Method and device for the electrolysis of co 2 and / or co

Abstract

The invention relates to a method (1, 10) and a device (100) for the electrolysis of CO2 and / or CO. In the method (1, 10), a copper-containing catalyst is used and a copper-oxidising oxidant is supplied to the catalyst (S3, S14). The device (100) comprises a copper-containing catalyst (5), an oxidant supply means (15) and a control unit (14) designed to control the oxidant supply.

Description

[0001] Description

[0002] Method and apparatus for the electrolysis of CO2 and / or CO

[0003] The invention relates to a method and a device for the electrolysis of C02 and / or CO .

[0004] The electrochemical reduction of CO2 and / or CO2 is a technology for converting CO2 and / or CO2 through electrolysis to hydrocarbons such as methane, ethane, ethene, ethyne, and / or oxygenates such as alcohols, aldehydes, and / or acids. CO2 can also be converted to CO2.

[0005] For this purpose, an electrolysis device can be used, which is equipped with a gas diffusion electrode as the working electrode for the direct, gaseous supply of CO2 or CO. An aqueous solution is typically used as the electrolyte, and copper-based materials are typically used as the catalyst.

[0006] At present, copper is the only known catalyst capable of forming C–C bonds to a significant extent and thus catalyzing the production of hydrocarbons and / or oxygenates with more than one carbon atom. At the same time, however, low long-term stability is observed for copper-based catalysts. Even if electrolysis on such a catalyst initially shows high selectivity for said hydrocarbons or oxygenates, the catalyst degrades over time. As a result, after a long electrolysis period, e.g., after a period of approximately one week, the reduction of the aqueous electrolyte, i.e., H2 production, mainly occurs, and the production of the desired hydrocarbons approaches zero. There are various explanations for the degradation of copper-based catalysts. One of these focuses on the residual concentration of oxygen anions and Cu+ - and Cu 2+ -cations on the catalyst. Their presence has a positive effect on the selectivity of the electrolysis. However, with continued electrolysis, the proportion of copper cations decreases progressively due to the reductive, i.e., cathodic, conditions.

[0007] The number of published studies addressing the long-term stability of CCp electrolysis, especially with gas diffusion electrodes, is small. The design of the gas diffusion electrode itself has a significant impact. The precise design of the copper catalyst influences the selectivity and long-term stability of the catalyst.

[0008] Oxide-derived copper (OD-Cu) has proven particularly suitable. Copper oxide is used as the starting material for the catalyst. This is then reduced to elemental copper, usually electrochemically in situ during electrolysis. Copper produced in this way is more suitable for electrolysis than conventional copper. A higher concentration of oxygen and copper ions is thought to be the main reason for this.

[0009] Independently of this, pulsed potential control was used as a stability-enhancing measure, as described, for example, in DE 10 2017 201 988 A1. In conventional operation, a constant working potential or a constant current is applied to the system. In the pulsed variant, however, the working potential is periodically interrupted by a less cathodic regeneration potential. As a result, the long-term stability and selectivity of ethene or hydrocarbon production are increased. There are various explanations for the mode of operation of the method. One of these is that the periodic reversal of polarity of the electrode repeatedly oxidizes the copper. After switching back to the working potential, the copper oxide produced is re-reduced.The idea is that the positive properties of OD copper can thus be retained and the amount of oxygen and copper ions on the catalyst does not decrease or at least decreases more slowly.

[0010] However, interfering with the potential control during electrolysis can have a detrimental effect on the stability of the electrolysis process, so complex process monitoring and control may be necessary. Furthermore, the periodic polarity reversal is associated with increased electrical energy consumption.

[0011] Against this background, the object of the invention is to provide an alternative electrolysis process with improved long-term stability. High Faraday efficiency for the target electrolysis products for as long a period as possible would be desirable.

[0012] This problem is solved by the subject matter of the independent claims. The dependent claims relate to embodiments of these inventive solutions.

[0013] A first aspect of the invention relates to a process for the electrolysis, i.e. for the electrochemical conversion, of CO2 and / or CO using a copper-containing catalyst.

[0014] Such electrolysis is usually carried out in an electrolysis cell in which an anode and a cathode serving as the working electrode are arranged at a distance from one another. The copper-containing catalyst can preferably be arranged on or at the working electrode and effect the reduction of the carbon present in the CO2 or CO. The hydrocarbons and / or oxygenates mentioned above can be formed as products in this case. The working electrode can in particular be designed as a gas diffusion electrode.

[0015] To improve the long-term stability of the copper-catalyzed electrolysis of CO2 and / or O2, it is proposed to add a copper-oxidizing oxidant to the catalyst. The oxidant can be added during operating times with electrolysis and / or during operating times without electrolysis. From the perspective of the inventors of the present invention, one possible explanation for the influence on long-term stability lies in the (partial) oxidation of the copper to Cu. + and / or Cu 2+, which is caused by the addition of the oxidizing agent. The copper ions mentioned appear to have a positive effect on the selectivity of the electrolysis, so that the desired target products, such as ethene, can be obtained over a long period of time with high Faradaic efficiency. In other words, the catalyst can be regenerated by adding the oxidizing agent, which has a positive effect on the long-term stability of the electrolysis.

[0016] The oxidizing agent can preferably be supplied in gaseous form. This has the advantage of good dosing and simple process implementation.

[0017] According to various embodiments, at least one oxidizing agent can be selected from a group comprising oxygen, singlet oxygen, NO2, H2O2, ozone and halogens, e.g. bromine, chlorine. This means that one of the substances mentioned or a mixture of several of the substances mentioned can be supplied as the oxidizing agent. Furthermore, different oxidizing agents or oxidizing agent mixtures can be supplied to the catalyst one after the other and / or spatially separated from one another. The oxidizing agent(s) can preferably be used in gaseous form.

[0018] The oxidizing effect of the oxidizing agents mentioned varies in strength, so that by selecting a specific oxidizing agent or oxidizing agent mixture, the oxidation of the catalyst and thus the long-term stability in general or with regard to a specific electrolysis product can be specifically influenced.

[0019] Oxygen can be used as the preferred oxidizing agent. Oxygen is readily available and, compared to the other oxidizing agents mentioned, inexpensive. Furthermore, unlike the other oxidizing agents mentioned, oxygen is not hazardous to health upon contact.

[0020] Particularly preferably, oxygen can be supplied as the oxidizing agent, which is or was formed at an anode involved in the electrolysis, i.e., the anode mentioned above arranged in the electrolysis cell. This has the advantage that, on the one hand, the oxidizing agent can be immediately reused as an electrolysis product, and, on the other hand, no other oxidizing agent needs to be stored.

[0021] Depending on the design, the oxidizing agent, e.g. oxygen, can be supplied periodically or cyclically.

[0022] For example, the duration of oxidant addition in a cycle can be between 0.5 min and 120 min. The time period between the start of two consecutive periods with oxidant addition can be between 1 h and 10 h. In other words, the cycle length can be between 1 h and 10 h, with each cycle comprising a period with oxidant addition with and / or without electrolysis operation and a period without oxidant addition but with electrolysis operation.

[0023] By periodically adding the oxidant, energy losses due to unwanted electrolytic reduction of the oxidant at the anode can be reduced. Since the product composition of the electrolysis can change during the oxidant addition, this period can be kept as short as possible with periodic oxidant addition. By varying the duration of the oxidant addition and / or the cycle length, the oxidation effect can be adjusted and the long-term stability can be specifically influenced, either generally or with respect to a specific electrolysis product.

[0024] According to further embodiments, the oxidizing agent, e.g. oxygen, can be supplied continuously.

[0025] Compared to periodic addition, this has the advantage that lower concentrations of the oxidizing agent may be sufficient to achieve the same oxidizing effect. Furthermore, it can simplify the control of the oxidizing agent addition.

[0026] According to further embodiments, a mixture of gaseous CO2 and / or CO and gaseous oxidizing agent can be fed to the catalyst.

[0027] For example, a gas diffusion electrode used as a working electrode may be supplied not only directly with gaseous CO2 and / or CO, but also with a mixture of gaseous CO2 and / or CO and the gaseous oxidant. This advantageously results in a simple process-engineered implementation of the oxidant supply to the catalyst, since only a change in the composition of the gas supplied to the catalyst is required.

[0028] With a periodic supply of oxidizing agent, e.g., with the supply of oxygen, the proportion of the gaseous oxidizing agent in the mixture with gaseous CO2 and / or CO can be between 0.5 vol.% and 8 vol.%, preferably between 1 vol.% and 3 vol.%. With a continuous supply of oxidizing agent, e.g., with the supply of oxygen, the proportion of the gaseous oxidizing agent in the mixture with gaseous CO2 and / or CO can be between 0.01 vol.% and 0.5 vol.%.

[0029] The concentration ranges mentioned have proven particularly suitable for the desired oxidation of copper, while also having only a minimal impact on the energy efficiency of electrolysis. If the oxidant concentration is too low, the desired oxidation effect is not achieved. If, on the other hand, the oxidant concentration is too high, oxygen reduction occurs to a greater extent at the working electrode. The current used for this cannot be used to convert CO2 or CO and is therefore considered a loss.

[0030] According to further embodiments, the total volume flow of the gases fed to the catalyst can be constant during electrolysis. In other words, the volume flow of the gaseous CO2 and / or CO can be reduced by the volume flow of the oxidizing agent.

[0031] For example, a constant gas flow rate can be supplied to the working electrode. Since simply adding an oxidizing agent, e.g., oxygen, could change the total gas flow rate, which could impact the prevailing pressure and is therefore undesirable, these effects can be avoided by adjusting the total gas flow rate accordingly or by keeping it unchanged.

[0032] According to further embodiments, the supply of the oxidizing agent, e.g., oxygen, can only occur during periods without electrolysis operation, i.e., when the electrolysis is switched off or interrupted. This prevents the desired product, e.g., ethene, from becoming contaminated with the oxidizing agent. In this case, the desired electrolysis products are only produced between the phases of the oxidizing agent supply and are therefore only collected then.

[0033] According to further embodiments, the oxidizing agent supply can be adjusted depending on the yield of one or more electrolysis products. The yield can be adjusted by the oxidizing agent supply itself.

[0034] For example, the dosage of the oxidizing agent, e.g., oxygen, can be linked to the yield of a desired electrolysis product, e.g., the ethylene yield, which can be determined by product gas analysis. If this yield falls below a predefined threshold, the catalyst is specifically regenerated by adding oxidizing agent.

[0035] The yield of the desired electrolysis product can be determined, for example, based on the Faraday efficiency for this product. For example, a threshold value of 10 to 20% Faraday efficiency can be set, below which the oxidant supply is initiated. Faraday efficiency is understood here as the ratio between the portion of the electrolysis current—i.e., the electrons released by the cathode—used to produce a specific electrolysis product and the electrolysis current used for other electrolysis products.

[0036] By coupling the yield of the desired electrolysis product and the supply of oxidizing agent, catalyst regeneration can be carried out as needed. This reduces the consumption of oxidizing agent, while largely avoiding the negative effects of supplying an excessive amount of reducing agent, such as increased energy consumption due to undesired reduction of the oxidizing agent at the anode, contamination of the desired electrolysis product with oxidizing agent, etc.

[0037] A further aspect of the invention relates to a device for the electrolysis of CO2 and / or 00. The device comprises a copper-containing catalyst, an oxidizing agent supply device and a control unit designed to control the oxidizing agent supply.

[0038] For example, the control unit can be designed to control the oxidant supply as a function of a yield of one or more products of the electrolysis of CO2 and / or 00.

[0039] Using the proposed device, for example, one of the above-described processes for the electrolysis of CO2 and / or CO2 can be carried out. Therefore, the above explanations for these processes also serve to describe the proposed device. The advantages of the process are correspondingly associated with the proposed device.

[0040] Based on instructions or a code programmed in the control unit, the control unit generates control signals according to one or more routines and transmits them to the oxidant supply device as an actuator. For this purpose, the control unit and the oxidant supply device are in a signal-based connection. The control unit can optionally be designed as a control unit, so that the supply of the oxidant can be controlled, for example, depending on the yield for one or more electrolysis products.

[0041] The above-described properties, features and advantages of this invention, as well as the manner in which they are achieved, will become clearer and more clearly understood in connection with the following description of the embodiments, which are explained in more detail in connection with the drawings, in which the figures show the following:

[0042] Figure 1 shows a flow diagram of an exemplary electrolysis process;

[0043] Figure 2 shows a representation of the concentration curves of CO2 (top) and oxygen (bottom) in the gas stream supplied to the working electrode for the process of Figure 1;

[0044] Figure 3 shows the Faraday efficiency and partial current density curves for products of a CO2 electrolysis with pulsed oxygen addition over 100 h;

[0045] Figure 4 shows the Faraday efficiency and partial current density curves for products of a CO2 electrolysis without oxygen addition over 60 h;

[0046] Figure 5 shows a flow chart of another exemplary

[0047] Electrolysis process; and Figure 6 is a schematic representation of an exemplary electrolysis device.

[0048] Figure 1 shows a flow chart of an exemplary electrolysis process 1. The electrolysis process 1 can be carried out, for example, using the electrolysis device 100 explained below with reference to Figure 6.

[0049] The electrolysis device 100 comprises an electrolysis cell 2 with a cathode compartment 6 and an anode compartment 7, which are separated from one another by an ion-conducting membrane 8. The membrane 8 can contain, for example, a perfluorinated copolymer with sulfo groups, also known under the name Nafion®. These ion-conducting membranes can also be fluorine-free. A cathode 3 is arranged in the cathode compartment 6, and an anode 4 is arranged in the anode compartment 7. The cathode 3 and the anode 4 are connected to a power supply 17.

[0050] To carry out the electrolysis, CO2 and / or CO is fed to the cathode chamber 6 via a gas inlet 9 and a feed line 19a, which is reduced at the cathode 3 to the desired electrolysis product, also referred to as the value product, e.g. ethene, and can be discharged from the cathode chamber 6 via a product outlet 11.

[0051] An aqueous electrolyte 18 is located in the anode compartment 7, from which oxygen is formed at the anode 4. An aqueous electrolyte 18 is also located in the cathode compartment 6, which may be identical to the aqueous electrolyte in the anode compartment 7 or may have a different composition.

[0052] In the exemplary embodiment, the cathode 3 or working electrode is a gas diffusion electrode which is constructed as follows. The base of the gas diffusion electrode forms a porous but mechanically stable carrier layer. Optionally, a hydrophobic, microporous layer can be arranged on the carrier layer in order to prevent penetration of the aqueous electrolyte 18. This is followed by a collector layer. The latter has the task of enabling good electrical conductivity in the plane so that the gas diffusion electrode can be contacted from the edge. Finally, a catalyst layer is arranged on the collector layer, i.e. positioned in the direction of the anode 4.

[0053] The catalyst layer comprises the catalyst 5, which contains copper and may, for example, contain copper or copper oxide nanoparticles. The copper particles can be mixed with a binder material, e.g., a resin or polymer, and fixed to the collector layer to form the catalyst layer. The copper-containing catalyst 5 catalyzes the desired electrolysis reaction.

[0054] In addition, the electrolysis device 100 has an oxidizing agent supply device 15 with an associated supply line 19b. By means of the oxidizing agent supply device 15, an oxidizing agent can be supplied to the cathode chamber 6 and thus to the catalyst 5 of the cathode 3 in order to effect oxidation of the catalyst 5 there and to improve the long-term stability of the electrolysis. In the exemplary embodiment, oxygen serves as the oxidizing agent, so that the oxidizing agent supply device 15 is designed accordingly for the supply of oxygen.

[0055] As shown in Figure 6, the supply lines 19a, 19b join outside the electrolysis cell 2, so that a gas mixture of CO2 and oxygen already reaches the cathode chamber 6. Optionally, the oxidant supply device 15 can be supplied by means of oxygen formed at the anode 4. In addition, the electrolysis device 100 has a control unit 14, which is designed to generate control signals 16a and to transmit them to the oxidant supply device 15 in order to control the oxidant supply. Optionally, the control unit 14 can also be designed to generate control signals 16b and to transmit them to the gas inlet 9 in order to control the supply of CO2 or CO. Possible control routines are explained in more detail below with reference to Figures 1 to 3.

[0056] It should be noted that the invention is not limited to the specific embodiment of the electrolysis device 100 and electrolysis devices 100 with a copper-containing catalyst 5 that differ from the exemplary embodiment can be used.

[0057] Referring again to Figure 1, after the start of process 1, CO2 is supplied to the working electrode or cathode 3 in process step S1, and CO2 electrolysis is carried out in process step S2. Process steps S1 and S2 essentially run in parallel.

[0058] After a certain period of time, which can be fixed or freely determined based on various criteria, a CO2-oxygen gas mixture is fed to the working electrode in process step S3. For this purpose, a corresponding control signal 16a can be output by the control unit 14 to the oxidant supply device 15, which causes oxygen to be fed into the supply line 19b. In process step S4, the CO2 electrolysis is carried out using the CO2-oxygen gas mixture. Process steps S3 and S4 essentially run in parallel.

[0059] After a certain period of time, which can be fixed or freely determined based on various criteria, process 1 continues with process step S 1 . In other words, process 1 comprises time periods in which only CO2 is supplied to the working electrode as a gas and time periods in which a CO2-oxygen gas mixture is supplied to the working electrode while the electrolysis is carried out continuously. Process 1 can be terminated at any time.

[0060] Optionally, it is possible to reduce the CO2 supply during the supply of the CO2-oxygen gas mixture in process step S3 such that the total volume flow of the supplied gas remains constant. For this purpose, the control unit 14 can output a corresponding control signal 16b to the gas inlet 9, which causes the temporary reduction of the partial CO2 volume flow.

[0061] To stabilize the electrochemical conversion of CO2 to, for example, ethene at the working electrode, a certain degree of oxidation of the copper-containing catalyst 5 is periodically induced at the working electrode. For this purpose, oxygen is periodically added as an oxidizing agent. The periodic addition of oxygen is achieved by temporarily adding oxygen to the CO2 flow to the working electrode.

[0062] It is important to select the correct oxygen concentration in the inflow. If the concentration is too low, the desired effect will not be achieved. However, if the oxygen concentration is too high, significant oxygen reduction occurs at the working electrode. The current used for this cannot be used to convert CO2 and is therefore considered a loss.

[0063] Furthermore, simply adding oxygen would change the total volume flow of the gas flow. This can impact the prevailing pressure and may therefore be undesirable. Therefore, in one embodiment, the CCp volume flow is adjusted so that the total volume flow remains unchanged while oxygen is being added. Furthermore, in this embodiment, oxygen is only added in pulses to reduce losses due to oxygen reduction. The rest of the time, pure CO2 is supplied to the working electrode. Typical oxygen concentration ranges are 0.5 vol% to 8 vol%, preferably 1 vol% to 3 vol%). Typical oxygen supply times in one cycle are 0.5 to 120 minutes. Typical periods, i.e. times between the start of two consecutive periods with oxygen supply, are 1 to 10 hours.

[0064] Figure 2 shows exemplary curves of the CO2 and oxygen concentrations in the gas stream supplied to the working electrode. After the start of electrolysis, a gas stream containing 100 vol.% CO2 is initially supplied to the working electrode for a period of 5 hours (process steps S1 and S2).

[0065] After 5 hours, a regeneration pulse (process steps S3 and S4) is applied, during which 2 vol.% oxygen is added to the gas stream and the CCp volumetric flow is reduced accordingly to 98 vol.% to keep the total volume flow constant. The duration of the regeneration pulse is 1 h.

[0066] After regeneration is complete, electrolysis is run again with 100 vol.% CO2 for 5 h. As shown in Figure 2, process steps S1 and S2, on the one hand, and process steps S3 and S4, on the other, can alternate accordingly.

[0067] With the described process 1, the long-term stability of CCp electrolysis to hydrocarbons and / or oxygenates can be significantly increased on gas diffusion electrodes with copper-based catalysts 5. Hydrogen evolution can thus be largely suppressed. Process parameters include the appropriate choice of oxygen concentration and the pulse times for dosing pure CO2 and oxygen.

[0068] For example, at an oxygen concentration of 2 vol.%, which was first adjusted after 15 h for 1 h every 5 h, the electrochemical reduction of CO2 to ethylene at -1.6 V versus Ag / AgCl was maintained for 100 h. Figure 3 shows the corresponding time-dependent curves of the Faraday efficiency FE (Figure 3 top) and the partial current densities j (Figure 3 bottom) for various electrolysis products and overall.

[0069] The formula symbols -j and j eff denote the same physical quantity, i.e., the current effectively used to form a specific product(s) and is neither used for another product nor lost through parasitic conductivity. To determine -j or eff, the number of molecules of a specific type formed per unit of time (exhaust gas flow and proportion of the respective gas) is measured. The number of electrons required to form a molecule, i.e., the charge required per molecule, is known from the chemical reaction equation. From this, the partial current used to form this molecule can be calculated as the current density (area of ​​the electrolysis electrode).

[0070] For ethylene (C2H4), the Faraday efficiency FE increased over the first 70 hours, reaching a maximum value of 63%. Only after 70 hours did the Faraday efficiency for ethylene decrease slightly. On average, a Faraday efficiency of 51% and a partial current density of 140 mA / cm2 were measured for ethylene over 100 hours. 2 Hydrogen evolution, however, remained consistently low, with an average Faradaic efficiency of 13%. The only other product produced in significant quantities was CO, with an average Faradaic efficiency of 20%. However, its formation decreased sharply over time. Periodic minor drops in the product formation rates are due to the addition of oxygen and the associated oxygen reduction.

[0071] Figure 4 shows a reference electrolysis for comparison. This was conducted using the same materials and under the same conditions. The only difference was that pure CO2 was added throughout. Compared to Figure 3, a significantly lower temporal stability of ethylene production can be seen. Furthermore, hydrogen formation increased significantly over time, so that hydrogen was the main product after just 50 hours.

[0072] Figure 5 shows a flow diagram of another exemplary method 10 for the electrolysis of CO2 and / or CO. After starting method 10, CO2 is supplied to the working electrode in method step S11. In method step S2, the CO2 electrolysis is carried out. Method steps S10 and S11 can be identical to method steps S1 and S2 of method 1 described with reference to Figure 1, so that reference can be made to the relevant explanations.

[0073] In contrast to process 1 in Figure 1, in process step S13 the CO2 supply to the working electrode and the electrolysis are interrupted, e.g. by interrupting the power supply, before oxygen is supplied to the working electrode in process step S14. In process step S15 the oxygen supply is terminated and process 10 is then continued with process step S11. Process 10 can be terminated at any time. In contrast to process 1 in Figure 1, in process 10 of this exemplary embodiment the regeneration or oxidation of the catalyst 5 takes place during operating times without electrolysis operation, i.e. while the electrolysis is switched off. This prevents the desired electrolysis product(s) from being contaminated with oxygen. In this case, products are only produced between the oxygen dosing phases and therefore only then.

[0074] In a further embodiment, the oxygen can be added continuously, typically with a volume fraction between 0.01 vol.% and 0.5 vol.% in the total volume flow.

[0075] In all proposed methods 1, 10, the dosage of oxygen can be linked to the yield of the desired electrolysis product(s) determined by product gas analysis, e.g., the ethylene yield. If this falls below a certain threshold, e.g., a threshold in the range between 10 and 20% Faraday efficiency (current state of research), or below 50-70% in the optimized industrial case, the catalyst 5 is specifically regenerated by adding oxygen. For this purpose, a corresponding control routine can be implemented in the control unit 14, i.e., the control unit 14 can receive sensor signals from sensors for product gas analysis, process these sensor signals based on instructions or a code programmed in the control unit 14 according to one or more routines, and send control signals 16a, 16b to the oxidant supply device 15 and, if applicable,the gas inlet 9 in response to the processed sensor signals in order to vary the oxygen supply and, if necessary, the CO2 supply.

[0076] The regeneration of the catalyst 5 can be carried out as described above by periodic addition of oxygen to the CO2, continuous addition of oxygen or during operating times without CC^ supply and electrolysis operation.

[0077] Although the invention has been illustrated and described in detail by the preferred embodiment, the invention is not limited to the disclosed examples and other variations can be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0078] In summary, the invention relates to a method 1, 10 and a device 100 for the electrolysis of CO2 and / or CO. The method 1, 10 provides that a copper-containing catalyst is used and a copper-oxidizing oxidizing agent is supplied to the catalyst S3, S14. The device 100 has a copper-containing catalyst 5, an oxidizing agent supply device 15 and a control unit 14 designed to control the oxidizing agent supply.

[0079] The low temporal stability of CO2 electrolysis is currently the greatest obstacle to making CO2 reduction economically attractive and thus commercializable. The proposed processes 1, 10, and the proposed device 100 contribute significantly to stabilizing CO2 reduction at working electrodes with a copper-containing catalyst 5. Only small amounts of oxygen are required for this purpose. Losses due to oxygen reduction are small and are more than compensated for many times over by the increased stability. In addition, the oxygen addition is technically simple to implement. List of reference symbols

[0080] 1 procedure

[0081] 2 electrolysis cells

[0082] 3 Cathode

[0083] 4 Anode

[0084] 5 Catalyst

[0085] 6 Cathode compartment

[0086] 7 Anode compartment

[0087] 8 Membran

[0088] 9 Gas inlet

[0089] 10 procedures

[0090] 11 Product from lass

[0091] 12 gaseous products

[0092] 13 liquid products

[0093] 14 Control unit

[0094] 15 Ox i dat ionungsmittel zuführeinrichtung

[0095] 16a, 16b control signal

[0096] 17 Power supply device

[0097] 18 aqueous electrolyte

[0098] 19a, 19b supply line

[0099] 20 CO2 and / or CO

[0100] 21 Oxidizing agents

[0101] 100 device

[0102] 51 Supplying CO2 to the working electrode

[0103] 52 Carrying out the CO2 electrolysis

[0104] 53 Supplying a C02-oxygen gas mixture to the work select rode

[0105] 54 Carrying out the CO2 electrolysis

[0106] 511 Supplying CO2 to the working electrode

[0107] 512 Carrying out the CO2 electrolysis

[0108] 513 Interrupting the CO2 supply to the working electrode and the electrolysis 514 Supplying oxygen to the working electrode

[0109] 515 Stop the oxygen supply to the working electrode

Claims

Patent claims 1. A process (1, 10) for the electrolysis of CO2 and / or CO (20) using a copper-containing catalyst (5), wherein a copper-oxidizing oxidizing agent (21) is fed to the catalyst (5) (S3, S14).

2. The method (1, 10) according to claim 1, wherein at least one oxidizing agent (21) is selected from a group comprising oxygen, singlet oxygen, NO2, H2O2, ozone and halogens.

3. The method according to claim 2, wherein oxygen is supplied as the oxidizing agent (21).

4. The method (1, 10) according to claim 3, wherein oxygen formed at an anode (4) involved in the electrolysis is supplied as an oxidizing agent (21).

5. Method (1, 10) according to one of the preceding claims, wherein the oxidizing agent (21) is supplied periodically (S3).

6. The method (1, 10) according to claim 5, wherein a time duration of the oxidant supply in a cycle is between 0.5 min and 120 min.

7. The method (1, 10) according to claim 5 or claim 6, wherein a time period between a start of two consecutive periods of oxidant supply is between 1 h and 10 h.

8. The method according to any one of claims 1 to 4, wherein the oxidizing agent (21) is supplied continuously.

9. Process (1) according to one of the preceding claims, wherein a mixture of gaseous CO2 and / or CO (20) and gaseous oxidizing agent (21) is fed to the catalyst (5) (S3).

10. The method (1) according to claim 9, wherein the proportion of the gaseous oxidizing agent (21) in the mixture with a periodic supply of oxidizing agent is between 0.5 vol.% and 8 vol.%, preferably between 1 vol.% and 3 vol.%.

11. The method according to claim 9, wherein the proportion of the gaseous oxidizing agent (21) in the mixture with a continuous supply of oxidizing agent is between 0.01 vol.% and 0.5 vol.%.

12. The method (1, 10) according to any one of claims 9 to 11, wherein the total volume flow of the gases supplied to the catalyst (5) is constant during the electrolysis.

13. Method (10) according to one of the preceding claims, wherein the supply of the oxidizing agent (21) takes place only during periods without electrolysis operation (S14).

14. The method (1, 10) according to any one of the preceding claims, wherein the supply of the oxidizing agent (21) is dependent on a yield for one or more electrolysis products (12, 13).

15. Device (100) for the electrolysis of CO2 and / or CO (20), the device (100) comprising: - a copper-containing catalyst (5) , - an oxidizing agent supply device (15) and - a control unit (14) designed to control the supply of oxidizing agent.

16. Device (100) according to claim 15, wherein the control unit (14) is designed to control the oxidant supply as a function of a yield for one or more electrolysis products (12, 13).

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