Hydrogen generation device, fuel cell system and method for generating hydrogen

Abstract

Hydrogen generation device with: a first electrolysis device (10) comprising a first anode electrode (12), a first cathode electrode (14) and a proton-permeable membrane (16) arranged between the first anode electrode (12) and the first cathode electrode (14); a second electrolysis device (18) comprising a second anode electrode (20), a second cathode electrode (22) and a hydroxide ion-permeable membrane (24) arranged between the second anode electrode (20) and the second cathode electrode (22); and an operator device (26, 26a, 26b) by means of which at least one operating voltage can be applied between the first anode electrode (12) and the first cathode electrode (14) and / or between the second anode electrode (20) and the second cathode electrode (22) such that water as a reactant can be decomposed by a first water electrolysis carried out by means of the first electrolysis device (10) and / or by means of a second water electrolysis carried out by means of the second electrolysis device (18); characterized by the fact that in the hydrogen generation device a vapor transfer path (30, 40) extending from the first cathode electrode (14) to the second cathode electrode (22) is designed such that water vapor of a hydrogen-water vapor mixture released at the first cathode electrode (14) can be transferred at least partially from the first cathode electrode (14) to the second cathode electrode (22) and can be separated by means of the second water electrolysis carried out by the second electrolysis device (18).

Description

[0001] The invention relates to a hydrogen generation device. It also relates to a fuel cell system for a vehicle. Furthermore, the invention relates to a method for generating hydrogen. State of the art

[0002] WO 2013 / 004 526 A1 describes an energy management system for hydrogen production in an industrial plant. This system comprises both an alkaline electrolysis unit and a PEM (polymer electrolyte membrane) electrolysis unit. Depending on the quantity of hydrogen currently required and the desired purity level, either only the alkaline electrolysis unit, only the PEM electrolysis unit, or both the alkaline and PEM electrolysis units are activated to electrolyze water into hydrogen and oxygen. This is intended to optimize the overall power consumption of the energy management system required to produce the current amount of hydrogen. DE 11 2005 000 495 T5 also discloses an electrolysis system for steam electrolysis. Disclosure of the invention

[0003] The invention provides a hydrogen generation device with the features of claim 1, a fuel cell system for a vehicle with the features of claim 8 and a method for generating hydrogen with the features of claim 9. Advantages of the invention

[0004] The present invention provides a means of "purifying" hydrogen produced by water electrolysis from water vapor with relatively low energy consumption. Despite minimizing the energy required to carry out the present invention, hydrogen of very high quality, in particular with a purity of over 99.99%, can be produced using this invention. Additional "purification" of the hydrogen produced by the present invention from water vapor, which is conventionally often carried out by cooling, condensation, and / or pressure swing absorption (PSA), is no longer necessary. Therefore, the considerable energy consumption required to carry out these conventional techniques for "purifying" hydrogen can also be saved.

[0005] The present invention can be implemented using cost-effective devices. It should be noted that, for example, the hydrogen generation device according to the invention does not require any moving parts, such as a pump, a blower, or a valve. Furthermore, the hydrogen generation device according to the invention can be implemented as a wear-free and maintenance-free system. The present invention thus contributes to the acceptance of hydrogen as an energy carrier, for example, for a vehicle's own fuel cell. Since the hydrogen generation device according to the invention can also be implemented with a relatively low weight and a small installation space requirement, it can be easily installed in a vehicle.

[0006] In an advantageous embodiment of the hydrogen generation device, the hydrogen that can be output to an external consumer and / or storage device by means of the hydrogen generation device has a final water vapor content that is lower than the initial water vapor content of the hydrogen-water vapor mixture released at the first cathode electrode. Due to its negligible water vapor contamination, the hydrogen that can be output to the external consumer and / or storage device by means of the hydrogen generation device is versatile in its applications. In particular, the hydrogen produced by means of the hydrogen generation device can be used by a fuel cell, especially a vehicle-integrated fuel cell, to generate energy.

[0007] Advantageously, the first anode electrode, the first cathode electrode, the second anode electrode, and the second cathode electrode can be immersed in a common container. This allows for a space-saving arrangement of the first and second electrolysis units. The hydrogen generation device according to the invention can therefore have a comparatively low weight and require relatively little installation space.

[0008] For example, the second anode electrode and the second cathode electrode can be located downstream of the first anode electrode and the first cathode electrode. However, the proton-permeable membrane, the first cathode electrode, the vapor transfer path, the second cathode electrode, and the hydroxide-permeable membrane can also be situated between the first anode electrode and the second anode electrode. Thus, various configurations of the hydrogen generation device are possible.

[0009] The vapor transfer path can be a connecting section between a liquid and / or gas path formed in the first cathode electrode and a liquid and / or gas path formed in the second cathode electrode. Likewise, the vapor transfer path can also be a space between the first and second cathode electrodes. This allows for considerable design freedom in the configuration of the vapor transfer path.

[0010] In an advantageous embodiment of the hydrogen generation device, the first anode electrode is electrically connected to the second anode electrode, the first cathode electrode is electrically connected to the second cathode electrode, and a common operating voltage can be applied simultaneously between the first anode electrode and the first cathode electrode and between the second anode electrode and the second cathode electrode. This allows for the use of cost-effective, lightweight electronics requiring minimal installation space in the operator's equipment.

[0011] The advantages described above also apply to a fuel cell system for a vehicle with such a hydrogen generation device.

[0012] The advantages described above can also be achieved by implementing the corresponding hydrogen generation method. It should be noted that the method can be further developed according to the various embodiments of the hydrogen generation device described above. Brief description of the drawings

[0013] Further features and advantages of the present invention are explained below with reference to the figures. They show: Fig. 1 a schematic representation of a first embodiment of the hydrogen generation device; Fig. 2 a schematic representation of a second embodiment of the hydrogen generation device; Fig. 3 a schematic representation of a third embodiment of the hydrogen generation device; and Fig. 4 A block diagram to illustrate one embodiment of the method for generating hydrogen. Embodiments of the invention

[0014] Fig. Figure 1 shows a schematic representation of a first embodiment of the hydrogen generation device. The schematic representation shown in Fig. 1

[0015] The hydrogen generation device has a first electrolysis unit 10 with at least one first anode electrode 12, a first cathode electrode 14, and a proton-permeable membrane 16 arranged between the first anode electrode 12 and the first cathode electrode 14. The proton-permeable membrane 16 is understood to be a membrane that is permeable to protons. Preferably, however, the transport of gases, such as oxygen or hydrogen, through the proton-permeable membrane 16 is prevented. For example, the proton-permeable membrane 16 can be a proton exchange membrane. The first electrolysis unit 10 can, in particular, be a (classic) PEM electrolysis unit (proton exchange membrane electrolyzer). The proton-permeable membrane 16 can, for example, be made of at least one ionomer.As an alternative or as a supplement to the at least one ionomer, the proton-permeable membrane 16 can also comprise at least one other material.

[0016] The hydrogen generation device also includes a second electrolysis unit 18 with at least one second anode electrode 20, a second cathode electrode 22, and a hydroxide ion-permeable membrane 24 arranged between the second anode electrode 20 and the second cathode electrode 22. The hydroxide ion-permeable membrane 24 is understood to be a membrane that is permeable / conductive to hydroxide ions. Preferably, however, the transport of gases, such as hydrogen and oxygen, through the hydroxide ion-permeable membrane 24 is prevented. The second electrolysis unit 18 can, in particular, be an alkaline membrane electrolysis unit (AEM electrolysis unit, alkaline anion exchange membrane electrolyzer). It should be noted that a variety of different materials can be used for the hydroxide ion-permeable membrane 24.The hydroxide ion-permeable membrane 24 can in particular be a plastic film or a potassium hydroxide felt.

[0017] The first anode electrode 12, the first cathode electrode 14, the second anode electrode 20 and / or the second cathode electrode 22 can each be a platinum electrode. However, instead of or in addition to platinum, at least one other material can also be contained in at least one of the electrodes 12, 14, 20 and 22.

[0018] Preferably, at least one liquid and / or gas path 12a, 14a, 20a, and 22a is configured in and / or on at least one of the electrodes 12, 14, 20, and 22 such that at least one liquid and / or at least one gas is conductive through the respective electrode 12, 14, 20, and 22. Preferably, each of the electrodes 12, 14, 20, and 22 is configured with a liquid and / or gas path 12a, 14a, 20a, and 22a present on and / or in it. In particular, each liquid and / or gas path 12a, 14a, 20a, and 22a can be configured such that the liquid and / or gas conveyed therein flows as extensively as possible along the respective electrode 12, 14, 20, or 22. It is noted that each of the electrodes 12, 14, 20 and 22 can be configured with a high degree of design freedom with its liquid and / or gas pathway 12a, 14a, 20a and 22a. The liquid and / or gas pathways 12a, 14a, 20a and 22a are therefore in Fig. 1 is shown only as an example of sections of arrows.

[0019] The hydrogen generation device also has an operator unit 26, by means of which (during operation of the hydrogen generation device) at least one operating voltage can be applied between the first anode electrode 12 and the first cathode electrode 14 and / or between the second anode electrode 20 and the second cathode electrode 22 such that water as a reactant can be decomposed by a first water electrolysis carried out by the first electrolysis unit 10 and / or by a second water electrolysis carried out by the second electrolysis unit 18. By means of the first water electrolysis carried out by the first electrolysis unit 10, the reactant water is split at the first anode electrode 12, whereby, as shown by arrow 28, protons migrate from the first anode electrode 12 through the proton-permeable membrane 16 to the first cathode electrode 14.A hydrogen-water vapor mixture is therefore released at the first cathode electrode 14. This can also be described as the hydrogen produced / released by the first water electrolysis performed by the first electrolysis unit 10 being saturated with water vapor. Furthermore, oxygen is produced / released at the first anode electrode 12 by the first water electrolysis.

[0020] The hydrogen generation device also includes a vapor transfer path 30 (or vapor / gas transfer path 30) extending from the first cathode electrode 14 to the second cathode electrode 22, configured such that the water vapor of the hydrogen-water vapor mixture released at the first cathode electrode 14 can be at least partially transferred from the first cathode electrode 14 to the second cathode electrode 22. The vapor transfer path 30 can, for example, be a connecting section 30 between a liquid and / or gas path 14a formed in the first cathode electrode 14 and a liquid and / or gas path 22a formed in the second cathode electrode 22.This ensures that the water vapor of the hydrogen-water vapor mixture released at the first cathode electrode 14 can be, or is, decomposed by the second water electrolysis performed by the second electrolysis unit 18. The water vapor is therefore decomposed into hydrogen and hydroxide ions at the second cathode electrode 22. As illustrated by arrow 32, the hydroxide ions migrate from the second cathode electrode 22 through the hydroxide-permeable membrane 24 to the second anode electrode 20. At the second anode electrode 20, the hydroxide ions react to form water and oxygen radicals (individual oxygen atoms).

[0021] The second electrolysis unit 18 thus enables the drying of the hydrogen-water vapor mixture produced by the first electrolysis unit 10. This can also be described as a "purification" of the hydrogen released at the first cathode electrode 14 from the water vapor. Therefore, hydrogen that can be output / discharged by the hydrogen generation device to an (not shown) external consumer and / or storage device has a final water vapor content that is (significantly) lower than the initial water vapor content of the hydrogen-water vapor mixture released at the first cathode electrode 14. The hydrogen that can be produced by the hydrogen generation device thus has a high degree of purity. In particular, the degree of purity of the hydrogen produced by the hydrogen generation device (and output / discharged to the external consumer and / or storage device) can be over 99.99%.While hydrogen product gas produced with conventional devices is often so saturated with water vapor that it cannot be used for many purposes without purification / drying of the hydrogen product gas, the hydrogen produced by the hydrogen generation device can be used directly and without further processing / drying for a wide variety of applications.

[0022] The hydrogen-water vapor mixture released at the first cathode electrode 14, or the hydrogen produced by the first electrolysis unit 10, is typically almost saturated with water vapor, with the initial water vapor content of the hydrogen-water vapor mixture being temperature-dependent. (At a temperature of 50 °C and 1 bar pressure, which is frequently present during operation of the hydrogen generation device at the first electrolysis unit 10, the initial water vapor content of the hydrogen-water vapor mixture is approximately 80 g / Nm³.) 3 .) However, due to the advantageous equipment of the hydrogen generation device with the second electrolysis unit 18, the final water vapor content can be reduced to a significantly lower value.

[0023] Advantageously, the second electrolysis unit 18 also converts the water vapor of the hydrogen-water vapor mixture released at the first cathode electrode 14 into the desired product, hydrogen, thereby increasing the yield of the hydrogen production device. The energy consumed by the second electrolysis unit 18 thus contributes to increasing the yield of the hydrogen production device. Furthermore, it should be noted that the second water electrolysis carried out by the second electrolysis unit 18 (by which the water vapor of the hydrogen-water vapor mixture is converted into hydrogen) has a comparatively low energy consumption.In particular, the energy consumption of the second electrolysis unit 18 is significantly lower than that of cooling, condensation, or pressure swing adsorption (PSA) required to dry hydrogen saturated with water vapor. While, for example, pressure swing adsorption (for absorber regeneration) consumes up to 10% of the hydrogen produced, the operation of the second electrolysis unit 18 contributes to increasing the hydrogen yield. Therefore, the overall efficiency of the hydrogen production device, consisting of the two electrolysis units 10 and 18, is increased.

[0024] For the second water electrolysis of water vapor into hydrogen and hydroxide ions carried out by means of the second electrolysis device 18, the following applies at an operating point of a U / I characteristic of 1.7 V (volts) at 0.4 A / cm² 2(Amperes / square centimeter) the energy consumption for converting 100 g (grams) of water into hydrogen per hour is approximately 410 W (watts).

[0025] With a feed stream of 100 g (grams) of water per hour, the second electrolysis unit 18 produces 9 g (grams) of hydrogen per hour (9 g / h). Based on the calorific value of hydrogen (33 kWh / kg), the additional calorific value generated by the second electrolysis unit 18 can be estimated at approximately 290 W (watts).

[0026] In summary, an electrical power of approximately 410 W (per Nm) supplied to the second electrolysis unit 18 can be used. 3The unwanted water vapor in the hydrogen-water vapor mixture is reliably broken down into additional hydrogen. This increases the yield of the hydrogen generation device to an additional 9 g (grams) of hydrogen per hour (9 g / h), thereby increasing the calorific value of the hydrogen that can be supplied to the external consumer and / or storage device (with a feed rate of 80 g water per hour) by an additional 290 W.

[0027] Without taking into account ohmic losses in the second water electrolysis carried out by means of the second electrolysis unit 18, only about 120 W (per Nm²) are required for drying the hydrogen-water vapor mixture. 3Hydrogen) is required. This is only about 4% of the calorific value of the hydrogen that can be supplied to the external consumer and / or storage device. This energy remains in the system as heat and can potentially be used in a CHP (combined heat and power) application of the hydrogen generation device. (In conventional pressure swing adsorption, approximately 10% by volume of the produced hydrogen gas is lost from the system as "exhaust gas.")

[0028] Optionally, a membrane surface of the hydroxide ion-permeable membrane 24 can be additionally cooled so that it also functions as a condensation surface. However, it should be noted that this is not necessary for the operation of the second electrolysis unit 18.

[0029] The additional equipment of the hydrogen production device with the second electrolysis unit 18 hardly increases its installation space requirements or its weight. For example, at the operating point of the U / I characteristic curve of 1.8 V (volts) at 0.4 A / cm² 2 (Amperes / square centimeter) a working area of ​​electrodes 20 and 22 of 375 cm² 2 (per Nm 3 Hydrogen) is sufficient. At an operating point of 2 V (volts) at 0.8 A / cm². 2 (Amperes / square centimeter) and the required working area of ​​electrodes 20 and 22 is approximately 185 cm². 2 . While a working area of ​​electrodes 12 and 14, for example, at 1330 cm 2 Since the temperature may be significantly lower, values ​​(14-29%) are sufficient for the second electrolysis unit 18.

[0030] It should be noted that the figures cited in the preceding paragraphs are to be understood as examples only. For instance, the designability of the hydrogen production device is not limited to a specific reactant current, a specific electrical power of the second electrolysis unit 18, a specific operating temperature of the second electrolysis unit 18, a specific operating point of the second electrolysis unit 18, or a specific working area of ​​one of the electrodes 12, 14, 20, and 22.

[0031] In the embodiment of the Fig. In this arrangement, the first anode electrode 12, the first cathode electrode 14, the second anode electrode 20, and the second cathode electrode 22 (together with the membranes 16 and 24) are immersed in a common container 34. This allows for a space-saving and weight-reducing arrangement of the electrodes 12, 14, 20, and 22. Alternatively, the first electrolysis unit 10 and the second electrolysis unit 18 can also be arranged in separate containers.

[0032] Examples of the embodiment of the Fig. 1 the second anode electrode 20 and the second cathode electrode 22 are also connected downstream of the first anode electrode 12 and the second cathode electrode 14. The in Fig. The hydrogen generation device depicted in Figure 1 can therefore be described as a PEM (PEM electrolyzer) with a downstream AEM (AEM electrolyzer). This can be understood as follows: a liquid and / or gas path 12a formed in the first anode electrode 12 is connected via a connecting section 36 to a liquid and / or gas path 20a formed in the second anode electrode 20, while the liquid and / or gas path 14a formed in the first cathode electrode 14 is connected via the connecting section 30 (as a vapor transfer path 30) to the further liquid and / or gas path 22a formed in the second cathode electrode 22. This can also be described by saying that the anode electrodes 12 and 20 are hydraulically / gas-side connected to each other, and the cathode electrodes 14 and 22 are also hydraulically / gas-side connected to each other.

[0033] The first anode electrode 12, the first cathode electrode 14, the second anode electrode 20, and the second cathode electrode 22 can also be aligned parallel to each other. In particular, an inner surface / working surface of the first anode electrode 12 and an inner surface / working surface of the second anode electrode 20 can lie in a first plane, while an inner surface / working surface of the first cathode electrode 14 and an inner surface / working surface of the second cathode electrode 22 lie in a second plane aligned parallel to the first plane.

[0034] In the embodiment of the Fig. Furthermore, the first anode electrode 12 is electrically connected to the second anode electrode 20. This is achieved, for example, by contact between the two anode electrodes 12 and 20. (The two anode electrodes 12 and 20 can thus also be formed as a single piece.) However, an electrical contact between the first anode electrode 12 and the second anode electrode 20 can also be achieved via at least one conducting element. Similarly, the first cathode electrode 14 is electrically connected to the second cathode electrode 22. This can also be achieved by the two cathode electrodes 14 and 22 touching or being formed as a single piece. Optionally, an electrical contact between the first cathode electrode 14 and the second cathode electrode 22 can also be established via at least one conducting element.

[0035] Thus, a common operating voltage can be applied simultaneously between the first anode electrode 12 and the first cathode electrode 14, and between the second anode electrode 20 and the second cathode electrode 22. The operator unit 26 is therefore relatively simple, cost-effective, lightweight, and space-saving in design.

[0036] Fig. Figure 2 shows a schematic representation of a second embodiment of the hydrogen generation device.

[0037] Even in the embodiment of Fig. 2. The first anode electrode 12, the first cathode electrode 14, the second anode electrode 20, and the second cathode electrode 22 are aligned parallel to each other, with the inner surface / working surface of the first anode electrode 12 and the inner surface / working surface of the second anode electrode 20 lying in a first plane, and the inner surface / working surface of the first cathode electrode 14 and the inner surface / working surface of the second cathode electrode 22 lying in a second plane aligned parallel to the first plane. However, in the hydrogen generation device of the Fig. 2. The first anode electrode 12 is electrically isolated from the second anode electrode 20, and the first cathode electrode 14 is electrically isolated from the second cathode electrode 22. Therefore, separate control of the two electrolysis units 10 and 18 with different operating voltages is possible. Separate subunits 26a and 26b of the operator unit can also be used for this purpose.

[0038] An example of a hydrogen generation device is the Fig. 2 An insulator 38 is arranged between the first electrolysis unit 10 and the second electrolysis unit 18. While the first anode electrode 12, the first cathode electrode 14 and the proton-permeable membrane 16 are arranged on a first side of the insulator 38, the second anode electrode 20, the second cathode electrode 22 and the hydroxide ion-permeable membrane 24 are located on a second side of the insulator 38 facing away from the first side.

[0039] Otherwise, the hydrogen generation device of the Fig. 2 all features of the previously described embodiments.

[0040] Fig. Figure 3 shows a schematic representation of a third embodiment of the hydrogen generation device.

[0041] At the in Fig. In the three schematically depicted hydrogen generation devices, the proton-permeable membrane 16, the first cathode electrode 14, the vapor transfer path 30, the second cathode electrode 22, and the hydroxide-permeable membrane 24 are arranged between the first anode electrode 12 and the second anode electrode 20. The vapor transfer path 40 (or vapor / gas transfer path 40) is thus an intermediate space between the first cathode electrode 14 and the second cathode electrode 22.

[0042] Therefore, it is not necessary for the anode electrodes 12 and 20 to be hydraulically / gas-side connected and / or for the cathode electrodes 14 and 22 to be hydraulically / gas-side connected. Furthermore, the second electrolysis unit 18 can be operated with a different pressure differential, particularly a lower pressure differential, compared to the first electrolysis unit 10. This often offers advantages in terms of process engineering and materials.

[0043] In this embodiment, different operating voltages can also be applied simultaneously between the first cathode electrode and the first anode electrode, and between the second cathode electrode and the second anode electrode. Alternatively, the first anode electrode 12 can be electrically connected to the second anode electrode 20 (e.g., via a conductor element), while the first cathode electrode 14 is electrically connected to the second cathode electrode 22 (e.g., via another conductor element). The hydrogen generation device of Fig. 3 can therefore also be operated with only one operating voltage.

[0044] Regarding further features of the hydrogen generation device of the Fig. 3. Reference is made to the descriptions of the preceding embodiments.

[0045] All the hydrogen production devices described above can electrochemically convert the unwanted water vapor in the product gas hydrogen into hydrogen using their second electrolysis unit 18. All the hydrogen production devices described above thus achieve advantageous drying of their product gas hydrogen. By converting the unwanted water vapor into the product gas hydrogen, the hydrogen yield of the hydrogen production devices is increased. At the same time, the energy consumption required for drying the hydrogen is minimized in all hydrogen production devices. This increases the overall "power-to-hydrogen" efficiency of all hydrogen production devices. Additional water vapor is generated at the anode side of the second electrolysis unit 18, which humidifies the oxygen that is also produced, or rather, increases the circulating reactant water (which also acts as a coolant).

[0046] It should be noted that all the hydrogen generation devices described above do not require any moving parts, such as at least one pump, at least one blower, and / or at least one valve. Each of the hydrogen generation devices is therefore a wear-free and maintenance-free system. This leads to high user acceptance of the hydrogen generation devices.

[0047] Due to their small footprint and low weight, each of the hydrogen generation devices described above can easily be installed in a vehicle. Therefore, a fuel cell system for a vehicle with such a hydrogen generation device also offers all the advantages described above.

[0048] Fig. Figure 4 shows a block diagram to explain one embodiment of the method for producing hydrogen.

[0049] The process described below can be carried out, for example, using one of the hydrogen generation devices explained above. However, the feasibility of the process is not limited to the use of just one of the hydrogen generation devices.

[0050] In process step S1, at least one operating voltage is applied between a first anode electrode and a first cathode electrode of a first electrolysis unit comprising at least the first anode electrode, the first cathode electrode, and a proton-permeable membrane arranged between the first anode electrode and the first cathode electrode, and / or between a second anode electrode and a second cathode electrode of a second electrolysis unit comprising at least the second anode electrode, the second cathode electrode, and a hydroxide-ion-permeable membrane arranged between the second anode electrode and the second cathode electrode. Process step S1 thus comprises a sub-step S1a for operating the first electrolysis unit and a sub-step S1b for operating the second electrolysis unit.

[0051] In sub-step S1a of process step S1, water is used as a reactant by operating the first electrolysis unit and undergoing a first water electrolysis. This releases a hydrogen-water vapor mixture at the first cathode electrode.

[0052] In process step S2, water vapor from the hydrogen-water vapor mixture released at the first cathode electrode is at least partially transferred from the first cathode electrode to the second cathode electrode. In substep S1b of process step S1, the water vapor transferred to the second cathode electrode is therefore at least partially decomposed by a second water electrolysis carried out by the second electrolysis unit, through the operation of the first electrolysis unit. In this way, the initial water vapor content of the hydrogen-water vapor mixture released at the first cathode electrode can be reduced to a final water vapor content lower than the initial water vapor content by means of the second water electrolysis carried out by the second electrolysis unit.

[0053] The method described here also creates the advantages explained above, which will not be listed again here.

Claims

[1] Hydrogen generation device with: a first electrolysis device (10) comprising a first anode electrode (12), a first cathode electrode (14) and a proton-permeable membrane (16) arranged between the first anode electrode (12) and the first cathode electrode (14); a second electrolysis device (18) comprising a second anode electrode (20), a second cathode electrode (22) and a hydroxide ion-permeable membrane (24) arranged between the second anode electrode (20) and the second cathode electrode (22); and an operator device (26, 26a, 26b) by means of which at least one operating voltage can be applied between the first anode electrode (12) and the first cathode electrode (14) and / or between the second anode electrode (20) and the second cathode electrode (22) such that water as a reactant can be decomposed by a first water electrolysis carried out by means of the first electrolysis device (10) and / or by means of a second water electrolysis carried out by means of the second electrolysis device (18); characterized by , that in the hydrogen generation device a vapor transfer path (30, 40) extending from the first cathode electrode (14) to the second cathode electrode (22) is designed such that water vapor of a hydrogen-water vapor mixture released at the first cathode electrode (14) can be transferred at least partially from the first cathode electrode (14) to the second cathode electrode (22) and can be separated by means of the second water electrolysis carried out by the second electrolysis device (18). [2] Hydrogen generation device according to one of the preceding claims, wherein the first anode electrode (12), the first cathode electrode (14), the second anode electrode (20) and the second cathode electrode (22) are immersed in a common container (34). [3] Hydrogen generation device according to claim 2, wherein the second anode electrode (20) and the second cathode electrode (22) are connected downstream of the first anode electrode (12) and the first cathode electrode (14). [4] Hydrogen generation device according to claim 3, wherein the vapor transfer path (30) is a connecting section (30) between a liquid and / or gas path (14a) formed in the first cathode electrode (14) and a liquid and / or gas path (22a) formed in the second cathode electrode (22). [5] Hydrogen generation device according to claim 2, wherein the proton-permeable membrane (16), the first cathode electrode (14), the vapor transfer path (40), the second cathode electrode (22) and the hydroxide ion-permeable membrane (24) are located between the first anode electrode (12) and the second anode electrode (20). [6] Hydrogen generation device according to one of the preceding claims, wherein the first anode electrode (12) is electrically connected to the second anode electrode (20), the first cathode electrode (14) is electrically connected to the second cathode electrode (22), and a common operating voltage can be applied simultaneously between the first anode electrode and the first cathode electrode (14) and between the second anode electrode (20) and the second cathode electrode (22). [7] Fuel cell system for a vehicle comprising a hydrogen generation device according to one of the preceding claims. [8] Method for producing hydrogen comprising the steps: Applying at least one operating voltage between a first anode electrode (12) and a first cathode electrode (14) of a first electrolysis unit (10) comprising at least the first anode electrode (12), the first cathode electrode (14) and a proton-permeable membrane (16) arranged between the first anode electrode (12) and the first cathode electrode (14) and / or between a second anode electrode (20) and a second cathode electrode (22) of a second electrolysis unit (18) comprising at least the second anode electrode (20), the second cathode electrode (22) and a hydroxide ion-permeable membrane (24) arranged between the second anode electrode (20) and the second cathode electrode (22) (S1) such that water as a reactant is decomposed by a first water electrolysis carried out by means of the first electrolysis unit (10) and / or by a second water electrolysis carried out by means of the second electrolysis unit (18). becomes; characterized by the step that Transferring water vapor from a hydrogen-water vapor mixture released at the first cathode electrode (14) at least partially from the first cathode electrode (14) to the second cathode electrode (22) (S2), whereby the water vapor transferred to the second cathode electrode (22) is at least partially decomposed by means of the second water electrolysis carried out by the second electrolysis device (18). [9] Method according to claim 8, wherein an initial water vapor content of the hydrogen-water vapor mixture released at the first cathode electrode (14) is reduced to a final water vapor content smaller than the initial water vapor content by means of the second water electrolysis carried out by the second electrolysis device (18).

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