DE102019211942A1 - Process for the electrochemical conversion of an educt gas on a gas diffusion electrode with differential pressure determination - Google Patents

Abstract

A method is described for the electrochemical conversion of an educt gas on a gas diffusion electrode, in which the differential pressure (Δp) is measured and this is modulated, a distinction being made between at least an operating differential pressure (ΔpB) and a regeneration differential pressure (ΔpR) and the The regeneration differential pressure (ΔpR) is less than the operating differential pressure (ΔpB).

Description

The present invention relates to a method for the electrochemical conversion of an educt gas on a gas diffusion electrode, comprising the measurement of the pressure on the gas side of the gas diffusion electrode and the pressure on the electrolyte side of the gas diffusion electrode.

Gas diffusion electrodes are currently used as cathodes in carbon dioxide electrolysis. Similar to the oxygen-consuming cathode in chlor-alkali electrolysis, the largest possible three-phase boundary between the liquid electrolyte, the gaseous carbon dioxide and the solid particles of an electrode catalyst is used here. In known processes for carbon dioxide electrolysis, an electrolysis cell with two electrolyte compartments, separated by an ion exchange membrane, is used. The anode is for example a platinum electrode or consists of an iridium mixed oxide. The cathode is designed as a gas diffusion electrode, that is to say it is in contact with an electrolyte on the one hand, and is supplied with carbon dioxide or a carbon dioxide-containing feed gas flow on the other. The gas diffusion electrode may contain various metals and metal compounds that have a catalytic effect on the carbon dioxide reduction reaction.

• Kathode: CO₂ + 2 e^- + H₂O → CO + 2 OH^- (Gleichung 1)
• Anode: 6 H₂O → O₂ + 4e^- + 4 H₃O⁺ (Gleichung 2)

The electrochemical conversion of carbon dioxide can take place, for example, on silver electrodes according to the following reaction equation:

• Cathode: CO ₂ + 2 e ^- + H ₂ O → CO + 2 OH ^- (equation 1)
• Anode: 6 H ₂ O → O ₂ + 4e ^- + 4 H ₃ O ⁺ (Equation 2)

The cathode reaction described then takes place when suitable catalysts are present on the cathode surface that promote the reduction of carbon dioxide to plastic monoxide. In addition, all requirements must be met, starting with the presence of carbon dioxide, sufficient active cathode surface, sufficient mass transfer rate of the educt gas and removal of the product gas.

Gas diffusion electrodes used to date consist of a carrier matrix, materials for mechanical stabilization, such as carrier grids, and a catalyst material. In addition, auxiliaries for adjusting the porosity or hydrophobicity can be included. When such a gas diffusion electrode is operated, a gas flow flows behind the porous electrode on the gas side, in particular with the feed gas, and the product gas either leaves the electrolysis cell on the gas side, which is referred to as flow-by operation, or the product gas leaves the electrolysis cell on the electrolyte side, which is called flow -through operation is referred to, wherein the reactant gas diffuses through the pores of the gas diffusion electrode, is converted, and the product gas, z. B. dissolved in the electrolyte, the electrolyte side leaves the electrolytic cell.

Both operating modes merge when the differential pressure, i.e. the gas pressure, is increased compared to the electrolyte pressure. As a rule, an increase in the performance of the electrolysis cell is achieved with a higher pressure on the gas side, since the surface on the gas side is then not covered by electrolyte that has penetrated by capillary action. In addition, a higher pressure on the gas side has the effect that the electrolyte paths are shortened to the detriment of the gas phase diffusion paths, which are usually less resistant. It has now been shown that during operation in both operating method variants, the pores of the gas diffusion electrode as material transport paths are closed by deposited salts and poorly soluble electrolyte components. Salts and dissolved electrolyte components precipitate on the gas-side surface of the electrode. Thus, the reactant gas to be converted no longer reaches all the catalytic centers in sufficient quantities, since these are either covered by the electrolyte or by deposited solid substances. The gas diffusion electrode continuously loses its conversion rate up to the point at which, in the absence of catalytic centers, hydrogen electrolysis begins. In flow-through operation, this can also lead to an increase in differential pressure above the mechanically tolerable limit.

Attempts have hitherto been made to improve the carbon dioxide electrolysis process in such a way that the differential pressure is selected in such a way that complete drying out of the gas side is avoided. However, this is basically not a suitable solution in flow-through operation; in flow-by operation, it causes a significantly poorer performance, since too many catalytic centers are covered by electrolytes and cannot be reached by the reactant gas.

Consequently, it is technically necessary to propose an improved solution which avoids the disadvantages known from the prior art. In particular, the solution to be proposed should enable a reduction in carbon dioxide by means of an electrolysis cell with a gas diffusion electrode, which has a good conversion rate during operation, and minimizes the salinization of the material transport routes.

These objects on which the present invention is based are achieved by a method according to patent claim 1 and by a device according to patent claim 6. Advantageous embodiments of the invention are the subject of the subclaims.

The method according to the invention for the electrochemical conversion of an educt gas comprising carbon dioxide on a gas diffusion electrode, comprises the measurement of the pressure difference between the gas side of the gas diffusion electrode and the electrolyte side of the gas diffusion electrode, further comprises the modulation of the differential pressure, with at least one operating differential pressure Δp _B and a regeneration differential pressure Δp _R is distinguished. The regeneration differential pressure is lower than the operating differential pressure. The modulation can include differential pressure control and / or differential pressure regulation.

The differential pressure can be regulated as described below, but it can also be set in a targeted manner, for example by means of a defined gas flow that is backed up at a throttle point. The differential pressure is expediently set or regulated with a sufficiently precise level.

The pressure measurements take place e.g. at the electrolysis cell outlet, i.e. H. on the gas side of the gas diffusion electrode at the gas outlet and on the electrolyte side of the gas diffusion electrode at the electrolyte outlet.

A differential pressure sensor can be used to measure the pressures or the pressures can be measured using two absolute pressure sensors p _gas and p _el and from this the difference can be formed; knowledge of the absolute pressures is not required.

The distinction between operating pressure and differential pressure has the advantage that a differential pressure that is geared towards optimized cell performance can very well be set, but the salinisation of the gas diffusion electrode pores can be effectively counteracted when the regeneration differential pressure is set. The regulation of the differential pressure also has the advantage that no continuously decreasing conversion rate has to be accepted during the operating period and the operating point of the gas diffusion electrode remains stable.

By lowering the differential pressure, an overpressure is created on the electrolyte side, as a result of which electrolyte penetrates further into the pores and dissolves salt deposited there again until it reaches the gas-side surface and exits the pores there. For example, the gas-side surface of the gas diffusion electrode can be flushed in the regeneration step in order to detach the salt on the surface. In particular, an additional cleaning step can be dispensed with and the lowering of the differential pressure for the regeneration of the electrolytic cell lasts so long that the gas-side surface is purged and cleaned solely by the emerging electrolyte. The continuous flow of educt gas can also be used to detach the salt from the surface. After sufficient cleaning, the differential pressure can then be set back to the operating differential pressure.

In a variant of the method, the regeneration differential pressure is set as a function of time after a predefinable operating time. Such a time control can be based on an empirical value. For example, a regeneration cycle can be used after one day of operation.

In an advantageous variant of the method, the determination of the Faraday efficiency is included by measuring the electrolysis yield and the regeneration differential pressure is set after the electrolysis yield falls below a limit value.

Die Faraday-Effizienz FE_i ist das Verhältnis aus an der Umsetzung von CO₂ zu CO beteiligten Elektronen zu eingesetzten Elektronen (Zellenstrom). Sie wird auf Messgrößen zurückgeführt (Gasfluss ${\dot{V}}_{CO},$

Stromdichte j, Zellenfläche A und weiteren Messgrößen und Konstanten).The Faraday efficiency is calculated according to the well-known rules of electrochemistry: $$\text{F.}{\mathrm{E.}}_i=\frac{{\dot{V}}_i}{\left(\frac{j\mathrm{A.}}{\mathrm{F.}}\right)\left(\frac{1}{z_i}\right)\left(\frac{ℝT}{p}\right)}$$

The Faraday efficiency FE _i is the ratio of the electrons involved in the conversion of CO ₂ to CO to the electrons used (cell current). It is traced back to measured variables (gas flow ${\dot{V}}_{\mathrm{C.}O},$

Current density j, cell area A and other measured variables and constants).

For example, the Faraday efficiency of the electrolysis cell should not drop below 80%. This efficiency-dependent control between operating and regeneration differential pressure has the advantage that, for. B. a varying product composition due to a decreasing product rate due to the salting of the catalytic centers is avoided.

In addition, gas diffusion electrodes from different manufacturing processes can also be subject to fluctuations in quality, which lead to different operating times. Accordingly, by measuring the product composition, it is also possible to react individually to the system. Also the problem of aging Gas diffusion electrode is avoided through efficiency-dependent regeneration phases.

After sufficient regeneration and cleaning of the gas diffusion electrode surface, the differential pressure can then be raised again to the operating differential pressure value. The cell can be operated regularly until the measurement of the Faraday efficiency falls below the specified limit value again. Ideally, the limit value is selected so high that the salinization cannot have caused any irreparable damage to the gas diffusion electrode. The limit value is particularly preferably selected such that a constant product gas composition is ensured in the operating mode.

As part of the regeneration step, the cell can continue to be operated with electricity, for example. A changed product gas composition is then either consciously accepted or the product gas that arises during the regeneration step is diverted from the electrolysis cell separately from the desired product gas through a shuttle valve. Alternatively, the cell can be de-energized during the regeneration step and the corresponding voltage for the electrolysis operation is only applied again after the differential pressure has been raised to the operating differential pressure.

The method described has the advantage that the useful life of the electrochemical process is no longer limited in time by the salinization.

In a further advantageous variant of the method, the regeneration differential pressure is set after a presettable pressure value has been exceeded on the gas side of the cathode. This method makes use of the fact that the salinization hinders the gas flow through the gas diffusion electrode in flow-through operation, but also the gas flow through the cathode gas space in flow-by operation. The increase in pressure associated with the salinization is then used as the triggering signal for the regeneration cycle. A differential pressure of zero is preferably set for the regeneration phase, at which the salt formed dissolves quickly and is washed off.

The regeneration of the gas diffusion electrode takes place in situ and is accordingly simple and efficient. There are no additional costs for the regeneration operation described. No additional components are required as built-in components in the electrolysis cell.

The described regulation between the operating differential pressure and the regeneration differential pressure extends the service life of the electrolysis system because, for example, high mechanical loads caused by an increasing differential pressure, in particular in flow-through operation, are avoided.
Another advantage of the method described is a significantly reduced maintenance effort.

In a particularly advantageous variant of the method, the acquisition of the time intervals between the triggered regeneration processes is also included, as well as the determination of an ideal time interval for setting the regeneration differential pressure. On the basis of the time intervals between the triggered regeneration processes, the cell operation is set in such a way that salinisation occurs less frequently or no longer at all. This ensures operation with optimal product yield close to the limit of salinization. Despite this self-optimization component of the pressure control, pressure and efficiency threshold values are still used for process monitoring and process security. Particularly preferably, in the self-optimized method, exceeding pressure or efficiency limit values are coupled to the triggering of an acoustic warning signal.

This process has the advantage of a consistently high product yield. In addition, the efficiency of the electrolysis system can be optimally used for the electrochemical conversion of carbon dioxide, since the operating differential pressure is optimally set for the product yield without any compromise to avoid salinization, and the salinization problem is overcome by the in situ regeneration steps. Accordingly, by means of the method described, continuous operation is possible without the running time limit of the gas diffusion electrode due to salinity.

In an alternative variant of the method for the electrochemical conversion of an educt gas at a gas diffusion electrode, the gas diffusion electrode is an anode.

The device according to the invention for the electrochemical conversion of an educt gas, comprising carbon dioxide, on a gas diffusion electrode has at least one electrolysis cell, an electrolyte line, at least one pump, an anode and a cathode, the cathode being designed as a gas diffusion electrode and being arranged in a cathode chamber which is divided by the cathode into a cathode gas space and a catholyte space. The device also has a first gas inlet into the cathode gas space for a feed gas containing carbon dioxide and a differential pressure sensor for determining the pressure difference between the cathode gas space and catholyte space, and a differential pressure control unit and / or control unit for modulating the differential pressure.

This device has the advantage of ensuring independent, reliable electrolysis operation even with quality or process parameter control. This is particularly useful when several cells are connected, e.g. B. in a cell stack advantageous. In addition, the electrolysis system does not need any additional system components in the electrolysis cell, such as nozzles for humidifying the feed gas or cleaning nozzles in the gas space.

It is also possible to implement the alternative method variant described above in a device for the electrochemical conversion of a reactant gas on a gas diffusion electrode, comprising at least one electrolysis cell, an electrolyte line, at least one pump, a cathode and an anode, which anode is used as a gas diffusion electrode ( GDA ) is designed, arranged in an anode space which is divided by the anode into an anode gas space and an anolyte space, comprising a first gas inlet into the anode gas space for a feed gas, and comprising a differential pressure sensor for determining the pressure difference between the anode gas space and anolyte space and, for example, a differential pressure -Control unit to control the differential pressure.

For example, the differential pressure control unit of the device according to the invention is connected to at least one data line via which signals can be sent to a pump. Preferably, the device further comprises at least one actuator, e.g. B. an actuator which has a water column container with a connecting line between the water column container and the gas outlet of the cathode compartment. These embodiments of the device described have the advantage that the differential pressure can be set in situ, for example via the hydrostatic pressure of the water column in the water column container, and the differential pressure can always be adapted to an optimal performance of the electrochemical conversion process.

In a further advantageous embodiment of the invention, the differential pressure control unit of the device is designed to set at least one operating differential pressure and a regeneration differential pressure, the regeneration differential pressure being lower than the operating differential pressure.

In a particularly advantageous embodiment, the operating differential pressure in particular is continuously regulated so that the continuous salinization and consequent displacement of the active zone within the gas diffusion electrode pores is continuously counteracted until the pressure limit value or the efficiency limit value or the corresponding point in time for switching to the regeneration differential pressure is reached. The regeneration differential pressure is usually 0.

In an exemplary embodiment of the device, this comprises a catholyte feed line and an anolyte feed line. For example, an electrolyte line splits into a catholyte feed line and an anolyte feed line. For this purpose, for example, a single pump can be provided in the electrolyte line or one pump each in the catholyte feed line and anolyte feed line.

The device advantageously comprises a separator which separates the cathode compartment and the anode compartment from one another. The cathode gas space can for example be designed as a pressure chamber. Alternatively, the cathode gas space is designed as a gas gap.

In a further advantageous embodiment of the invention, the device comprises an electrolyte reservoir, in which catholyte line and anolyte line are brought together and to which the electrolyte line is connected. Such an electrolyte reservoir is used to balance ions and pH in the electrolyte circuit.

In a particularly advantageous embodiment variant of the invention, the device comprises a controllable valve for adjusting the flow rate of the educt gas, which valve is connected to the differential pressure control unit via at least one data line. As an alternative or in addition to regulating the differential pressure via the electrolyte inflow, the educt gas flow can be influenced via the controllable valve. For example, the flow rate of the reactant gas can be increased in the regeneration step for the purpose of flushing the electrode surface.

In the following, the invention is described in an exemplary manner with reference to FIG 1 to 6th described.

Will the cell was using differential pressure Δp operated, e.g. in flow-through operation, salt forms on the gas side. The differential pressure is used for regeneration Δp reduced to O, the salt dissolves again and can be washed off.

In the 1 is an example of an electrolysis trainer for setting the differential pressure Δp shown. Two separate electrolyte circuits 13 , 15th are via a cathode or anode-side pump 4th realized the electrolyte from a reservoir 3 in the cathode II or anode compartment III the electrolytic cell 20th and back to the reservoir 3 promote. Both compartments II , III are separated from each other by a membrane SEP. Educt gas flows through a gas supply line 11 into the cell 20th and is converted to carbon monoxide CO at the gas diffusion electrode, for example containing silver particles, according to equations 1 and 2 mentioned above. Hydrogen gas H _{2 is produced} as a by-product. The gases leave via the gas outlet 12 finally the gas compartment I. the cell 20th . The differential pressure sensor 1 between gas outlet 12 and catholyte outlet 14th is switched, measures the pressure conditions on both sides of the gas diffusion electrode GDK as a difference value Δp . This difference value Δp = p _gas − p _El can be influenced, for example, via the hydrostatic pressure in a water column and advantageously adjusted for the electrochemical reaction. The hydrostatic pressure increases with the depth of immersion of the gas-out tube in the water column container. The higher the hydrostatic pressure, the higher the differential pressure Δp between the gas and catholyte side of the gas diffusion cathode GDK , and vice versa.

This example shows the setting of the differential pressure Δp Via the hydrostatic pressure of a water column between the gas and electrolyte side of a gas diffusion electrode GDK .

In 2 is schematically the displacement of the active zone 10 with the differential pressure Δp outlined. The higher the differential pressure Δp the further the active zone shifts 10 inside the gas diffusion electrode GDK towards the catholyte side el . The lower the differential pressure Δp becomes, the further it shifts towards the gas side G .

3 shows a diagram in which the Faraday efficiency FE is plotted in% over the operating time t in h. The phases i, operating differential pressure Δp _B of, for example, 30 mbar, ii, regeneration differential pressure Δp _R of eg 13 mbar and iii, operating differential pressure Δp _B run through eg 30 mbar. The cell is operated at, for example, a current density of 200 mA / cm ² .

The differential pressure Δp is reached after an operating time t of approx. 2 hours from the operating differential pressure Δp _B from eg 30 mbar to the regeneration differential pressure Δp _R reduced by, for example, 13 mbar. The Faraday efficiency for the carbon monoxide formation FE-CO decreases from 91% to 85% and for the hydrogen formation FE-H _{2 it increases} from 9% to 15%. According to the model picture 2 thus becomes the active zone 10 towards the gas side G postponed. The model shift is supported by the observation that instantaneous with the differential pressure decrease from the operating differential pressure Δp _B on the regeneration differential pressure Δp _R a permeate flow from the cathode II in the gas compartment I. the cell 20th begins. A drop formation on the gas-side GDK surface can be observed. If you increase the differential pressure Δp then back to the operating differential pressure Δp _B , the Faraday efficiencies FE-CO and FE-H2 regenerate and the permeate flow disappears after a few seconds.

4th shows a further diagram in which the Faraday efficiency FE is plotted in% over the operating time t in h, for a further exemplary embodiment which advantageously uses the differential pressure variation described above in order to carry out an electrode wash during the test.

At time A there is an increased salt concentration in the gas space I. the cell 20th observed. If the salt concentration continued to rise, this could clog the gas space I. and ultimately lead to the complete breakdown of carbon monoxide evolution. At time B, the differential pressure was Δp analogous to the experiment in 3 humiliated. Permeate water from the cathode compartment II now penetrates the gas space I. and dissolves the accumulated salt there (point in time B and C), which is finally released via a gas-out tube, for example 12 into a collecting reservoir (e.g. the water column container 2 ) is transported away. Then the differential pressure Δp again increased. The Faraday efficiency FE-CO for carbon monoxide formation and FE-H ₂ for hydrogen formation finally regenerate again and the gas space I. is freed from a blocking salt concentration (time D).

• Beispielsweise kann die Differenzdruck-Regeleinheit 5 in Form eines Rechners realisiert sein. Dieser ist verbunden mit einem Stellglied 6, welches z.B. ein Wassersäulenbehältnis 2 umfasst, ein Ventil für den Gaszulauf und/oder eine Pumpe 4 für die Elektrolytdurchlaufgeschwindigkeit. Die Regelstrecke 7 umfasst ein Mehrgrößensystem und ist begrenzt durch die Drücke p_gas und p_el . Außerdem ist bevorzugt eine Eingabe-Bedienungsschnittstelle 8 vorgesehen. Zur Prozessüberwachung 9 wird beispielsweise ein Computerprogramm zur Führung eines Protokolls, Ausgabe von Fehlermeldungen und/oder akustischen Signalen sowie zur Ausführung einer Notabschaltung genutzt.

In 5 A flow chart is shown to clarify the differential pressure control:

• For example, the differential pressure control unit 5 be implemented in the form of a computer. This is connected to an actuator 6th , which, for example, a water column container 2 includes a valve for the gas inlet and / or a pump 4th for the electrolyte flow rate. The controlled system 7th comprises a multivariable system and is limited by the pressures p _gas and p _el . In addition, an input control interface is preferred 8th intended. For process monitoring 9 For example, a computer program is used to keep a log, output error messages and / or acoustic signals and to carry out an emergency shutdown.

A controllable valve for adjusting the flow rate of the educt gas is used as an actuator 6th via at least one data line 41 with the differential pressure control unit 5 connected. Via the data line 41 For example, process parameters, combinatorial, analog or sequential such as flow rate, composition, pressure, pH value can be passed on. Another data line 42 is e.g. for feedback such as Signals (in particular binary signals), measured values (in particular analog signals) provided, compare 6th . Another data line is preferred 43 for e.g. feedback to process monitoring 9 intended.

As an alternative or in addition to regulating the differential pressure Δp The electrolyte flow can be controlled via the controllable valve 6th the feed gas flow can be influenced. For example, in regeneration step ii, the flow rate of the educt gas can be increased for the purpose of flushing the electrode surface.

List of reference symbols

Δp

Differential pressure

P _gas

Pressure on the gas side of the GDE , measured at the gas outlet

P _el

Pressure on the electrolyte side of the GDE , measured at the electrolyte outlet

1

Differential pressure sensor

2

Water column container for setting the differential pressure

3

Electrolyte reservoir

4th

pump

5

Differential pressure control unit, e.g. computer

6

Actuator (includes e.g. water column container 2 , Valve for gas inlet, pump 4th for electrolyte flow rate)

7th

Controlled system, multi-variable system, limitation by p _gas and p _el

8th

Input operating interface

9

Process monitoring with computer program for keeping a protocol, outputting error messages and / or acoustic signals, executing an emergency shutdown

Δh

Change in height of water column

Δp

Actual value / measured value differential pressure

Δp _{B / R}

Reference variable

Δp _R

Regeneration differential pressure

Δp _B

Operating differential pressure

d (t)

Disturbance, e.g. due to the composition of the electrolyte, gas bubble formation in the electrolyte or salinity of the gas diffusion cathode GDK

GDE

Gas diffusion electrode (general)

GDK

Gas diffusion cathode

GDA

Gas diffusion anode

10

Active zone

11

Feed gas inlet

12

Gas outlet

13

Catholyte inlet

14th

Catholyte outlet

15th

Anolyte inlet

16

Anolyte outlet

20th

Cell for the electrochemical conversion of a product gas / location of the process sequence of the electrochemical conversion

21st

Feed gas line

22nd

Product gas line

22b

Connection line to the water column container

23

Catholyte feed

24

Catholyte discharge

24b

Connection line to the differential pressure sensor

25th

Anolyte feed line

26th

Anolyte discharge

G

Gas compartment

el

Catholyte compartment

31

Material input, includes e.g. reactant gas, electrolyte

32

Product output, includes e.g. electrolysis products, by-products, circulating material, redeemed reactant gas

41

Data line, e.g. for transferring process parameters combinatorially, analogously or sequentially such as flow rate, composition, pressure, pH value

42

Data line, e.g. for feedback such as signals (especially binary signals), measured values (especially analog signals)

43

Data line, e.g. for feedback to process monitoring

I.

Cathode gas space

II

Catholyte dream

III

Anode compartment

Claims (15)

A method for the electrochemical conversion of an educt gas at a gas diffusion electrode (GDK) comprising determining the differential pressure Δp, further comprising modulating the differential pressure (Δp), with at least a distinction between an operating differential pressure (Δp _B ) and a regeneration differential pressure (Δp _R ) and the regeneration differential pressure (Δp _R ) is less than the operating differential pressure (Δp _B ). Procedure according to Claim 1 in which the regeneration differential pressure (Δp _R ) is set as a function of time after a predefinable operating time. Method according to one of the preceding claims, further comprising determining the Faraday efficiency by measuring the electrolysis yield, the regeneration differential pressure (Δp _R ) being set after the electrolysis yield falls below a limit value. Method according to one of the preceding claims, in which the regeneration differential pressure (Δp _R ) is set after a presettable pressure value (p _{gas, lim} ) has been exceeded on the gas side of the cathode (GDK). Method according to one of the preceding Claims 3 and / or 4 comprising the detection of the time intervals between the regeneration processes triggered and the determination of an ideal time interval for setting the regeneration differential pressure (Δp _R ). Device for the electrochemical conversion of an educt gas on a gas diffusion electrode comprising at least one electrolysis cell (20), an electrolyte line (13), at least one pump (4), an anode (A) and a cathode, which cathode is designed as a gas diffusion electrode (GDK) in a cathode compartment, which is divided by the cathode into a cathode gas compartment (I) and a catholyte compartment (II), comprising a first gas inlet (11) into the cathode gas compartment (I) for a carbon dioxide-containing feed gas, and comprising a differential pressure sensor (1) for determination the pressure difference (Δp) between cathode gas space (I) and catholyte space (II) and a differential pressure control unit and / or control unit (5) for modulating the differential pressure (Δp). Device according to Claim 6 wherein the differential pressure control unit (5) is connected to at least one data line (41) via which signals can be sent to a pump (4). Device according to one of the preceding Claims 6 or 7th , comprising at least one actuator (6), for example having a water column container (2) with a connecting line (22b) between the water column container (2) and the gas outlet of the cathode gas space (I). Device according to one of the preceding Claims 6 to 8th wherein the differential pressure control unit (5) is designed to set at least one operating differential pressure (Δp _B ) and a regeneration differential pressure (Δp _R ), the regeneration differential pressure (Δp _R ) being less than the operating differential pressure (Δp _B ). Device according to one of the preceding Claims 6 to 9 , comprising a catholyte feed line (13) and an anolyte feed line (15). Device according to one of the preceding Claims 6 to 10 , comprising a separator (SEP) which separates the cathode compartment (I / II) and the anode compartment (III) from one another. Device according to one of the preceding Claims 6 to 11 , wherein the cathode gas space (I) is designed as a pressure chamber. Device according to one of the preceding Claims 6 to 11 , wherein the cathode gas space (I) is designed as a gas gap. Device according to one of the preceding Claims 6 to 13 comprising an electrolyte reservoir (3). Device according to one of the preceding Claims 6 to 14th , with a controllable valve for adjusting the flow rate of the educt gas, which valve is connected to the differential pressure control unit (5) via at least one data line (41).

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