METHOD FOR PRODUCING HYDROGEN AND OXYGEN BY MEANS OF AN ELECTROLYZER

Abstract

A method for generating hydrogen and oxygen using an electrolyzer, including at least one anode chamber having an anode and at least one cathode chamber having a cathode, wherein the at least one anode and the at least one cathode are energized by a modulated current and the generation of hydrogen and oxygen takes place within the electrolyzer using a defined pulse pattern sequence, which is formed from at least one pulse pattern.

Claims

1-9. (canceled)

10. A method for producing hydrogen and oxygen using an electrolyzer, comprising at least one anode chamber having an anode and at least one cathode chamber having a cathode, the method comprising the steps of: energizing the at least one anode and the at least one cathode by a modulated current; and executing the generation of hydrogen and oxygen within the electrolyzer by applying a defined pulse pattern sequence that is formed from at least one pulse pattern.

11. The method according to claim 10, including supplying the modulated current from at least one pulse rectifier that has a negative pole electrically connected to the at least one cathode and a positive pole electrically connected to the at least one anode.

12. The method according to claim 11, wherein the at least one pulse rectifier is electrically connected to a central control unit that controls and/or regulates the generation of hydrogen and oxygen.

13. The method according to claim 12, including transmitting the at least one pulse pattern in the pulse pattern sequence from the central control unit to the at least one pulse rectifier.

14. The method according to claim 10, wherein the at least one pulse pattern in the pulse pattern sequence comprises at least one cathodic pulse, which is defined by a pulse duration, and at least one pulse interval.

15. The method according to claim 14, wherein the pulse duration of the cathodic pulse is 200 μs to 500 ms.

16. The method according to claim 14, wherein a pulse interval between two sequential cathodic pulses lies in a range of 0.01-times to 10-times the cathodic pulse.

17. The method according to claim 10, wherein the electrolyzer is a membrane-based electrolyzer.

18. A method for generating hydrogen and oxygen in an electrolyzer using a modulated current by applying a defined pulse pattern sequence that is formed from at least one pulse pattern.

Description

[0029] The invention, and the technical field, are described in greater detail hereinafter with reference to the figures. It should be observed that the invention is not to be limited by the exemplary embodiments illustrated. In particular, unless explicitly indicated otherwise, it is also possible for sub-aspects of the content described in the figures to be extracted and combined with other constituents and elements of knowledge from the present description and/or figures. In particular, it should be observed that the figures, and particularly the scale ratios represented, are schematic only. Identical reference numbers identify identical objects such that, optionally, comments on other figures can additionally be considered. In the figures:

[0030] FIG. 1 shows an electrolyzer for producing hydrogen and oxygen, in a schematic representation,

[0031] FIG. 2 shows a first variant of embodiment of a pulse pattern, which can form part of the pulse pattern sequence,

[0032] FIG. 3 shows a second variant of embodiment of a pulse pattern, which can form part of the pulse pattern sequence,

[0033] FIG. 4 shows a third variant of embodiment of a pulse pattern, which can form part of the pulse pattern sequence, and

[0034] FIG. 5 shows a fourth variant of embodiment of a pulse pattern, which can form part of the pulse pattern sequence.

[0035] FIG. 1 shows a layout of an electrolyzer 1 known from the prior art for producing hydrogen and oxygen, by means of which water can be electrolytically split into the two products. The electrolyzer 1 represented here is configured in the form of a PEM electrolyzer, and comprises an anode chamber 2 having an anode 3, and a cathode chamber 4 having a cathode 5. Between the two electrodes 3, 5, a semi-permeable membrane 6 is arranged, which is permeable to protons, as symbolized by the arrow 7.

[0036] The anode chamber 2 comprises a water infeed 8 via which, preferably continuously, water or an electrolyte is admitted to the anode chamber 2, and an outlet opening 9 via which the oxygen generated can be extracted. As can further be seen from the representation according to FIG. 1, the cathode chamber 4 also comprises an outlet opening 10, via which the hydrogen generated in the electrolyzer 1 can then be extracted.

[0037] For the execution of the production process, the anode 3 and the cathode 5 are energized by means of a modulated current, which is supplied by a pulse rectifier 11, which can be configured using switched-mode power supply technology. The pulse rectifier 11 is electrically connected via its negative pole to the cathode 5, and the positive pole is electrically connected to the anode 3. By means of the modulated current, both electrodes 3, 5 can be energized, such that the process is executable by application of a defined pulse pattern sequence 12, which is formed from individual pulse patterns 13.

[0038] Advantageously, the pulse rectifier 11 is electrically connected to a central control unit 14, by means of which the respective desired pulse pattern 13 in the pulse pattern sequence 12 can be transmitted thereto.

[0039] FIGS. 2 to 5 show different variants of embodiment of pulse patterns 13 which form part of the pulse pattern sequence 12 in accordance with which the present production process can be executed.

[0040] FIG. 2 represents a variant of embodiment of a pulse pattern 12, which shows a recurrent pulse pattern 12 which is configured equivalently in terms of current magnitude (I) and time (t). The pulse pattern 12 shows a number of sequential square-wave cathodic pulses of pulse duration (t.sub.1), each having the identical current strength (I). The individual pulses are arranged within the pulse pattern 12 mutually separated by a pulse interval (t.sub.2), wherein t.sub.2=t.sub.1.

[0041] By way of distinction, the broken line in FIGS. 2 to 5 represents a temporally constant cathodic current, of the type employed in conventional direct current electrolysis (DC electrolysis).

[0042] FIG. 3 represents a variant of embodiment of a pulse pattern 12, which also shows a recurrent pulse pattern 12 which is configured equivalently in terms of current magnitude and time. The pulse pattern 12 shows a number of sequential crenelated cathodic pulses of pulse duration (t.sub.3), which are arranged in each case mutually separated by a pulse interval (t.sub.4), wherein t.sub.4=½ t.sub.1. Each of the crenelated pulses comprises three sub-pulses, each having an equal pulse duration (t.sub.1) and an equal current strength (I). As can be seen from the pulse pattern 12, the individual sub-pulses are mutually separated by a pulse interval (t.sub.2), which has a holding current to a value of ⅔ of the current strength of the sub-pulse. The pulse duration (t.sub.1) and the pulse interval (t.sub.2) are of equal length (t.sub.2=t.sub.1) here.

[0043] FIG. 4 represents a further pulse pattern 12, which has a recurrent pulse pattern 12 which is configured equivalently in terms of current magnitude and time. The pulse pattern 12 shows a number of sequential square-wave cathodic pulses of pulse duration (t.sub.1), each having the identical current strength (I). The individual pulses are arranged within the pulse pattern 12 mutually separated by a pulse interval (t.sub.2), wherein t.sub.2=t.sub.1. In the present case, the holding current in the pulse interval (t.sub.2) is equal to ¼ of the current strength of the pulse.

[0044] FIG. 5 shows a further variant of embodiment of a pulse pattern 12. The pulse pattern 12 shows an alternating sequence of square-wave cathodic pulses of different current strength. The first two pulses respectively have an equal pulse duration (t.sub.1) and the identical current strength (I). The current magnitude of the next two pulses is reduced by one half (I.sub.2=½ I.sub.1). All the pulses are mutually separated by a pulse interval (t.sub.2), wherein a relationship of t.sub.2=2 t.sub.1 applies.

EXAMPLES

[0045] A PEM electrolyzer was employed, as represented by the basic layout according to FIG. 1. An aqueous NaOH solution was employed as an electrolyte. The electrolyzer was operated with a current strength of 0.5 A/cm.sup.2 and at a cell voltage of approximately 2 V.

[0046] In a comparative example, water was firstly broken down into oxygen and hydrogen by conventional direct current electrolysis, wherein a hydrogen volume of 50 ml/min was able to be detected.

[0047] In the example according to the invention, the electrolyzer was energized by means of a modulated current, wherein a pulse pattern sequence was employed, which consisted of the pulse pattern represented in FIG. 2. A hydrogen volume of 60 ml/min was able to be detected with an equal input electric power.

LIST OF REFERENCE NUMBERS

[0048] 1 Electrolyzer [0049] 2 Anode chamber [0050] 3 Anode [0051] 4 Cathode chamber [0052] 5 Cathode [0053] 6 Membrane [0054] 7 Arrow/direction of proton transport [0055] 8 Water infeed [0056] 9 Oxygen outlet opening [0057] 10 Hydrogen outlet opening [0058] 11 Pulse rectifier [0059] 12 Pulse pattern sequence [0060] 13 Pulse pattern [0061] 14 Control unit