Bipolar multilayer electrode design for stable electrochemical reduction of co2 to hydrocarbons

Abstract

The invention relates to a multi-layer electrode for CO2 electrolysis, in particular to a bipolar multi-layer electrode for the stable electrochemical reduction of CO2 to hydrocarbons and a corresponding electrochemical cell. Accordingly, a multi-layer electrode (10) for CO2 electrolysis is proposed, comprising a gas diffusion layer (12) having a predetermined pore size suitable for CO2 diffusion, a catalyst layer (14) adjacent to the gas diffusion layer (12) and comprising a copper-based cathode catalyst, and an electrically conductive layer (16) adjacent to the catalyst layer (14), wherein the gas diffusion layer (12), the catalyst layer (14) and the electrically conductive layer (16) together form a gas diffusion electrode, and wherein the catalyst layer (14) comprises a predetermined amount of anion exchange ionomer (18) and the electrically conductive layer (16) comprises at least one layer comprising a predetermined amount of cation exchange ionomer (24). According to the invention, the electrically conductive layer (16) comprises a graphite layer (20) comprising a predetermined portion of the cation exchange ionomer (24).

Description

Technical Field

[0001] This invention relates to a multilayer electrode for CO2 electrolysis, and more particularly to a bipolar multilayer electrode for the stable electrochemical reduction of CO2 to hydrocarbons and a corresponding electrochemical cell. Background Technology

[0002] The electrochemical reduction of carbon dioxide (CO2) to hydrocarbons (CO2RR) is a promising alternative to other energy storage strategies. Electrochemical conversion of CO2 is an attractive approach that can utilize renewable electricity (such as solar and wind power) and can combine CO2 with the products. However, developing systems with sufficiently high selectivity, efficiency, and stability has been a challenge, particularly in the selective hydrocarbon generation.

[0003] In this regard, catalysts used for CO2 reduction reactions are particularly likely to face the problem of poor stability in the formation of the desired products. Among a group of potential catalysts including, for example, copper (Cu), silver (Ag), gold (Au), palladium (Pd), and tin (Sn), copper is the only transition metal catalyst capable of converting CO2RR into value-added C2+ products (such as ethylene, ethanol, or propanol). Such copper-based catalysts are typically used on the cathode side of an electrochemical cell, where a typical electrochemical cell usually consists of a gas supply gap, a cathode gas diffusion electrode containing a copper-based catalyst, a separator membrane, and an anode gas diffusion electrode. Another gap for the electrolyte may exist between the membrane and the cathode electrode, and between the anode electrode and, for example, the anode end plate. At the cathode, CO2 can be reduced to a variety of compounds, including carbon monoxide, formate, ethylene, ethanol, propanol, and some other minor products such as methane or allyl alcohol. However, undesirable side reactions often occur at the cathode, including the hydrogen evolution reaction (HER). Unfortunately, the thermodynamic equilibrium potentials for the above reactions, compared to those for standard hydrogen, indicate that the reduction of CO2 to the CO2RR product and the generation of hydrogen are thermodynamically favorable within the same and very narrow potential range. This situation poses a significant challenge to the selectivity of the target product (e.g., primarily obtaining the value-added product ethylene). Despite ongoing efforts to improve catalysts and electrodes to control product selectivity (e.g., for ethylene), to date, there has been no breakthrough in the reduction of CO2 to hydrocarbons that can be applied on an industrial scale to provide selective operation on a specific product over extended periods (e.g., >10,000 hours).

[0004] To achieve a CO2-rich gaseous environment at the cathode from the gas side, a gas diffusion electrode (GDE) is typically employed, comprising a porous gas diffusion layer and an active catalyst layer. This facilitates the formation of a three-phase boundary, consisting of gaseous CO2, a solid copper-based catalyst, and water with an existing potential, acting as the driving force for the electrochemical reaction. However, current copper-based electrodes or catalysts are not stable in terms of industrially relevant long-term durability (e.g., >10,000 hours). Depending on factors such as the electrode, catalyst, and operating conditions, the Faraday efficiency of the CO2 reduction reaction decreases after 1 to 200 hours, and the hydrogen evolution reaction becomes dominant.

[0005] Loss of stability may be caused, for example, by catalyst surface remodeling, flooding of the gas diffusion electrode hindering CO2 supply and diffusion, and / or the accumulation of impurities or salts leading to electrode dysfunction. Furthermore, loss of selectivity may be caused, for example, by electrolyte permeation into the pores of the gas diffusion electrode, thereby disrupting the three-phase boundary and blocking pores available for CO2 transport and / or local catalytic active sites for CO2 reduction.

[0006] Despite ongoing efforts to improve the stability and selectivity of CO2 reduction, most improvement schemes have proven to lead to undesirable salt formation and / or be applicable only to small-scale or nanoscale conditions. Such conditions, such as those requiring strongly alkaline conditions (e.g., pH > 13) or acidic conditions (e.g., pH < 1), have been found to be unsuitable and / or not scalable to industrial scale.

[0007] Therefore, it is necessary to improve the selectivity and long-term stability of CO2 reduction to hydrocarbons.

[0008] US 2023 / 155153 A1 discloses a cathode catalyst for a carbon oxide electrolyzer, which is based on providing conductive support particles and metal catalyst particles. In addition to the cathode layer and anode layer, an ion-conducting layer is also taught to exist.

[0009] CN 114941148 A teaches the use of silver nanoparticles in acidic cation exchange membrane systems employing acidic electrolyte cation exchange membranes.

[0010] In addition, WO 2020 / 112919 A1 describes a membrane electrode assembly in which the cathode layer may include anion-conducting polymer, and in which the MEA may be bipolar.

[0011] WO 2020 / 020691 A1 teaches the use of copper-aluminum alloys as multimetal catalysts and recommends setting a further particulate layer on a PTFE support. Summary of the Invention

[0012] One object of the present invention is to provide an improved electrode design for CO2 reduction. In particular, the object is to improve the selectivity and stability of the reduction reaction of such electrodes.

[0013] Accordingly, in a first aspect, a multilayer electrode for CO2 electrolysis is provided, comprising: a gas diffusion layer having a predetermined pore size suitable for CO2 diffusion; a catalyst layer adjacent to the gas diffusion layer and comprising a copper-based cathode catalyst; and a conductive layer adjacent to the catalyst layer. The gas diffusion layer, the catalyst layer, and the conductive layer together form a gas diffusion electrode, wherein the catalyst layer comprises a predetermined amount of anion-exchange ionomer, and the conductive layer comprises at least one layer comprising a predetermined amount of cation-exchange ionomer. According to the invention, the conductive layer comprises a graphite layer comprising a predetermined portion of the cation-exchange ionomer.

[0014] The inventors have discovered that providing bipolar gas diffusion electrodes via anion-exchange ionomers and cation-exchange ionomers is particularly advantageous for achieving the selectivity and stability of the desired CO2 reduction reaction. Specifically, when implemented in an electrochemical cell, the use of a cation-exchange ionomer (preferably formed as an outer layer) in the conductive layer of the electrode enables the local enrichment of OH- anions in the active catalyst layer by restricting and / or slowing the transport of OH- anions generated in the active catalyst layer away from the active catalyst layer towards the anode along the electroosmotic direction. This enrichment of OH- anions in the active catalyst layer provides a more alkaline environment due to the correspondingly higher local pH, which has been found to favor the desired CC coupling reaction mechanism, producing, for example, ethylene (C2H4) as a product. These advantageous effects can be further enhanced by any combination with conductive polymers (e.g., polyacetylene, polyphenylenevinylene, polypyrrole, polythiophene, polyaniline, or polyphenylene sulfide) and / or with highly hydrophobic polymers (e.g., polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), or polyethylene (PE)). Alternatively, cation exchange ionomers and / or anion exchange ionomers can be replaced by one or more of these polymers, especially highly hydrophobic polymers.

[0015] Furthermore, using these cation-exchange ionomers specifically or only in the conductive layer of the electrode reduces the availability of carbonate anions in adjacent catalyst layers. In this respect, the use of anion-exchange ionomers in the active catalyst layer (preferably the inner layer forming the electrode) limits the availability of potassium ions (K+) within that layer. Therefore, the coexistence of potassium ions and carbonate anions is effectively avoided, particularly in the active catalyst layer and the gas diffusion layer.

[0016] Therefore, the occurrence or probability of typical salt formation due to the coexistence of potassium ions and carbonate anions in the active catalyst layer and gas diffusion layer is significantly reduced. By reducing salt formation, undesirable flooding in the gas diffusion layer can be prevented, or at least minimized, thereby ensuring a persistent and effective three-phase boundary for gaseous CO2.

[0017] Furthermore, not only do the implementations of anion-exchange ionomers and cation-exchange ionomers ensure the availability of the desired levels of anion or cation permeability, but the hydrophobicity of the corresponding layers is also optimized, as well as their water absorption capacity due to their swelling properties. This is because the ion exchange materials are preferably formed from a hydrophobic polymer backbone with hydrophilic ion-exchange functional groups. Therefore, sufficient three-phase boundaries can be further ensured through the corresponding hydrophobicity and, for example, reducing the amount of water that may be present within the pores of the gas diffusion layer. Thus, the electrode design according to the invention provides a synergistic solution to the current problems of poor selectivity and stability. The invention achieves selective permeation, local pH control, effective barrier properties (e.g., against salt-forming carbonates and potassium compounds), and a well-balanced hydrophobicity to promote the availability of the three-phase boundary. Consequently, the selective production of, for example, ethylene, ethanol, and / or propanol can be significantly improved over a longer period, enabling production to reach a higher level of technology readiness (TRL).

[0018] The multilayer configuration of the bipolar gas diffusion electrode can be viewed as a stacked structure of layers, such that (preferably wetted or humidified) gaseous CO2 can pass through the gas diffusion layer before reaching the catalyst layer. The catalyst layer is copper-based and preferably formed of copper oxide (CuO). A conductive layer in the stacked structure is correspondingly arranged on the side of the catalyst layer opposite to the side of the adjacent gas diffusion layer. Thus, the conductive layer forms a separate layer, which can be stacked directly adjacent to or formed on top of the catalyst layer. In the assembled state, particularly in an electrochemical cell, the conductive layer can therefore be arranged, for example, between the electrolyte flow chamber and the gas supply chamber, and is therefore neither formed by nor adjacent to a separator, which is formed, for example, a cation exchange membrane, an anion exchange membrane, or a diaphragm membrane.

[0019] The amounts of anion-exchange ionomers and cation-exchange ionomers can be selected to provide a predetermined hydrophobicity for the entire gas diffusion electrode, wherein the corresponding ionomers can be provided in monolayer, multilayer, or gradient form within the respective layers.

[0020] Ionomers can also be provided as corresponding membranes (i.e., anion exchange membranes or cation exchange membranes), for example, to define corresponding layers that can be simply applied to another layer of a multilayer electrode. However, the ionomers are preferably incorporated into or embedded in the corresponding layers, for example, using droplet coating. The advantage is that the corresponding ionomers can at least partially permeate into the corresponding layers, and their accessibility can be improved. Furthermore, this allows for very precise metering of the corresponding ionomers, which is particularly advantageous because the amount added to the corresponding layers is a very sensitive parameter. For example, an excessive amount of the corresponding ionomer may block active catalyst sites by forming a thick diffusion layer, while a suboptimal amount may limit the extent to which the three-phase boundary needs to be reached.

[0021] Therefore, the weight percentage of the anion exchange ionomer is preferably between 0.01 wt.% and 20 wt.%, and the weight percentage of the cation exchange ionomer in the corresponding layer is preferably between 0.01 wt.% and 20 wt.%. In particular, the weight percentage of the anion exchange ionomer can be between 1 wt.% and 15 wt.%.

[0022] It has been found that the aforementioned percentage ranges for anion-exchange ionomers and cation-exchange ionomers, particularly the percentage range for cation-exchange ionomers, are particularly advantageous in controlling local pH, defining overall hydrophobicity, and blocking the possibility of potential salt-forming components. This advantageously avoids flooding of the gas diffusion layer and facilitates CO2 reduction reactions, such as ethylene. Therefore, the aforementioned preferred percentages significantly improve the selectivity, durability, or stability of CO2 reduction provided by the multilayer electrode.

[0023] To avoid clogging of the gas diffusion layer pores due to the application of anion exchange ionomers, the anion exchange ionomers are preferably arranged on the side of the catalyst layer opposite to the gas diffusion layer. In other words, the anion exchange ionomers are preferably located on the side adjacent to the conductive layer. To facilitate this arrangement, the anion exchange ionomers are preferably applied by drop casting, for example, layer-by-layer preparation. However, alternative or additional methods can also be implemented, such as drop casting, air brushing, spraying, transfer printing, dry or wet calendering, physical vapor deposition, or chemical vapor deposition.

[0024] The implementation of a graphite layer (preferably formed as the outer layer of a gas diffusion electrode) provides improved conductivity and corresponding electron mobility. This is because graphite typically has a hexagonal structure, in which one free valence electron can be used to facilitate electron migration. By including a predetermined portion of cation exchange ionomers in the graphite layer, a balance is provided between improved conductivity toward the catalyst layer and local pH control, reduced salt formation, and the formation and / or accessibility of the three-phase boundary layer.

[0025] The hexagonal structure of graphite also facilitates control over the density of the layer. Therefore, the density of the graphite layer is preferably around 1 mg / cm³. 2 Up to 20 mg / cm 2 More preferably, it is between 5 mg / cm³. 2 Up to 10 mg / cm 2 Between these ranges, it was found that, particularly within a more specific density range, an optimal trade-off can be achieved between the desired structural stability, the porosity of the cation exchange ionomer, and the conductivity.

[0026] In addition, the conductive layer may also include a carbon nanoparticle layer containing a predetermined portion of a cation exchange polymer and disposed between the graphite layer and the catalyst layer.

[0027] The advantage of implementing an additional carbon nanoparticle layer (e.g., as an outer or outermost layer of a gas diffusion layer) is that it can provide an improved surface area for the cation exchange ionomer. The carbon nanoparticles can also stabilize copper to suppress or prevent its fading under electroreduction conditions. For the graphite layer, the predetermined portion of the cation exchange ionomer can be between 0.01 wt.% and 20 wt.% to further support selective CO2 reduction reactions and improve the stability of the bipolar gas diffusion electrode.

[0028] The density of the carbon nanoparticle layer is preferably 0.05 mg / cm³. 2 Up to 2 mg / cm 2 Between. It has been found that this relatively low density, compared to graphite layers, is advantageous for the function of cation exchange ionomers and / or for achieving a predetermined level of swelling due to the corresponding hydrophobicity of the cation exchange ionomers.

[0029] Specifically, the weight percentage of the cation exchange ionomer can be between 0.01 wt.% and 20 wt.%, for example, between 1 wt.% and 10 wt.%, wherein each of the preferred graphite layer and carbon nanoparticle layer can contain substantially the same weight percentage of cation exchange ionomer. Such a weight percentage results in the total amount of cation exchange ionomer substantially corresponding to the total amount of anion exchange ionomer present in the catalyst layer. In this respect, the size and / or weight of the catalyst layer, as well as the graphite layer and carbon nanoparticle layer, can be adjusted.

[0030] The conductive layer and / or catalyst layer may also contain a hydrophobic agent. This hydrophobic agent may be present in addition to the corresponding cation exchange ionomers and anion exchange ionomers, and may, for example, provide additional hydrophobicity to achieve the intended overall hydrophobicity without significantly affecting the bipolarity of the gas diffusion electrode. Preferred hydrophobic agents may comprise or consist substantially of hydrophobic polymers, such as polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), polypropylene (PP), or polyethylene (PE).

[0031] In addition, the multilayer bipolar gas diffusion electrode may include a protective layer and / or a current collector, the protective layer and / or the current collector being disposed adjacent to the conductive layer on the side opposite to the catalyst layer and / or at least partially surrounding the conductive layer.

[0032] Therefore, the additional layer forms a layer separate from the conductive layer, but is preferably stacked or formed on top of the conductive layer in a directly adjacent manner. The additional layer can be formed, for example, of a metal or a mixture of metal and polymer, and is preferably formed as a mesh or cage structure. This facilitates the fixing of the gas diffusion electrode in place and / or the efficient collection of any current applied to or transmitted to the gas diffusion electrode. Therefore, when the bipolar gas diffusion electrode is used in an electrochemical cell for CO2 electrolysis or reduction, the protective layer and / or current collector are preferably arranged to be in direct contact with the electrolyte, for example, present in the electrolyte flow chamber.

[0033] According to another aspect of the invention, an electrochemical cell for CO2 electrolysis is provided, comprising a multilayer electrode according to the invention. The electrochemical cell preferably comprises an anode catalyst layer, a separator adjacent to the anode catalyst layer, and an electrolyte flow chamber disposed between the multilayer electrode and the separator.

[0034] The electrochemical cell may include a gas supply chamber located upstream and adjacent to the gas diffusion layer, through which humidified or moistened CO2 permeates or is delivered in a predetermined and controlled manner. Gaseous CO2 reduction reaction products may also be enriched or transferred to the gas supply chamber. On the other side of the gas diffusion electrode, an electrolyte may be provided in an electrolyte flow chamber. Liquid CO2 reduction reaction products may also be collected via the flow chamber.

[0035] Preferred electrolyte solutions include potassium hydroxide, potassium carbonate (bicarbonate), cesium bicarbonate, potassium sulfate, calcium bicarbonate, sodium bicarbonate, lithium bicarbonate, ionic liquids, or solid electrolytes.

[0036] On the anode side, i.e., at the anode catalyst layer (separated by separators such as cation or anion exchange membranes), water is oxidized to oxygen and hydrogen ions / hydrated hydrogen ions or hydroxide ions, depending on the membrane used.

[0037] By employing the bipolar gas diffusion electrode according to the invention, the electrochemical cell enables the CO2 reduction reaction to selectively and stably produce CO2 reduction reaction products, particularly ethylene, ethanol, and propanol, as illustrated below in conjunction with examples and figures. Attached Figure Description

[0038] The invention will be more readily understood by referring to the following detailed description taken in conjunction with the accompanying drawings, in which: Figure 1 This is a schematic diagram of the multilayer bipolar gas diffusion electrode according to the present invention; Figure 2 This is a schematic diagram of an embodiment of an electrochemical cell according to the present invention; Figure 3 The results show the Faraday efficiency as a function of time for obtaining different products using a bipolar gas diffusion electrode; Figure 4 More detailed Faraday efficiencies for obtaining different products after 24 hours using a bipolar gas diffusion electrode are shown; and Figure 5 The results show the Faraday efficiency versus time for obtaining different products using a bipolar gas diffusion electrode, where... Figure 3 The weight percentages of the anion-exchange ionomer and the cation-exchange ionomer differ between the examples. Detailed Implementation

[0039] The invention will now be explained in more detail with reference to the accompanying drawings. In the drawings, the same elements are denoted by the same reference numerals, and repeated descriptions may be omitted to avoid redundancy.

[0040] Figure 1 A schematic diagram of a multilayer bipolar gas diffusion electrode 10 according to the present invention is shown. As shown, the multilayer electrode 10 includes a gas diffusion layer 12 having a predetermined pore size suitable for the diffusion of CO2 (preferably humidified CO2). The gas diffusion layer 12 is arranged directly adjacent to a cathode catalyst layer 14, which forms the main reaction layer for the reduction of CO2 at the three-phase boundary. On the side of the cathode catalyst layer 14 opposite to the gas diffusion layer 12 (i.e., the side not adjacent to the gas diffusion layer 12), there is a conductive layer 16, wherein the gas diffusion layer 12, the cathode catalyst layer 14, and the conductive layer 16 together form the gas diffusion electrode 10.

[0041] A layer comprising anion exchange ionomers 18 is also depicted on the side of the cathode catalyst layer 14 opposite to the gas diffusion layer 12. Although the anion exchange ionomers are depicted as a single layer (e.g., formed using droplet coating), it should be understood that the anion exchange ionomers 18 can also be distributed throughout the cathode catalyst layer, for example, the cathode catalyst layer 14 having a corresponding porosity. However, these anion exchange ionomers 18 are preferably present only on the side of the cathode catalyst layer 14 adjacent to the conductive layer 16 and / or not on the side of the cathode catalyst layer 14 adjacent to the gas diffusion layer 12. This ensures that the porosity of the gas diffusion layer 12 is not significantly affected, or at least not significantly affected, by the application and presence of the anion exchange ionomers 18.

[0042] According to this example, the conductive layer 16 is formed of or comprises two layers: a graphite layer 20 and an optional carbon nanoparticle layer 22 (as shown by dashed lines). Each of the layers 20 and 22 contains a predetermined portion of cation exchange ionomer 24. Providing anion exchange ionomer 18 in the cathode catalyst layer 14 and cation exchange ionomer 24 in the conductive layer 16 makes the multilayer gas diffusion electrode 10 bipolar. As described above, the advantage of this configuration is that it can significantly improve the selectivity of CO2 reduction products and the stability of the corresponding reaction and cathode catalyst layer 14, as will be discussed below. Figure 3 , 4 And 5 shows it in more detail.

[0043] exist Figure 1 In the depicted embodiment, the protective layer and / or current collector layer 26 is shown as the outer layer adjacent to the multilayer electrode 10 (i.e., adjacent to the conductive layer). This layer 26 (optionally shown as dashed lines) can be formed, for example, as a metal mesh or cage structure, which preferably protects the conductive layer 16 and serves as an effective means of current collection.

[0044] Although there are gaps between some adjacent layers, these gaps are only for illustrative purposes to distinguish the layers, and it should be understood that in practical applications, the layers are in direct contact with each other.

[0045] Figure 2A schematic diagram of an embodiment of the electrochemical cell 28 is depicted, in which a multilayer electrode 10 according to the invention has been employed. Thus, the multilayer electrode 10 forms a cathode, through which humidified CO2 can be supplied to its gas diffusion layer 12 via an adjacent gas supply chamber 30. On the opposite side of the multilayer electrode 10, an electrolyte flow chamber 32 is present, which provides a liquid barrier between the multilayer electrode 10 and the anode catalyst layer 34 and the adjacent anode gap 38. Between the multilayer electrode 10 and the anode catalyst layer 34, a separator 36 (e.g., a cation exchange membrane, an anion exchange membrane, or a diaphragm membrane) is also present, which is in direct contact with the electrolyte present in the electrolyte flow chamber 32 and is arranged adjacent to the anode catalyst layer 34. On the side adjacent to the anode gap 38 and opposite to the anode catalyst layer 34, an anolyte flow chamber (not shown) may be present, through which the anode catalyst 38 flows.

[0046] When a voltage is applied, CO2 is reduced at the multilayer electrode 10, wherein the gaseous CO2 reduction product can be collected on the gas supply chamber 30 side and the liquid CO2 reduction product can be collected on the electrolyte flow chamber side.

[0047] Figure 3 The copper-based electrode according to the present invention is shown in an active cell with an area of ​​10 cm². 2 The current density in the CO2 electrolysis flow cell is 100 mA / cm². 2 The electrochemical performance was assessed using a multilayer electrode configuration 10, which incorporates a conductive layer 16 comprising a carbon nanoparticle layer 22 and a graphite layer 20, both containing cation exchange ionomers 24. As shown by the triangular data points representing ethylene (C2H4) production, this inventive configuration of the cathode electrode (a first in this research field) significantly improves CO2 reduction by ensuring stable reaction times exceeding 720 hours while selectively providing, for example, a large proportion of value-added ethylene. In particular, the relative amount of ethylene produced remains stable compared to carbon monoxide (represented by dots) or undesirable byproducts such as hydrogen (represented by squares), as shown by the Faraday efficiency (FE) percentage, between approximately 20% and approximately 25%. Therefore, this performance achievement elevates the technological maturity of copper-based CO2 electrolysis to another level by extending stable operating time from days to months.

[0048] Figure 4 A more detailed Faraday efficiency for obtaining different products after 24 hours using a bipolar gas diffusion electrode is shown, in which the same method was employed. Figure 3 The same multilayer electrode 10 configuration as in the embodiment. Figure 4 In the figure, the data at 300 mA / cm² is depicted in the form of a stacked diagram. 2The complete product spectrum obtained from the copper-based CO2 electrochemical reduction is shown. From bottom to top, the cumulative percentages of ethylene, acetate, ethanol, propanol, propionaldehyde, propionate, carbon monoxide, formate, and hydrogen are displayed. Therefore, approximately 50% Faradaic efficiency can be achieved for C2+ products from ethylene to propionate, with over 30% attributed to ethylene. Consequently, the durability, stability, and selectivity of the CO2 reduction reactions for the desired products are significantly improved.

[0049] Use and Figure 3 The same test conditions yielded Figure 5 The results described in the text. However, compared with those used to obtain... Figure 3 Compared to the examples shown, and within a preferred weight percentage between 0.01 wt.% and 20 wt.%, the corresponding layers used a lower weight percentage of anion-exchange ionomer and a higher weight percentage of cation-exchange ionomer. As shown, the Faradaic efficiencies of the different products indicate that a similar Faradaic efficiency (FE) percentage, between about 20% and about 25%, can be achieved for ethylene (represented by triangles). Therefore, compared to... Figure 3 The results are similar; by optimizing different weight percentages, a stable reaction of over 720 hours can be provided, while selectively producing, for example, a large proportion of value-added ethylene.

[0050] It will be apparent to those skilled in the art that these embodiments and options represent only examples among many possibilities. Therefore, the embodiments shown herein should not be construed as limiting these features and configurations. Any possible combination and configuration of the described features may be selected according to the scope of the invention.

[0051] List of reference numerals 10 Multilayer Electrodes 12 Gas diffusion layer 14 Cathode catalyst layer 16 conductive layers 18 Anion exchange ionomers 20 graphite layers 22 Carbon nanoparticle layers 24 Cation exchange ionomers 26. Protective layer and / or flow collection layer 28 Electrochemical Cell 30 Gas supply chamber 32 Electrolyte Flow Chamber 34 Anode catalyst layer 36 dividers 38 Anode gap

Claims

1. A multilayer electrode (10) for CO2 electrolysis, the multilayer electrode (10) comprising: A gas diffusion layer (12) having a predetermined pore size suitable for CO2 diffusion; Catalyst layer (14), said catalyst layer (14) being adjacent to said gas diffusion layer (12) and comprising a copper-based cathode catalyst; and A conductive layer (16) is adjacent to the catalyst layer (14). The gas diffusion layer (12), the catalyst layer (14), and the conductive layer (16) together form a gas diffusion electrode, and The catalyst layer (14) contains a predetermined amount of anion exchange ionomer (18), and the conductive layer (16) includes at least one layer containing a predetermined amount of cation exchange ionomer (24). Its features are, The conductive layer (16) includes a graphite layer (20) that contains a predetermined portion of the cation exchange ionomer (24).

2. The multilayer electrode (10) according to claim 1, wherein, The weight percentage of the anion exchange ionomer (18) is between 0.01 wt.% and 20 wt.%, and the weight percentage of the cation exchange ionomer (24) in the corresponding layer is between 0.01 wt.% and 20 wt.%.

3. The multilayer electrode (10) according to claim 2, wherein, The weight percentage of the anion exchange ionomer (18) is between 1 wt.% and 15 wt.%.

4. The multilayer electrode (10) according to any one of the preceding claims, wherein, The anion exchange ionomer (18) is arranged on the side of the catalyst layer (14) opposite to the gas diffusion layer (12).

5. The multilayer electrode (10) according to any one of claims 1 to 3, wherein, The density of the graphite layer (20) is 1 mg / cm³. 2 Up to 20 mg / cm 2 between.

6. The multilayer electrode (10) according to claim 5, wherein, The density of the graphite layer (20) is 5 mg / cm³. 2 Up to 10 mg / cm 2 between.

7. The multilayer electrode (10) according to any one of claims 1 to 3, wherein, The conductive layer (16) includes a carbon nanoparticle layer (22), which contains a predetermined portion of the cation exchange ionomer (24) and is disposed between the graphite layer (20) and the catalyst layer (14).

8. The multilayer electrode (10) according to claim 7, wherein, The density of the carbon nanoparticle layer (22) is 0.05 mg / cm³. 2 Up to 2 mg / cm 2 between.

9. The multilayer electrode (10) according to claim 8, wherein, The density of the carbon nanoparticle layer (22) is 0.2 mg / cm³. 2 Up to 1 mg / cm 2 between.

10. The multilayer electrode (10) according to claim 7, wherein, The weight percentage of the cation exchange ionomer (24) in the graphite layer (20) is the same as the weight percentage of the cation exchange ionomer (24) in the carbon nanoparticle layer (22).

11. The multilayer electrode (10) according to any one of claims 1 to 3, wherein, The weight percentage of the cation exchange ionomer (24) is between 1 wt.% and 20 wt.%.

12. The multilayer electrode (10) according to claim 11, wherein, The weight percentage of the cation exchange ionomer (24) is between 2.5 wt.% and 7.5 wt.%.

13. The multilayer electrode (10) according to any one of claims 1 to 3, wherein, The conductive layer (16) and / or the catalyst layer (14) contain a hydrophobic agent.

14. The multilayer electrode (10) according to any one of claims 1 to 3, wherein the multilayer electrode (10) further comprises a protective layer and / or a current collector (26), the protective layer and / or the current collector (26) being disposed adjacent to the conductive layer (16) on a side opposite to the catalyst layer (14) and / or at least partially surrounding the conductive layer (16).

15. An electrochemical cell (28) for CO2 electrolysis, said electrochemical cell (28) comprising a multilayer electrode (10) according to any one of the preceding claims.

16. The electrochemical cell (28) according to claim 15, wherein the electrochemical cell (28) comprises: Anode catalyst layer (34); The separator (36) is adjacent to the anode catalyst layer (34); and An electrolyte flow chamber (32) is arranged between the multilayer electrode (10) and the separator (36), wherein the multilayer electrode (10) forms a cathode.

17. The electrochemical cell (28) according to claim 16, wherein the separator is a cation exchange membrane.

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