023] In some preferred embodiments, the electrolyzer includes a conduit that fluidly connects the cathode of one cell in the stack to the cathode of a different cell in the stack.

[0024] In some preferred embodiments, the cathode electrocatalyst in each of the cells is in the form of unsupported particles or particles supported on a conductive support, the particles having an average size between 0.6 nm and 100 nm.

[0025] In some preferred embodiments, the anode electrocatalyst in each of the cells comprises a base metal catalyst. More preferably, the anode electrocatalyst consists essentially of one or more base metal catalysts.

[0026] In some preferred embodiments, the cathode electrocatalyst in each of said cells comprises a base metal catalyst, hi some more preferred embodiments, the cathode electrocatalyst consists essentially of one or more base metal catalysts.

[0027] In some preferred embodiments, the membrane in at least one of the cells comprises a positively charged amine.In some preferred embodiments, the membrane in at least one of the cells comprises a positively charged cyclic amine.

[0028] In some preferred embodiments, the positively charged amine is an imidazolium, piperidinium, or pyridinium.

[0029] In some preferred embodiments, the membrane comprises: (i) Copolymers of styrene and chloromethylstyrene; (ii) polymers containing benzene rings; (iii) polymers containing phenylene groups; (iv) a polymer chain composed essentially of carbon and hydrogen; and (v) a polymer chain composed essentially of carbon, hydrogen and fluorine; Contains at least one of the following:

[0030] In some preferred embodiments, the membrane comprises styrene and / or phenylene.

[0031] In some preferred embodiments, the film consists essentially of carbon, hydrogen, nitrogen, oxygen and fluorine.

[0032] In some preferred embodiments, at least one cathode comprises an ionomer. In some preferred embodiments, the cathode in each of the cells comprises an ionomer. [Brief description of the drawings]

[0033] [Figure 1A] FIG. 1A is a perspective view of an electrolyzer stack including three electrolyzer cells 101 , 102 and 103 .

[0034] [Figure 1B] FIG. 1B is another perspective view of the electrolyzer stack including three electrolyzer cells 101 , 102 and 103 .

[0035] [Diagram 2]FIG. 2 is an exploded view of an electrolyzer cell assembly including a membrane electrode assembly interposed between two flow field plates having reactant flow channels formed in the major surfaces of the plates facing the electrodes.

[0036] [Diagram 3] FIG. 3 is a cross-sectional, partially see-through, perspective view of the electrolyzer stack of FIG. 1A, with the minimum ion conduction path between anode 101a and anode 102b labeled as path 200.

[0037] [Figure 4] FIG. 4 is a perspective view of a water electrolysis device constructed according to the description in Example 1. As shown in FIG.

[0038] [Diagram 5] 5 is an exploded perspective view of a five-cell electrolyzer stack with internal fluid connections, with the top cell of the stack further enlarged to reveal the internal components. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0039] It is understood that the process is not limited to the specific methods, protocols, and reagents described herein, as they may vary as will be appreciated by those skilled in the art to which this pertains. Similarly, it should be understood that the terminology used herein is used only to describe specific embodiments, and is not intended to limit the scope of the process. Similarly, it should be noted that the singular forms "a," "an," and "the" used herein and in the appended claims include plural references unless the context clearly dictates otherwise. Thus, for example, a reference to "a linker" is a reference to one or more linkers and their equivalents known to those skilled in the art. Similarly, the term "and / or" is used to indicate that one or both of the described cases may occur, and A and / or B includes (A and B) and (A or B).

[0040] Unless otherwise defined, technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the process pertains. The process and its various features and advantageous details are more fully described in connection with non-limiting embodiments and / or illustrated in the accompanying drawings and detailed in the following specification. Features illustrated in the drawings are not necessarily drawn to scale, and features of one embodiment can be utilized in other embodiments, even if not explicitly described herein, as would be recognized by one skilled in the art.

[0041] Any numerical range recited herein includes all values ​​from the lower value to the upper value in increments of one unit, provided that there is a separation of at least two units between any lower value and any upper value. As an example, if the value of a component concentration or a process variable, such as size, angle size, pressure, time, etc., is recited as being, for example, 1-98, specifically 20-80, more specifically 30-70, then values ​​such as 15-85, 22-68, 43-51, 30-32, etc. are intended to be explicitly recited herein. For values ​​less than one, one unit is considered to be 0.0001, 0.001, 0.01, or 0.1, as appropriate. These are merely examples of what is specifically intended, and all possible combinations of numerical values ​​between the minimum and maximum values ​​are intended to be treated in the same manner.

[0042] Additionally, provided below is a "Definitions" section in which certain terms related to the process are specifically defined. Although specific methods, devices, and materials are described, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the processes.

[0043] definition As used herein, "polymer electrolyte membrane" refers to both cation exchange membranes, which generally comprise a polymer having a large number of covalently attached negatively charged groups, and anion exchange membranes, which generally comprise a polymer having a large number of covalently attached positively charged groups. Exemplary cation exchange membranes include proton conducting membranes, such as perfluorosulfonic acid polymers available under the tradename NAFION from EI du Pont de Nemour and Company, Wilmington, Del.

[0044] As used herein, the term "anion exchange membrane electrolyzer" refers to an electrolyzer with an anion-conducting polymer electrolyte membrane separating the anode from the cathode.

[0045] As used herein, the term "hydrogen evolution reaction", or "HER" for short, refers to the electrochemical reaction 2H + +2e - →H 2 means.

[0046] As used herein, the term "MEA" means a membrane electrode assembly.

[0047] As used herein, the term "UEA" refers to a unitized electrode assembly.

[0048] As used herein, the term "Millipore water" means water produced by a Millipore filtration system having a resistivity of at least 18.2 megaohm-cm.

[0049] As used herein, the term "imidazolium" refers to a positively charged ligand containing an imidazole group, including bare or substituted imidazoles. [ka] Specifically included are ligands of the form, where R 1 ~R 5 are each independently selected from among hydrogen, halide, linear alkyl, branched alkyl, cyclic alkyl, heteroalkyl, aryl, heteroaryl, alkylaryl, heteroalkylaryl, and polymers thereof, such as the vinylbenzyl copolymers described herein.

[0050] The term "pyridinium" as used herein means a positively charged ligand containing a pyridine group, including bare or substituted pyridines. [ka] Specifically included are ligands of the form, where R 6 ~R 11are each independently selected from among hydrogen, halide, linear alkyl, branched alkyl, cyclic alkyl, heteroalkyl, aryl, heteroaryl, alkylaryl, heteroalkylaryl, and polymers thereof, such as the vinylbenzyl copolymers described herein.

[0051] The term "phosphonium" as used herein means a positively charged ligand containing phosphorus. This includes substituted phosphorus. P + (R 12 R 13 R 14 R 15 ) Specifically included are ligands of the form, where R 12 ~R 15 are each independently selected from among hydrogen, halide, linear alkyl, branched alkyl, cyclic alkyl, heteroalkyl, aryl, heteroaryl, alkylaryl, heteroalkylaryl, and polymers thereof, such as the vinylbenzyl copolymers described herein.

[0052] As used herein, the term "piperidinium" means [ka] where R 19 ~R 25 are each independently selected from among hydrogen, halide, linear alkyl, branched alkyl, cyclic alkyl, heteroalkyl, aryl, heteroaryl, alkylaryl, heteroalkylaryl, and polymers thereof, such as the vinylbenzyl copolymers described herein.

[0053] As used herein, the term "positively charged cyclic amine" refers to a positively charged ligand containing a cyclic amine, specifically including imidazolium, pyridinium, pyrazolium, pyrrolidinium, pyrrolium, pyrimidium, piperidinium, indolium, triazinium, and polymers thereof, such as the vinylbenzyl copolymers described herein.

[0054] As used herein, the term "simple amine" refers to: N(R 16 R 17 R 18 ) where R 16 ~R 18 are each independently selected from hydrogen, linear alkyl, branched alkyl, cyclic alkyl, heteroalkyl, aryl, heteroaryl, alkylaryl, heteroalkylaryl, but not polymer.

[0055] As used herein, the term "noble metal" means one or more of Ru, Rh, Pd, Ag, Re, Os, Ir, Pt and Au.

[0056] As used herein, the term "base metal catalyst" means a catalyst that is substantially free of precious metals.

[0057] As used herein, the term "shunt current" refers to the portion of the current applied to the stack that is routed through the fluid connections between adjacent cells rather than through the membranes. The current can be transmitted through the fluid in the connections or through conduits and fittings.

[0058] The term "bipolar plate" as used herein is a single conductive plate that serves as the cathode or cathode flow field for one cell and the anode or anode flow field for an adjacent cell in a stack.

[0059] As used herein, the term "shortest ionic conduction path between the anodes of adjacent cells" means the shortest ionic conduction path from the anode of a given cell to the anode of an adjacent cell.

[0060] The term "water electrolyser" is a device for using electricity to split water to produce hydrogen.

[0061] In most, if not all, embodiments of an alkaline water electrolyzer or anion exchange membrane (AEM) water electrolyzer, hydrogen is produced through the following reaction: 2H 2 O+2e - →H 2 +2OH -

[0062] In most, if not all, embodiments of a proton exchange membrane (PEM) electrolyser, hydrogen is produced through the following reaction: 2H + +2e - →H 2 EXAMPLES

[0063] Example 1 The objective of this embodiment is to provide an electrolyzer design that has low shunt current when replenished with solutions having a conductivity above 0.1 S / cm.

[0064] Figure 1A shows a schematic of a three-cell electrolyzer stack. The stack consists of: (a) an electrolyzer cell 101 comprising an anode 101a and a cathode 101c; (b) an electrolyzer cell 102 comprising an anode 102a and a cathode 102c; (c) an electrolyzer cell 103 comprising an anode 103a and a cathode 103c; (d) anode inlet manifold 110; (e) pipes 111, 112 and 113 connecting the anode inlet manifold 110 to the respective anodes 101a, 102a and 103a; (f) cathode inlet manifold 120; (g) Pipe 121 connecting cathode inlet manifold 120 to cathode 101c. There are also pipes numbered 122 and 123 (hidden in FIG. 1A) connecting cathode inlet manifold 120 to the respective cathodes 102c and 103c. (h) anode outlet manifold 130; (i) pipes 131, 132 and 133 connecting the anode outlet manifold 130 to the respective anodes 101a, 102a and 103a; (j) a cathode outlet manifold 140; and (k) Pipes 141, 142, and 143 connecting the cathode outlet manifold 140 to the respective cathodes 101c, 102c, and 103c.

[0065] Cathode 101c is in electrical contact with anode 102a. Cathode 102c is in electrical contact with anode 103a. Although Figure 1A shows adjacent anodes and cathodes (e.g., cathode 101c and anode 102a) as separate components, adjacent components can be combined into a single bipolar plate.

[0066] FIG. 2 illustrates an exploded view of one of the cells in the stack illustrated in FIG. 1A. The cell 30 includes a membrane electrode assembly 32 interposed between rigid flow field plates 34 and 36. The membrane electrode assembly 32 includes an anion exchange membrane 42 interposed between two gas diffusion layers (GDLs), an anode GDL 44 and a cathode GDL 46. The anode GDL 44 and the cathode GDL 46 are typically formed of porous conductive sheet material, such as carbon fiber paper or nickel fiber paper, and have planar major surfaces. The anode GDL 44 and the cathode GDL 46 have a thin layer of catalytic material disposed on their major surfaces at the interface with the membrane 42, making them electrochemically active. The anode flow field plate 34 has at least one open-faced channel 34a formed in its major surface facing the membrane electrode assembly 32. Similarly, the cathode flow field plate 36 has at least one open-faced channel 36a formed in its major surface facing the membrane electrode assembly 32. When assembled against cooperating surfaces of the anode GDL 44 and cathode GDL 46, the channels 34a and 36a form reactant flow field passageways for the anode reactant (fuel) and cathode reactant (oxidant) streams, respectively.

[0067] The cell may also house a metal mesh, perforated metal sheet or metal foam between the GDL and the flow plate. Optimal openings are 1-20mm. The flow plate may have channels machined into its body or a flat plate may be used with the metal mesh or metal plate serving as the channels.

[0068] Alternatively, the catalytic material can be deposited directly onto the membrane.

[0069] In the case of an AEM water electrolysis device, the anion exchange membrane 42 (see FIG. 2 ) is an anion exchange membrane that contains a positively charged amine and a hydrocarbon backbone, such as, but not limited to: i) copolymers of styrene and chloromethylstyrene; ii) polymers containing benzene rings; iii) polymers containing phenylene groups; iv) a polymer chain composed essentially of carbon and hydrogen; and v) polymer chains composed essentially of carbon, hydrogen and fluorine; Typically, positively charged cyclic amines such as imidazolium, piperidinium and / or pyridinium are utilized.

[0070] Although US Pat. No. 5,999,363 teaches that the catalyst layer on the cathode should not contain any ionomer, better performance was observed in the electrolyzer of the present invention when ionomer was used. Better performance was also observed when the membrane 42 and the anode GDL 44 and cathode GDL 46 were bonded together to form a unitized electrode assembly (UEA).

[0071] During operation, a mixture containing water and base is replenished into the anode and / or cathode inlet manifolds. The solution flows through the cells and exits through the outlet manifold. The solution typically has a pH greater than 8 and may contain seawater, salts, and other constituents.

[0072] 1A / cm 2 If higher currents are desired, the solution must have a pH of at least 12.

[0073] Empirically, it has been found that suitable performance is obtained when the solution conductivity is greater than 0.05 S / cm, and best performance is obtained when the solution conductivity is between 0.1 and 0.4 S / cm.

[0074] Once the solution is flowing, a voltage is applied between the anode of one of the cells (e.g., anode 101a) and the cathode of a different cell (e.g., cathode 103c) to drive the desired electrochemical reactions. Within the AEM water electrolysis system, the following reactions occur at the cathode: 2H 2 O+2e - →H 2 +2OH - (1) The hydroxyl radicals then pass through the membrane, where they react at the anode to produce oxygen: 2OH - →1 / 2O 2 +H 2 O+2e - (2) The net reaction is: H 2 O → 1 / 2O 2 +H 2 (3)

[0075] While it would be highly desirable for all of the current supplied to the cell to be used in the production of hydrogen and oxygen, in practice a portion of the current, referred to as the "shunt current," bypasses the MEA. For example, in FIG. 1A, if the solution entering the anode inlet manifold 110 is a good conductor, current can flow out of pipe 111 from anode 101a into anode inlet manifold 110, back into pipe 112, and then bypass the MEA in cell 101 to anode 102a. The current that bypasses the MEA is wasted since it does not produce any reaction products, and it is therefore desirable to eliminate or reduce the shunt current.

[0076] Prior patent literature describes several methods to avoid shunt current in electrolyzers. Generally, the approach has been to include polytetrafluoroethylene (PTFE) or other hydrophobic materials in the flow paths between adjacent cells. Air bubbles generated during the electrochemical process build up in the flow paths, thereby blocking the shunt current. While such an approach works when sufficient gas is developed near the inlets and outlets of the cells, it does not work for commercial-scale AEM water electrolyzers because there are few or no air bubbles near the inlets to the cathodes and anodes of the cells, and the solution flow rates are high enough to prevent bubble accumulation. Therefore, a different approach to reduce shunt current is required.

[0077] The AEM electrolyzer design of FIG. 1A utilizes two different approaches to reduce shunt current: (a) Connecting pipes 111, 112, 113, 121, 122, 123, 131, 132, 133, 141, 142 and 143 are all formed of non-conductive materials, thus eliminating the path of shunt current due to electronic conduction through metals. (b) the ion path back through the manifold is long, thus resulting in very few ions flowing from anode 101a to anode 102a;

[0078] 3 illustrates the shortest ion conduction path between the anodes of cells 101 and 102. In this case, the shortest conduction path 200 extends from a point on the anode near the fitting, down through pipe 111, through the anode inlet manifold 110, and back up through pipe 112.

[0079] For each cell in the stack, determine the shortest ion conduction path (L ano ) is the length of L ano >10 * t * σ sol / σ mem (4) It has been discovered that the shunt current can be reduced to less than 5% of the cell current when sol is the conductivity of the solution being replenished in the anode in S / cm, and σ mem is the ionic conductivity of the membrane measured in solution at the operating temperature. Typically, σ mem is measured in 1M KOH at 60°C.

[0080] L ano is calculated in the following way: (a) Number the cells: 1, 2, 3, ···; (b) Make a list of all cell pairs; (c) The shortest ion conduction path (L ano(i,j) ,) for all cell pairs in the stack; (d)L ano is the sum of all the calculated Lano(i,j) Equal to the minimum of the values.

[0081] For example, if a stack has four cells numbered 1, 2, 3, and 4, there are six cell pairs: (1,2), (1,3), (1,4), (2,3), (2,4), and (3,4). Then, L ano(1,2) , L ano(1,3) , L ano(1,4) , L ano(2,3) , L ano(2,4) , L ano(3,4) will be calculated or measured. ano =Min(L ano(1,2) , L ano(1,3) , L ano(1,4) , L ano(2,3) , L ano(2,4) , L ano(3,4) ).

[0082] Similarly, the current split between adjacent anodes is typically: L ano >50 * t * σ sol / σ mem (5) If so, it will be less than 1% of the cell current.

[0083] The current split between the cathodes must be considered as well. The current split between adjacent cathodes is: L cat >10 * t * σ sol / σ mem (6) When L is 0.5V, the cell current is less than 5%. cat is the length of the shortest ion-conducting path between the cathodes of two different cells in the stack, calculated by the following method: (a) Number the cells: 1, 2, 3 · · ·; (b) Make a list of all cell pairs; (c) The shortest ion conduction path (L cat(i,j) ) for every cell pair in the stack; (d)L catis the sum of all the calculated L cat(i,j) Equal to the minimum of the values.

[0084] Similarly, the current split between adjacent cathodes is: L cat >50 * t * σ sol / σ mem (7) If so, it will be less than 1% of the cell current.

[0085] An illustration of an actual AEM water electrolysis device is shown in Figure 4. Note that the electrolysis device has long tubes 221, 222 and 223 to connect cells 201, 202 and 203 to cathode header 220. The long tubes minimize or at least reduce shunt currents.

[0086] Example 2 The anode inlet manifold 110 in Figure 1A is external to the stack. Example 2 describes an alternative design of an AEM water electrolysis device in which the inlet manifold is internal to the stack and insulated from the metal plates.

[0087] Figure 5 illustrates such a design with an internal inlet manifold. The stack shown includes cells 301, 302, 303, 304 and 305. Cell 305 includes: (a) A bipolar plate 355 serving as the anode of a given cell and the cathode of an adjacent cell; (b) Plastic frame 365; (c) an opening through the plastic frame that serves as the anode header 310; (d) notch 315 that serves as an interface between the anode header 310 and the anode GDL 375; (e) an insulating gasket 385 that isolates the bipolar plate 355 from the anode header 310 and notch 315; and (f) A second hole 320 that serves as a cathode header.

[0088] In such a case, the shortest ion conduction path may not be between adjacent anode / bipolar plates. Instead, the shortest ion conduction path may be between the anode GDL in one cell and the anode GDL in the second cell. In that case, equations 4, 5, 6 and 7 should be replaced with the following equations: L GDLA >10*t*σ sol / σ mem (8) L GDLA >50*t*σ sol / σ mem (9) L GDLC >10*t*σ sol / σ mem (10) L GDLC >50*t*σ sol / σ mem (11) In the formula, L GDLA is the length of the shortest ion-conducting path between the anode GDL of one cell in the stack and the anode GDL of another cell in the stack. L GDLC is the length of the shortest ion-conducting path between the cathode GDL of one cell in the stack and the cathode GDL in another cell in the stack.

[0089] L GDLA is calculated in the following way: (a) Number the cells: 1, 2, 3, ···; (b) Make a list of all cell pairs; (c) Anode of cell i GDL and the anode of cell j GDL The shortest ion conduction path between GDLA(i,j) ) for every cell pair in the stack; (d)L GDLA is the sum of all the calculated L GDLA(i,j) Equal to the minimum of the values.

[0090] L GDLC is calculated in the following way: (a) Number the cells: 1, 2, 3, ···; (b) Make a list of all cell pairs; (c) Cathode of cell i GDL and the cathode of cell j GDL The shortest ion conduction path between GDLC(i,j) ) for every cell pair in the stack; (d)L GDLC is the sum of all the calculated L GDLC(i,j) Equal to the minimum of the values.

[0091] If equations 9 and 11 are satisfied, the shunt current will be less than 1% of the total cell current.

[0092] While particular elements, embodiments and fields of application of the present invention have been illustrated and described, it is understood that the invention is not limited thereto and modifications may be made by those skilled in the art, especially in light of the foregoing teachings, without departing from the scope of the disclosure.

[0093] The examples set forth above are merely illustrative and are not intended to be an exhaustive list of all possible embodiments, applications, or modifications of the electrochemical device. Thus, various modifications and variations of the described methods and systems of the invention will become apparent to those skilled in the art without departing from the scope or spirit of the invention. Although the invention has been described in connection with specific embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. Indeed, various modifications of the described modes for carrying out the invention will be apparent to those skilled in the chemical or related arts and are intended to be within the scope of the appended claims.

Claims

1. 1. A water electrolysis apparatus for producing hydrogen gas comprising an electrolyzer stack, the electrolyzer stack comprising at least two electrochemical cells, each of the electrochemical cells comprising: (a) an anode comprising an anode gas diffusion layer (GDL) and a quantity of an anode electrocatalyst; (b) a cathode comprising a cathode GDL and a quantity of a cathode electrocatalyst; (c) a source of a solution comprising water directed to at least one of the anode and the cathode; (d) an anion exchange membrane interposed between the anode and the cathode; Including, Each of the anion exchange membranes has an average thickness (t); The shortest ion conduction path (L ＧＤＬＡ )but; L ＧＤＬＡ >10 ＊ t ＊ s ｓｏｌ / s ｍｅｍ where σ ｓｏｌ is the conductivity of the solution at 60° C. (S / cm), and σ ｍｅｍ is the conductivity of each of the anion exchange membranes measured in 1 M KOH at 60° C., L ＧＤＬＡ >3 cm, Water electrolysis equipment.

2. L ＧＤＬＡ >50 ＊ t ＊ s ｓｏｌ / s ｍｅｍ The water electrolysis apparatus according to claim 1 ,

3. The shortest ion conduction path (L) between any two of the cathode GDLs of the electrochemical cells in the electrolyzer stack ＧＤＬＣ )but: L ＧＤＬＣ >10 ＊ t ＊ s ｓｏｌ / s ｍｅｍ The water electrolysis apparatus according to claim 1 ,

4. 2. The water electrolysis apparatus of claim 1, wherein the solution has a pH of greater than 8 at 25°C.

5. 5. The water electrolysis apparatus of claim 4, wherein the solution has a pH greater than 12 at 25°C.

6. 2. The water electrolysis apparatus of claim 1, wherein the solution has a conductivity of greater than 0.05 S / cm at 25°C.

7. 2. The water electrolysis apparatus of claim 1, wherein the cathode electrocatalyst in each of the electrochemical cells is in the form of unsupported particles or particles supported on a conductive support, the particles having an average size of 0.6 nm to 100 nm.

8. 10. The water electrolysis apparatus of claim 1, wherein the anode electrocatalyst in each of the electrochemical cells comprises a base metal catalyst.

9. 9. The water electrolysis apparatus of claim 8, wherein the anode electrocatalyst in each of the electrochemical cells consists essentially of one or more base metal catalysts.

10. The water electrolysis apparatus of claim 1 , wherein the cathode electrocatalyst in each of the electrochemical cells comprises a base metal catalyst.

11. 11. The water electrolysis apparatus of claim 10, wherein the cathode electrocatalyst in each of the electrochemical cells consists essentially of one or more base metal catalysts.

12. 10. The water electrolysis apparatus of claim 1, wherein the anion exchange membrane in each of the electrochemical cells comprises a positively charged amine.

13. 13. The water electrolysis device of claim 12, wherein the positively charged amine is an imidazolium, piperidinium or pyridinium.

14. The water electrolysis apparatus of claim 1 , wherein the cathode in each of the electrochemical cells comprises an ionomer.

15. An AEM water electrolysis apparatus for substantially converting water to H2 and O2, comprising: an electrolyzer stack comprising at least two electrochemical cells, each of the electrochemical cells comprising: (a) an anode comprising an anode gas diffusion layer (GDL) and a quantity of an anode electrocatalyst; (b) a cathode comprising a cathode GDL and a quantity of a cathode electrocatalyst; (c) a source of a solution comprising water directed to at least one of the anode and the cathode; (d) an anion exchange membrane interposed between the anode and the cathode; Including, The AEM water electrolysis device, wherein the shortest ion conduction path (L GDLA ) between any two of said anode GDLs of at least two of said electrochemical cells in said electrolyzer stack is greater than 3 cm.

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