Multistage electrochemical hydrogen pump and use thereof, vacuum pumping system and extreme ultraviolet lithography system

Abstract

This invention discloses a multi-stage electrochemical hydrogen pump, comprising a first electrochemical hydrogen pump stage fluidly connected to a second electrochemical hydrogen pump stage. The first electrochemical pump stage is configured to receive a first gas mixture including hydrogen, electrochemically separate the hydrogen from the first gas mixture to generate a second gas mixture, and output the second gas mixture to the second electrochemical pump stage. The second electrochemical hydrogen pump stage is configured to receive the second gas mixture from the first electrochemical hydrogen pump stage, electrochemically separate the hydrogen from the second gas mixture to generate a third gas mixture, and output the third gas mixture.

Description

[Technical Field]

[0001] This invention relates to an electrochemical hydrogen pump. [Previous Technology]

[0002] Electrochemical hydrogen pumps are a known type of pump used in various industries (e.g., wire annealing). Electrochemical hydrogen pumps typically operate by using one or more electrochemical cells to separate hydrogen from a mixture of gases.

[0003] Figure 1 is a schematic diagram (not to scale) of a conventional electrochemical hydrogen pump 100. The electrochemical hydrogen pump 100 includes a housing 110, a plurality of electrochemical cells 120, a first current collector 130, a second current collector 140, an input line 150, and an output line 160.

[0004] The housing 110 defines a space in which the remaining components of the electrochemical pump 100 are located. Specifically, a plurality of electrochemical cells 120, a first current collector 130, a second current collector 140, an input line 150, and an output line 160 are located in the space defined by the housing 110.

[0005] A plurality of electrochemical cells 120 are each configured to receive a first gas mixture including hydrogen, electrochemically separate the hydrogen from the first gas mixture, and output a second gas mixture including the separated hydrogen. The plurality of electrochemical cells 120 are stacked and fluidly connected in parallel with each other. Each of the plurality of electrochemical cells 120 includes an anode chamber 122, a cathode chamber 124, and an ion exchange mechanism 126. Each anode chamber 122 includes an anode and is configured to receive the first gas mixture from an input line 150. Each cathode chamber 124 includes a cathode and is configured to output the second gas mixture to an output line 160. Each ion exchange mechanism 126 is positioned between its respective anode and cathode chambers 122, 124 and separates its respective anode and cathode chambers 122, 124 such that the ion exchange mechanism 126 acts as a partial barrier to the fluid flow between its respective anode and cathode chambers 122, 124. The ion exchange mechanism 126 of each electrochemical cell 120 is semi-permeable, wherein it is configured to selectively allow hydrogen ions to travel through it to migrate from their respective anode chamber 122 to their respective cathode chamber 124, while substantially preventing other components of the first gas mixture from traveling through it.

[0006] The first gas mixture consists of hydrogen mixed with one or more other types of gases. The second gas mixture is the result of electrochemical hydrogen separation performed by the electrochemical cell 120 and therefore has a much higher proportion of hydrogen than the first gas mixture. Specifically, the second gas mixture consists almost entirely of hydrogen, but still contains trace amounts of one or more other types of gases (which may be referred to as impurities or contaminants) that have managed to migrate across the ion exchange mechanism 126 due to imperfections in the ion exchange mechanism 126.

[0007] The anode may be made of a catalytic material comprising platinum nanoparticles, which may or may not be supported on carbon microparticles. The cathode may also be made of a catalytic material comprising platinum nanoparticles, which may or may not be supported on carbon microparticles. The ion exchange mechanism 126 may be made of an ion exchange mechanism material (such as, but not limited to, Nafion film or polybenzimidazole (PBI)). However, it will be understood that any suitable material or combination of materials may be used, provided that the components function in the manner described herein.

[0008] The first and second current collectors 130 and 140 electrically connect the anodes and cathodes of the plurality of electrochemical cells 120 to a power source (not shown) to maintain the positive voltage potential of the anode and the negative voltage potential of the cathode.

[0009] The input line 150 is configured to receive a first gas mixture from a source (not shown) of an electrochemical hydrogen pump 100 at a distance and to deliver the first gas mixture to the anode chamber 122 of a plurality of electrochemical cells 120.

[0010] The output line 160 is configured to receive the second gas mixture from the cathode chamber 124 of the plurality of electrochemical cells 120 and deliver the second gas mixture to a desired location (not shown) at a distance from one of the electrochemical hydrogen pumps 100.

[0011] The precise physical / chemical mechanisms underlying the operation of the electrochemical cell 120 are well known and will not be described in detail herein for the sake of brevity. However, in brief, during the operation of the electrochemical hydrogen pump 100, hydrogen in the first gas mixture is oxidized at the anode in the anode chamber 122 to produce hydrogen ions. The hydrogen ions then travel through the ion exchange mechanism 126 to the cathode chamber 124 and undergo a reduction reaction at the cathode to reform hydrogen. Because the ion exchange mechanism 126 selectively allows hydrogen ions to travel through it while substantially preventing other components of the first gas mixture from traveling through it, the concentration of hydrogen in the second gas mixture increases compared to the concentration of hydrogen in the first gas mixture. Therefore, hydrogen is effectively and selectively pumped (or separated) from the first gas mixture by the electrochemical cell 220.

[0012] Figure 2 is a schematic diagram (not to scale) showing a more detailed cross-sectional view of an ion exchange mechanism 126. The ion exchange mechanism forms part of a thin-film electrode assembly (MEA) including an anode, a cathode, an ion exchange membrane 126a, an anode catalyst layer 126b, a cathode catalyst layer 126c, an anode gas diffusion layer 126d, and a cathode gas diffusion layer 126e. In some embodiments, the anode catalyst layer 126b is the anode of the MEA. In some embodiments, the cathode catalyst layer 126c is the cathode of the MEA. The ion exchange membrane 126a is sandwiched between the anode catalyst layer 126b and the cathode catalyst layer 126c. The anode catalyst layer 126b is sandwiched between the ion exchange membrane 126a and the anode gas diffusion layer 126d. The cathode catalyst layer 126c is sandwiched between the ion exchange membrane 126a and the cathode gas diffusion layer 126e. In other words, the ion exchange membrane 126a, the anode catalyst layer 126b, the cathode catalyst layer 126c, the anode gas diffusion layer 126d, and the cathode gas diffusion layer 126e form a layered stack serving as an ion exchange mechanism. The precise manner in which the MEA operates is well known and will not be described in any further detail herein for the sake of brevity. Improvements to the conventional electrochemical hydrogen pump 100 described above are expected. [Summary of the Invention]

[0013] In a first embodiment, a multi-stage electrochemical hydrogen pump is provided, comprising a first electrochemical hydrogen pump stage fluidly connected to a second electrochemical hydrogen pump stage. The first electrochemical pump stage is configured to receive a first gas mixture comprising hydrogen, electrochemically separate the hydrogen from the first gas mixture to generate a second gas mixture, and output the second gas mixture to the second electrochemical pump stage. The second electrochemical hydrogen pump stage is configured to receive the second gas mixture from the first electrochemical hydrogen pump stage, electrochemically separate the hydrogen from the second gas mixture to generate a third gas mixture, and output the third gas mixture.

[0014] One or both of the first and second electrochemical hydrogen pump stages may include a plurality of electrochemical cells that are fluidly connected in parallel with each other.

[0015] The plurality of electrochemical cells of one or both of the first and second electrochemical hydrogen pump stages can be configured as a stack.

[0016] Each of the first and second electrochemical hydrogen pump stages may include a plurality of electrochemical cells that are fluidly connected in parallel with each other.

[0017] The output of one of the plurality of electrochemical cells of the first electrochemical hydrogen pump stage can be fluidly connected to the input of one of the plurality of electrochemical cells of the second electrochemical hydrogen pump stage.

[0018] The first and second electrochemical hydrogen pump stages may be fluidly connected to each other via fluid lines or via a channel defined by bipolar plates.

[0019] The multi-stage electrochemical hydrogen pump may further include a housing, wherein the first and second electrochemical hydrogen pump stages are located within the housing.

[0020] The second gas mixture may have a greater proportion of hydrogen than the first gas mixture, and the third gas mixture may have a greater proportion of hydrogen than the second gas mixture.

[0021] The first gas mixture may consist of hydrogen and one or more other types of gases, wherein the one or more other types of gases are selected from the group consisting of: nitrogen, carbon dioxide, helium, argon, and carbon monoxide.

[0022] The hydrogen gas may include one or more of the following: protium, deuterium and tritium.

[0023] The multi-stage electrochemical hydrogen pump may further include series fluid connections to one or more of the first and second electrochemical hydrogen pump stages.

[0024] In a second state sample, a vacuum pumping system is provided, which includes a multi-stage electrochemical hydrogen pump of the first state sample.

[0025] The multistage electrochemical hydrogen pump is fluidly connected to a vacuum pump and configured to receive a first gas mixture from the vacuum pump.

[0026] In a third state sample, an extreme ultraviolet lithography system is provided, which includes a vacuum pumping system of the second state sample.

[0027] The first gas mixture may be composed of hydrogen and nitrogen.

[0028] In a fourth state sample, the use of a multi-stage electrochemical hydrogen pump of the first state sample is provided.

Implementation Method

[0033] Figure 3 is a schematic diagram (not to scale) of a multi-stage electrochemical hydrogen pump 200 according to one embodiment.

[0034] The electrochemical hydrogen pump 200 includes a housing 210, a first electrochemical hydrogen pump stage 300, a second electrochemical hydrogen pump stage 400, a first current collector 230 and a second current collector 240.

[0035] The housing 210 defines a space in which the remaining components of the electrochemical pump 200 are located. Specifically, the first electrochemical hydrogen pump stage 300, the second electrochemical hydrogen pump stage 400, the first current collector 230, and the second current collector 240 are located in the space defined by the housing 110.

[0036] The first electrochemical hydrogen pump stage 300 includes a plurality of first electrochemical cells 220a, a first input line 250a and a first output line 260a.

[0037] A plurality of first electrochemical cells 220a are each configured to receive a first gas mixture including hydrogen, electrochemically separate the hydrogen from the first gas mixture, and output a second gas mixture including the separated hydrogen.

[0038] The hydrogen in the first and second gas mixtures may include any or any combination of different isotopes of hydrogen (i.e., protium, deuterium, tritium).

[0039] A plurality of first electrochemical cells 220a are stacked and fluidly connected in parallel with each other. Each of the plurality of first electrochemical cells 220a includes a first anode chamber 222a, a first cathode chamber 224a, and a first ion exchange mechanism 226a. Each first anode chamber 222a includes an anode and is configured to receive a first gas mixture from a first input line 250a. Each first cathode chamber 224a includes a cathode and is configured to output a second gas mixture to a first output line 260a. Each first ion exchange mechanism 226a is positioned between its respective first anode and cathode chambers 222a, 224a and separates its respective first anode and cathode chambers 222a, 224a from each other such that the first ion exchange mechanism 226a acts as a partial barrier to the fluid flow between its respective first anode and cathode chambers 222a, 224a. Each first ion exchange mechanism 226a of the first electrochemical cell 220a is semi-permeable, wherein it is configured to selectively allow hydrogen ions to travel through it to migrate from their respective first anode chamber 222a to their respective first cathode chamber 224a, while substantially preventing other components of the first gas mixture from traveling through it. Each first ion exchange mechanism 226a has the same structure as the ion exchange mechanism 126 described above with reference to FIG2.

[0040] The first gas mixture consists of hydrogen mixed with one or more other types of gases (e.g., nitrogen, carbon dioxide, helium, argon, carbon monoxide). For example, the first gas mixture may be 50% hydrogen and 50% one or more other types of gases. The second gas mixture is the result of electrochemical hydrogen separation performed by the first electrochemical cell 220a and therefore has a much higher proportion of hydrogen than the first gas mixture. Specifically, the second gas mixture is almost entirely composed of hydrogen, but still contains trace amounts of one or more other types of gases that have managed to migrate across the first ion exchange mechanism 226 due to imperfections in the selective permeability of the first ion exchange mechanism 226. For example, the second gas mixture may contain about 100 parts per million of one or more other types of gases (i.e., impurities or contaminants) and the remainder is hydrogen.

[0041] The first input line 250a is configured to receive a first gas mixture from a source (not shown) at a distance from the electrochemical hydrogen pump 200 and to deliver the first gas mixture to the first anode chamber 222a of a plurality of first electrochemical cells 220a. The first input line 250a is a fluid line, for example, a conduit or tube made of any suitable material.

[0042] The first output line 260a is configured to receive the second gas mixture from the first cathode chamber 224a of a plurality of first electrochemical cells 220a and to deliver the second gas mixture to the second electrochemical hydrogen pump stage 400. The first output line 260a is a fluid line, for example, a conduit or tube made of any suitable material.

[0043] The second electrochemical hydrogen pump stage 400 includes a plurality of second electrochemical cells 220b, a second input line 250b and a second output line 260b.

[0044] A plurality of second electrochemical cells 220b are each configured to receive a second gas mixture, electrochemically separate hydrogen from the second gas mixture, and output a third gas mixture including one of the separated hydrogen gases. The plurality of second electrochemical cells 220b are stacked and fluidly connected in parallel with each other. Each of the plurality of second electrochemical cells 220b includes a second anode chamber 222b, a second cathode chamber 224b, and a second ion exchange mechanism 226b. Each second anode chamber 222b includes an anode and is configured to receive the second gas mixture from a second input line 250b. Each second cathode chamber 224b includes a cathode and is configured to output the third gas mixture to a second output line 260b. Each second ion exchange mechanism 226b is positioned between its respective second anode and cathode chambers 222b and 224b, and separates the respective second anode and cathode chambers 222b and 224b from each other, such that the second ion exchange mechanism 226b acts as a partial barrier to the fluid flow between the respective second anode and cathode chambers 222b and 224b. The second ion exchange mechanism 226b of each second electrochemical cell 220b is semi-permeable, configured to selectively allow hydrogen ions to travel through it to migrate from the respective second anode chamber 222b to the respective second cathode chamber 224b, while substantially preventing other components of the second gas mixture from traveling through it. Each second ion exchange mechanism 226b has the same structure as the ion exchange mechanism 126 described above with reference to FIG. 2.

[0045] The third gas mixture is a further stage of electrochemical hydrogen separation performed by the second electrochemical cell 220b, and therefore has a hydrogen content of one or even higher than that of the second gas mixture. In other words, the third gas mixture has a non-hydrogen gas content of one or even lower than that of the second gas mixture. For example, the third gas mixture may have about 40 parts per billion of impurities or contaminants, with the remainder being hydrogen.

[0046] The second input line 250b is fluidly connected to the first output line 260a. The second input line 250b is configured to receive the second gas mixture from the first output line 160a of the first electrochemical hydrogen pump stage 300 and to deliver the second gas mixture to the second anode chamber 222b of a plurality of second electrochemical cells 220b. The second input line 250b is a fluid line, for example, a conduit or tube made of any suitable material.

[0047] The second output line 260b is configured to receive the third gas mixture from the second cathode chamber 224b of the plurality of second electrochemical cells 220b and to deliver the third gas mixture to a desired location (not shown) remotely from one of the electrochemical hydrogen pumps 200. The second output line 260b is a fluid line, for example, a conduit or tube made of any suitable material.

[0048] The first and second current collectors 230 and 240 electrically connect the anode and cathode of the first and second electrochemical cells 220a and 220b to a power source (not shown) to maintain the positive charge of the anode and the negative charge of the cathode.

[0049] The precise physical / chemical mechanisms underlying the operation of the first and second electrochemical cells 220a and 220b are well known and will not be described in detail herein for the sake of brevity. However, in brief, during the operation of the electrochemical hydrogen pump 200, hydrogen in the first gas mixture is oxidized at the anode of the first and second anode chambers 222a and 222b to generate hydrogen ions. The hydrogen ions then travel through the first and second ion exchange mechanisms 226a and 226b to the first and second cathode chambers 224a and 224b and undergo a reduction reaction at the cathode to reform into hydrogen. Since the first and second ion exchange mechanisms 226a and 226b selectively allow hydrogen ions to travel through them while substantially preventing other components of the first and second gas mixtures from traveling through them, the concentration of hydrogen in the second gas mixture increases compared to the concentration of hydrogen in the first gas mixture, and the concentration of hydrogen in the third gas mixture increases compared to the concentration of hydrogen in the second gas mixture. Therefore, hydrogen is effectively and selectively pumped (or separated) from the first and second gas mixtures by the first and second electrochemical cells 220a and 220b, respectively.

[0050] Figure 4 is a schematic diagram (not to scale) of a multi-stage electrochemical hydrogen pump 500 according to another embodiment. The embodiment of Figure 4 is the same as that of Figure 3, except that the anode chamber and cathode chamber are fluidly connected by channels and holes defined (or machined into) by bipolar plates (not shown) that sandwich each electrochemical cell, instead of using fluid lines. In this embodiment, each electrochemical cell is sandwiched between a pair of bipolar plates, and the anode and cathode chambers of each electrochemical cell are each defined between one of the pairs of bipolar plates and the ion exchange mechanism of the electrochemical cell.

[0051] More specifically, the first anode chamber of the first electrochemical hydrogen pump stage is fluidly connected to each other via a first channel 510a extending through a bipolar plate and a respective first orifice 520a in the bipolar plate. The first anode chamber is configured to receive a first gas mixture from a source remotely located at the electrochemical hydrogen pump 500 via the first channel 510a and the first orifice 520a.

[0052] The second cathode chamber of the second electrochemical hydrogen pump stage is fluidly connected to each other via a second channel 510b extending through a bipolar plate and one of the respective second holes 520b in the bipolar plate. The second cathode chamber is configured to output a third gas mixture from the electrochemical hydrogen pump 500 via the second hole 520b and the second channel 510b.

[0053] The first cathode chamber of the first electrochemical hydrogen pump stage is fluidly connected to each other via a third channel 510c extending through one of the bipolar plates and a respective third hole 520c in the bipolar plates. The first cathode chamber is configured to output a second gas mixture to the third channel 510c via the third hole 520c.

[0054] The second anode chamber of the second electrochemical hydrogen pump stage is fluidly connected to each other via a third channel 510c and a respective fourth hole 520d. The second anode chamber is configured to receive a second gas mixture from the third channel 510c via the fourth hole 520d.

[0055] The first cathode chamber of the first electrochemical hydrogen pump stage and the second anode chamber of the second electrochemical hydrogen pump stage are fluidly connected to each other via a third channel 510c. The third channel 510c is configured to transport the second gas mixture from the first cathode chamber of the first electrochemical hydrogen pump stage to the second anode chamber of the second electrochemical hydrogen pump stage. Therefore, advantageously, the embodiment of FIG4 tends to use a relatively tight fluid connection between the two electrochemical hydrogen pump stages and avoids the use of fluid lines (such as conduits) to perform this function.

[0056] Therefore, a multi-stage electrochemical hydrogen pump is provided.

[0057] The aforementioned multistage electrochemical hydrogen pump can be used to provide hydrogen in any suitable system requiring hydrogen. For example, the aforementioned multistage electrochemical hydrogen pump can be used as part of an extreme ultraviolet (EUV) lithography system. Specifically, the multistage electrochemical hydrogen pump can be part of a vacuum pumping system of an EUV lithography system and configured to receive a first gas mixture from a vacuum pump and output a third gas mixture to a location in the EUV lithography system where it is required. One example of this location is at the input of an EUV lithography tool as part of a semi-closed-loop hydrogen circulation procedure. The EUV tool requires a large amount of hydrogen input, which is eventually discharged (with impurities) through a vacuum pumping system. By removing impurities and pressurizing the hydrogen through a multistage electrochemical pump, the hydrogen, which would normally be discarded as contaminated waste, is recycled back into the EUV lithography tool. In the EUV lithography system, the first gas mixture can consist of hydrogen and nitrogen.

[0058] Advantageously, compared to conventional single-stage electrochemical hydrogen pumps (such as the single-stage electrochemical hydrogen pump illustrated in Figure 1), the aforementioned multi-stage electrochemical hydrogen pump tends to output a final gas mixture with a higher proportion of hydrogen. In other words, the final gas mixture output by the aforementioned multi-stage electrochemical hydrogen pump (i.e., the third gas mixture) tends to have a lower amount of non-hydrogen gases (i.e., contaminants or impurities). For example, tests have found that the output of a multi-stage electrochemical hydrogen pump (such as the multi-stage electrochemical hydrogen pump described above with reference to Figures 3 and 4) tends to have approximately 40 parts per billion of impurities, while the output of a single-stage electrochemical hydrogen pump (such as the single-stage electrochemical hydrogen pump described above with reference to Figure 1) tends to have 100 parts per million of impurities (i.e., more than 2,500 times that of the multi-stage electrochemical hydrogen pump). Therefore, the aforementioned multi-stage electrochemical hydrogen pump tends to have an output with a purity far exceeding that of conventional single-stage electrochemical hydrogen pumps. Therefore, the use of multi-stage electrochemical pumps tends to be particularly advantageous for systems that require very high purity hydrogen (e.g., extreme ultraviolet (EUV) lithography systems).

[0059] In the embodiments described above, the multi-stage electrochemical hydrogen pump has only two electrochemical hydrogen pump stages connected in series. However, in other embodiments, more than two electrochemical hydrogen pump stages connected in series are used to further reduce the proportion of impurities or contaminants in the gas output by the multi-stage electrochemical hydrogen pump. [Simplified Explanation of the Diagram]

[0029] Figure 1 is a schematic diagram of a conventional electrochemical hydrogen pump (not to scale);

[0030] Figure 2 is a schematic diagram (not to scale) showing a cross-sectional view of one of the ion exchange mechanisms of a conventional electrochemical hydrogen pump;

[0031] Figure 3 is a schematic diagram (not to scale) of one of the multi-stage electrochemical hydrogen pumps; and

[0032] Figure 4 is a schematic diagram of another multi-stage electrochemical hydrogen pump (not to scale).

Claims

1. A multi-stage electrochemical hydrogen pump, comprising: A first electrochemical hydrogen pump stage is fluidly connected to a second electrochemical hydrogen pump stage, wherein the first electrochemical hydrogen pump stage is configured to receive a first gas mixture including hydrogen, electrochemically separate the hydrogen from the first gas mixture to generate a second gas mixture, and output the second gas mixture to the second electrochemical hydrogen pump stage, wherein the second electrochemical hydrogen pump stage is configured to receive the second gas mixture from the first electrochemical hydrogen pump stage, electrochemically separate the hydrogen from the second gas mixture to generate a third gas mixture, and output the third gas mixture; and wherein the first and second electrochemical hydrogen pump stages are fluidly connected to each other via fluid lines or via a channel defined by bipolar plates.

2. The multistage electrochemical hydrogen pump of claim 1, wherein one or both of the first and second electrochemical hydrogen pump stages comprise a plurality of electrochemical cells fluidly connected in parallel with each other.

3. The multi-stage electrochemical hydrogen pump of claim 2, wherein the plurality of electrochemical cells of one or both of the first and second electrochemical hydrogen pump stages are configured as a stack.

4. A multistage electrochemical hydrogen pump as claimed in either claim 2 or 3, wherein each of the first and second electrochemical hydrogen pump stages comprises a plurality of electrochemical cells fluidly connected in parallel with each other, and wherein the output of one of the plurality of electrochemical cells of the first electrochemical hydrogen pump stage is fluidly connected to the input of one of the plurality of electrochemical cells of the second electrochemical hydrogen pump stage.

5. A multi-stage electrochemical hydrogen pump as claimed in any of claims 1 to 3, further comprising a housing in which the first and second electrochemical hydrogen pump stages are located.

6. A multi-stage electrochemical hydrogen pump as claimed in any of claims 1 to 3, wherein the second gas mixture has a greater proportion of hydrogen than the first gas mixture, and the third gas mixture has a greater proportion of hydrogen than the second gas mixture.

7. A multistage electrochemical hydrogen pump as claimed in any of claims 1 to 3, wherein the first gas mixture consists of hydrogen and one or more other types of gases, wherein the one or more other types of gases are selected from the group consisting of: nitrogen, carbon dioxide, helium, argon, and carbon monoxide.

8. A multistage electrochemical hydrogen pump as claimed in any of claims 1 to 3, wherein the hydrogen includes one or more of the following: protium, deuterium and tritium.

9. A multi-stage electrochemical hydrogen pump as claimed in any of claims 1 to 3, further comprising being fluidly connected in series to one or more further electrochemical hydrogen pump stages of the first and second electrochemical hydrogen pump stages.

10. A vacuum pumping system comprising a multistage electrochemical hydrogen pump as claimed in any one of claims 1 to 9.

11. The vacuum pumping system of claim 10, wherein the multistage electrochemical hydrogen pump is fluidly connected to a vacuum pump and configured to receive a first gas mixture from the vacuum pump.

12. An extreme ultraviolet lithography system comprising a vacuum pumping system as claimed in claim 10 or 11.

13. The extreme ultraviolet lithography system of claim 12, wherein the first gas mixture is composed of hydrogen and nitrogen.

14. A method of using a multi-stage electrochemical hydrogen pump as claimed in any one of claims 1 to 9 for pumping hydrogen.

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