DEVICE AND METHOD FOR CARBON DIOXIDE ELECTROLYSIS OR CARBON MONOXIDE ELECTROLYSIS

Abstract

An anode-side half cell for an electrochemical cell of an electrolytic apparatus for carbon dioxide electrolysis and/or carbon monoxide electrolysis, having a separator in the form of a diaphragm, which has an anode-side separator surface and a cathode-side separator surface opposite the anode-side separator surface; a catalyst layer, which has a first catalyst surface and a second catalyst surface opposite the first catalyst surface, the first catalyst surface facing the anode-side separator surface; and a fluid-permeable anode plate, which has a first anode surface, the first anode surface facing the second catalyst surface.

Claims

1. An anode-side half-cell for an electrochemical cell of an electrolysis device for carbon dioxide electrolysis and/or for carbon monoxide electrolysis, comprising: a separator which is in the form of a membrane and has an anode-side separator surface and a cathode-side separator surface on the opposite side from the anode-side separator surface, a catalyst layer having a first catalyst surface and a second catalyst surface on the opposite side from the first catalyst surface, wherein the first catalyst surface faces the anode-side separator surface, and a fluid-permeable anode plate having a first anode surface, wherein the first anode surface faces the second catalyst surface.

2. The anode-side half-cell as claimed in claim 1, wherein the anode plate has a second anode surface on the opposite side from the first anode surface, wherein where a contact plate is disposed on the second anode surface and wherein at least the anode plate or the contact plate serves for electrical connection to an electrical energy source which provides an electrical anode potential.

3. The anode-side half-cell as claimed in claim 1, wherein at least the anode plate or a contact plate includes titanium and/or a titanium alloy.

4. The anode-side half-cell as claimed in claim 1, wherein the anode plate is at least partly porous.

5. The anode-side half-cell as claimed in claim 1, wherein the first anode surface is connected to the second catalyst surface by an electrically conductive bonding technique.

6. The anode-side half-cell as claimed in claim 5, wherein the bonding technique uses an electrically conductive adhesive.

7. The anode-side half-cell as claimed in claim 1, wherein the second catalyst surface has projections that protrude from this surface and project into the anode plate through the first anode surface for bonding to the anode plate.

8. The anode-side half-cell as claimed in claim 7, wherein the projections are formed from the same material as the catalyst layer.

9. The anode-side half-cell as claimed in claim 7, wherein the projections are formed by mutually spaced pins and the anode plate has receiving openings for receiving the pins.

10. The anode-side half-cell as claimed in claim 1, wherein a contact plate has a contact plate surface which is on the opposite side from the second anode surface and has connecting elements at least for mechanical connection of the contact plate surface to the second anode surface.

11. The anode-side half-cell as claimed in claim 10, wherein the connecting elements and the contact plate are electrically conductive.

12. An electrochemical cell of an electrolysis device for carbon dioxide electrolysis and/or for carbon monoxide electrolysis, comprising: a cathode region having an electrical cathode connection, a gas diffusion electrode, a first feed connection for supply of carbon dioxide and a first drain connection for draining of electrolysis substances at least partly formed in the intended operation of the electrochemical cell, an anode region which is formed separately from the cathode region by a separator and has an electrical anode connection, an anode plate, a second feed connection for supply of a proton-releasing substance and a second drain connection for draining of electrolysis residues at least partly formed in the intended operation of the electrochemical cell, wherein the cathode connection and the anode connection are designed to be electrically coupled to corresponding electrical connections of an electrical energy source that provides an electrical electrolysis voltage, wherein the anode region and the separator are designed as anode-side half-cell as claimed in claim 1.

13. The electrochemical cell as claimed in claim 12, wherein characterized in that the elements of the cathode region and of the anode region are arranged in a stack.

14. An electrolysis device for carbon dioxide electrolysis and/or for carbon monoxide electrolysis, characterized by comprising: electrochemical cells as claimed in claim 12, wherein the electrochemical cells are in a spatially directly adjoining arrangement.

15. A method of producing an anode-side half-cell for an electrochemical cell of an electrolysis device for carbon dioxide electrolysis and/or for carbon monoxide electrolysis, comprising: arranging an anode-side separator surface of a separator which is in the form of a membrane and has a cathode-side separator surface on the opposite side from the anode-side separator surface at a first catalyst surface of a catalyst layer, which catalyst layer has a second catalyst surface on the opposite side from the first catalyst surface, and arranging a first anode surface of a fluid-permeable anode plate at the second catalyst surface.

16. The anode-side half-cell as claimed in claim 6, wherein the electrically conductive adhesive includes particles of iridium(IV) oxide.

17. The anode-side half-cell as claimed in claim 9, wherein the first anode surface has receiving openings for receiving the pins.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] FIG. 1 shows a schematic function block view of an electrolysis device for carbon dioxide electrolysis having a multitude of electrically series-connected electrochemical cells;

[0057] FIG. 2 shows a schematic section view of an electrochemical cell of the electrolysis device according to FIG. 1;

[0058] FIG. 3 shows a schematic section view of the anode-side half-cell of the electrochemical cell according to FIG. 2 in a first configuration;

[0059] FIG. 4 shows a schematic section view like FIG. 3 in a second configuration;

[0060] FIG. 5 shows a schematic section view like FIG. 3 in a third configuration;

[0061] FIG. 6 shows a schematic enlarged representation of a region VI in FIG. 5;

[0062] FIG. 7 shows a schematic section view based on FIG. 3 in a fourth configuration;

[0063] FIG. 8 shows a schematic perspective diagram of a catalyst surface with projections in the form of pins, in the configuration according to FIG. 7;

[0064] FIG. 9 shows an enlarged representation of a region IX in FIG. 8; and

[0065] FIG. 10 shows a schematic top view of a first anode surface of an anode plate which serves for connection to the catalyst layer according to FIG. 8.

DETAILED DESCRIPTION OF INVENTION

[0066] FIG. 1 shows, in a schematic function block diagram, an electrolysis device 12 for carbon dioxide electrolysis, in which carbon monoxide is produced at least in part from carbon dioxide in operation as intended. The electrolysis device 12 comprises a multitude of electrochemical cells 10 in which the carbon dioxide electrolysis takes place, two of which are shown by way of example in FIG. 1. In the present configuration, the electrochemical cells 10 are electrically connected in series, with the series connection being connected to an electrical energy source 36 by means of electrical wires 82 in order to subject the electrochemical cells 10 in a corresponding manner to electrical potentials on the respective electrodes, as elucidated hereinafter.

[0067] Each of the electrochemical cells 10 has a cathode region 14 and an anode region 26 that are separated from one another by means of a separator 24. The cathode region 14 comprises an electrical cathode connection 16, a gas diffusion electrode 18 electrically coupled to the cathode connection 16, a first feed connection 20 for supply of carbon dioxide and a first drain connection 22 for draining of electrolysis substances that have formed at least in part in the intended operation of the electrochemical cell 10, which include carbon monoxide. In addition, it is of course also possible for the electrolysis substances to include a residue of carbon dioxide that has not been converted in the electrochemical cell 10. In addition, further residues are possible. Furthermore, the cathode region 14 is connected to conduits 30 for supply and draining of a catholyte, here a salt solution.

[0068] The anode region 26 comprises an electrical anode connection 28, an anode plate 50 electrically coupled to the electrical anode connection 28, a second feed connection 32 for supply of a proton-releasing substance, and a second drain connection 34 for draining of electrolysis residues at least partly formed in the intended operation of the electrochemical cell 10.

[0069] The cathode connection 16 and the anode connection 28 are designed to be electrically coupled to a suitable or appropriate electrical electrolysis voltage from the electrical energy source 36. The respective first and second feed connections 20, 32, and the respective first and second drain connections 22, 34, are each correspondingly connected in parallel for flow purposes, such that the electrochemical cells 10 can be supplied from respective sources for the appropriate substances in operation as intended.

[0070] FIG. 2 shows, in a schematic section diagram, one of the electrochemical cells 10 according to FIG. 1. For the sake of clarity, the feed connections 20, 32 and the drain connections 22, 34 are not shown.

[0071] FIG. 2 shows a section view of one of the electrochemical cells 10. It is apparent that the electrochemical cell 10 has a stacked construction. The cathode region 14 comprises a catholyte element 74 adjoining a gas diffusion electrode 18 which, in the present context, at least partly constitutes the cathode. The gas diffusion electrode 18 also adjoins a contact frame 76 which, in the present context, is formed from silver or a silver alloy. The contact frame 76 adjoins a gas spacer element 78, one purpose of which is to supply carbon dioxide and to remove carbon monoxide. The gas spacer element 78 adjoins a window 80 that concludes the cathode region 14. In alternative configurations, rather than the window 80 or in addition thereto, it is also possible to provide an end plate or the like.

[0072] The catholyte element 74 also adjoins the separator 24, specifically a cathode-side separator surface 42. On the opposite side from the cathode-side separator surface, the separator 24 has an anode-side separator surface. The separator 24 in the present context is formed from a substance which is permeable to protons. In the present configuration, the material provided for the separator 24 is Nafion. In alternative configurations, it is of course possible here too to provide a different, correspondingly suitable material.

[0073] The construction and function of the gas diffusion electrode 18 is known, for example, from European patent application 19 182 017.4. Therefore, reference is made in this regard to the disclosure in this regard.

[0074] In the present configuration, the anode region 26 is formed as a construction unit together with the separator 24. In this way, it is possible to create a unit that can be handled separately, which simplifies the production of the electrochemical cell 10 and, with regard to reliability, is capable of providing improvement not just in production but also in operation as intended.

[0075] For this purpose, in the anode region 26, the separator 24 is formed with a catalyst layer 44 in the manner of a membrane-electrode assembly (MEA). For this purpose, the separator 24 likewise takes the form of a membrane. The separator 24 has the anode-side separator surface 40 and the cathode-side separator surface 42 on the opposite side from the anode-side separator surface 40. In addition, the catalyst layer 44 has a first catalyst surface 46 and a second catalyst surface 48 on the opposite side from the first catalyst surface 46. The first catalyst surface 46 faces the anode-side separator surface 40. In the present configuration, the first catalyst surface 46 is bonded in a fixed manner to the anode-side separator surface 40. The catalyst layer 44 may therefore be applied in the manner of a coating on the anode-side separator surface 40. This achieves a reliable fixed connection between the catalyst layer 44 and the separator 24.

[0076] The anode region 26 further comprises a fluid-permeable anode plate 50 having a first anode surface 52 and a second anode surface 54 on the opposite side from the first anode surface 52. The first anode surface 52 faces the second catalyst surface 48. In the present configuration, the first anode surface 52 is bonded to the second catalyst surface 48. As will be set out hereinafter, this connection can be implemented in different ways, specifically in accordance with the different working examples discussed hereinafter.

[0077] In the present context, the anode plate 50 is porous, in order to be able to achieve the desired gas permeability or else the desired permeability for a liquid, for example water or the like.

[0078] A contact plate 56 is disposed on the second anode surface 54. In this regard, the contact plate 56 has a contact plate surface 68 connected to the second anode surface 54. The contact plate 56 is electrically coupled to the electrical anode connection 28. At an opposite surface of the contact plate 56 from the contact plate surface 68 is disposed an end plate 72 that concludes the anode region 26 in the outward direction.

[0079] The separator 24, the catalyst layer 44 and the anode plate 50 form an anode-side half-cell 38 as a construction unit. According to the construction and requirements, the construction unit may also include the contact plate 56. The anode-side half-cell 38, especially the construction thereof, is elucidated in detail with reference to the further working examples that follow.

[0080] The catalyst layer 44 in the present context is formed predominantly from iridium(IV) oxide. However, it is also possible in principle—according to the desired functionality—to use a different metal oxide or else mixtures thereof.

[0081] The anode plate 50 and also the contact plate 56 in the present context are formed from a titanium alloy. This can achieve good electrical conductivity, such that the electrical anode potential over the anode surfaces 52, 54 is very substantially uniform or homogeneous. This promotes the efficacy of the electrolysis operation in the electrochemical cell 10.

[0082] The anolyte used may be water or else a salt solution, which simultaneously also provides the proton-releasing substance, such that protons can be provided for the desired electrochemical reaction of the carbon dioxide electrolysis.

[0083] At the anode, it is possible to achieve a chemical reaction according to the following equation:

2H.sub.2O(l)+4OH.sup.−.fwdarw.O.sub.2(g)+4e−+4H.sub.2O(l)

[0084] At the cathode, a main reaction takes place according to the following chemical equation:

CO.sub.2(g)+H.sub.2O(l)+2e.sup.−.fwdarw.CO(g)+2OH.sup.−

2H.sub.2O(l)+2e.sup.−.fwdarw.H.sub.2(g)+2OH.sup.−

[0085] FIG. 3 shows a first embodiment of the anode-side half-cell 38. It is apparent from FIG. 3 that the second catalyst surface 48 is bonded to the first anode surface 52 by means of an adhesive 58. The adhesive 58 in this configuration is a diffusion-open adhesive that establishes a cohesive bond between the second catalyst surface 48 and the first anode surface 52. The adhesive may, for example, include PTFE, PVDF and also N-methyl-2-pyrrolidone as solvent. N-Methyl-2-pyrrolidone dissolves the two aforementioned polymers after addition and then, after evaporation, forms a solid adhesive layer. However, it is also possible in principle to use other adhesion adhesives, for example based on epoxy resin or based on cyanoacrylate.

[0086] The adhesive 58 preferably consists of an identical or similar substance to the separator 24. It should generally be noted that, when Nafion, being a perfluorinated copolymer containing a sulfone group as ionic group, is used as material for the separator 24 as in the present context, a similar substance should as far as possible be used for the adhesive, which is capable of introducing no extraneous chemical components into the electrolysis process if at all possible, such that the electrolysis process can remain unimpaired if possible. Accordingly, the use of other adhesives is limited essentially in that the electrolysis process is not significantly impaired.

[0087] The second anode surface 54 is mechanically and electrically connected to the contact plate 56 via connecting elements 70. The connecting elements 70 may provide punctiform or continuous mechanical and electrical connection, for example by means of weld points or bonding points or by means of soldering or the like, according to suitability.

[0088] In the present configuration, the anode plate 50 is electrically coupled to the electrical energy source 36, specifically to the electrical anode potential thereof. By means of the contact plate 56, in the case of the porous anode plate 50, it is possible to achieve an essentially homogeneous adjustment of the electrical anode potential over the anode surfaces 52, 54 even in the case of high current density.

[0089] FIG. 4 shows a further configuration of an anode-side half-cell 38 based on the configuration according to FIG. 3. By contrast with the configuration according to FIG. 3, in the configuration according to FIG. 4, the adhesive 58 is replaced by the adhesive 60. The further construction corresponds to the working example according to FIG. 3.

[0090] The adhesive 60 may in principle take the same form as the adhesive 58, but it also comprises fibers of iridium(IV) oxide. This can further improve function, especially with regard to catalytic action. Otherwise, the construction of the anode-side half-cell 38 corresponds to the construction as already elucidated with reference to FIG. 3. The adhesive 60 especially has higher electrical conductivity compared to the adhesive 58.

[0091] FIG. 5 shows a further configuration for an anode-side half-cell 38 based on the configuration according to FIG. 4, and reference is therefore made additionally to the details in this regard.

[0092] In the configuration according to FIG. 5, iridium(IV) oxide fibers or iridium(IV) oxide-coated separator strips or optionally also other plastic or metal fibers or strips are applied on one side of the separator 24 as early as in the production of the separator 24, specifically on the anode-side separator surface 40. In a subsequent manufacturing step, the separator 24, which already contains the catalyst layer 44 as a result, is then bonded to the first anode surface 52 of the anode plate 50. The connection can be effected as elucidated with reference to FIGS. 3 and 4. In this way, it is possible to bond the catalyst layer 44 to the separator 24 in a more mechanically stable manner.

[0093] The adhesive 58, 60 between the catalyst layer 44 and the anode plate 50 may, according to the application, be arranged over the whole area or else in a punctiform manner. FIG. 6 shows an enlarged detail of FIG. 5 in region VI.

[0094] FIG. 7 shows a further configuration of an anode-side half-cell 38, which is based in principle on the above-described configurations according to FIGS. 3 to 6, and reference is therefore made additionally to the details in this regard. By contrast with the configurations according to FIGS. 3 to 6, no adhesive is provided in the configuration according to FIG. 7. Instead, the second catalyst surface 48 of the catalyst layer 44 has projections 62 of catalyst material that project through the first anode surface 52 into the anode plate 50. In this configuration, the electrical energy source 36 is additionally electrically coupled to the contact plate 56. In this way, it is possible to achieve both good electrical and mechanical connection, and simultaneously also good efficacy in relation to the envisaged electrolysis of carbon dioxide.

[0095] FIGS. 8 to 10 show a configuration based on the configuration according to FIG. 7. As apparent from FIGS. 8 to 10, the membrane arrangement composed of the separator 24 and the catalyst layer 44 may be connected to the anode plate 50 in a plug-connectable manner. This can achieve not just simple assembly but also releasability, which permits, if required, separability of the anode plate 50 from the membrane construction composed of the separator 24 and the catalyst layer 44. For this purpose, the configuration according to FIG. 7 envisages that the catalyst layer 44 provides the projections 62 as pins 66. These project from the second catalyst surface 48 (FIG. 8). FIG. 9 shows an enlarged detail in the region IX of FIG. 8.

[0096] FIG. 10 shows, in a schematic top view of the first anode surface 52, the anode plate 50. It is apparent that, according to the arrangement of the pins 66 in the catalyst layer 44 according to FIG. 8, receiving openings 64 are provided. In the case of bonding of the catalyst layer 44 to the anode plate 50, the pins 66 are introduced into the receiving openings 64. This can achieve a reliable mechanical and electrical connection between the anode plate 50 and the catalyst layer 44.

[0097] It may advantageously be the case that the connection is releasable. This can be achieved by means of an appropriate separation force, such that, ultimately, the anode plate 50 can be separated again in a simple manner from the catalyst layer 44. However, it is also possible in principle to provide an essentially force-free connection in that the anode plate 50 comprises a locking element that permits, in a first locking state, virtually force-free introduction of the pins 66 into the receiving openings 64 and, in a second locking state, fixing of the pins 66 in the receiving openings 64. In this way, it is simultaneously also possible to achieve simple releasable assembly.

[0098] Overall, the invention can achieve distinct simplification of the construction of the electrochemical cell 10 and of the electrolysis device 12. Furthermore, it is also possible to increase reliability. The catholyte used may, for example, be potassium hydrogencarbonate or else potassium sulfate or the like.

[0099] The anode-side half-cell 38 of the invention can achieve a Faraday efficiency within a range from about 90% to 100%, preferably about 95%. The electrolysis is preferably effected in a temperature range above room temperature. The temperature range may preferably be chosen from about 40° C. to about 90° C., more preferably at about 60° C.

[0100] The invention can achieve the following advantages: [0101] A fixed connection can be achieved between a contact structure on an anodic side by a composite composed of the catalyst layer and the separator. [0102] Frequent contact connection can achieve the effect that the anode potential, even in the case of a high current density, is essentially uniform over the area. [0103] The construction unit composed of the separator and the catalyst layer has much less of a tendency to swell and hence also less of a tendency to buckle from the contact connection. [0104] The coating of the separator with the catalyst can be protected from mechanical abrasion in the case of further handling in the realm of manufacturing or else in operation as intended. [0105] There is no need to expend any great force for the contact connection. [0106] It is possible to achieve improved handling in production and simplified assembly.

[0107] The aforementioned working examples serve exclusively to elucidate the invention and are not intended to restrict it.