Method and Device for Electrolysis

Abstract

A method for electrolysis, wherein an anolyte is brought into contact with an anode, and a catholyte is brought into contact with a cathode, wherein the anolyte contains hydroxide ions and the catholyte contains an auxiliary, wherein an electrical voltage is applied between the anode and the cathode such that the hydroxide ions in the anolyte are oxidized at the anode and the auxiliary in the catholyte is reduced at the cathode, and wherein H2O and the reduced auxiliary are brought into contact with a catalyst such that the reduced auxiliary is oxidized and hydrogen is formed from the H2O. By means of the auxiliary, the electrolysis can be carried out under low pressure, and hydrogen can still be obtained at high pressure. This facilitates the construction of the electrolytic cell and prevents an efficiency-reducing gas cross-permeation.

Claims

1. A method for electrolysis, wherein an anolyte is brought into contact with an anode, and a catholyte is brought into contact with a cathode, wherein the anolyte contains hydroxide ions and the catholyte contains an auxiliary, wherein an electrical voltage is applied between the anode and the cathode such that the hydroxide ions in the anolyte are oxidized at the anode and the auxiliary in the catholyte is reduced at the cathode, and wherein H2O and the reduced auxiliary are brought into contact with a catalyst such that the reduced auxiliary is oxidized and hydrogen is formed from the H2O.

2. The method according to claim 1, wherein the auxiliary and the reduced auxiliary form a redox pair having a negative potential with respect to a reversible hydrogen electrode.

3. The method according to claim 1, wherein the auxiliary is suitable for reversible hydrogen uptake and hydrogen delivery.

4. The method according to claim 1, wherein the anode is arranged in an anode chamber of an electrolytic cell, the cathode is arranged in a cathode chamber of the electrolytic cell, and the catalyst is arranged in a gas separator connected to the cathode chamber.

5. The method according to claim 4, wherein the anode chamber and the cathode chamber are separated from one another by a membrane which is permeable to hydroxide ions.

6. The method according to claim 4, wherein H2O and the reduced auxiliary are introduced continuously into the gas separator, and gaseous hydrogen is withdrawn continuously from the gas separator.

7. The method according to claim 4, wherein H2O and the reduced auxiliary are introduced discontinuously into the gas separator, and gaseous hydrogen is withdrawn discontinuously from the gas separator.

8. The method according to claim 1, wherein the anolyte has a pH of more than 12.

9. The method for electrolysis, wherein an anolyte is brought into contact with an anode of a first electrolytic cell, and a first catholyte is brought into contact with a cathode of the first electrolytic cell, wherein the anolyte contains hydroxide ions and the first catholyte contains a first auxiliary, wherein an electrical voltage is applied between the anode and the cathode of the first electrolytic cell such that the hydroxide ions in the anolyte are oxidized at the anode of the first electrolytic cell, and the first auxiliary in the first catholyte is reduced at the cathode of the first electrolytic cell, wherein the first catholyte, together with the first reduced auxiliary, is brought into contact with an anode of a second electrolytic cell, and a second catholyte is brought into contact with a cathode of the second electrolytic cell, wherein the second catholyte contains a second auxiliary, wherein an electrical voltage is applied between the anode and the cathode of the second electrolytic cell such that the reduced first auxiliary is oxidized at the anode of the second electrolytic cell, and the second auxiliary is reduced at the cathode of the second electrolytic cell, and wherein H2O and the reduced second auxiliary are reacted with one another such that the reduced second auxiliary is oxidized and hydrogen is formed from the H2O.

10. A device for electrolysis by means of a method according to claim 1, comprising an electrolytic cell having an anode chamber and an anode arranged therein, a cathode chamber and a cathode arranged therein, and a gas separator which is connected to the cathode chamber.

Description

[0055] The invention is explained in more detail below with reference to the drawings. The drawings show particularly preferred exemplary embodiments to which the invention is not limited, however. The drawings and the proportions shown therein are only schematic. In the drawings:

[0056] FIG. 1 shows a first embodiment of a device according to the invention for electrolysis,

[0057] FIG. 2 shows a second embodiment of a device according to the invention for electrolysis,

[0058] FIG. 3 shows a third embodiment of a device according to the invention for electrolysis.

[0059] FIG. 1 shows a first embodiment of a device 1 for electrolysis. The device 1 comprises an electrolytic cell 7. The electrolytic cell 7 comprises an anode chamber 5 having an anode 2 arranged therein, and a cathode chamber 6 having a cathode 3 arranged therein. The anode chamber 5 and the cathode chamber 6 are separated from one another by a membrane 9. The anode 2 and the cathode 3 are each connected to a voltage source. Furthermore, the device 1 comprises a gas separator 8 for the anode 2 and the cathode 3, in each case. A catalyst 4 made of platinum is arranged in the cathodic gas separator 8.

[0060] The device 1 can be used to produce oxygen and hydrogen. To this end, an anolyte comprising hydroxide ions is brought into contact with the anode 2 by introducing the anolyte into the anode chamber 5. A catholyte is brought into contact with the cathode 3 by introducing the catholyte into the cathode chamber 6. The catholyte contains an auxiliary formed by hydroxyquinones. An electrical voltage is applied between the anode 2 and the cathode 3, via the voltage source. As a result, the hydroxide ions are oxidized at the anode 2; the auxiliary is reduced at the cathode 3. The hydroxide ions formed on the cathode 3 in the process can pass through the membrane 9 into the anode chamber 5. In addition, the anolyte has a pH of more than 12. In this respect, the hydroxide ions are provided which are oxidized at the anode 2. By passing the catholyte into the cathodic gas separator 8, H.sub.2O and the reduced auxiliary can be brought into contact with the catalyst 4. As a result, the reduced auxiliary is oxidized; hydrogen is formed from the H.sub.2O.

[0061] In the embodiment according to FIG. 1, the catholyte, together with the H.sub.2O and the reduced auxiliary can be continuously introduced into the cathodic gas separator 8. Gaseous hydrogen can thereby be continuously removed from the gas separator 8.

[0062] FIG. 2 shows a second embodiment of a device 1 for electrolysis. This device 1 is described only to the extent that it deviates from the embodiment according to FIG. 1. Thus, the device 1 according to FIG. 2 additionally comprises a buffer container 10. This makes it possible to introduce the H.sub.2O and the reduced auxiliary discontinuously into the gas separator 8, and to withdraw the gaseous hydrogen discontinuously from the gas separator 8.

[0063] FIG. 3 shows a third embodiment of a device 1 according to the invention for electrolysis. The device 1 comprises a first electrolytic cell 11 and a second electrolytic cell 14. The first electrolytic cell 11 and the second electrolytic cell 14 each comprise an anode chamber 5 having an anode 12,15 arranged therein, and a cathode chamber 6 having a cathode 13,16 arranged therein. The anode chamber 5 and the cathode chamber 6 are each separated from one another by a membrane 9. The anode 12 of the first electrolytic cell 11 and the cathode 16 of the second electrolytic cell 14 are each connected to a voltage source. The cathode 13 of the first electrolytic cell 11 and the anode 15 of the second electrolytic cell 14 are electrically conductively connected to one another. Furthermore, the device 1 comprises a gas separator 8 in each case for the anode 12 of the first electrolytic cell 11 and the cathode 16 of the second electrolytic cell 14. A catalyst 4 made of platinum is arranged in the cathodic gas separator 8. Analogously to FIG. 2, a buffer container 10 could also be connected between the second electrolytic cell 14 and the cathodic gas separator 8.

[0064] The device 1 according to FIG. 3 can also be used to produce oxygen and hydrogen. To this end, an anolyte comprising hydroxide ions is brought into contact with the anode 12 of the first electrolytic cell 11 by introducing the anolyte into the anode chamber 5 of the first electrolytic cell 11. A first catholyte is brought into contact with the cathode 13 of the first electrolytic cell 11 by introducing the first catholyte into the cathode chamber 6 of the first electrolytic cell 11. The first catholyte contains ferrocyanine as a first auxiliary. An electrical voltage can be applied between the anode 12 of the first electrolytic cell 11 and the cathode 16 of the second electrolytic cell 14, via the voltage source. This also results in an electrical voltage between the anode 12 and the cathode 13 of the first electrolytic cell 11. As a result, the hydroxide ions in the anolyte are oxidized at the anode 12 of the first electrolytic cell 11, with oxygen also being formed. The first auxiliary is reduced at the cathode 13 of the first electrolytic cell 11.

[0065] The first catholyte, together with the first reduced auxiliary, is brought into contact with the anode 15 of the second electrolytic cell 14; a second catholyte is brought into contact with the cathode 16 of the second electrolytic cell 14. The second catholyte contains a second auxiliary formed by hydroxyquinones. The electrical voltage applied by the voltage source also results in an electrical voltage between the anode 15 and the cathode 16 of the second electrolytic cell 14. As a result, the reduced first auxiliary is oxidized at the anode 15 of the second electrolytic cell 14, and the second auxiliary is reduced at the cathode 16 of the second electrolytic cell 14. The remaining process sequence is as in the embodiments according to FIG. 1 or 2.

[0066] By means of the auxiliary, the electrolysis can be carried out under low pressure, and hydrogen can still be obtained at high pressure. This facilitates the construction of the electrolytic cell and prevents an efficiency-reducing gas cross-permeation.

LIST OF REFERENCE SIGNS

[0067] 1 device [0068] 2 anode [0069] 3 cathode [0070] 4 catalyst [0071] 5 anode chamber [0072] 6 cathode chamber [0073] 7 electrolytic cell [0074] 8 gas separator [0075] 9 membrane [0076] 10 buffer container [0077] 11 first electrolytic cell [0078] 12 anode of the first electrolytic cell [0079] 13 cathode of the first electrolytic cell [0080] 14 second electrolytic cell [0081] 15 anode of the second electrolytic cell [0082] 16 cathode of the second electrolytic cell