Devices, systems, and methods for electrochemically purifying hydrogen

Abstract

Hydrogen gas purifier electrochemical cells (10, 50, 150), systems (200) for purifying hydrogen gas, and methods for purifying hydrogen gas are provided. The cells, systems, and methods use dual membrane electrode (DMEA) electrochemical cells (24, 26, 152) that enhance purification while avoiding the complexity and cost of conventional cells. The purity of the hydrogen gas produced by the cells, systems, and methods can be improved by removing at least some intermediate gas impurities from the cell. The purity of the hydrogen gas produced by the cells, systems, and methods can also be increased by introducing hydrogen gas into the cell to replenish any lost hydrogen. A water electrolysis electrochemical cell (250) and a method for electrolyzing water to produce hydrogen gas are also disclosed.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to pending U.S. patent application Ser. No. 17 / 934,341, filed Sep. 22, 2022, the disclosure of which is incorporated herein by reference in its entirety. [Background technology]

[0002] Background of the Invention Technical Field The present invention relates generally to the electrochemical purification and / or compression of hydrogen gas. Specifically, aspects of the present invention include electrochemical cells, systems, and methods for purifying and / or compressing hydrogen gas that use one or more membrane electrode assemblies (MEAs) within a single MEA cell, avoiding external handling of gas flow between separate MEA cells.

[0003] Description of the Prior Art

[0003] As is known in the art, high-purity hydrogen, i.e., hydrogen gas having a hydrogen content of greater than 99.99 volume percent, has many uses. However, hydrogen gas is typically mixed with other undesirable gases, such as nitrogen, argon, carbon dioxide, oxygen, and carbon monoxide, among others. Therefore, there is a need in the art for improved methods of separating hydrogen gas from undesirable gases to provide a purer form of hydrogen gas.

[0004]

[0004] Purification of hydrogen is not easily achieved. Hydrogen gas is generally difficult to separate from other gases, especially because the hydrogen molecule is relatively small and hydrogen gas is flammable. Existing means for purifying hydrogen gas from undesirable non-hydrogen gases include molecular sieves, membranes, palladium membranes, and electrochemical hydrogen pumps (EHPs).

[0005]

[0005] Molecular sieves separate hydrogen molecules by selective adsorption, preferentially retaining some molecules over others. However, in many cases, molecular sieve adsorption systems have only a small, undesirable effect on hydrogen gas purity. One such case is the separation of nitrogen gas (N2) and hydrogen gas (H2).

[0006]

[0006] Palladium selectively allows only hydrogen atoms to pass through, generating high-purity hydrogen. However, palladium is expensive, the process requires compressed gas, and high hydrogen recovery requires high pressures and / or large amounts of palladium.

[0007] Electrochemical hydrogen pumps (EHPs) selectively extract hydrogen from mixtures of hydrogen gas and other gases, such as nitrogen and argon. However, other undesirable gases typically diffuse across the pump's membrane, resulting in limited hydrogen gas purity. As a result, multiple individual electrochemical hydrogen pumps can be used, each with an associated housing, cell stack, supply conduit, and exhaust conduit in series, among other separate hardware and control systems, to purify the hydrogen gas stream twice and thus attempt to increase hydrogen gas purity. However, such a configuration requires multiple separate electrochemical pump cell stacks and multiple sets of electrochemical stack hardware connected to each other. This undesirably increases the system's complexity and cost.

[0008] Another approach to purifying hydrogen is to increase the film thickness in the electrochemical cell. However, increasing the film thickness is typically limited to only reducing impurity diffusion across the film as a function of the film thickness. Other approaches to purifying hydrogen gas require undesirable gas pressure compression, undesirable multiple pumps, recover less hydrogen gas, consume more energy, and / or do not produce the high-purity hydrogen gas required by today's hydrogen gas users, such as the semiconductor industry.

[0009]

[0009] Therefore, there is a need in the art for improved hydrogen purification systems, methods, and devices. Summary of the Invention [Problem to be solved by the invention]

[0010] Summary of the Invention

[0010] In their various aspects, embodiments of the present invention address this recognized need by providing improved hydrogen purification that can meet and exceed the hydrogen gas purity required by a variety of applications. Aspects of the present invention use a unique combination of membrane electrode assemblies (MEAs) or "dual" MEAs (DMEAs), which have been shown to provide the improved hydrogen gas purity required by today's users. [Means for solving the problem]

[0011] One embodiment of the present invention is a hydrogen gas purifier cell comprising a first membrane electrode assembly (MEA), a first anode disposed in contact with a first gas stream having a first hydrogen gas content and a first impurity gas content, the first anode containing a catalyst, e.g., a platinum-group containing catalyst, adapted to oxidize at least a portion of the first hydrogen gas content to produce hydrogen ions and electrons, a first electrolyte, e.g., an acidic electrolyte, disposed and adapted to receive and transfer at least a portion of the hydrogen ions produced by the first anode, and a first cathode disposed to receive at least a portion of the hydrogen ions transferred by the first electrolyte, the first cathode containing a catalyst adapted to reduce at least a portion of the hydrogen ions to produce a second gas stream having a second hydrogen gas content greater than the first hydrogen gas content and a second impurity gas content less than the first impurity gas content. and a second MEA comprising: a second anode arranged to receive a second gas stream from the first cathode of the first MEA, the second anode containing a catalyst adapted to oxidize at least a portion of a second hydrogen gas content in the second gas stream to produce hydrogen ions and electrons; a second electrolyte, for example, an acidic electrolyte, arranged and adapted to receive and transfer at least a portion of the hydrogen ions produced by the second anode; and a second cathode arranged to receive at least a portion of the hydrogen ions transferred by the second electrolyte of the second MEA, the second cathode containing a catalyst adapted to reduce at least a portion of the hydrogen ions and electrons to produce a third gas stream having a third hydrogen gas content greater than the first hydrogen gas content and a third impurity gas content less than the first impurity gas content.

[0012] In one aspect, the purifier cell can further comprise at least one passageway between the first electrolyte and the second electrolyte for exhausting at least a portion of the second gas stream. For example, the at least one passageway can be located between the first cathode and the second anode. In one aspect, the at least one passageway located between the first cathode and the second anode can comprise a space or void between the mating surfaces of the first cathode and the second anode. In another aspect, the purifier cell can further comprise a gas permeable layer or gas diffusion layer (GDL) between the first cathode and the second anode, the GDL providing at least one passageway for exhausting at least a portion of the second gas stream. In another aspect, a gas distribution or flow field insert, with or without a GDL, can be disposed between the first cathode and the second anode to facilitate or enhance distribution of the second gas stream across the surface of the second anode. The flow field insert may be an electrically conductive porous or perforated plate, e.g., a porous or perforated metal plate, or a screen-like insert, e.g., a metal screen-like insert, positioned and adapted to provide at least a portion of the gas distribution about the surface of the second anode. In another aspect, the at least one passage for exhausting at least a portion of the second gas stream may be at least one channel proximate to the first cathode, the second anode, or both.

[0013] In another aspect, the purifier cell can further comprise or include at least one passageway between the first electrolyte and the second electrolyte for introducing a hydrogen-containing gas into the second gas stream. For example, the at least one passageway may be located between the first cathode and the second anode. In one aspect, the at least one passageway may be a space or void between the mating surfaces of the first cathode and the second anode. In one aspect, the purifier cell can further include a gas permeable layer or gas diffusion layer (GDL) between the first cathode and the second anode, where the GDL can provide at least one passageway for introducing a hydrogen-containing gas into the second gas stream. In another aspect, a gas distribution or flow field insert, with or without a GDL, can be disposed between the first cathode and the second anode to facilitate or enhance distribution of the second gas stream across the surface of the second anode. The flow field insert may be a porous or perforated plate, e.g., a porous or perforated metal plate, or a screen-like insert, e.g., a metal screen-like insert, positioned and adapted to provide at least some gas distribution around the surface of the second anode.

[0014]

[0014] In another aspect, the at least one passage for introducing hydrogen-containing gas into the second gas stream may comprise at least one channel proximate to the first cathode, the second anode, or both.

[0015] In one aspect, the first gas flow can have a first gas pressure and the third gas flow can have a third gas pressure, the third gas pressure being greater than the first gas pressure. In another aspect, the third gas pressure can be less than the first gas pressure.

[0016] Another embodiment of the present invention is a hydrogen gas purification system comprising or including at least one hydrogen gas purifier cell as disclosed herein and at least two conductive plates, one of the at least two plates attached to a first end of the at least one hydrogen gas purifier cell and one of the at least two plates attached to a second end of the at least one hydrogen gas purifier cell opposite the first end. For example, in one aspect, the at least one hydrogen gas purifier cell may comprise a plurality of hydrogen gas purifier cells, e.g., a stack of hydrogen gas purifier cells.

[0017] Another embodiment of the present invention is a method for reducing the impurity gas content of a gas stream having a hydrogen gas content and an impurity gas content, the method including: introducing a first gas stream having a first hydrogen content and a first impurity gas content to a first anode containing a catalyst; catalytically oxidizing at least a portion of the first hydrogen gas content at the first anode to produce hydrogen ions and electrons; migrating at least a portion of the hydrogen ions and at least a portion of the impurity gas content through a first electrolyte to a first cathode containing a catalyst; and catalytically reducing at least a portion of the hydrogen ions that have migrated through the first electrolyte at the first cathode to produce a second hydrogen content greater than the first hydrogen content and less than the first impurity gas content. generating a second gas stream having a second impurity gas content free of the first hydrogen content; introducing the second gas stream to a second anode having a catalyst; catalytically oxidizing at least a portion of a second hydrogen gas content in the second gas stream at the second anode to produce hydrogen ions and electrons; migrating at least a portion of the hydrogen ions produced at the second anode and at least a portion of the second impurity gas content through a second electrolyte to a second cathode; and catalytically reducing at least a portion of the hydrogen ions that have migrated through the second electrolyte at the second cathode to produce a third gas stream having a third hydrogen content greater than the first hydrogen content and a third impurity gas content less than the first impurity gas content.

[0018] In one aspect, the method can further include removing at least a portion of the second gas stream to produce a reformed gas stream having a non-hydrogen gas partial pressure lower than the partial pressure of the non-hydrogen gas in the second gas stream. In another aspect, introducing the second gas stream to the second anode includes introducing the reformed gas stream to the second anode. In one aspect, removing at least a portion of the second gas stream can be performed by removing at least a portion of the second gas stream through a passage between the first electrolyte and the second electrolyte; for example, the passage can be located between the first cathode and the second anode. In one aspect, the passage for removing at least a portion of the second gas stream can be a space or void between the mating surfaces of the first cathode and the second anode. In another aspect, removing at least a portion of the second gas stream can be performed by removing at least a portion of the second gas stream through a gas diffusion layer (GDL) and / or a flow field insert disposed between the first cathode and the second anode. In another aspect, removing at least a portion of the second gas stream may be performed by removing at least a portion of the second gas stream through at least one channel proximate to the first cathode, the second cathode, or both.

[0019] In another aspect, the method may further include introducing a portion of the hydrogen gas into a second gas stream, e.g., a "make-up" gas stream. In one aspect, introducing a portion of the hydrogen gas into the second gas stream can replenish at least a portion of the hydrogen gas removed from the second gas stream. In one aspect, the make-up hydrogen gas stream can include at least a portion of a third gas stream having a third hydrogen content. For example, the third gas stream may be introduced into the second gas stream by diffusion through the second electrolyte. This diffusion through the second electrolyte may be referred to as "back-diffusion" of at least a portion of the third gas stream having a third hydrogen content into the second gas stream through the second electrolyte.

[0020] In one aspect, by employing the electrochemical cells and methods disclosed herein, the purified hydrogen gas produced, e.g., the third impurity gas content, may be at least 100 times lower by volume than the impurity content of the input gas content, e.g., the first impurity gas content. In another aspect, the impurity gas content of the produced hydrogen gas may be at least 1,000, 10,000, 100,000, or even 1,00,000 times lower than the impurity content of the first hydrogen gas stream.

[0021] In one aspect, the impurity gas content of the hydrogen gas produced by any of the methods, cells, and systems of the present invention, for example in the third gas stream, may be at most 100 parts per million (ppm), i.e., the third gas stream may contain at most 100 ppm of impurity gas. In other aspects of the present invention, the impurity gas content of the produced hydrogen gas may be at most 20 ppm, or at most 10 ppm, or at most 5 ppm, or at most 2 ppm, or at most 1 ppm. In other aspects of the present invention, the impurity gas content of the produced hydrogen gas may be at most 750 parts per billion (ppb) (i.e., at most 0.750 ppm), or at most 500 ppb, or at most 200 ppb, or even at most 100 ppb. As known in the art, these impurity contents of the produced hydrogen gas, e.g., 1,000 times lower than the impurity gas content of the first gas stream, or impurity gas contents in ppm or ppb, are typically on a "dry basis." As known in the art, "on a dry basis" means that there may be some water vapor in the produced gas stream that has not yet been reduced or removed, for example, in a subsequent drying process.

[0022]

[0022] Another embodiment of the present invention is a method for reducing the impurity gas content of a gas stream having a hydrogen gas content and an impurity gas content, the method comprising or including: introducing a first gas stream having a first hydrogen content and a first impurity gas content into a first membrane electrode assembly (MEA) having a first anode containing a catalyst, a first electrolyte, and a first cathode containing a catalyst to produce a second gas stream having a second hydrogen gas content and a second impurity gas content; and passing the second gas stream directly through a second MEA having a second anode containing a catalyst, a second electrolyte, and a second cathode containing a catalyst to produce a third gas stream having a third hydrogen gas content greater than the first hydrogen content and a third impurity gas content less than the first impurity gas content.

[0023]

[0023] In one aspect, the first MEA and the second MEA may be disposed within a hydrogen purification cell, and passing the second gas stream directly through the second MEA may include passing the second gas stream through the second MEA without allowing the second gas stream to leave the hydrogen purification cell.

[0024] In one aspect, the method may further include removing at least a portion of the second gas stream to produce a reformed second gas stream having a reduced non-hydrogen gas partial pressure relative to the second gas stream, and then introducing the reformed second gas stream having the reduced non-hydrogen gas partial pressure into a second MEA. In one aspect, the method may further include introducing at least a portion of hydrogen gas into the second gas stream or the reformed second gas stream.

[0025] A further embodiment of the present invention is a hydrogen gas purifier cell comprising a membrane electrode assembly (MEA), the MEA comprising an anode disposed in contact with a first gas stream having a first hydrogen gas content and a first impurity gas content, the anode containing a catalyst adapted to oxidize at least a portion of the first hydrogen gas content to produce hydrogen ions and electrons, a first electrolyte disposed and adapted to receive and transfer at least a portion of the hydrogen ions received from the anode, and a dual cathode disposed to receive at least a portion of the hydrogen ions transferred by the first electrolyte, the dual cathode reducing at least a portion of the hydrogen ions to produce a second hydrogen gas stream having a second hydrogen gas content. a dual electrode containing a catalyst adapted to oxidize at least a portion of a second hydrogen gas content in the second gas stream to produce hydrogen ions and electrons; a second electrolyte positioned and adapted to receive and transfer at least a portion of the hydrogen ions received from the dual electrode; and a cathode positioned to receive at least a portion of the hydrogen ions transferred by the second electrolyte, the cathode containing a catalyst adapted to reduce at least a portion of the hydrogen ions to produce a third gas stream having a third hydrogen gas content greater than the first hydrogen gas content and a third impurity gas content less than the first impurity gas content.

[0026] In one aspect, the hydrogen gas purifier cell further includes at least one passage for removing at least a portion of the second gas stream. For example, the at least one passage for removing at least a portion of the second gas stream may be through the bipolar electrode, e.g., a permeable, gas-permeable diffusion layer of the bipolar electrode, and / or the second electrolyte.

[0027] In one aspect, the hydrogen gas purifier cell further includes at least one passageway for introducing at least a portion of the hydrogen gas into the second gas stream. For example, the at least one passageway for introducing at least a portion of the hydrogen gas may be through the bipolar electrode, e.g., a permeable, gas-permeable diffusion layer of the bipolar electrode, and / or the second electrolyte, e.g., via "back diffusion."

[0028]

[0028] A further embodiment of the present invention is a method for purifying hydrogen gas comprising or including: introducing a first gas stream having a first hydrogen gas content and a first impurity gas content to an anode containing a catalyst; catalytically oxidizing at least a portion of the first hydrogen gas content at the anode to produce hydrogen ions and electrons; transferring at least a portion of the hydrogen ions produced at the anode through a first electrolyte to a dual electrode; catalytically reducing at least a portion of the hydrogen ions that migrated through the first electrolyte at the dual electrode to produce a second gas stream having a second hydrogen gas content and catalytically oxidizing at least a portion of the second hydrogen gas content in the second gas stream to produce hydrogen ions and electrons; transferring at least a portion of the hydrogen ions produced in the dual electrode through the second electrolyte to a cathode; and catalytically reducing at least a portion of the hydrogen ions that migrated through the second electrolyte at the cathode to produce a third gas stream having a third hydrogen gas content greater than the first hydrogen gas content and a third impurity gas content less than the first impurity gas content.

[0029] In one aspect, the method can further include removing at least a portion of the second gas stream, e.g., through at least one passageway. For example, the at least one passageway for removing at least a portion of the second gas stream can be a gas diffusion layer, a gas-permeable bielectrode, and / or a second electrolyte, e.g., via "back diffusion."

[0030] In one aspect, the method can further include introducing at least a portion of the hydrogen gas into the second gas stream, for example, through at least one passageway. For example, the at least one passageway for introducing at least a portion of the hydrogen gas can be through the gas diffusion layer, through the gas permeable bielectrode, and / or through the second electrolyte.

[0031] A further embodiment of the present invention is a water electrolyzer cell comprising a first membrane electrode assembly (MEA), a first anode disposed in contact with a first H2O-containing fluid stream, the first anode containing a catalyst adapted to oxidize at least a portion of the H2O in the first H2O-containing fluid stream to produce oxygen gas, hydrogen ions, and electrons, a first electrolyte disposed and adapted to receive and transfer at least a portion of the hydrogen ions produced by the first anode, and a first cathode disposed to receive at least a portion of the hydrogen ions transferred by the first electrolyte, the first cathode containing a catalyst adapted to reduce at least a portion of the hydrogen ions to produce a second fluid stream containing hydrogen gas. A second MEA comprising: a second anode arranged to receive a second fluid stream containing hydrogen gas from the first cathode of the first MEA, the second anode containing a catalyst adapted to oxidize at least a portion of the hydrogen gas to produce hydrogen ions and electrons; a second electrolyte arranged and adapted to receive and transfer at least a portion of the hydrogen ions produced by the second anode; and a second cathode arranged to receive at least a portion of the hydrogen ions transferred by the second electrolyte of the second MEA, the second cathode containing a catalyst adapted to reduce at least a portion of the hydrogen ions to produce a third fluid stream containing hydrogen gas.

[0032] In one aspect, the electrolyzer cell can further include at least one passageway between the first electrolyte and the second electrolyte for discharging at least a portion of the second fluid stream. For example, the passageway for discharging the second fluid stream can be located between the first cathode and the second anode. For example, the at least one passageway located between the first cathode and the second anode can be a gap between the mating surfaces of the first cathode and the second anode, and / or a gas permeable layer (GDL) and / or a flow field insert between the first cathode and the second anode.

[0033] In another aspect, the water electrolyzer cell may further include at least one passageway between the first electrolyte and the second electrolyte for introducing a hydrogen-containing gas into the second gas stream. For example, the passageway for introducing hydrogen gas may be a gap between the mating surfaces of the first cathode and the second anode, and / or a GDL and / or flow field insert located between the first cathode and the second anode.

[0034] Another embodiment of the present invention is a method for electrolyzing water, the method comprising: introducing a first H2O-containing fluid stream to a first anode containing a catalyst; catalytically oxidizing at least a portion of the H2O in the first H2O-containing fluid stream at the first anode to produce oxygen gas, hydrogen ions, and electrons; transferring at least a portion of the hydrogen ions through a first electrolyte to a first cathode containing a catalyst; and catalytically reducing at least a portion of the hydrogen ions transferred through the first electrolyte at the first cathode to produce a second hydrogen ion having hydrogen gas. generating a second fluid stream, introducing the second fluid stream having hydrogen gas to a second anode having a catalyst, catalytically oxidizing at least a portion of the hydrogen gas in the second fluid stream at the second anode to produce hydrogen ions and electrons, transferring at least a portion of the hydrogen ions produced at the second anode through a second electrolyte to a second cathode, and catalytically reducing at least a portion of the hydrogen ions transferred through the second electrolyte at the second cathode to produce a third fluid stream having hydrogen gas. According to aspects of the present invention, a "fluid stream" may be a liquid stream, a gas stream, and / or a liquid and gas stream.

[0035] In one aspect, the method may further include removing at least a portion of the second fluid stream to produce a reformed fluid stream having a non-hydrogen gas partial pressure that is lower than the partial pressure of the non-hydrogen gas in the second fluid stream. The method may further include introducing the reformed fluid stream to a second anode.

[0036]

[0036] In another aspect, the method may further include introducing a portion of hydrogen gas into the second fluid stream, for example, the introduced hydrogen gas may replenish at least a portion of the hydrogen gas removed from the second fluid stream.

[0037] A further embodiment of the present invention is a water electrolyzer cell comprising or including a membrane electrode assembly (MEA) with an anode arranged in contact with a first H2O containing fluid stream, the anode containing a catalyst adapted to oxidize at least a portion of the H2O in the first H2O containing fluid stream to produce oxygen gas, hydrogen ions, and electrons, a first electrolyte arranged and adapted to receive and transfer at least a portion of the hydrogen ions produced by the anode, and a dual cathode arranged to receive at least a portion of the hydrogen ions transferred by the first electrolyte, a second electrolyte disposed and adapted to receive and transfer at least a portion of the hydrogen ions transferred by the second electrolyte of the second MEA, the cathode containing a catalyst adapted to reduce at least a portion of the hydrogen ions to produce a third fluid stream containing hydrogen gas.

[0038]

[0038] Another embodiment of the present invention is a method for electrolyzing water comprising or including: introducing a first H2O-containing fluid stream to an anode containing a catalyst; catalytically oxidizing at the anode at least a portion of the H2O in the first H2O-containing fluid stream to produce oxygen gas, hydrogen ions, and electrons; transferring at least a portion of the hydrogen ions produced at the anode through a first electrolyte to a dual electrode; catalytically reducing at least a portion of the hydrogen ions that have migrated through the first electrolyte at the dual electrode to produce a second fluid stream having a second hydrogen gas content and catalytically oxidizing at least a portion of the second hydrogen gas content in the second gas stream to produce hydrogen ions and electrons; transferring at least a portion of the hydrogen ions produced in the dual electrode through the second electrolyte to a cathode; and catalytically reducing at least a portion of the hydrogen ions that have migrated through the second electrolyte at the cathode to produce a third fluid stream having hydrogen gas.

[0039]

[0039] These and other aspects, features, and advantages of the present invention will become apparent from the following detailed description of various aspects of the invention taken in conjunction with the accompanying drawings.

[0040] BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of this specification. The above and other objects, features, and advantages of the present invention will be readily understood from the following detailed description of embodiments of the invention taken in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0041] [Figure 1] FIG. 1 is a schematic diagram of a hydrogen gas purifier cell according to one embodiment of the present invention. [Figure 2]

[0042] FIG. 2 is a schematic diagram of a hydrogen gas purifier cell according to another aspect of the present invention. [Figure 3]

[0043] 3 is a schematic front view of a hydrogen purifier stack assembly having the hydrogen gas purifier cell shown in FIG. 1 or FIG. 2 according to an embodiment of the present invention. [Figure 3A]

[0044] 3A is a detailed view of the hydrogen purifier stack assembly shown in FIG. 3, identified by detail 3A shown in FIG. 3. [Figure 3B]

[0045] FIG. 3B is a detail view similar to FIG. 3A according to another embodiment of the present invention. [Figure 4]

[0046] FIG. 4 is a schematic front view of a hydrogen purifier stack having multiple hydrogen purifier cells as shown in FIG. 1 and / or FIG. 3, according to one embodiment of the present invention. [Figure 5]

[0047] FIG. 2 is a schematic diagram of a hydrogen gas purifier cell according to another aspect of the present invention. [Figure 6]

[0048] FIG. 5 is a schematic diagram of a hydrogen gas purifier system having one or more hydrogen purifiers with one or more hydrogen purifier stacks shown in FIG. 4, according to one embodiment of the present invention. [Figure 7]

[0049] FIG. 2 is a schematic diagram of a water electrolyzer cell according to another embodiment of the present invention. [Figure 8]

[0050] FIG. 2 is a schematic diagram of a water electrolyzer cell according to another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] Detailed Description of the Invention

[0051] FIG. 1 is a schematic diagram of a hydrogen gas purifier cell 10 according to one embodiment of the present invention. According to this embodiment, the purifier cell 10 is configured and adapted to receive a feed or first gas stream 12 having at least a portion of hydrogen gas content 14 (i.e., diatomic hydrogen gas, H) and at least a portion of non-hydrogen gases 16 and produce a gas stream 18 having a reduced non-hydrogen gas content, i.e., a purer hydrogen gas content. The non-hydrogen gas 16 typically can include, among other gases, nitrogen (N), argon (Ar), carbon monoxide (CO), methane (CH), oxygen (O), and / or carbon dioxide (CO). According to one embodiment of the present invention, the term "non-hydrogen gas" can refer to a gas that is not diatomic hydrogen gas, H. The reduced non-hydrogen gas content gas stream 18 may be referred to as an exhaust gas stream 18 or a third gas stream 18. Third gas stream 18 may typically include an enhanced hydrogen gas content 20 and a reduced non-hydrogen gas content 22, e.g., a higher purity hydrogen gas stream, e.g., a hydrogen gas stream having a non-hydrogen content of up to 100 ppm on a dry basis. In other aspects of the invention, the non-hydrogen content 22 of gas stream 18 may be up to 20 ppm, or up to 10 ppm, or up to 5 ppm, or up to 2 ppm, or up to 1 ppm. In addition to reducing the content of non-hydrogen gases in gas stream 18, in aspects of the invention, gas stream 18 may typically have an increased hydrogen gas content 20, e.g., in volume percent, and an increased hydrogen gas pressure, e.g., a pressure higher than the pressure of feed gas stream 12. In one aspect, the pressure of gas stream 18 may be lower than the pressure of gas stream 12. Because the desired function of the purifier cell 10 is to reduce or substantially eliminate the content of the non-hydrogen gas 16, the non-hydrogen gas 16 may be referred to as an "impurity gas" 16 or a "first impurity gas" 16.

[0043]

[0052] As shown schematically in FIG. 1, a hydrogen gas purifier cell 10 typically comprises a multi-layer structure having components, such as an anode and a cathode, with thin planar or thin layered structures; the structure shown in FIG. 1 may comprise a side view or transaxial cross-section of purifier cell 10, which is not drawn to scale but is drawn to facilitate disclosure of the present invention.

[0044]

[0053] According to aspects of the present invention, to provide the desired increased hydrogen gas content 20, and typically increased hydrogen gas pressure, purifier cell 10 typically includes a first membrane electrode assembly (MEA) 24 and at least one second MEA 26. First MEA 24 includes a first electrode 28, specifically a first "anode" 28 as referred to in the art. Anode 28, and any anodes disclosed herein, may typically be gas permeable, specifically hydrogen gas permeable, such that at least a portion of the hydrogen gas content 14 and at least a portion of the non-hydrogen gas content 16 in first gas stream 12 may pass through anode 28, e.g., axially as indicated by the arrows in first gas stream 12. Additionally, anode 28, and any anodes or cathodes disclosed herein, may contain at least a portion of a catalyst, e.g., hydrogen ions (H + anode 28 contains at least a portion of a platinum group metal-containing catalyst, e.g., a platinum-containing catalyst, capable of enhancing the oxidation of hydrogen to Cr, although in some embodiments, non-platinum group metal-containing catalysts may be used for anode 28 and any anode or cathode disclosed herein. As is known in the art, the platinum group metal-containing catalyst may be a catalyst containing at least a portion of nickel (Ni), at least a portion of palladium (Pa), and / or at least a portion of platinum (Pt).

[0045]

[0054] First anode 28 is positioned in contact with first gas stream 12 having first hydrogen gas content 14 and first impurity gas content 16. The relative contents of first hydrogen gas 14 and first impurity gas content 16 in first gas stream 12 are indicated generally in FIG. 1 and other figures by the partial shading of the arrow identified as first gas stream 12. This partial shading of gas flow arrow 12 (and gas flow arrows 38 and 18 in FIG. 1) is for illustrative purposes only and does not represent the actual relative gas contents of these gas streams in accordance with embodiments of the present invention.

[0046]

[0055] 1 may be disposed between the first gas stream 12 and the anode 28 to enhance distribution of the first gas stream 12 around the surface of the anode 28; for example, a GDL may be applied to the surface of the anode 28 that is contacted by the first gas stream 12. In one embodiment, the GDL used in the cell 10, or the GDL layer used in any embodiment disclosed herein, may be a carbon fiber-type GDL, such as one provided by SGL Carbon GmbH, or its equivalent. In another embodiment, a gas distribution or flow field insert (as disclosed herein), with or without a GDL, may be disposed on the anode 102 to facilitate or enhance distribution of the first gas stream 12 across the surface of the anode 28.

[0047]

[0056] According to an embodiment of the present invention, the catalyst included in the first anode 28 converts hydrogen ions (H + ) and electrons (e - ) to promote or enhance the oxidation of at least the hydrogen gas (H2) content 14 introduced to the anode 28. H2=>2H + +2e - formula 1 The permeability of the anode 28 allows hydrogen gas (H) to enter the anode 28, and the conductivity of the anode 28 allows electrons (e -) are conducted from the anode 28, and in accordance with an embodiment of the present invention, hydrogen ions (H+) are introduced into the electrolyte 30. As is known in the art, hydrogen ions (H + ) are protons. However, it is recognized in the art that at least some of the undesired non-hydrogen gases 16 also pass through the anode 28.

[0048]

[0057] As is typical in the art, at least a portion of input or first gas stream 12 may not be oxidized at anode 28, but may be removed as gas stream 13, e.g., an "exhaust gas stream." Exhaust stream 13, which typically has a lower hydrogen gas content due to the oxidation of hydrogen gas that occurs within first anode 28, may be captured and directed, e.g., via channels, manifolds, and ports, for further processing, or disposed of as needed.

[0049]

[0058] The electrolyte 30 or the first electrolyte 30 contains hydrogen ions (H + The anode 28 is positioned and adapted to receive and transfer at least a portion of the hydrogen ions (H + ) and non-hydrogen gases pass from the anode 28 to the electrolyte 30. The first electrolyte 30 comprises a barrier between the first anode 28 and the electrode 32. The first electrolyte 30 contains hydrogen ions (H +), for example, can include any material or substance that can selectively transfer hydrogen ions (H+), i.e., protons, from first anode 28 to electrode 32. That is, in one aspect, electrolyte 30, and any electrolyte disclosed herein, can be referred to as a "proton-conducting material" while substantially preventing the flow of gases and electrons. First electrolyte 30, and any electrolyte disclosed herein, can typically be an acidic polymer containing perfluorosulfonic acid (PFSA). In one aspect, electrolyte 30, and any electrolyte disclosed herein, can be a membrane commercially available under the trademark Nafion™ by The Chemours Company of Wilmington, Delaware, or its equivalent. In other aspects, electrolyte 30, and any electrolyte disclosed herein, can be a membrane commercially available under the trademark Nafion™ by The Chemours Company of Wilmington, Delaware, or its equivalent. In other aspects, electrolyte 30, and any electrolyte disclosed herein, can be a membrane commercially available from the following acids: phosphoric acid [H3PO4], sulfuric acid [H2SO4], or any other hydrogen ion (H + ) conductive acids. In one embodiment, the first electrolyte 30 can include a proton exchange membrane (PEM), as known in the art.

[0050]

[0059] As is known in the art, the passage of gas through electrolyte 30, and through any electrolyte disclosed herein, is driven by a partial pressure gradient of the gas across the electrolyte, for example, from one side of electrolyte 30 to the other opposite side of electrolyte 30. Thus, any undesirable non-hydrogen gas with a sufficient partial pressure gradient can also diffuse through electrolyte 30, and through any electrolyte disclosed herein. In addition to pressure gradients across the electrolyte, defects in the electrolyte, for example, small holes or voids in the electrolyte, can also undesirably allow gas to flow through an electrolyte, such as electrolyte 30.

[0051]

[0060] The electrode 32, sometimes referred to as the “cathode” 32 or first cathode 32 as known in the art, receives hydrogen ions (H +Like first anode 28, first cathode 32, and any cathode disclosed herein, typically receives at least a portion of the electrons (e - ) passing through the first electrolyte 30. + The catalyst comprises a catalyst, e.g., a platinum group metal-containing catalyst, adapted to enhance the reaction (i.e., reduction) of at least a portion of the catalyst. 2H + +2e - =>H2 formula 2

[0052]

[0061] The resulting or "generated" hydrogen gas (H2) 34, or second hydrogen gas content 34, and any non-hydrogen gases 36, or second impurity gas content 36, that are transferred through the first cathode 32 are shown in FIG. 1 as gas stream 38, or second gas stream 38.

[0053]

[0062] In one embodiment, to enhance the distribution of hydrogen gas around the surface of the first cathode 32, a gas diffusion layer (GDL) and / or a flow field insert, not shown in FIG. 1 , may be disposed between the first electrolyte 30 and the first cathode 32; for example, the GDL and / or the flow field insert may be applied onto the surface of the first cathode 32.

[0054]

[0063] According to an aspect of the present invention, the second hydrogen gas content 34 is greater than the first hydrogen gas content 14 and the second impurity gas content 36 is less than the first impurity gas content 16 .

[0055]

[0064] As shown in FIG. 1 , according to an embodiment of the present invention, a second gas stream 38 having a second hydrogen gas content 34 and a second impurity gas content 36 can then be introduced into a second MEA 26, specifically, into an electrode 40 or second anode 40 of the second MEA 26. In the schematic diagram of the purifier cell 10 shown in FIG. 1 , the first MEA 24 is shown spaced apart from the second MEA 26 for ease of illustration and disclosure of the present invention. However, according to an embodiment of the present invention, the spacing between the first MEA 24 and the second MEA 26 can be minimal, for example, where the surface of the first cathode 32 can abut or contact the surface of the second anode 40. However, in one embodiment, at least some spacing, e.g., 0.1 millimeters [mm] to 0.5 mm, can exist between the surface of the first cathode 32 and the surface of the second anode 40.

[0056]

[0065] According to an aspect of the present invention, in contrast to existing technology, second gas stream 38 having second hydrogen gas content 34 and second impurity gas content 36 may then be introduced into second MEA 26 without removing or extracting second gas stream 38 from purifier cell 10. In other words, although some portion of gas stream 38 may undesirably "escape" from purifier cell 10, according to one aspect of the present invention, substantially all of gas stream 38 produced at or diffused through first cathode 32 is received by second anode 40. For example, in one aspect, second gas stream 38 may be allowed to pass from first cathode 32 of MEA 24 to second anode 40 of MEA 26 without any intervening handling or processing, e.g., without passing outside of cell 10. In one embodiment, evolved hydrogen gas (H) formed at first cathode 32 can be substantially immediately oxidized to hydrogen ions (H) at second anode 40. In one embodiment, second gas stream 38 can be passed directly from first cathode 32 of MEA 24 of purifier cell 10 to second anode 40 of MEA 26, for example, without passing outside of cell 10 before reaching second cathode 40.

[0057]

[0066] The second anode 40 is positioned to be contacted by a second gas stream 38 having a second hydrogen gas content 34 and a second impurity gas content 36. The second anode 40 of the second MEA 26 may be similar to, if not identical to, the first anode 28 of the MEA 24. The second anode 40 may be hydrogen gas permeable, such that at least a portion of the hydrogen gas content 34 and at least a portion of the non-hydrogen gas content 36 in the second gas stream 38 may pass through the second anode 40, e.g., axially, as indicated by the arrows of the second gas stream 38. Furthermore, the second anode 40 may be configured to convert the hydrogen ions (H ) of the hydrogen gas into hydrogen ions (H ) as shown by Equation 1. + ) and electrons (e - ) to HCl.

[0058]

[0067] In one embodiment, a gas diffusion layer or GDL and / or flow field insert, not shown in FIG. 1 , may be disposed between the first cathode 32 and the second anode 40 to enhance distribution of the second gas stream 38 around the surface of the second anode 40; for example, the GDL and / or flow field insert may be applied onto the surface of the second anode 40 that is contacted by the second gas stream 38.

[0059]

[0068] According to an embodiment of the present invention, the catalyst included in the second anode 40 promotes or enhances the oxidation of the hydrogen gas content 34 introduced to the second anode 40 to produce hydrogen ions (H + ) and electrons (e - In one embodiment, the electrons (e - ) are directed back to the first cathode 32, as shown by arrow 41 in FIG. 1, to generate hydrogen ions (H + ) to hydrogen (H2) -Due to the permeability of second anode 40, some impurity gases and any unoxidized hydrogen (H) may pass through second anode 40 and be introduced into or contact with electrolyte 42, in accordance with aspects of the present invention.

[0060]

[0069] The electrolyte 42 of the MEA 26, or the second electrolyte 42, receives hydrogen ions (H + ) between the second anode 40 and the electrode 44. The second electrolyte 42 may be similar to, if not substantially identical to, the first electrolyte 30 and may include any material or substance capable of transferring hydrogen ions (H+), e.g., selectively transferring hydrogen ions (H+), i.e., protons, from the second anode 40 to the electrode 44. Again, as noted with respect to the electrolyte 30, in one embodiment, the electrolyte 42 may be referred to as a “proton-conducting material.” The second electrolyte 42 may typically be acidic and may contain, for example, one or more of the acids identified above with respect to the first electrolyte 30. However, in one embodiment, the second electrolyte 42 may include a PEM, as known in the art.

[0061]

[0070] The electrode 44, which may be referred to as the “cathode” 44 or second cathode 44 as known in the art, receives the hydrogen ions (H + Similar to second anode 40, second cathode 44 is typically positioned to receive at least a portion of the electrons (e - ) to generate hydrogen ions (H +1. The resulting or "generated" hydrogen gas (H) content 20, or third hydrogen gas content 20, and any non-hydrogen gases 22, or second impurity gas content 22, that have traveled through the electrolyte 30 are shown in FIG. 1 as gas stream 18, or exhaust gas stream 18, or third gas stream 18.

[0062]

[0071] In one embodiment, hydrogen ions (H + To enhance the distribution of CO₂, a gas diffusion layer (GDL) and / or a flow field insert (not shown in FIG. 1 ) may be disposed between the second electrolyte 42 and the second cathode 44; for example, the GDL and / or the flow field insert may be applied onto the surface of the second cathode 44.

[0063]

[0072] According to an embodiment of the present invention, the third hydrogen gas content 20 of the third gas stream 18 is greater than the first hydrogen gas content 14 and the second hydrogen gas content 34, and the third impurity gas content 22 is less than the first impurity gas content 16 and the second impurity gas content 36. However, typically, the third gas stream 18 may have a higher percentage purity, on a "dry basis," than the purity of the first gas stream 12. For example, the third hydrogen gas content 20 in the third gas stream 18 may be at least 10 volume percent greater than the first hydrogen gas content 14 in the first gas stream 12. In one embodiment, the third hydrogen gas content 20 may be 20 volume percent to 30 volume percent greater than the first hydrogen gas content 14. Also, in one embodiment, the third gas stream 18 may be at least 1,000 times purer in hydrogen by volume than the first gas stream 12. In one embodiment, third gas stream 18 may be 10,000 to 10,000,000 (ten million) times purer by volume in hydrogen than first gas stream 12. However, typically, third gas stream 18 may be 100,000 to 2,000,000 (two million) times purer by volume in hydrogen content than first gas stream 12. For example, in one embodiment, the purity of third gas stream 18 may be at least 99.99 volume percent hydrogen, or at least 99.999 (five nines) volume percent, or 99.9999 (six nines) volume percent. According to another embodiment of the present invention, the purity of third gas stream 18 may be expressed based on third impurity gas content 22. For example, in one embodiment, third impurity gas content 22 may be at most 100 ppm impurity gas. In other aspects of the invention, the third impurity gas content 22 produced may be at most 20 ppm, or at most 10 ppm, or at most 5 ppm, or at most 2 ppm, or at most 1 ppm. In other aspects of the invention, the third impurity gas content 22 of the produced hydrogen gas 18 may be at most 750 ppb (i.e., at most 0.750 ppm), or at most 500 ppb, or at most 200 ppb, or even at most 100 ppb. As known in the art, these impurity contents of the produced hydrogen gas are typically on a "dry basis."

[0064]

[0073] According to aspects of the present invention, passing a second gas stream 38 having a hydrogen gas content 34 from the first cathode 32 of the MEA 24 to the second anode 40 of the second MEA 26 in the purifier cell 10 not only provides a more compact purifier, but also a more efficient device, providing a purer hydrogen gas content 22 than the prior art. Notably, passing the second gas stream 38 from the first cathode 32 to the second anode 40 avoids the recognized added components, efficiency losses, and hydrogen gas content losses that characterize the performance of, for example, direct prior art hydrogen gas purifiers.

[0065]

[0074] Additionally, according to embodiments of the present invention, the resulting gas stream, i.e., third gas stream 18 having a higher hydrogen gas content 20, may typically be provided at a pressure higher than the pressure of feed or first gas stream 12. For example, according to embodiments of the present invention, where first gas stream 12 may have a pressure of approximately 1 pound per square inch-gauge (psig), third gas stream 18 may have a pressure of at least 150 psig. In one embodiment, the pressure of third gas stream 18 may be at least 120 psig, or at least 200 psig, or even at least 10,000 psig (ten thousand). In other embodiments of the present invention, the pressure of third gas stream 18 may be equal to or lower than the pressure of feed or first gas stream 12, and in one embodiment, the pressure of third gas stream 18 may be less than the pressure of first gas stream 12.

[0066]

[0075] FIG. 2 is a schematic diagram of a hydrogen gas purifier cell 50 according to another embodiment of the present invention. According to this embodiment, purifier cell 50 can have many of the features of purifier cell 10, but purifier cell 50 further includes at least one gas exhaust or release port between the MEAs. According to this embodiment, testing has shown that venting or venting at least a portion of the second gas stream (38 in FIG. 2) from purifier cell 50 results in a higher hydrogen gas content compared to purifiers that do not allow for removal of at least a portion of the second gas stream between the MEAs. This venting of at least a portion of the second gas stream is believed to reduce the partial pressure of non-hydrogen gases between the MEAs and, therefore, reduce the partial pressure gradient driving force of undesired non-hydrogen gases through the second MEA. In a further embodiment, because some desired hydrogen gas is lost when removing a portion of the second gas stream, at least a portion of hydrogen gas can be introduced between the MEAs to serve as “make-up” hydrogen gas for hydrogen gas that may be lost with the removal of a portion of the second gas stream.

[0067]

[0076] As shown in FIG. 2, in a manner similar to purifier cell 10, purifier cell 50 is configured and adapted to receive a feed or first gas stream 12 similar to or identical to first gas stream 12 shown in FIG. 1 and at least a portion of non-hydrogen gases 16, and to produce a gas stream 52 with increased hydrogen gas content and reduced non-hydrogen gas content. Gas stream 52 may be referred to as exhaust gas stream 52 or third gas stream 52. Similar to purifier cell 10, third gas stream 52 may typically include an enhanced hydrogen gas content 54 and a reduced non-hydrogen gas content 56. As shown schematically in FIG. 2, similar to purifier cell 10, hydrogen gas purifier cell 50 typically comprises a multi-layer structure having components, such as an anode and a cathode, with thin planar or thin layered structures; the structure shown in FIG. 2 may comprise a side view or transaxial cross-section of purifier cell 50, which is not drawn to scale but is drawn to facilitate disclosure of the present invention.

[0068]

[0077] In one embodiment, the hydrogen gas purifier cell 50 shown in FIG. 2 can have a first MEA 24 substantially identical to the purifier cell 10, i.e., having a first anode 28, a first electrolyte 30, and a first cathode 32, to at least partially purify the first gas stream 12 and produce a second gas stream 38 having a hydrogen gas content 34 and a non-hydrogen gas content 36 in substantially the same manner as the purifier cell 10 shown in FIG. 1. As is typical in the art, at least a portion of the input or first gas stream 12 may not diffuse through the anode 28 and may be removed as a gas stream 13, e.g., an "exhaust gas stream." Additionally, the hydrogen gas purifier cell 50 can have a substantially identical second MEA 26 having a second anode 40, a second electrolyte 42, and a second cathode 44 to at least partially purify the gas stream 38 to produce a third gas stream 52 having a hydrogen gas content 54 and a non-hydrogen gas content 56. 2, however, hydrogen gas purifier cell 50 includes at least one exhaust or replacement gas stream 58 having a non-hydrogen gas content 60 and a hydrogen gas content 62. It is recognized that the non-hydrogen gas content 60 and the hydrogen gas content 62 of exhaust gas stream 58 can be substantially the same as the non-hydrogen gas content 36 and the hydrogen gas content 34 of second gas stream 38.

[0069]

[0078] In one embodiment, one or more gas diffusion layers (GDLs) and / or flow field inserts, not shown in Figure 2, can be disposed within cell 50 to enhance gas flow distribution around the electrode surfaces. For example, cell 50 can include GDLs and / or flow field inserts associated with first anode 28, first cathode 32, second anode 40, and / or second cathode 44.

[0070]

[0079] According to this embodiment, after first gas stream 12 is processed by first MEA 24 to produce second gas stream 38 having hydrogen gas content 34 and non-hydrogen gas content 36, at least a portion of gas stream 38 is removed via gas stream 58. Removal of gas stream 58 from gas stream 38 results in reformed or intermediate gas stream 64 having hydrogen gas content 66 and non-hydrogen gas content 68. It is recognized that the non-hydrogen gas content 68 and hydrogen gas content 66 of reformed gas stream 64 may be substantially the same as the non-hydrogen gas content 36 and hydrogen gas content 34 of second gas stream 38. According to this embodiment of the invention, removal of gas stream 58 reduces the partial pressure of the non-hydrogen gas content 68 in reformed gas stream 64, which reduces the partial pressure gradient of the non-hydrogen gas content 58 across second MEA 26, which reduces passage of the non-hydrogen gas content 68 through second MEA 26 to third gas stream 52. Thus, according to aspects of the present invention, the non-hydrogen gas content 56 of the third gas stream 52 is reduced.

[0071]

[0080] Removal of gas stream 58 having non-hydrogen content 60 can be accomplished by various means. In one embodiment, gas stream 58 can be removed by simply venting at least a portion of second gas stream 38, for example, through the inherent spacing between first MEA 24 and second MEA 26, for example, through the inherent space or gap between the surface of first cathode 32 and second anode 40. In another embodiment, gas stream 58 can be removed by providing passages, channels, or grooves, for example, radial or lateral channels or grooves, in the mating surface of first cathode 32, the mating surface of second anode 40, or both the mating surfaces of first cathode 32 and second anode 40. In another embodiment, gas stream 58 can be removed through a GDL and / or flow field insert disposed between the mating surface of first cathode 32 and the mating surface of second anode 40. As is known in the art, the GDL is typically a porous material, such as carbon paper, through which the gas stream 58 can pass. In another embodiment, the gas stream 58 can be eliminated by providing one or more spacers between the mating surfaces of the first cathode 32 and the second anode 40 to provide a path for the gas stream 58. In one embodiment, a vacuum source can be introduced to draw at least a portion of the second gas stream 38 through the gas stream 58.

[0072]

[0081] According to another aspect of the present invention, after first gas stream 12 is processed by first MEA 24 to produce second gas stream 38 having hydrogen gas content 34 and non-hydrogen gas content 36, at least a portion of hydrogen gas can be introduced into gas stream 38. As shown in FIG. 2 , in one aspect, hydrogen gas can be introduced into second gas stream 38 via gas stream 59 (shown in phantom in FIG. 2 ) to replace hydrogen gas 62 lost from second gas stream 38 via gas stream 58 and produce reformed gas stream 64. In one aspect, gas stream 38 can be high-purity hydrogen gas, for example, having a purity at least higher than hydrogen content 14 of first gas stream 12, while in other aspects, gas stream 59 can be a hydrogen gas-containing stream having at least a portion of hydrogen gas content, but can also have a non-hydrogen gas content.

[0073]

[0082] Introduction of hydrogen-containing gas stream 59, e.g., a "make-up gas stream," can be performed with or without removal of gas stream 58. Introduction of gas stream 59 into gas stream 38 may be performed in any one or more convenient ways, such as by introducing hydrogen gas-containing stream 59 through gas permeable electrolyte 42 driven by a hydrogen gas partial pressure gradient, through gas permeable first cathode 32, through a gas permeable GDL and / or flow field insert, through channels in first cathode 32, channels in second anode 40, or through channels in both first cathode 32 and second anode 40. Optional channels that may be provided for hydrogen gas-containing stream 59 may be located on one or both of the opposing surfaces of first cathode 32 and second anode 40, i.e., on the surfaces of the space occupied by second gas stream 38. In one embodiment, make-up hydrogen gas stream 59 may comprise at least a portion of third gas stream 52 having a third hydrogen content 54. For example, at least a portion of the third gas stream 52 may be introduced into the second gas stream 38 by diffusion through the second electrolyte 42, as shown in phantom by gas stream 59A in Figure 2. This diffusion through the second electrolyte 42 may be referred to as "back-diffusion" of at least a portion of the third gas stream 52 having the third hydrogen content 54 through the second electrolyte 42 to provide at least a portion of the make-up gas stream 59 to the second gas stream 38 or the reformulated gas stream 64. The make-up gas stream 59 may be provided by any one or more of these mechanisms.

[0074]

[0083] According to an embodiment of the present invention, the third hydrogen gas content 54 of the third gas stream 52 is greater than the first hydrogen gas content 14 and the second hydrogen gas content 34, and the third impurity gas content 56 is less than the first impurity gas content 16 and the second impurity gas content 36. However, typically, the third gas stream 52 can have a higher percent purity, on a "dry basis," than the purity of the first gas stream 12. For example, in one embodiment, the purity of the third hydrogen gas content 54 may be at least 99.99 percent by volume, or at least 99.999 (five nines) percent by volume, or 99.9999 (six nines) percent by volume. According to another embodiment of the present invention, the purity of the third gas stream 52 can be expressed based on the third impurity gas content 56. For example, in one embodiment, the third impurity gas content 56 can be up to 100 ppm impurity gas. In other aspects of the invention, the third impurity gas content 56 produced may be at most 20 ppm, or at most 10 ppm, or at most 5 ppm, or at most 2 ppm, or at most 1 ppm. In other aspects of the invention, the third impurity gas content 56 of the produced hydrogen gas may be at most 750 ppb (i.e., at most 0.750 ppm), or at most 500 ppb, or at most 200 ppb, or even at most 100 ppb. As known in the art, these impurity contents of the produced hydrogen gas are typically on a "dry basis."

[0075]

[0084] 3 is a schematic front view of a hydrogen purifier stack assembly 80 having a hydrogen gas purifier cell 82, e.g., the hydrogen gas purifier cell 10 or cell 50 disclosed herein, disposed between opposing electrically conductive but gas-impermeable layers or plates 84 and 86 and electrically conductive layers or bus bars 88 and 90, according to one embodiment of the present invention. The electrically conductive but gas-impermeable layers or plates 84 and 86 may be referred to as "bipolar plates," as known in the art, because the plates 84 and 86 may typically contain passages or channels adapted to introduce or remove gas from the cell 82. The electrically conductive layers or bus bars 88 and 90 may also be referred to as "current collectors." As shown, in one embodiment, the cell 82 may include at least two MEAs: a first MEA 92 and at least a second MEA 94. However, according to embodiments of the present invention, it is contemplated that a cell 82 may include, for example, three or more MEAs 92, 94, or five or more MEAs 92, 94 disposed between bus bars 88 and 90. In one embodiment, at least ten MEAs 92, 94 may be disposed between bus bars 88 and 90.

[0076]

[0085] In one embodiment, the hydrogen gas purifier cell 82 may be referred to as a "dual membrane electrode assembly" or "DMEA." The first MEA 92 includes a first anode 96, a first electrolyte 98, and a first cathode 90. The first anode 96 may be similar to, or not identical to, the first anode 28 disclosed herein, the first electrolyte 98 may be similar to, or not identical to, the first electrolyte 30 disclosed herein, and the first cathode 90 may be similar to, or not identical to, the first cathode 32 disclosed herein. The second MEA 94 includes a second anode 102, a second electrolyte 104, and a second cathode 106. The second anode 102 may be similar to, if not identical to, the second anode 40 disclosed herein, the second electrolyte 104 may be similar to, if not identical to, the second electrolyte 42 disclosed herein, and the second cathode 106 may be similar to, if not identical to, the second cathode 44 disclosed herein.

[0077]

[0086] The electrically conductive, gas-impermeable layers or plates (or bipolar plates) 84 and 86 may typically be fabricated from a corrosion-resistant or non-oxidizing material for the electrochemistry of cell 82. While it is contemplated that any electrically conductive, substantially gas-impermeable, and substantially corrosion-resistant material, e.g., metal, may be used for plates 84 and 86 in embodiments of the present invention, typically, plates 84 and 86 may be fabricated from an electrically conductive, substantially gas-impermeable, and substantially corrosion-resistant graphite-containing material. For example, plates 84 and 86 may be fabricated from a material containing graphite powder and resin. In one embodiment, bipolar plates 84 and 86 may be fabricated from a non-metallic material, e.g., plastic, in which electrically conductive inserts and / or particles are disposed to provide the desired conductivity.

[0078]

[0087] In one aspect, it is contemplated that bipolar plates 84 and 86 may include portions that are at least semi-permeable to allow for fluid permeability as needed, for example, for heat management and / or water management.

[0079]

[0088] According to one aspect of the present invention, conductive current collectors 88 and 90 can have a relatively high electrical conductivity relative to, for example, plates 84 and 86. In one aspect, current collectors 88 and 90 can be plated, for example, with gold or silver, to improve conductivity. For example, current collectors 88 and 90 can include stainless steel, aluminum, or copper plates that can be plated with gold or silver.

[0080]

[0089] According to an embodiment of the present invention, as shown in FIG. 3, a first gas stream 108 containing hydrogen gas (H) and a non-hydrogen gas may be introduced to the first anode 96 as disclosed herein, where at least a portion of the hydrogen gas (H) converts to hydrogen ions (H +) and electrons (e-). The first gas stream 108 may be introduced to the first anode 96 by any conventional means, such as through passages and / or channels in the bipolar plate 84. For example, as shown in FIG. 3, the first gas stream 108 may be introduced to the first anode 96 through a plurality of transverse passages 110 that communicate with a plurality of longitudinal passages or channels 112 that discharge onto the first anode 96. The first anode 96 may include a GDL and / or flow field insert (not shown in FIG. 3), such as a carbon paper-type GDL, to enhance distribution of the first gas stream 108 across the surface of the first anode 96.

[0081]

[0090] Upon introduction to the anode 96, the reactions and fluid flows described with respect to FIGS. 1 and 2 are generated within the MEAs 92 and 94, specifically, in accordance with an embodiment of the present invention, a second gas stream 114 from the first cathode 100 (not shown in FIG. 3 ) and a third gas stream 116 from the second cathode 106 are generated. As disclosed herein, the second anode 102 receives the second gas stream 114 (again, not shown in FIG. 3 ). In one embodiment, the second anode 102 may include or be accompanied by a GDL and / or a flow field insert (not shown in FIG. 3 ), e.g., a carbon paper-type GDL, to enhance distribution of the second gas stream 114 across the surface of the second anode 102. The third gas stream 116 can be collected from the second cathode 106 by conventional means. 3, the third gas stream 116 may be removed from the second cathode 106 via a plurality of transverse passages 118 in communication with a plurality of longitudinal passages or channels 120 in fluid communication with the second cathode 106, with or without passing through a gas diffusion layer (not shown). The plurality of transverse passages 118 may comprise a plurality of substantially parallel passages or a plurality of serpentine passages within the bipolar plate 86. As known in the art, the parallel or serpentine passages within the bipolar plate 86 may be in fluid communication with one or more manifolds, e.g., vertical or longitudinal manifolds, which may be in fluid communication with one or more ports for introducing, exhausting, or redirecting the gas flow.

[0082]

[0091] According to aspects of the invention, the third gas stream 116 can include a higher content of hydrogen gas (H) and a lower content of non-hydrogen gases than the first gas stream 108. For example, as disclosed herein, the non-hydrogen gas content of the third gas stream 116 can have a non-hydrogen gas content of up to 100 ppm, or up to 20 ppm, or up to 10 ppm, or up to 5 ppm, or up to 2 ppm, or up to 1 ppm, or even up to 500 ppb "dry basis." Additionally, the third gas stream 116 can typically have a higher pressure than the pressure of the first gas stream 108, although in other aspects, the third gas stream 116 can have a lower pressure than the pressure of the first gas stream 108.

[0083]

[0092] A schematic detailed view of the interface between a first cathode 100 and a second anode 102 according to one embodiment of the present invention is shown in FIG. 3A. FIG. 3A is a detailed view of a portion of the hydrogen purifier stack assembly 80 shown in FIG. 3, as identified by detail 3A shown in FIG. 3. As shown in FIG. 3A, a second gas stream 114 having a hydrogen gas content 34 (see FIGS. 1 and 2) and a non-hydrogen gas content 36 exits the first cathode 100 and enters a space 101 between the mating surfaces of the first cathode 100 and the second anode 102. A space, void, or interstitial space 101 typically exists between the first cathode 100 and the second anode 102 due to imperfections in the mating surfaces of the first cathode 100 and the second anode 102, as well as due to manufacturing imperfections and / or tolerances, among other factors. These spaces or voids 101, although small, are typically present between the mating surfaces of the first cathode 100 and second anode 102 and other mating electrodes disclosed herein and may provide a pathway for gas flow, e.g., removal and / or introduction of a gas stream. According to embodiments of the present invention, a second gas stream 114 enters the second anode 102, typically through direct contact or through a space 101, where catalytic oxidation of the hydrogen gas content 34 in the second gas stream 114 occurs, according to embodiments of the present invention described herein. In one embodiment, as shown in FIG. 3B, a GDL 105 may be disposed between the first cathode 100 and second anode 102 to facilitate or enhance distribution of the second gas stream 114 across the surface of the second anode 102. In another embodiment, a gas distribution or flow field insert, with or without a GDL, may be positioned between the first cathode 100 and the second anode 102 (or between any electrodes disclosed herein), as shown by GDL 105 in Figure 3B, to facilitate or enhance distribution of the second gas flow 114 across the surface of the second anode 102. The flow field insert may be a conductive, porous, or perforated plate, e.g., a porous or perforated metal plate, or a screen-like insert, e.g., a metal screen-like insert, positioned and adapted to provide at least some gas distribution around the surface of the second anode 102.The flow field inserts disclosed herein may also include channels or passages to allow for the introduction or removal of gas flow from or to adjacent electrodes.

[0084]

[0093] As disclosed herein, gas purifier cell 82 may comprise hydrogen gas purifier cell 10 as disclosed and described with respect to Figure 1, or hydrogen gas purifier cell 50 as disclosed and described with respect to Figure 2. The detailed views shown in Figures 3A and 3B also illustrate these aspects of the invention. Specifically, when gas purifier cell 82 of Figure 3 comprises purifier cell 10, as shown in Figure 3A, substantially all of second gas stream 114 leaving first cathode 100 passes, e.g., directly, through direct contact or via space 101 to second anode 102 (with or without GDL 105 and / or flow field insert) for subsequent catalytic oxidation, as disclosed herein.

[0085]

[0094] In an embodiment of the invention in which the gas purifier cell 82 of FIG. 3 includes the purifier cell 50, as shown in FIGS. 3A and 3B, at least a portion of the second gas stream 114 leaving the first cathode 100 is removed as gas stream 58 (see FIG. 2). According to this embodiment, the removed gas stream 58 can include at least some non-hydrogen gases, and once removed, the remaining reformed gas stream has a lower partial pressure relative to the non-hydrogen gases. The lower partial pressure of the non-hydrogen gases is less likely to be transmitted through the second electrolyte 104 to the output or third gas stream 116 (see FIG. 3). As shown in FIG. 3A, the removed or exhausted gas stream 58 may be passed from the space 101, and / or as shown in FIG. 3B, the removed or exhausted gas stream 58 may be passed through the GDL 105 and / or a flow field insert.

[0086]

[0095] 3A and 3B, in one embodiment, hydrogen-containing gas stream 59 (shown in phantom in FIGS. 3A and 3B) and / or 59A may also be introduced into second gas stream 114, with or without the removal of gas stream 58. For example, as disclosed herein, hydrogen-containing gas stream 59 and / or 59A may be provided to enrich the hydrogen gas content of second gas stream 114 introduced to second anode 102, e.g., to enrich the hydrogen content in third gas stream 116 (see FIG. 3), i.e., output stream 116, and / or to replace at least a portion of the hydrogen gas content removed in gas stream 58. As shown in Figures 3A and 3B, the introduction of hydrogen-containing gas stream 59 and / or 59A into space 101 may be performed in conjunction with or in the presence of GDLs 105; for example, as shown in Figure 3B, hydrogen-containing gas stream 59 may be introduced through gas-permeable GDLs 105 and / or flow field inserts.

[0087]

[0096] 4 is a schematic front view of a hydrogen purifier stack 130 having a plurality of hydrogen purifier cells 132A-132N, e.g., two or more hydrogen purifier cells 10 shown in FIG. 1 and / or two or more hydrogen cells 50 shown in FIG. 2, according to one embodiment of the present invention. According to an embodiment of the present invention, "N" is the number of purifier cells that may be included in the hydrogen purifier stack 130 according to an embodiment of the present invention. Specifically, N may range from 1 to 1,000 cells, but is typically expected to range from 40 cells to 100 cells, e.g., 80 cells.

[0088]

[0097] According to this aspect of the invention, each of the hydrogen purifier cells 132A-132N includes a dual MEA (DMEA) separated by an electrically conductive and gas impermeable layer or plate 134A-134N+1, e.g., a "bipolar plate," as disclosed herein. The layers or plates 134A-134N+1 can be similar to and have the same characteristics as the layers or plates 84 and 86 shown and described with respect to FIG. 3. For example, the layers or plates 134A-134N+1 may have one or more lateral passages and a plurality of axial passages or channels, e.g., flow distribution passages, adapted and positioned to introduce gas flow into and / or remove gas flow from the hydrogen purifier cells 132A-132N. According to an embodiment of the present invention, some plates 134A-134N+1, e.g., plate 134B shown in FIG. 4, may include passages, e.g., isolated and separate passages, adapted and positioned to both remove gas flow from the second cathode of DMEA 132A and introduce gas flow from the first anode of DMEA 132B. In contrast, terminal plate 134A may include passages adapted and positioned to introduce gas flow only to the first anode of DMEA 132A, and terminal plate 134N+1 may include passages adapted and positioned to remove gas flow only from the second cathode of DMEA 132N. In one embodiment, terminal plate 134A and / or terminal plate 134N+1 may not have passages, i.e., they may lack passages.

[0089]

[0098] According to aspects of the present invention, as disclosed herein, a reduction reaction associated with a cathode according to Equation 2 provides electrons (e) for an oxidation reaction associated with an anode, e.g., a previous or preceding anode in a stack, according to Equation 1. - In one embodiment, the electrons (e -This flow of electrons (e) is such that the DMEAs of the hydrogen purifier stack 130 are electrically in series. However, for ease of illustrating and disclosing this aspect of the invention, the flow of electrons (e) from, for example, the second anode to the first cathode of adjacent cells in the hydrogen purifier stack 130 is shown. - ) and electrons (e - ) flow is omitted from Figure 4.

[0090]

[0099] The hydrogen purifier stack 130 also includes opposing bus bars or current collectors 136 and 138 and end plates 137 and 139 (shown in phantom in FIG. 4 ). The current collectors 136 and 138 may be similar in design, size, and construction to the current collectors 88 and 90 shown and disclosed with respect to FIG. 3 . The end plates 137 and 139 may be relatively thick metal plates that function to assist in compressing the stack 130, for example, via multiple mechanical fasteners (not shown) extending between the end plates 137 and 139, as known in the art. For example, the end plates 137 and 139 may be associated with multiple threaded bolts having threaded nuts that compress the stack 130 between the plates 137 and 139 when the bolts are tightened.

[0091]

[0100] As shown in FIG. 4, multiple input or first gas streams 140A-140N having hydrogen gas (H) content and non-hydrogen gas content can be introduced into the DMEAs 132A-132N via inlets and flow distribution passages in the plates 134A-134N. As shown in FIG. 4, the first gas streams 140A-140N can be provided, for example, via one or more gas supply manifolds 141 (shown in phantom in FIG. 4), such as a common gas supply manifold. Also shown in FIG. 4, multiple exhaust or third gas streams 142A-142N can be removed from the DMEAs 132A-132N, for example, via flow extraction passages and outlets in the plates 134A-134N. As shown in FIG. 4, the third gas streams 142A-142N can be exhausted, for example, via one or more gas collection manifolds 143 (shown in phantom in FIG. 4), such as a common gas collection manifold. As disclosed herein, the plurality of output or third gas streams 142A-142N each have a higher hydrogen gas (H) content and a lower non-hydrogen gas content than the plurality of input gas streams 140A-140N. For example, as disclosed herein, the non-hydrogen gas content of the third gas streams 142A-N can have a non-hydrogen gas content of at most 100 ppm "dry basis," or at most 20 ppm, or at most 10 ppm, or at most 5 ppm, or at most 2 ppm, or at most 1 ppm, or even at most 500 ppb "dry basis," or even at most 500 ppb "dry basis." According to embodiments of the invention, each of the gas streams flowing from the input streams 140A-140N to the output streams 142A-142N may flow in parallel through the DMEA 132A-132N, for example, from one or more gas supply manifolds 141 to one or more gas collection manifolds 143.

[0092]

[0101] Although not shown in FIG. 4 for ease of illustration and disclosure of the present invention, according to embodiments of the present invention, the hydrogen purifier stack 130 may typically include multiple anode exhaust ports, passages, and / or manifolds to allow excess source gas from streams 140A-140N to be exhausted from the hydrogen purifier stack 130.

[0093]

[0102] Also shown in FIG. 4 , the hydrogen purifier stack 130 can be powered by a voltage ΔV and a current I between current collectors 136 and 138. The voltage ΔV may be provided externally, for example, from one or more DC power sources, a local power grid, a fuel cell, solar power, and / or a wind turbine, and / or internally, for example, from the electrochemical potential and reactions occurring within the DMEAs 132A-132N in the stack 130. In one embodiment, the voltage ΔV can be adjusted to adjust the current through the stack 130. A higher current can enhance the chemical reactions in the stack 130 and increase the rate of hydrogen gas production. The amount of amperage required to improve the power output of embodiments of the present invention depends, among other things, on the size of the purifier and the number of cells in the purifier.

[0094]

[0103] As also shown in FIG. 4, according to one embodiment of the present invention, one or more DMEAs 132A-132N in the hydrogen purifier stack 130 can include the purifier cell 50 shown and described with respect to FIG. 2. That is, in one embodiment, one or more DMEAs 132A-132N, e.g., all of the DMEAs 132A-132N, can be adapted to remove at least a portion of the gas stream generated from the first cathode of the DMEAs 132A-132N, e.g., second gas stream 38 shown in FIG. 2. This removal of at least a portion of the gas stream from the second gas stream of the DMEAs 132A-132N is illustrated by gas streams 144A-144N (shown in phantom) in FIG. 4. Gas flows 144A-144N in FIG. 4 correspond to gas stream 58 in FIG. 2. As disclosed herein, according to one embodiment of the present invention, it is understood that removing gas streams 144A-144N having at least a portion of the non-hydrogen gas content reduces the partial pressure of the non-hydrogen gas introduced to the second anode of DMEA 132A-132N, and therefore reduces the passage of the non-hydrogen gas through the second anode. According to one embodiment, gas flow streams 144A-144N can be exhausted from hydrogen purifier stack 130 via exhaust passages within hydrogen purifier stack 130, such as an exhaust gas manifold (not shown in FIG. 4).

[0095]

[0104] Additionally, because some of the gas flow streams 144A-144N (dashed lines) in FIG. 4 may contain some hydrogen gas content, in one embodiment, at least some hydrogen gas can be introduced into the second gas stream within the DMEA 132A-132N (i.e., second gas stream 38 shown in FIG. 2) to replenish at least some of the lost hydrogen gas and improve the content of the hydrogen gas introduced to the second anode of the DMEA 132A-132N. By replenishing any lost hydrogen gas via gas flow streams 144A-144N, embodiments of the present invention can improve the hydrogen content of the hydrogen gas produced by the hydrogen purifier stack 130. This introduction of at least some hydrogen gas into the second gas stream of the DMEA 132A-132N is illustrated by gas streams 146A-146N (phantom lines) in FIG. 4. According to one embodiment, gas streams 146A-146N may be introduced to hydrogen purifier stack 130 through passages within hydrogen purifier stack 130, such as gas manifolds (not shown in FIG. 4).

[0096]

[0105] 5 is a schematic diagram of a hydrogen gas purifier cell 150 according to a further embodiment of the present invention. According to this embodiment, purifier cell 150 can have many of the features of purifier cell 10 and purifier cell 50 disclosed herein. Specifically, purifier cell 150 includes DMEA 152 arranged to receive input or first gas stream 154 having first hydrogen gas content 156 and first non-hydrogen gas content 158, and provides output or third gas stream 160 having output or third hydrogen gas content 162 above first hydrogen gas content 156 and output or third non-hydrogen gas content 164 below first non-hydrogen gas content 158. As is typical in the art, at least a portion of input or first gas stream 154 may not be oxidized at anode 166 but may be removed as gas stream 155, e.g., an "exhaust gas stream." Typically, the exhaust stream 155 is captured and may be directed, for example, via channels, manifolds, and ports, for further processing or disposed of as desired.

[0097]

[0106] Again, the output or third gas stream 160 will typically have a pressure greater than that of the input or first gas stream 154, although the pressure may be lower than that of the first gas stream 154. However, according to this aspect of the invention, the DMEA 152 of the purifier cell 150 includes only three electrodes, with the second electrode performing the dual function of both the first cathode and the second anode as disclosed herein.

[0098]

[0107] 5, the DMEA 152 of the purifier cell 150 includes a first anode 166, a first electrolyte 168, a first cathode / second anode (or "dual electrode") 170, a second electrolyte 172, and a second cathode 174. Similar to the components and operation of the cells 10 and 50 disclosed herein, the first anode 166 may have all the features of the first anodes disclosed herein, the first electrolyte 168 and the second electrolyte 172 may have all the features of the electrolytes disclosed herein, and the second cathode 174 may have all the features of the second cathodes disclosed herein.

[0099]

[0108] Additionally, the dual electrode 170 of the cell 150 may have all the features and characteristics of an anode or cathode disclosed herein, such as being electrically conductive, gas permeable, and containing a catalyst. However, according to this aspect of the invention, the dual electrode 170 initially receives hydrogen ions (H + ) to electrons (e - ) to produce hydrogen gas (H2), which is then oxidized to hydrogen ions (H + ) and electrons (e - In one embodiment, the electrons (e) produced in the oxidation of hydrogen gas (H) within the dual electrode 170 - ) is the hydrogen ion (H + ) consumed in the reduction of - ) in the dual electrode 170 of the DMEA 152. -This internal movement of electrons 150 is represented by the electron loop 176 shown in dashed lines in Figure 5. According to an embodiment of the present invention, one or more cells 150 may be used for cells 132A-132N of stack 130 shown in Figure 4.

[0100]

[0109] According to one aspect of the present invention, an exhaust gas stream (gas stream 58 in FIG. 2 ) may be removed from the bipolar electrode 170 of the cell 150, and / or a make-up gas stream (gas streams 59 and / or 59A in FIG. 2 ) may be introduced into the bipolar electrode 170. As shown in FIG. 5 , gas stream 178 may be removed from the bipolar electrode 170, for example, through the gas-permeable structure of the bipolar electrode 170, to reduce the partial pressure of non-hydrogen gases passed through the first electrode 168, as disclosed herein. Also, regardless of whether gas stream 178 is removed, a make-up hydrogen (H 2 ) gas-containing gas stream 180 (shown in phantom in FIG. 5 ) may be introduced into the bipolar electrode 170, for example, through the gas-permeable structure of the bipolar electrode 170, to replace or enhance the hydrogen gas (H 2 ) content of the gas stream introduced into the second electrolyte 172, as disclosed herein. As with other aspects of the present invention, the supplemental hydrogen (H) gas-containing gas stream 180 can be introduced to the bipolar electrode 170 by "back diffusion," in which at least a portion of the gas stream 160 passes through the second electrode 172 and returns to the bipolar electrode 170.

[0101]

[0110] In one embodiment, a gas flow around the electrode surface and / or hydrogen ions (H + 5 and / or a flow field insert such as that described with respect to FIG. 3B may be disposed within cell 150 to enhance the distribution of CO. For example, cell 150 may include a GDL and / or a flow field insert associated with first anode 166, dual electrode 170, and / or second cathode 174.

[0102]

[0111] Similar to other embodiments of the invention, the hydrogen purifier cell 150 has only three electrodes 166, 170, and 174, but the third hydrogen gas content 162 of the third gas stream 160 is greater than the first hydrogen gas content 156 and the third impurity gas content 164 is less than the first impurity gas content 158. For example, the third gas stream 160 can have a higher percent purity, on a "dry basis," than the purity of the first hydrogen gas content 156 of the first gas stream 154. For example, in one embodiment, the purity of the third gas stream 160 can be at least 99.99 percent hydrogen by volume, or at least 99.999 (five nines) percent by volume, or 99.9999 (six nines) percent by volume. According to another embodiment of the invention, the purity of the third gas stream 160 can be expressed based on the third impurity gas content 164. For example, in one embodiment, the third impurity gas content 164 may be at most 100 ppm of impurity gas. In other embodiments of the invention, the third impurity gas content 164 produced may be at most 20 ppm, or at most 10 ppm, or at most 5 ppm, or at most 2 ppm, or at most 1 ppm. In other embodiments of the invention, the third impurity gas content 164 of the produced hydrogen gas may be at most 750 ppb (i.e., at most 0.750 ppm), or at most 500 ppb, or at most 200 ppb, or even at most 100 ppb. As known in the art, these impurity contents of the produced hydrogen gas are typically on a "dry basis."

[0103]

[0112] Additionally, according to embodiments of the present invention, the resulting gas stream, i.e., third gas stream 160 of FIG. 5 , having a higher hydrogen gas content 162 and a lower impurity gas content 164, can typically be provided at a higher pressure than the pressure of feed or first gas stream 154. For example, according to embodiments of the present invention, where first gas stream 154 can have a pressure of up to 1 psig, third gas stream 160 can have a pressure of at least 150 psig. In one embodiment, the pressure of third gas stream 160 can be at least 120 psig, or at least 200 psig, or even at least 10,000 psig. In other embodiments of the present invention, the pressure of third gas stream 160 can be equal to or less than the pressure of feed or first gas stream 154, and in one embodiment, the pressure of third gas stream 160 can be less than the pressure of first gas stream 154.

[0104]

[0113] 6 is a schematic diagram of a hydrogen gas purifier system 200 having one or more hydrogen purifiers 202 with one or more hydrogen purifier stacks 130 shown in FIG. 4, according to one embodiment of the present invention. The one or more hydrogen purifier stacks 130 may include any one or more of the hydrogen purifier cells disclosed herein, such as one or more cells 10, one or more cells 50, and / or one or more cells 150, or combinations thereof. The one or more hydrogen purifier stacks 130 may be contained by end plates 204 and 206, for example, similar to end plates 137 and 139 shown in FIG. 4.

[0105]

[0114] As shown in Figure 6, the hydrogen gas purifier system 200 includes a hydrogen-containing gas source 208 operably connected to one or more hydrogen purifiers 202 via one or more conduits or pipes 210. The hydrogen-containing gas source 208 may be a storage tank, another gas purifier 202, one or more fuel cells, or one of various industrial processes. As disclosed herein, the hydrogen-containing gas source 208 typically contains at least some non-hydrogen or impurity gases, such as nitrogen (N), argon (Ar), carbon dioxide (CO), carbon monoxide (CO), methane (CH), and / or oxygen (O). As shown in Figure 6, the flow gas from the hydrogen-containing gas source 208 can be regulated by one or more flow control valves 212, e.g., manual or automatic valves controlled by a suitable control system (not shown), and / or a pressure regulator 213. In one embodiment, the hydrogen-containing gas 208 may be introduced into the system 200 under pressure, for example, by a gas pressurization device (not shown), such as one or more blowers, fans, or compressors. In another embodiment, the hydrogen-containing gas 208 may be drawn into the system 200 by a gas decompression or vacuum device (not shown), such as one or more blowers, fans, or compressors. For example, a vacuum source may be operably connected to one or more conduits or pipes 214, one or more exhaust conduits 220, and / or one or more exhaust conduits 221 of FIG. 6.

[0106]

[0115] After introduction of hydrogen-containing gas from source 208 and appropriate oxidation and reduction as disclosed herein, higher purity hydrogen gas is discharged from one or more hydrogen purifier stacks 202 into one or more conduits or pipes 214 for storage or further processing 216. For example, further processing 216 can be a dryer or desiccator to remove at least some water vapor and / or for further purification, e.g., to remove at least some trace impurities, if present. The purification process can include a pressure swing adsorption (PSA) system, a temperature swing adsorption (TSA), a “getter” gas purifier, or another gas purifier system 200. In one aspect, further processing 216 can include a liquefaction device, e.g., a cryocooler. As shown in FIG. 6 , the flow of gas from one or more hydrogen purifier stacks 202 can be regulated by one or more flow control valves 218, e.g., manual or automatic valves controlled by a suitable control system (not shown).

[0107]

[0116] 6, the hydrogen-containing gas from the source 208 may typically have a pressure or first pressure P1, and the gas introduced into the storage 216 after passing through one or more hydrogen purifier stacks 202 may typically have a higher pressure or third or output pressure P2, as disclosed herein, that is greater than the first pressure P1. The pressure P2 can be any one of the output pressures disclosed herein. In one aspect, the pressure P2 can include, for example, a pressure lower than the pressure P1 when the hydrogen-containing gas 208 is drawn into the system 200, for example, by vacuum.

[0108]

[0117] Also, as shown in Figure 6, in one embodiment, one or more hydrogen purifier stacks 202 may include one or more purifier cells 50 (and as disclosed and described with respect to Figure 2) having a vent or replacement gas stream 58 and possibly a hydrogen-containing gas stream 59. As shown in Figure 6, gas purifier system 200 includes one or more vent conduits 220 for removing gas stream 58 (Figure 2) and one or more vent conduits 221 for removing anode exhaust gas (e.g., anode gas stream 13 shown in Figure 1) from one or more hydrogen purifier stacks 202, and can direct the vent gas stream in conduit 220 and / or the exhaust gas stream in conduit 221 for further treatment, storage, or disposal 222. Other treatment of the gas streams in conduits 220 and 221 may include, for example, purification via another system 200, venting to the atmosphere, combustion via a "flare," or other treatment, among others. As shown in Figure 6, the flow of gas exhausted from one or more hydrogen purifier stacks 202 via conduit 220 can be regulated by one or more flow control valves 224, e.g., manual or automatic valves controlled by a suitable control system (not shown). In one embodiment, at least a portion of the exhaust gas stream (Stream 58 in Figure 2) can be introduced into a purifier 200, such as purifier 200 shown in Figure 6 or another purifier 200, for example, to recover and / or purify any hydrogen gas in the exhaust gas in conduit 220. For example, as shown in Figure 6, at least a portion of the exhaust gas (Stream 58 in Figure 2) in conduit 220 can be routed to input conduit 210 via conduit or pipe 223 (shown in phantom in Figure 6). The flow in conduit 223 can include appropriate flow and / or pressure controls (not shown), as disclosed herein.

[0109]

[0118] In one embodiment, one or more purifier cells 50 may be provided with a hydrogen-containing "make-up" gas stream 59 (see, e.g., FIG. 2 ) from a source 226, e.g., from an exhaust conduit 214 from this or another system 200 or another hydrogen gas source, via one or more conduits or pipes 228. The flow of the "make-up" gas through one or more conduits 228 to one or more hydrogen purifier stacks 202 may be regulated by one or more flow control valves 230, e.g., manual or automatic valves controlled by a suitable control system (not shown). In one embodiment, the flow of the "make-up" gas to the cells of one or more hydrogen purifier stacks 202 may be regulated to control or "tune" the purity of the hydrogen gas produced and, e.g., forwarded to storage or further processing 216. For example, the flow of "make-up" gas may be adjusted to control the purity of the hydrogen gas produced, among other methods, by controlling one or more flow control valves 230, by adjusting the pressure within one or more stacks 202 (e.g., as detected by pressure sensor 236), by introducing a flow control orifice (e.g., in conduit 228), and / or by adjusting the "back diffusion" of hydrogen gas through membranes within cells of stack 202. In one aspect, the flow of make-up gas (flow 59 in FIG. 2) need not be supplied externally as shown in FIG. 6, but may be supplied and routed from within stack 130, for example, from one or more cells 50 (see FIG. 2) to one or more cells 50, and the flow may be adjusted and controlled based on flow and / or pressure.

[0110]

[0119] According to one embodiment of the present invention, the temperature of one or more hydrogen purifier stacks 130 of the gas purifier system 200 may be adjusted and controlled to, among other things, optimize the DMEA purification performance of the stack 130 and / or to avoid overheating of the stack 130. For example, in one embodiment, the temperature of the stack 130 may be maintained at at least 30°C, but is typically maintained in the range of 50°C to 80°C. It is understood that reducing the operating temperature of the electrolyte in the cells of the stack 130, for example, to 45°C to 55°C, may improve the purity of the hydrogen gas produced while requiring more reasonable power consumption. In one embodiment, as shown in FIG. 6 , the temperature of the one or more hydrogen purifier stacks 130 may be monitored and adjusted by one or more temperature sensors 232. The temperature of the one or more hydrogen purifier stacks 130 detected by the temperature sensor 232 may be controlled by one or more heating or cooling circuits adjusted and controlled by an appropriate control system (not shown). The heating or cooling circuit of the one or more hydrogen purifier stacks 130 may include passages within the one or more hydrogen purifier stacks 130 through which a heating or cooling fluid can be passed to regulate the temperature of the one or more hydrogen purifier stacks 130.

[0111]

[0120] According to one aspect of the present invention, the pressure of one or more hydrogen purifier stacks 130, the pressure of gas from source 208, and / or the pressure of the exhaust gas of gas purifier system 200 can be adjusted and controlled to, among other things, optimize the performance of the reaction within the DMEA of stack 130. For example, in one aspect, the pressure of hydrogen gas produced by one or more stacks 130 can be monitored and adjusted by one or more pressure sensors 234. It is understood that in some aspects, the pressure of hydrogen gas produced in system 200 can affect the purity of the produced hydrogen gas. The pressure of the produced hydrogen gas, as detected by pressure sensor 234, can be adjusted and controlled by an appropriate control system (not shown).

[0112]

[0121] Additionally, in one embodiment, the pressure of one or more stacks 130 can be adjusted and controlled to improve the performance, e.g., efficiency, of the DMEA in the stack 130. In one embodiment, the pressure of the first cathode and / or the second anode of one or more hydrogen purifier stacks 130 can be adjusted and controlled to improve the performance, e.g., efficiency, of the DMEA in the stack 130. In one embodiment, as shown in FIG. 6 , the pressure of one or more stacks 130, e.g., the pressure of the first cathode and / or the second anode, may be monitored and adjusted by one or more pressure sensors 236. The pressure of one or more hydrogen purifier stacks 130 detected by the pressure sensor 236 can be controlled by an appropriate control system (not shown).

[0113]

[0122] FIG. 7 is a schematic diagram of a water electrolyzer cell 250 according to another embodiment of the present invention. According to this embodiment, the water electrolyzer cell 250 comprises an electrochemical cell for electrolyzing water to generate hydrogen gas, specifically hydrogen gas that is low in undesirable impurity gases, such as oxygen (O). As shown in FIG. 7, the water electrolyzer cell 250 is positioned and adapted to receive a feed or first fluid stream 252 containing water. The first fluid stream 252 can include liquid water and / or gaseous water (i.e., steam). (It should be understood that any reference to "fluid" herein can refer to a liquid fluid, a gaseous fluid, or both a liquid fluid and a gaseous fluid.) According to an embodiment of the present invention, the cell 250 is adapted to produce a hydrogen gas stream or third gas stream 254 that contains little or no oxygen gas and little or no gaseous impurities. The third gas stream 254 may be referred to as an exhaust gas stream 254.

[0114]

[0123] As shown schematically in FIG. 7, the water electrolyzer cell 250, like the hydrogen gas purifier cells disclosed herein, typically comprises a multi-layer structure with components, e.g., an anode and a cathode, having thin planar or thin layered structures; the structure shown in FIG. 7 is not drawn to scale, but may comprise a side view or transaxial cross-section of the water electrolyzer cell 250 drawn to facilitate disclosure of the present invention.

[0115]

[0124] According to an embodiment of the present invention, to provide the desired hydrogen gas 254, the water electrolyzer cell 250 typically includes a first MEA 256 and at least one second MEA 258. The first MEA 256 includes a first anode 260, which may typically be fluid permeable, specifically water or gas permeable, in a manner similar to the other anodes disclosed herein, such that at least a portion of the water in the first fluid stream 252 may pass into the anode 260, e.g., axially as indicated by the arrow in the first fluid stream 252. In addition, the anode 260 may also be configured to convert gaseous oxygen (O), hydrogen ions (H), and the like, e.g., according to Equation 3: + ), and electrons (e - The catalyst may comprise at least a portion of a catalyst, such as at least a portion of a platinum group metal-containing or iridium-containing catalyst, capable of enhancing the oxidation of water to methyl ... H2O=>1 / 2O2+2e - +2H + formula 3

[0116]

[0125] 7 may be disposed between first fluid stream 252 and anode 260 to enhance distribution of first fluid stream 252 around the surface of anode 260, e.g., a GDL may be applied onto the surface of anode 260 that is contacted by first fluid stream 252. In one embodiment, the GDL used in cell 250, or the GDL layer used in any embodiment disclosed herein, may be a metal-based GDL, e.g., a platinum-coated titanium GDL, or equivalent.

[0117]

[0126] Due to the permeability of the anode 260, water (HO) enters the anode 260 and due to the conductivity of the anode 260, electrons (e - ) is conducted away from anode 260, and according to an embodiment of the present invention, hydrogen ions (H+) generated at anode 260 are introduced into electrolyte 262. Electrolyte 262 may be similar to any of the other electrolytes disclosed herein; for example, electrolyte 262 may be an acidic electrolyte.

[0118]

[0127] As is typical in the art, at least a portion of input or first fluid stream 252 does not diffuse through anode 260 but may be removed as fluid stream 264, e.g., an "exhaust gas stream." Typically, exhaust stream 264 is captured and may be directed, e.g., via channels, manifolds, and ports, for further processing or disposed of as needed.

[0119]

[0128] The electrolyte 262 or the first electrolyte 262 contains hydrogen ions (H + ) are positioned and adapted to receive and transfer at least a portion of the hydrogen ions (H + ) migrate from the anode 260 to the electrolyte 262. The first electrolyte 262 comprises a barrier between the first anode 260 and the electrode 266. The first electrolyte 262 transports hydrogen ions (H + ) from first anode 260 to electrode 266, for example, can include any material or substance that can selectively transfer hydrogen ions (H+), i.e., protons. That is, in one aspect, electrolyte 262, and any electrolyte disclosed herein, can be referred to as a "proton-conducting material" while substantially preventing the flow of gas. First electrolyte 262 may typically be an acidic polymer containing perfluorosulfonic acid (PFSA). In one aspect, electrolyte 262 may be a membrane commercially available under the trademark Nafion™ by The Chemours Company of Wilmington, Delaware, or its equivalent. In other aspects, electrolyte 262 may be a membrane containing one of the following acids: phosphoric acid [H3PO4], sulfuric acid [H2SO4], or any other hydrogen ion (H + ) conductive acids. In one embodiment, the first electrolyte 262 can include a proton exchange membrane (PEM), as known in the art.

[0120]

[0129] The electrode 266, which may be referred to as the “cathode” 266 or first cathode 266 as known in the art, receives hydrogen ions (H + ) according to Equation 4, as known in the art. - ) passing through the first electrolyte 262. + The catalyst comprises a catalyst, such as a platinum-group-containing catalyst, adapted to enhance the reaction (i.e., reduction) of at least a portion of the 2H + +2e - =>H2 formula 4

[0121]

[0130] The resulting or "generated" hydrogen gas (H2) 268, or second fluid stream 268 containing hydrogen gas (H2), is transported through gas-permeable first cathode 266, shown as gas stream 268, or second fluid stream 268 in FIG. 7.

[0122]

[0131] In one embodiment, a gas diffusion layer (GDL) and / or flow field insert, not shown in FIG. 7, may be disposed between the first cathode 266 and the second anode 270 to enhance the distribution of hydrogen gas (H) around the surface of the second anode 270; for example, the GDL and / or flow field insert may be applied onto the surface of the second anode 270.

[0123]

[0132] As shown in FIG. 7 , according to an embodiment of the present invention, a second fluid stream 268 containing hydrogen gas (H 2 ) may then be introduced to a second MEA 258, specifically, an electrode 270 or second anode 270 of the second MEA 258. In the schematic diagram of the electrolyzer cell 250 shown in FIG. 7 , the first MEA 256 is shown spaced apart from the second MEA 258 to facilitate illustration and disclosure of the present invention. However, according to an embodiment of the present invention, the spacing between the first MEA 256 and the second MEA 270 may be minimal, for example, where the surface of the first cathode 266 may abut or contact the surface of the second anode 270. However, in one embodiment, at least some spacing, e.g., 0.1 millimeters [mm] to 0.5 mm, may exist between the surface of the first cathode 266 and the surface of the second anode 270.

[0124]

[0133] According to an embodiment of the present invention, in contrast to existing technology, the second fluid stream 268 having hydrogen gas (H) may then be introduced into the second MEA 258 without removing or extracting the second fluid stream 268 from the electrolyzer cell 250. In other words, although some portion of the second fluid stream 268 may undesirably "escape" from the electrolyzer cell 250, according to an embodiment of the present invention, substantially all of the second fluid stream 268 produced at the first cathode 266 is received by the second anode 270. For example, in one embodiment, the second fluid stream 268 may be allowed to pass from the first cathode 266 of the MEA 258 to the second anode 270 of the MEA 256 without any intervening handling or processing, e.g., without passing outside the electrolyzer cell 250. In one embodiment, evolved hydrogen gas (H) formed at the first cathode 266 is substantially immediately converted to hydrogen ions (H + In one embodiment, the second fluid stream 268 may be allowed to pass directly from the first cathode 266 of the MEA 258 of the electrolyzer cell 250 to the second anode 270 of the MEA 258, for example, without passing outside of the electrolyzer cell 250 before reaching the second cathode 270.

[0125]

[0134] The second anode 270 is positioned to be contacted by a second fluid stream 268 having hydrogen gas (H). The second anode 270 of the second MEA 258 may be similar to, if not identical to, the first anode 260 of the MEA 256. The second anode 270 may be hydrogen gas permeable, such that at least a portion of the hydrogen gas in the second fluid stream 268 may pass through the second anode 270, e.g., axially, as indicated by the arrows in the second fluid stream 268. Additionally, the second anode 270 may convert the hydrogen ions (H) of the hydrogen gas into hydrogen ions (H), as shown by Equation 1, reproduced below: + ) to HCl. H2=>2H + +2e - formula 1

[0126]

[0135] In one embodiment, to enhance distribution of second fluid stream 268 around the surface of second anode 270, a gas diffusion layer or GDL and / or flow field insert, not shown in FIG. 7, may be disposed between second fluid stream 268 and second anode 270; for example, a GDL and / or flow field insert may be applied onto the surface of second anode 270 that is contacted by second fluid stream 268.

[0127]

[0136] According to an embodiment of the present invention, the catalyst included in the second anode 270 promotes or enhances the oxidation of hydrogen gas in the second fluid stream 268 to produce hydrogen ions (H + ) and electrons (e - In one embodiment, the electrons (e - ) are directed back to the first cathode 266, as shown by arrow 272 in FIG. 7, to generate hydrogen ions (H + ) to hydrogen (H2) -Due to the permeability of second anode 270, at least a portion of the hydrogen gas (H) produced within second anode 270 can pass through second anode 270 and, according to an embodiment of the present invention, be introduced into or contact with electrolyte 274.

[0128]

[0137] The electrolyte 274 of the MEA 258 or the second electrolyte 274 receives hydrogen ions (H + ) are positioned and adapted to receive and transfer at least a portion of the hydrogen ions (H + ), e.g., hydrogen ions (H + ), i.e., any material or substance capable of selectively conducting protons from second anode 270 to cathode 276. Again, as noted with respect to first electrolyte 262, in one embodiment, second electrolyte 274 may be referred to as a "proton conducting material." Second electrolyte 274 may typically be acidic, containing, for example, one or more of the acids identified herein. However, in one embodiment, second electrolyte 274 may include a PEM, as known in the art.

[0129]

[0138] The electrode 276 or second cathode 276 receives hydrogen ions (H + Like the second anode 266, the second cathode 276 is typically transparent and is positioned to receive at least some of the electrons (e - ) to generate at least some hydrogen ions (H + The catalyst comprises a catalyst, e.g., a platinum-containing catalyst, adapted to enhance the reduction of . 2H + +2e - =>H2 formula 2 The resulting or "evolved" hydrogen gas (H2), or a third fluid stream 254 containing hydrogen gas (H2), is produced by the electrolysis cell 250.

[0130]

[0139] In one embodiment, hydrogen ions (H + 7 may be disposed between the second electrolyte 274 and the second cathode 276 to enhance the distribution of the third fluid stream 254; for example, a GDL and / or flow field insert may be applied to a surface of the second cathode 276. In one embodiment, a GDL or flow field insert not shown in FIG. 7 may be disposed adjacent to a downstream surface of the second cathode 276 to enhance the removal of the third fluid stream 254.

[0131]

[0140] According to embodiments of the present invention, the third fluid stream 254 of the electrolysis cell 250 may typically contain hydrogen gas (H) with little or no undesirable impurity gases, for example, little or no oxygen gas.

[0132]

[0141] According to aspects of the present invention, by passing second fluid stream 268 from first anode 266 of MEA 256 to second cathode 270 of second MEA 258 in electrolysis cell 250, a more efficient device for providing pure hydrogen gas than the prior art can be provided. Notably, passing second fluid stream 268 from first cathode 266 to second anode 270, for example, directly, minimizes the content of impurities, such as oxygen gas impurities, in third fluid stream 254.

[0133]

[0142] 8 is a schematic diagram of a water electrolyzer cell 300 according to another embodiment of the present invention. According to this embodiment, the electrolyzer cell 300 can have many of the features of the electrolyzer cell 250, but the electrolyzer cell 300 further includes at least one gas vent or release between the MEAs. This reduction in the second fluid stream content is believed to reduce the partial pressure of non-hydrogen gases, e.g., the partial pressure of oxygen, between the MEAs, and therefore reduce the partial pressure gradient driving force of undesired non-hydrogen gases through the second MEA. In a further embodiment, because some desired hydrogen gas is lost when removing a portion of the second fluid stream, at least some hydrogen gas can be introduced between the MEAs to serve as a "make-up" hydrogen gas for hydrogen gas that may be lost with the removal of a portion of the second fluid stream.

[0134]

[0143] As shown in Figure 8, the water electrolyzer cell 300 is positioned and adapted to receive a feed or first fluid stream 302 to the electrolyzer cell 300. According to an embodiment of the present invention, the cell 300 is adapted to produce a hydrogen gas stream or third fluid stream 304 that contains little or no oxygen gas and little or no gas impurities. The third gas stream 254 may be referred to as an exhaust gas stream 254. As shown in Figure 8, like the electrolyzer cell 250, the electrolyzer cell 300 typically comprises a multi-layer structure having components, for example, an anode and a cathode, with thin planar or thin layered structures; the structure shown in Figure 8 may comprise a side elevation view or a transaxial cross-section of the electrolyzer cell 300, which is not drawn to scale but is drawn to facilitate disclosure of the present invention.

[0135]

[0144] In one embodiment, the electrolyzer cell 300 shown in Figure 8 may have a first MEA 306 substantially similar to the electrolyzer cell 250, i.e., having a first anode 308, a first electrolyte 310, and a first cathode 312 for oxidizing and reducing a first fluid stream 302 to produce a second fluid stream 314 containing hydrogen gas (H), in substantially the same manner as the MEA 256 of the electrolyzer cell 250 shown in Figure 7. As is typical in the art, at least a portion of the input or first fluid stream 302 may not be oxidized at the first anode 308, but may be removed as a fluid stream 303, e.g., an "exhaust fluid stream". Additionally, the electrolyzer cell 300 may have a substantially identical second MEA 316 having a second anode 318, a second electrolyte 320, and a second cathode 322 to oxidize and reduce a second fluid stream 314 to produce a third fluid stream 304 containing hydrogen gas (H), in substantially the same manner as the electrolyzer cell 250 shown in Figure 7. However, according to the embodiment of the invention shown in Figure 8, the electrolyzer cell 300 includes at least one exhaust or replacement gas stream 324 having hydrogen gas and a non-hydrogen gas, such as oxygen.

[0136]

[0145] In one aspect, one or more gas diffusion layers (GDLs) and / or gas distribution media, not shown in Figure 8, can be disposed within the electrolyzer cell 300 to enhance gas flow distribution around the electrode surfaces. For example, the electrolyzer cell 300 can include GDLs and / or flow field inserts associated with the first anode 308, the first cathode 312, the second anode 318, and / or the second cathode 322.

[0137]

[0146] According to this embodiment, after first fluid stream 302 is processed and passed through first MEA 306 to produce second fluid stream 314 having hydrogen gas content and non-hydrogen gas content 36, at least a portion of second fluid stream 314 is removed via fluid stream 324. Removal of fluid stream 324 from fluid stream 314 results in modified or intermediate fluid stream 326. According to an embodiment of the invention, removal of fluid stream 324 reduces the partial pressure of non-hydrogen gases in reformed fluid stream 326, and this reduction in partial pressure reduces the partial pressure gradient of the non-hydrogen gas content across second MEA 316, which reduces the passage of non-hydrogen gases through second MEA 316 to third fluid stream 304. Thus, according to an embodiment of the invention, the non-hydrogen gas content, e.g., oxygen gas content, of third fluid stream 304 is reduced, providing a purer hydrogen gas stream.

[0138]

[0147] Removal of fluid stream 324 can be accomplished by various means. In one embodiment, fluid stream 324 may be removed by simply venting at least a portion of second fluid stream 314, for example, through the inherent spacing between first MEA 306 and second MEA 316, for example, through the inherent space or gap between the surface of first cathode 312 and second anode 318. In another embodiment, fluid stream 324 may be removed by providing pathways, channels, or grooves, for example, radial or lateral channels or grooves, in the mating surface of first cathode 312, the mating surface of second anode 318, or both the mating surfaces of first cathode 312 and second anode 318. In another embodiment, fluid stream 324 may be removed through a GDL and / or flow field insert disposed between the mating surface of first cathode 312 and the mating surface of second anode 318. As is known in the art, the GDL is typically a porous material, such as carbon paper, through which the gas stream 324 can pass. In another embodiment, the fluid stream 324 can be removed by providing one or more spacers between the mating surfaces of the first cathode 312 and the second anode 318 to provide a path for the fluid stream 324. In one embodiment, a sub-atmospheric pressure source, i.e., a vacuum, can be introduced to draw at least a portion of the second fluid stream 314 through the fluid stream 324.

[0139]

[0148] According to another aspect of the present invention, after first fluid stream 302 has been processed and passed through first MEA 306 to produce second fluid stream 314, at least a portion of the hydrogen gas can be introduced into second fluid stream 314. As shown in FIG. 8 , in one aspect, hydrogen gas can be introduced into second fluid stream 314 via fluid stream 324 (shown in phantom in FIG. 8 ) to replace hydrogen gas lost from second fluid stream 314 via fluid stream 328 to produce reformed fluid stream 326. In one aspect, fluid stream 328 can be high-purity hydrogen gas, for example, having a purity at least higher than the hydrogen content of first fluid stream 302, while in other aspects, fluid stream 328 can be a hydrogen gas-containing stream having at least a portion of the hydrogen gas content, but can also have a non-hydrogen gas content.

[0140]

[0149] Introduction of a hydrogen-containing gas stream 328, e.g., a "make-up gas stream," into the electrolysis cell 300 may be carried out with or without the removal of fluid stream 324. Introduction of the fluid stream 328 into the second fluid stream 314 may be carried out in any one or more convenient ways, such as by introducing the hydrogen gas-containing stream 328 through the electrolyte 310, which may be gas permeable, driven by a hydrogen gas partial pressure gradient, through the gas permeable first cathode 312, through a gas permeable GDL and / or flow field insert, through channels in the first cathode 312, channels in the second anode 318, or through channels in both the first cathode 312 and the second anode 318. Any channels that may be provided for the hydrogen gas-containing stream 328 may be located on one or both of the opposing surfaces of the first cathode 312 and the second anode 318.

[0141]

[0150] In one aspect, the make-up hydrogen gas stream 328 can include at least a portion of the third fluid stream 304 having a hydrogen content. For example, at least a portion of the third fluid stream 304 can be introduced into the second fluid stream 314 by diffusion through the second electrolyte 320, as shown in phantom by gas stream 328A in FIG. 8. This diffusion through the second electrolyte 320 can be referred to as a “back-diffusion” of at least a portion of the third fluid stream 304 having at least some hydrogen gas (H). The make-up gas stream 328 can be provided by any one or more of these sources or mechanisms.

[0142]

[0151] In another embodiment of the invention, the three-electrode cell 150 shown in Figure 5 can also function as an electrolyzer. For example, as shown in Figure 5, the DMEA 152 of the purifier cell 150 includes a first anode 166, a first electrolyte 168, a first cathode / second anode (or "dual electrode") 170, a second electrolyte 172, and a second cathode 174. Similar to the components and operation of the electrolyzer cell 250 shown in Figure 7, in the electrolyzer cell 150 shown in Figure 5, the anode 166 may have all the features of the first anode disclosed herein, the first electrolyte 168 and the second electrolyte 172 may have all the features of the electrolytes disclosed herein, and the second cathode 174 may have all the features of the second cathode disclosed herein. In this aspect of the invention, the components and fluid flows of the electrolyzer cell 150 shown in FIG. 5 can have all the functions and features of the purifier cell 150 disclosed herein, including oxidation at the first anode 166 according to Equation 3 and reduction at the second cathode 174 according to Equation 4. However, in the case of the electrolyzer cell 150, the first fluid stream 154 of FIG. 5 can contain liquid water and / or gaseous water (i.e., steam). (It should be understood that any reference to "fluid" herein can refer to a liquid fluid, a gaseous fluid, or both a liquid and a gaseous fluid.) According to aspects of the invention, the electrolyzer cell 150 of FIG. 5 can be adapted to produce a hydrogen gas stream or third fluid stream 160 that contains little or no oxygen gas and has little or no gaseous impurities.

[0143]

[0152] According to an embodiment of the present invention, one or more water electrolysis cells 250 and 300 may be provided to generate high purity hydrogen gas. In one embodiment, a water electrolysis stack having one or more electrolysis cells 250 and / or 300 may be provided, for example, a water electrolysis stack similar to the hydrogen purifier stack 130 shown in FIG. 4. Also, in one embodiment, a water electrolyzer system having one or more electrolysis cell stacks having one or more electrolysis cells 250 and / or 300 may be provided, for example, a water electrolysis system similar to the hydrogen purifier system 200 shown in FIG. 6.

[0144]

[0153] As disclosed above, embodiments of the present invention, in many of their aspects, provide improved hydrogen purification and water electrolysis that can meet and exceed the hydrogen gas purity required by hydrogen gas users. Aspects of the present invention use a unique combination of membrane electrode assemblies (MEAs) or dual MEAs (DMEAs) that have been shown to provide the required high hydrogen gas purity.

[0145]

[0154] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0146]

[0155] Corresponding structure, materials, acts, and equivalents of all means or step-plus-function elements in the following claims are intended to include any structure, material, or acts for performing the function in combination with other claimed elements as specifically claimed. The description of the present disclosure has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the disclosure in the form disclosed. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the present disclosure. The embodiments were chosen and described in order to best explain the principles and practical applications of the disclosure and to enable others skilled in the art to understand the disclosure in various embodiments with various modifications suitable for the particular use contemplated.

[0147]

[0156] While several embodiments of the present invention have been described and illustrated herein, alternative embodiments may be devised by those skilled in the art to accomplish the same purposes, and it is therefore intended by the appended claims to cover all such alternative embodiments as fall within the true spirit and scope of the invention.

Claims

1. A hydrogen gas purification cell, A first membrane electrode assembly (MEA), A first anode is positioned in contact with a first gas stream having a first hydrogen gas content and a first impurity gas content, and contains a catalyst adapted to oxidize at least a portion of the first hydrogen gas content to generate hydrogen ions and electrons, A first electrolyte arranged and adapted to receive and transfer at least a portion of the hydrogen ions generated by the first anode, A first MEA comprising: a first cathode disposed to receive at least a portion of the hydrogen ions moved by the first electrolyte, and containing a catalyst adapted to reduce the at least portion of the hydrogen ions to produce a second gas stream having a second hydrogen gas content greater than the first hydrogen gas content and a second impurity gas content less than the first impurity gas content; It is the second MEA, A second anode is positioned adjacent to the first cathode of the first MEA to receive the second gas flow from the first cathode, and contains a catalyst adapted to oxidize at least a portion of the second hydrogen gas content in the second gas flow to generate hydrogen ions and electrons; A second electrolyte arranged and adapted to receive and transfer at least a portion of the hydrogen ions generated by the second anode, A second MEA comprising: a second cathode disposed to receive at least a portion of the hydrogen ions transferred by the second electrolyte of the second MEA, the second cathode containing a catalyst adapted to reduce the at least portion of the hydrogen ions to produce a third gas stream having a third hydrogen gas content greater than the first hydrogen gas content and a third impurity gas content less than the first impurity gas content; A hydrogen gas purification cell equipped with the following features.

2. The hydrogen gas purifier cell according to claim 1, further comprising at least one passage between the first electrolyte and the second electrolyte for discharging at least a portion of the second gas flow.

3. The hydrogen gas purifier cell according to claim 2, wherein the at least one passage is located between the first cathode and the second anode.

4. The hydrogen gas purifier cell according to claim 3, wherein the at least one passage located between the first cathode and the second anode includes a gap between the mating surfaces of the first cathode and the second anode.

5. The hydrogen gas purifier cell according to claim 3, further comprising a gas permeable layer (GDL) between the first cathode and the second anode, wherein the GDL provides the at least one passage located between the first cathode and the second anode.

6. The hydrogen gas purifier cell according to claim 5, wherein the GDL includes a carbon-based gas permeable layer.

7. The hydrogen gas purifier cell according to claim 2, wherein the at least one passage comprises at least one channel adjacent to at least one of the first cathode and the second anode.

8. The hydrogen gas purifier cell according to claim 1, further comprising at least one passage between the first electrolyte and the second electrolyte for introducing a hydrogen-containing gas into the second gas stream.

9. The hydrogen gas purifier cell according to claim 8, wherein the at least one passage is located between the first cathode and the second anode.

10. The hydrogen gas purifier cell according to claim 9, wherein the at least one passage located between the first cathode and the second anode includes a gap between the mating surfaces of the first cathode and the second anode.

11. The hydrogen gas purifier cell according to claim 1, wherein the second gas flow passes directly from the first cathode to the second anode.

12. The hydrogen gas purifier cell according to claim 11, wherein the second gas flow passes directly from the first cathode to the second anode without passing outside the hydrogen gas purifier cell.

13. The hydrogen gas purifier cell according to claim 1, wherein the distance between the second anode and the first cathode is minimized.

14. The hydrogen gas purifier cell according to claim 1, wherein the distance between the second anode and the first cathode is 0.1 mm to 0.5 mm.

15. The hydrogen gas purifier cell according to claim 1, wherein the second anode is in contact with the first cathode.

16. The hydrogen gas purifier cell according to claim 1, wherein the second gas flow passes from the first cathode to the second anode without any intervening handling.

17. A hydrogen gas purification cell, A first membrane electrode assembly (MEA), A first anode is positioned in contact with a first gas stream having a first hydrogen gas content and a first impurity gas content, and contains a catalyst adapted to oxidize at least a portion of the first hydrogen gas content to generate hydrogen ions and electrons, A first electrolyte arranged and adapted to receive and transfer at least a portion of the hydrogen ions generated by the first anode, A first MEA comprising: a first cathode disposed to receive at least a portion of the hydrogen ions moved by the first electrolyte, and containing a catalyst adapted to reduce the at least portion of the hydrogen ions to produce a second gas stream having a second hydrogen gas content greater than the first hydrogen gas content and a second impurity gas content less than the first impurity gas content; It is the second MEA, A second anode, configured to receive the second gas flow from the first cathode of the first MEA, comprising a catalyst adapted to oxidize at least a portion of the second hydrogen gas content in the second gas flow to generate hydrogen ions and electrons, A second electrolyte arranged and adapted to receive and transfer at least a portion of the hydrogen ions generated by the second anode, A second MEA comprising: a second cathode disposed to receive at least a portion of the hydrogen ions transferred by the second electrolyte of the second MEA, the second cathode containing a catalyst adapted to reduce the at least portion of the hydrogen ions to produce a third gas stream having a third hydrogen gas content greater than the first hydrogen gas content and a third impurity gas content less than the first impurity gas content; At least one passage between the first electrolyte and the second electrolyte for discharging at least a portion of the second gas flow, the passage including a gap between the mating surfaces of the first cathode and the second anode, A hydrogen gas purification cell equipped with the following features.

18. The hydrogen gas purifier cell according to claim 17, further comprising at least one passage between the first electrolyte and the second electrolyte for introducing a hydrogen-containing gas into the second gas stream.

19. The hydrogen gas purifier cell according to claim 18, wherein the at least one passage between the first electrolyte and the second electrolyte for introducing a hydrogen-containing gas into the second gas flow includes the void between the mating surfaces of the first cathode and the second anode.

20. A hydrogen gas purification cell, A first membrane electrode assembly (MEA), A first anode is positioned in contact with a first gas stream having a first hydrogen gas content and a first impurity gas content, and contains a catalyst adapted to oxidize at least a portion of the first hydrogen gas content to generate hydrogen ions and electrons, A first electrolyte arranged and adapted to receive and transfer at least a portion of the hydrogen ions generated by the first anode, A first MEA comprising: a first cathode disposed to receive at least a portion of the hydrogen ions moved by the first electrolyte, and containing a catalyst adapted to reduce the at least portion of the hydrogen ions to produce a second gas stream having a second hydrogen gas content greater than the first hydrogen gas content and a second impurity gas content less than the first impurity gas content; It is the second MEA, A second anode, configured to receive the second gas flow from the first cathode of the first MEA, comprising a catalyst adapted to oxidize at least a portion of the second hydrogen gas content in the second gas flow to generate hydrogen ions and electrons, A second electrolyte arranged and adapted to receive and transfer at least a portion of the hydrogen ions generated by the second anode, A second MEA comprising: a second cathode disposed to receive at least a portion of the hydrogen ions transferred by the second electrolyte of the second MEA, the second cathode containing a catalyst adapted to reduce the at least portion of the hydrogen ions to produce a third gas stream having a third hydrogen gas content greater than the first hydrogen gas content and a third impurity gas content less than the first impurity gas content; A passage between the first electrolyte and the second electrolyte for introducing a hydrogen-containing gas into the second gas flow, the passage including a gap between the mating surfaces of the first cathode and the second anode, A hydrogen gas purification cell equipped with the following features.

21. The hydrogen gas purifier cell according to claim 20, further comprising at least one passage between the first electrolyte and the second electrolyte for discharging at least a portion of the second gas flow.

22. The hydrogen gas purifier cell according to claim 21, wherein the at least one passage between the first electrolyte and the second electrolyte for discharging at least a portion of the second gas flow includes the void between the mating surfaces of the first cathode and the second anode.

Images