EP-4735671-A1 - NOVEL MEMBRANE ELECTRODE ASSEMBLY DESIGN FOR C2H4 SELECTIVE CEM-TYPE CO2-ELECTROLYZERS

Abstract

The present invention pertains to a membrane assembly, in particular a membrane electrode assembly, for CO 2 electrolysis in a zero-gap cell, as well as a corresponding zero-gap cell and method for producing such membrane assembly. Accordingly, a membrane assembly (10) for supporting CO 2 electrolysis in a zero-gap cell electrolyzer is suggested, comprising an anion exchange ionomer layer, wherein said anion exchange ionomer layer comprises microparticles and/or nanoparticles at a weight percent between 1 wt. % and 50 wt. %, wherein the microparticles and/or nanoparticles comprise or are formed of a metal oxide. According to the invention, the membrane assembly (10) furthermore comprises a catalyst layer (12) comprising a copper-based cathode catalyst, the anion exchange ionomer layer and the catalyst layer (12) together forming a membrane electrode assembly.

Inventors

• Sahin, Baran
• SIMON, ELFRIEDE
• Wiesner-Fleischer, Kerstin
• MAGORI, ERHARD
• PASTUSIAK, REMIGIUSZ
• TAWIL, ANGELIKA

Assignees

• Siemens Energy Global GmbH & Co. KG

Dates

Publication Date

20260506

Application Date

20240806

Claims (1)

1. 2023PF12207 Subsequent Filing Version 24 Patent claims 1. A membrane assembly (10) for supporting CO 2 electrolysis in a zero-gap cell electrolyzer, comprising an anion exchange ionomer layer, wherein said anion exchange ionomer layer comprises microparticles and/nanoparticles at a weight percent between 1 wt. % and 50 wt. %, wherein the mi- croparticles and/or nanoparticles comprise or are formed of a metal oxide, characterized in that the membrane assembly (10) comprises a catalyst layer (12) comprising a copper-based cathode catalyst, the anion ex- change ionomer layer and the catalyst layer (12) together forming a membrane electrode assembly. 2. The membrane assembly (10) according to claim 1, wherein the microparticles and/or nanoparticles are present in the anion exchange ionomer layer at a weight percent between 5 wt. % and 35 wt. %, preferably between 15 wt. % and 25 wt. %. 3. The membrane assembly (10) according to claim 1 or 2, wherein the microparticles and/or nanoparticles have a size between 10 nm and 80 µm, said particles preferably having an essentially uniform size. 4. The membrane assembly (10) according to claim 3, wherein the microparticles and/or nanoparticles have a size between 80 nm and 120 nm or between 3 µm and 7 µm, the microparticles and/or nanoparticles preferably being present in the anion exchange ionomer layer at a weight percent between 15 wt. % and 25 wt. %. 5. The membrane assembly (10) according to any of the pre- ceding claims, wherein the microparticles and/or nanoparti- cles comprise or are formed of titanium dioxide, zirconium 2023PF12207 Subsequent Filing Version 25 dioxide, cerium dioxide, aluminium oxide, yttrium oxide, or silicon dioxide. 6. The membrane assembly (10) according to any of the pre- ceding claims, wherein the anion exchange layer has been di- rectly formed on the catalyst layer (12). 7. The membrane assembly (10) according to claim 6, wherein the catalyst layer (12) comprises a predefined amount of ani- on exchange ionomer. 8. The membrane assembly (10) according to claim 7, further comprising a conductive layer arranged between the catalyst layer (12) and the anion exchange ionomer layer, wherein the catalyst layer (12) and the conductive layer together form a gas diffusion electrode, and wherein the conductive layer comprises at least one layer comprising a predefined amount of cation exchange ionomer. 9. The membrane assembly (10) according to claim 8, wherein the weight percent of anion exchange ionomer in the catalyst layer (12) is between 1 wt. % and 25 wt. %, wherein the amount of cation exchange ionomer in the conductive layer preferably corresponds to the amount of anion exchange iono- mer. 10. The membrane assembly (10) according to claim 8 or 9, wherein the conductive layer comprises a carbon nanoparticle layer, wherein the weight percent of cation exchange ionomer for said layer is between 1 wt. % and 25 wt. %. 11. A zero-gap electrochemical cell (28) for CO 2 electroly- sis, comprising an anode catalyst layer (34), a cation exchange membrane (14) arranged adjacent to the an- ode catalyst layer (34), and 2023PF12207 Subsequent Filing Version 26 a membrane assembly (10) according to any of the preceding claims arranged adjacent to the cation exchange membrane (14). 12. A method for producing a membrane assembly (10) for sup- porting CO 2 electrolysis in a zero-gap cell electrolyzer (28), wherein a mixture of anion exchange ionomer and micro- particles and/or nanoparticles comprising or being formed of a metal oxide forms an anion exchange ionomer layer by physi- cal vapor deposition, chemical vapor deposition, drop cast- ing, spray coating, or dry pressing, wherein the mixture com- prises the microparticles and/or nanoparticles at a weight percent between 1 wt. % and 50 wt, characterized in that the mixture is applied onto a copper-based cathode catalyst layer (12). 13. The method according to claim 12, wherein the mixture is applied directly onto the copper-based cathode catalyst layer (12) by drop casting or wherein the anion exchange ionomer layer is formed by hot or cold dry pressing the mixture be- tween the cation exchange membrane (14) and the cathode cata- lyst layer (12). 14. The method according to claim 12 or 13, wherein the mi- croparticles and/or nanoparticles comprise or are formed of titanium dioxide, zirconium dioxide, cerium dioxide, alumini- um oxide, yttrium oxide, or silicon dioxide.

Description

2023PF12207 Subsequent Filing Version 1 Description Novel membrane electrode assembly design for C2H4 selective CEM-type CO2-electrolyzers Technical Field The invention relates to a membrane assembly, in particular a membrane electrode assembly, for carbon dioxide (CO2) elec- trolysis in a zero-gap cell, as well as a corresponding zero- gap cell and method for producing such membrane assembly. Technological Background Electrochemical CO2 reduction reaction (CO2RR) to hydrocar- bons poses a promising alternative to other energy storage strategies in the future. The conversion of CO2 by electro- chemistry is an attractive means by which renewable electric- ity, such as solar energy and wind energy, can be used and CO2 can be bound as a product. However, it has been a chal- lenge to develop systems that are sufficiently selective, ef- ficient and stable, in particular in view of selective hydro- carbon formation. In this regard, catalysts for CO2 reduction reaction can par- ticularly suffer from poor stability of the desired products’ formation. From the group of potential catalysts including e.g. copper (Cu), silver (Ag), gold (Au), palladium (Pd), tin (Sn), copper is the only transition metal catalyst for CO2RR to value added C2+ products, such as ethylene, ethanol, or propanol. Such copper-based catalysts are commonly used on the cathode side of the electrochemical cells. In the cathode, CO2 may be reduced to a variety of compounds, including carbon monoxide, formate, ethylene, ethanol, propa- nol and some other minor products, such as methane or allyl alcohol. However, undesired side reactions typically occur at the cathode, including a hydrogen evolving reaction (HER). In 2023PF12207 Subsequent Filing Version 2 this regard, the thermodynamical equilibrium potentials ver- sus standard hydrogen of the above-mentioned reactions unfor- tunately suggest that the CO2 reduction to CO2RR products and the occurrence of hydrogen formation are thermodynamically favored in the same and very narrow potential range. While copper-based cathode electrodes may theoretically be implemented in various electrolyzer cell architectures, not all of these architecture designs are compatible for use with a CO2 electrolyzer. For example, an electrolyzer cell archi- tecture that has been implemented both in research and on larger scale in industrial electrolyzer cells is a cation ex- change membrane (CEM) based zero-gap cell. While such design hence readily enables scalability, zero-gap cells are contem- plated for water electrolysis. In accordance, it has been found that the cation exchange membrane interfacial microen- vironment entirely inhibits the CO2 reduction reaction while promoting the hydrogen evolving reaction, such that attempts to implement copper-based cathode electrodes in such cells have so far been unsuccessful. In particular, it was found on the level of the cation ex- change membrane that the membrane develops an acidic surface due to the dissolved sulfonate side chains of the per- fluorosulfonic acid (PFSA) backbone. These side chains form spherically shaped ionic clusters, which associate protons, thereby accumulating several hydronium ions per sulfonate group. As a result, a pH shift occurs towards acidic values in the membrane vicinity, wherein these local acidic condi- tions in the cathode electrode proximity increase the kinetic overpotentials for CO2 reduction reactions, leading to an al- most exclusive selectivity to the competing and undesired hy- drogen evolving reaction. So far efforts have been made to resolve these challenges, for example, by implementing an anion exchange membrane. How- ever, for anion exchange membranes there exists an intrinsic efficiency problem, since the CO2 feed is turned into car- 2023PF12207 Subsequent Filing Version 3 bonate and bicarbonate in alkaline conditions and the anions are hence transferred through the anion exchange membrane, leading to CO2 losses and undesired salt formation. On the other hand, carbon exchange membranes can ensure an almost CO2 free anode, thereby minimizing CO2 losses. Other efforts aiming at strong acidic conditions with the presence of po- tassium ions have not been found to provide prolonged stabil- ity. Accordingly, a need exists to improve the reaction conditions and microenvironment necessary for CO2 reduction reactions and, in particular, to abrogate the issues in widely used CEM-based zero-gap cells inhibiting CO2 reduction reactions to facilitate industrial scalability for CO2 electrolysis. From EP 3434810 A1 a co-electrolysis cell is known that is designed for efficient CO2 reduction from a gas phase at low temperatures and abrogates the problem of parasitic CO2 pump- ing from cathode to anode. The cell includes an anode and cathode as well as a polymer ion exchange membrane between cathode and anode and an additional ion exchange polymer film between the cathode and the polymer ion exchange membrane. The cathode comprises a layer