Tailoring formulations based on anionic conductive polymers (ionomers) for the production of electrochemically active layers

Abstract

The present invention relates to a dispersion intended for the production of electrochemically active layer structures. The present invention further relates to the production of electrochemically active layer structures, in connection with which the dispersion according to the invention is provided. The present invention also relates in particular to an electrochemically active layer structure obtainable by said production method, and also to an electrochemical cell comprising at least such a layer structure. Furthermore, the present invention relates to a method for the production of hydrogen and oxygen by the splitting of water, using said electrochemical cell.

Description

[Technical field]

[0001] The present invention relates to a dispersion intended for the production of electrochemically active layer structures. The present invention further relates to the production of electrochemically active layer structures, in connection with which the dispersion according to the invention is provided. The present invention also relates in particular to an electrochemically active layer structure obtainable by said production method, and also to an electrochemical cell comprising at least such a layer structure. Furthermore, the present invention relates to a method for the production of hydrogen and oxygen by the splitting of water, using said electrochemical cell. [Background technology]

[0002] Electrochemical cells are technical devices in which electrochemical processes are carried out. They generally comprise an anode, a cathode and a separator placed between the anode and the cathode, dividing the electrochemical cell into two compartments. Examples of electrochemical cells include batteries, fuel cells and electrolyzers. Electrolysis takes place in electrolyzers, i.e. electrical energy is used to break or form chemical bonds.

[0003] An important electrolysis is the electrolysis of water, which splits water into oxygen and hydrogen. The separators in water electrolysers can be designed as ion-conducting membranes. A distinction is made between anion-conducting membranes (anion exchange membranes - AEM) and proton-conducting membranes (proton exchange membranes - PEM). Water splitting with the aid of anion-conducting membranes is often abbreviated as AEM-WE (anion exchange membrane water electrolysis) and is also called alkaline membrane water electrolysis. The well-known alkaline water electrolysis using porous diaphragms is not an AEM-WE in the today's sense, since the diaphragm is fluid-conducting. However, the membranes of AEM-WE are liquid-tight membranes. Anion conduction occurs at the level of the ions.

[0004] A good overview of the electrochemical cell structures and materials currently used in AEM-WE is given by: Miller, Hamish Andrew et al.: Green hydrogen from anion exchange membrane water electrolysis: A review of recent developments in key materials and operating conditions. Sustainable Energy Fuels, 2020, 4, 2114 DOI: 10.1039 / c9se01240k

[0005] In electrochemical processes, the conversion takes place at the surface of an electrocatalyst. To generate a catalytically active surface and allow the transport of materials, electrocatalysts are used in porous conductive layers. These layers are applied to other components of the electrochemical cell or used as separate components. In general, what is of interest here is the electrochemically active layer structure, whether or not the layer structure performs other functions in the cell in addition to catalysis.

[0006] In the field of water electrolysers it is customary to coat membranes with electrocatalytically active materials to obtain catalyst coated membranes (CCMs), see Miller et al., section 5.2. This kind of CCM is the first example of an electrochemically active layer structure.

[0007] Another example of an electrochemically active layer structure may be an electrode in which a conductive substrate is coated with an electrocatalytically active material to obtain a catalyst-coated substrate (CCS). See Miller et al., section 5.1. This type of CCS is a second example of an electrochemically active layer structure.

[0008] The morphology of the electrochemically active layer structure is determined by the catalyst particles and their arrangement in the layer structure. The polymer binder is suitable for permanent mechanical adhesion of the catalyst particles to each other or to a support material, in particular a support material that allows ion transport via the electrochemical reaction (ionically conductive polymers, often also called "ionomers").

[0009] The efficiency and service life of the electrochemically active layer structure depend, inter alia, on the selection and adjustment of the individual components and their processing. Already a crucial factor is the preparation of a suitable catalyst-ionomer formulation.

[0010] Several catalytic ionomer formulations and related processes for producing electrochemically active layer structures are already known in the scientific literature.

[0011] For example, Chen et al. describe the preparation of CCMs for fuel cells based on ionomeric poly(fluorenylarylpiperidinium): Chen, N., Wang, HH, Kim, S. P. et al. Poly(fluorenylarylpiperidinium) membranes and ionomers for anion exchange membrane fuel cells. Nat Commun 12, 2367 (2021). DOI10.1038 / s41467-021-22612-3

[0012] Park et al. describe coating an anion conducting membrane from Fumatech (FUMATECH BWT GmbH, Bietigheim-Bissingen, Germany) with a mixture of iridium oxide and platinum / carbon to obtain a CCM for water electrolysers: Ji Eun Park, Sun Young Kang, Seung-Hyeon Oh et al. High-performance anion exchange membrane water electrolysis, Electrochimica Acta, Vol. 295, 2019, pp. 99-106. DOI10.1016 / j.electacta.2018.10.143

[0013] Park et al. use the polymer FAA-3-Br from Fumatech (FUMATECH BWT GmbH, Bietigheim-Bissingen, Germany) as the ionomer, but do not provide the exact specifications of the ionomer FAA-3-Br.

[0014] Leng et al. fabricated catalyst-coated electrodes for alkaline fuel cells by spraying a Pt-containing ink onto a carbon nonwoven fabric. The ink contained a precursor of a Nafion ionomer. The ionomer was first crosslinked in-situ on the carbon nonwoven fabric: Yongjun Leng, Lizhu Wang, Michael A. Hickner et al., Alkaline membrane fuel cells using in-situ crosslinked ionomers, Electrochimica Acta, Vol. 152, 2015, pp. 93-100. DOI10.1016 / j.electacta.2014.11.055

[0015] In a similar manner, Faid et al. use a catalyst ink that contains dissolved ionomer, catalyst, isopropanol, and water. The catalyst systems used are Ni, Ni / C and Pt / C, and Ir: Alaa Y. Faid et al.: Effect of anion exchange ionomer content on electrode performance in AEM water electrolysis, International Journal of Hydrogen Energy, Vol. 45, No. 53, 2020, pp. 28272-28284, DOI10.1016 / j.ijhydene.2020.07 .202

[0016] US 2021 / 0009726 discloses the manufacture of an electrochemically active layer structure. More precisely, the layer structure is an MEA (membrane electrode assembly) intended for use in a fuel cell. In the manufacture of the MEA, the ionomer is dissolved in a water / alcohol mixture and the catalyst particles are dispersed in the solution. The dispersion is applied to the substrate. This procedure assumes that the ionomer is soluble in water / alcohol. An electrochemically active layer structure intended to be used in water electrolysis must not contain any water-soluble ionomer, as it will dissolve again during the operation of the cell.

[0017] Pandiarajan T. et al. coat the MEA with a dispersion of catalyst, ionomer, DMSO, 2-propanol, and water. Spinel Ce doped manganese / iron is used as the catalyst. Pandiarajan T., Berchmans LJ, Ravichandran S.: Fabrication of spinel ferrite based alkaline anion exchange membrane water electrolyser for hydrogen production. DOI:10.1039 / c5ra01123j

[0018] WO 2021 / 013694 discloses an anionically conductive polymer having the formula (I) that can be used to prepare membranes. The preparation of CCMs, CCSs, and other electrochemically active layer structures is not disclosed therein.

[0019] The preparation of ionomers having structural formula (II) is described in European Patent Application No. 21152487.1, which was unpublished at the filing date of the present application.

[0020] The preparation of ionomers having structural formula (III) is described in European Patent Application No. 21162711.2, which was unpublished at the filing date of the present application. [Prior art documents] [Patent documents]

[0021] [Patent Document 1] US Patent Application Publication No. 2021 / 0009726 [Patent Document 2] International Publication No. 2021 / 013694 Brochure Summary of the Invention [Problem to be solved by the invention]

[0022] The aim of the present invention was to prepare anionically conductive polymers which can be used as ionomers for the manufacture of electrochemically active layer structures. [Means for solving the problem]

[0023] This object is achieved by a dispersion according to claim 1, a method for producing an electrochemically active layer structure according to claim 8, an electrochemically active layer structure according to claims 13 and 15, an electrochemical cell according to claim 16 and a method for producing hydrogen and oxygen, respectively, according to claim 17. Preferred embodiments of the invention are described in the dependent claims.

[0024] All these subject matters are based on the unifying concept of taking the ionomers according to formula (I), formula (II) and formula (III) into solution, processing them in a dispersion and using this dispersion to produce catalytically active layer structures for electrochemical cells. Thus, all the subject matters disclosed herein form a common inventive complex.

[0025] During the course of the investigations, it was found that this type of polymer (ionomer) can be successfully processed into catalyst layers, especially in conjunction with the catalytic ionomer formulations prepared as described below, which are particularly suitable for electrochemical processes in which anion transport takes place. This works particularly well for the AEM-WE process. Thus, layer structures produced from the dispersions described herein are particularly suitable for use as CCMs or CCSs in alkaline water electrolysis.

[0026] The common advantages of the ionomers of formula (I), (II) or (III) are excellent ionic conductivity, high chemical and mechanical resistance in alkaline medium, and low synthesis costs.

[0027] The anionically conductive polymer processed into a dispersion conforms to structural formula (I), structural formula (II), or structural formula (III).

[0028] The anionic conductive polymer of structural formula (I) is defined as follows:

[0029] [ka]

[0030] (Wherein, X is C 1 and C 2 Z is a component containing a positively charged nitrogen atom bonded to C, which is bonded via two bonds to one or two hydrocarbon groups having 1 to 12, preferably 1 to 6, particularly preferably 1 or 5 carbon atoms. 3 and C 4 and at least one aromatic six-membered ring directly bonded to one of the oxygen atoms. The aromatic six-membered ring may be substituted with one or more halogens and / or one or more C1- to C4-alkyl groups.

[0031] The anionic conductive polymer of structural formula (II) is defined as follows:

[0032] [ka]

[0033] (Wherein, X is C 1 and C 2 Z is a component containing a positively charged nitrogen atom bonded to C, which is bonded via two bonds to one or two hydrocarbon groups having 1 to 12, preferably 1 to 6, particularly preferably 1 or 5 carbon atoms. 3 and C 4 and at least one aromatic six-membered ring directly bonded to one of the oxygen atoms. The aromatic six-membered ring may be substituted in the 3- and 5-positions with identical or different C1- to C4-alkyl groups, in particular with methyl, isopropyl or tert-butyl groups, preferably with methyl groups.

[0034] The anionic conductive polymer of structural formula (III) is defined as follows:

[0035] [ka]

[0036] (wherein X is a ketone group or a sulfone group. Z is an entity that contains at least one tertiary carbon atom and at least one six-membered aromatic ring, which is directly bonded to one of the two oxygen atoms. Y is an entity that includes at least one positively charged nitrogen atom, the nitrogen atom being bonded to entity Z.

[0037] A first subject of the invention is therefore a dispersion comprising at least the following components: - a solution of an anionic conductive polymer, - particles comprising at least one electrocatalytically active material, - Optionally, at least one dispersant. The anionically conductive polymer comprises at least one structure selected from the group comprising structural formulas (I), (II) and (III) defined above.

[0038] In the dispersion, the mass ratio of the anionically conductive polymer to the particles is 1:1 to 1:20, or 1:1 to 1:5, or 1:6 to 1:10. This means that the weight ratio of the particles containing electrocatalytically active substances is greater than the weight ratio of the anionically conductive polymer. In this way, a high density of catalytically active centers is obtained. The layer structures produced from the dispersion thus have a particularly high electrochemical activity.

[0039] These ionomers are particularly soluble in solvents from the following group: N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC) or dimethylsulfoxide (DMSO). DMSO is preferred. The solvent can be removed by drying so that the ionomer remains solid in the form of a polymer film. The concentration of the anionic conductive polymer should be between 10 mg / mL and 500 mg / mL, or between 50 mg / mL and 100 mg / mL, relative to the volume of the solvent.

[0040] Preferably, electrocatalytically active materials are used that contain at least one transition element. Transition elements in the context of this specification are Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ac, Rf, Db, Sg, Bh, Hs, Mt, Ds, Rg. Materials that contain transition elements are particularly electrocatalytically active than materials that do not contain transition elements. Furthermore, the relatively good electrical conductivity of transition metals reduces the internal resistance of the electrochemical cell.

[0041] The electrolytic activity of the layered structure produced from the dispersion is brought about by adding an electrocatalyst to the dispersion. The electrocatalyst is then fixed in the layered structure by an ionomer. Examples of electrocatalysts used include particles containing an electrocatalytically active material selected from the group including iridium (Ir), iridium oxide (IrOx), nickel oxide (NiOx), cobalt oxide (CoOx), nickel-iron mixed oxide (NiFeOx), nickel-cobalt mixed oxide (NiCoOx), lead-ruthenium mixed oxide (PbRuOx), platinum on carbon (Pt / C). To achieve an effective density of catalytically active centers in the layered structure, the mass ratio of the anionic conductive polymer to the particles in the dispersion is adjusted to 1:1 to 1:20, or 1:1 to 1:5, or 1:6 to 1:10.

[0042] The anionically conductive polymer is particularly preferably processed in a dispersion described by at least one of the following structural formulas (IVa) to (IVd):

[0043] [ka]

[0044] (In the formula, M a and M. bis a natural number from 1 to 500, preferably from 5 to 250, and the aromatic ring may be further substituted by one or more halogens and / or one or more C1- to C4-alkyl groups, in particular methyl groups.

[0045] The dispersion does not necessarily have to contain a separate dispersant. Under certain circumstances, the solvent also acts as a dispersant. However, it is preferred that at least one dispersant is added to increase the processability of the dispersion. As a result, the dispersion is free-flowing. It is also possible to use a mixture of two or more dispersants. In particular, it has been found to be advantageous when the formulation of the dispersion comprises two dispersants, namely water and alcohol, with a volume ratio of water to alcohol of 1:3 to 3:1. Preferably, water and alcohol are used in a ratio of 1:1. Suitable alcohols are ethanol, methanol, 1-propanol or 2-propanol. Such water / alcohol mixtures evaporate easily when drying the dispersion.

[0046] To ensure good processability, the solids concentration of the dispersion is preferably 5 mg / mL to 100 mg / mL, or 10 mg / mL to 25 mg / mL, based on the total amount of liquid components of the dispersion in each case. The solids present in the dispersion correspond to catalytically active particles. The ionomer in the solution is considered to be a liquid.

[0047] The dispersions described herein are intended to produce electrochemically active layer structures.

[0048] Therefore, the present invention further provides a method for producing an electrochemically active layer structure, comprising the steps of: a) containing at least the following components: - Dispersants - Organic solvent different from the dispersant -Anionic conductive polymers in organic solvents - particles comprising at least one electrocatalytically active material Providing a dispersion according to the invention comprising b) providing a substrate; c) applying the dispersion to a substrate; d) drying the dispersion applied to the substrate; e) obtaining a layer structure comprising a substrate and applied thereto at least a two-phase coating, the coating comprising as a first phase an anionically conductive polymer and as a second phase particles, the second phase being dispersed in the first phase.

[0049] The solvents and dispersants which are optionally present are not present in the layer structure as they evaporate on drying.

[0050] The dispersion is applied to the substrate in known manner by bar coating, spraying, or screen printing.

[0051] An advantage of the dispersions described herein is that they can be used to coat fiber substrates. Electrochemically active layer structures based on fiber structures have a particularly large surface area and therefore can achieve high process strength. The substrates used are therefore preferably fiber fabrics. The fiber fabrics are nonwoven, felt, woven or knitted. The fabrics are composed of fibers, threads or yarns. Preferably, a felt or nonwoven fabric is coated with a dispersion composed of nickel, carbon or steel fibers. Such substrates are practically available at low cost, are electrically conductive and are stable in the alkaline medium of the AEM-WE process. They are therefore suitable as electrodes in CCS structures.

[0052] Membranes composed of anionically conductive polymers can also be coated with the dispersions described herein. When anionically conductive membranes are used as substrates, the resulting layer structure is a CCM. The membranes used as substrates preferably also contain ionomers according to structure (I) or (II) or (III). Then, because the ionomers are compatible, a particularly good bond between the catalyst particles and the membrane is achieved.

[0053] A dispersion suitable for the production of an electrochemically active layer structure is prepared by the following procedure. i) providing a dispersant; ii) providing an organic solvent different from the dispersant; iii) providing an anionic conductive polymer; iv) providing particles; v) dissolving the anionic conductive polymer in an organic solvent so as to obtain a solution of the anionic conductive polymer; vi) suspending the particles in a dispersant to obtain a suspension; vii) Add the solution to the suspension.

[0054] This procedure results in a particularly homogeneous and stable dispersion of the electrocatalytically active particles in the anionically conductive polymer.

[0055] A mixture of water and alcohol is particularly suitable as a dispersant, since the particles are well suspended therein and the water and alcohol dry quickly after application of the dispersion. The boiling points of water and alcohol are in fact lower than, for example, the boiling point of DMSO (189 ° C). Thus, in the manufacture of electrochemically active layer structures, the use of water / alcohol as a dispersant allows the layers to be built up quickly. However, water is not suitable as a solvent, since the anionically conductive polymers to be used for water electrolysis must in principle be insoluble in water. Otherwise the water electrolysis cell will break down rapidly during operation. Alcohol also hardly dissolves the anionically conductive polymers described herein, so it is necessary to use much stronger organic solvents. Preferably, at least one of the following substances is used as the organic solvent: N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC) or dimethylsulfoxide (DMSO). Preference is given to DMSO. These solvents can also be removed by drying, and the ionomer remains as a solid in the form of a polymer film. However, as precipitation experiments show, the specified organic substances are not suitable as dispersants for all catalyst systems. It therefore makes sense to use different substances as solvents or dispersants depending on the catalyst system selected.

[0056] The invention further relates to an electrochemically active layer structure comprising a substrate and at least a two-phase coating applied to the substrate. The coating comprises particles comprising an anionically conducting polymer as a first phase and an electrocatalytically active material as a second phase. The second phase is dispersed in the first phase. The anionically conducting polymer comprises at least one structure according to formula (I), (II) or (III). Depending on the substrate chosen, the layer structure is in particular CCM or CCS. In both cases the loading of electrochemically active material is preferably less than 0.2 mg / cm. 2 ~10mg / cm 2 , or 0.4 mg / cm 2 ~2mg / cm 2 It is.

[0057] The electrochemically active layer structure particularly preferably comprises an anion-conducting polymer represented by at least one of the following structural formulae (IVa) to (IVd):

[0058] [ka]

[0059] (In the formula, M a and M. b is a natural number from 1 to 500 or 5 to 250, and the aromatic ring may be further substituted by one or more halogens and / or one or more C1- to C4-alkyl groups, in particular methyl groups.

[0060] Such ionomers have good ionic conductivity, high chemical and mechanical resistance in alkaline media, low synthesis costs, they also anchor the catalyst particles firmly on the substrate and can be processed very well in dispersion.

[0061] Depending on the formulation of the dispersion chosen, the application method chosen and the time / temperature regime of the drying process, the coating on the substrate, or more precisely the first dispersed phase of the anionically conductive polymer, acquires a specific structure that improves the accessibility of the catalytically active centers of the particles in the coating to the electrolyte.The electrochemically active layer structure obtained by the coating process according to the invention is therefore also a subject of the present invention.

[0062] The electrochemically active layer structures produced from the dispersions can be ideally used in electrochemical cells, for example as CCMs or CCSs, which in addition to the layer structures may also include further components, such as other electrodes or separators, or fluid conductors or contact plates.

[0063] Due to the particular stability of the ionomers and the catalytic activity of the particles treated in the dispersion and re-present in the layer structure, an electrochemical cell comprising the layer structure is preferably used to carry out a process for the production of hydrogen and oxygen by electrochemical decomposition of water, whereby an aqueous electrolyte having a pH of 7 to 15 is filled into the electrochemical cell. Such an AEM-WE process is also the subject of the present invention.

[0064] The invention will now be explained in more detail by means of examples. [Brief description of the drawings]

[0065] [Figure 1] : Electrochemical cell configuration [Diagram 2] :Electrochemical cell test equipment [Diagram 3] :Graph display of current-voltage curve [Figure 4] :Graph display of current-voltage curve

[0066] The basis for the production of formulations containing the above polymers (ionomers) is the production of an ionomer solution. Examples of suitable solvents are N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), or dimethylsulfoxide (DMSO). DMSO is preferred, since it is classified as non-hazardous. The proportion of polymer is 10 mg / mL to 500 mg / mL, or 25 mg / mL to 200 mg / mL.

[0067] The mass ratio of ionomer to catalytically active material is, for example, 1:1 to 1:20, or 1:3 to 1:5, for catalysts based on platinum on carbon (Pt / C), iridium (Ir), iridium oxide (IrOx), nickel oxide (NiOx), cobalt oxide (CoOx), nickel-iron mixed oxide (NiFeOx), nickel-cobalt mixed oxide (NiCoOx) or lead-ruthenium mixed oxide (PbRuOx).

[0068] The catalyst and ionomer solutions are first reduced in particle size (d 50 After dispersion, the catalyst may be applied directly (for example, by screen printing or knife coating), after which it may be applied, particularly in the case of application by spraying, by ultrasonic or (for example, particle size d 50The ionomer solution can be added to the solution of water and lower alcohol (preferably ethanol, 1-propanol or 2-propanol) under the action of a disperser (using ULTRA-TURRAX® dispersing system manufactured by IKA, Staufen, Germany, to further adjust the particle size to the range of 0.1 μm to 50 μm), and then the ionomer solution (preferably 50 mg / mL) can be added thereto and further dispersed under ultrasonic waves to produce an aqueous dispersion. The solid content concentration is 5 mg / mL to 100 mg / mL, preferably 10 mg / mL to 25 mg / mL. The unit of ionomer solution (mg / mL) is based on the mass of polymer / volume of solvent or dispersion to the mass of catalyst / volume of liquid component.

[0069] Particularly suitable substrates for the application of the prepared formulations are non-woven carbon or metal (nickel, stainless steel, titanium) fabrics, and ionically conductive polymer membranes.

[0070] The catalyst loading on the substrate was 0.2 mg / cm 2 ~10mg / cm 2 , or 0.4 mg / cm 2 ~2mg / cm 2 It is.

[0071] Table 1 shows the composition of some dispersions according to the invention with which a catalyst layer can be applied to a substrate.

[0072] The ionomer used is the material prepared as described in Example 3 of WO 2021 / 013694.

[0073] The ionomer was first dissolved in dimethylsulfoxide with stirring at temperature (60°C) for 16 hours. The catalyst was then dispersed in a dispersant containing equal amounts of water and ethanol using ultrasound (BRANSON ICTM B-1200 E2, Branson Ultrasonics Corporation, Brookfield, Connecticut, USA) at 30 W power for 30 minutes in an ice bath or ULTRA-TURRAX® T10 Basic Dispersion System (IKA, Staufen, Germany) for 3 minutes in stage 3. After the ionomer solution was added, it was further dispersed using ultrasound in an ice bath at a power setting of 30 W for 1 minute and dispersed using a shaker (MS1 Minishaker, IKA, Staufen, Germany) at 2500 rpm for 10 seconds. The ratios were selected according to Table 1.

[0074] The dispersions according to the invention were sprayed onto the substrates using a PRISM 400 ultrasonic spray coater (Ultrasonic Systems, Inc., Haverhill, Massachusetts, USA). The formulations were continuously stirred during the process. The substrates were kept at a temperature of 60° C., which allowed the dispersant to continuously evaporate, resulting in the production of the layer structure according to the invention.

[0075] The layer structure thus obtained can be used as an electrode for producing hydrogen and / or oxygen in alkaline membrane water electrolysis (AEM-WE). The electrochemical cell of Fig. 1 essentially consists of two electrically active layer structures (A, A') (at least one of which was produced by the method according to the invention), which were separated by an anion-conducting membrane (B). The electrolyte supply (1 M KOH, 60°C) was provided via a flow and current distributor (C) electrically isolated by a seal (D).

[0076] The function of the produced layer structure is shown in the typical current-voltage curves (constant current: 0.02–1.50 A / cm) shown in Figures 3 and 4. 2 ) was used in the cell test setup described above (Figure 2).

[0077] In principle, catalyst layers produced on the basis of the described catalyst-ionomer formulations (dispersions) can also be used for electrochemical processes other than alkaline membrane water electrolysis (AEM-WE), examples of which include alkaline fuel cells or the electrolysis (reduction) of carbon dioxide. Table 1: Dispersion composition

[0078] [Table 1]

[0079] Precipitation experiments The stability of the dispersions needs to be investigated by precipitation experiments. For this purpose, four different compositions are available, each with and without ionomer, and are considered. As catalysts, platinum / carbon or nickel oxide are used.

[0080] procedure Dispersions are prepared in snap-cap vials. Dispersion 1: 11 mg / mL Pt / C in DMSO Dispersion 2: 11 mg / mL Pt / C in ethanol:water Dispersion 3: 11 mg / mL NiO in DMSO Dispersion 4: 11 mg / mL NiO in ethanol:water

[0081] Dispersions 1-4 are placed in an ultrasonic bath for 30 minutes and then shaken. Observe and record any precipitation. After about 30 minutes the ionomer is added. Dispersion 1 and Dispersion 2: 3.7 mg / mL ionomer added Dispersion 3 and Dispersion 4: 2.8 mg / mL ionomer added The dispersion is placed in an ultrasonic bath for 1 minute, shaken and observed for precipitation.

[0082] observation The Pt / C plus ionomer dispersion in DMSO precipitated and formed two phases after 15 minutes. The top phase was clear and the bottom phase was black. Nickel oxide dispersions in ethanol and water (with and without ionomer) also separated into two phases. Without ionomer, this occurred after about 3 minutes. A black layer precipitated at the bottom and a dark grey layer formed above it. The dispersion with ionomer also showed a slight separation into light and dark layers after 3 minutes, but this was more noticeable after 15 minutes. The top phase was milky white and the bottom phase was black.

[0083] Pt / C dispersions in ethanol and water (with and without ionomer), nickel oxide in DMSO (with and without ionomer), and Pt / C in DMSO showed no abnormalities over the test period.

Claims

1. At least the following ingredients: -Anionic conductive polymer solution particles comprising at least one electrocatalytically active material; - optionally at least one dispersant a dispersion comprising: The anionic conductive polymer has structural formula (I): 【Chemistry 1】 (Wherein, X is C １ and C ２ is a component containing a positively charged nitrogen atom bonded to a C ３ and C ４ and contains at least one aromatic six-membered ring bonded directly to one of the oxygen atoms. The aromatic six-membered ring may be one or more halogens and / or one or more C １ - C ４ - may be substituted with an alkyl group. Structural formula (II): 【Chemistry 2】 (Wherein, X is C １ and C ２ is a component containing a positively charged nitrogen atom bonded to a C ３ and C ４ and contains at least one aromatic six-membered ring bonded directly to one of the oxygen atoms. The aromatic 6-membered ring may have the same or different C １ - C ４ may be substituted with an alkyl group. and structural formula (iii): 【Transformation 3】 (wherein X is a ketone group or a sulfone group. Z is an entity that includes at least one tertiary carbon atom and at least one aromatic six-membered ring, said aromatic six-membered ring being directly bonded to one of the two oxygen atoms. Y is a component containing at least one positively charged nitrogen atom, said nitrogen atom being bonded to said component Z. and wherein the at least one structure is selected from the group comprising: a mass ratio of the anionically conductive polymer to the particles in the dispersion is from 1:1 to 1:20, or from 1:1 to 1:5, or from 1:6 to 1:

10.

2. 2. The dispersion of claim 1, wherein the solution of the anionically conductive polymer comprises at least one solvent selected from the group comprising N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAC), or dimethyl sulfoxide (DMSO), and the concentration of the anionically conductive polymer is 10 mg / mL to 500 mg / mL or 50 mg / mL to 100 mg / mL based on the volume of the solvent.

3. The dispersion of claim 1 , wherein the electrocatalytically active material comprises at least one transition element.

4. 2. The dispersion of claim 1, wherein the particles comprise at least one electrocatalytically active material selected from the group comprising iridium (Ir), iridium oxide (IrOx), nickel oxide (NiOx), cobalt oxide (CoOx), nickel-iron mixed oxide (NiFeOx), nickel-cobalt mixed oxide (NiCoOx), lead-ruthenium mixed oxide (PbRuOx), platinum on carbon (PT / C), and the mass ratio of the anion-conducting polymer to the particles in the dispersion is from 1:1 to 1:20, or from 1:1 to 1:5, or from 1:6 to 1:

10.

5. The anion conductive polymer is represented by the following structural formula (IVa) to structural formula (IVd): 【Chemistry 4】 (In the formula, M ａ and M ｂ is a natural number from 1 to 500 or from 5 to 250, and the aromatic ring contains one or more halogens and / or one or more C １ - C ４ may be further substituted by alkyl groups, in particular methyl groups.

5. The dispersion of claim 4, represented by at least one of:

6. 6. The dispersion of claim 5, comprising two dispersants, namely water and alcohol, the volume ratio of said alcohol to said water being from 1:3 to 3:

1.

7. 3. The dispersion of claim 2, wherein the solids concentration is from 5 mg / mL to 100 mg / mL, or from 10 mg / mL to 25 mg / mL, in each case relative to the total volume of the liquid components of the dispersion.

8. a) at least the following ingredients: -Dispersant - Organic solvent different from the dispersant -Anionic conductive polymers in organic solvents particles comprising at least one electrocatalytically active material providing a dispersion according to any one of claims 1 to 7, b) providing a substrate; c) applying the dispersion to the substrate; d) drying the dispersion applied to the substrate; e) obtaining a layer structure comprising said substrate and at least a two-phase coating applied thereto, said coating comprising said anionically conductive polymer as a first phase and said particles as a second phase, said second phase being dispersed in said first phase.

10. A method for producing an electrochemically active layer structure, comprising:

9. The method of claim 8, wherein the application is by bar coating, spraying, or screen printing.

10. 9. The method of claim 8, wherein the substrate is a fibrous fabric comprising nickel, carbon, or steel fibers.

11. The method of claim 8 , wherein the substrate is a membrane made of an anionically conductive polymer.

12. The dispersion is selected from the group consisting of: i) providing said dispersant; ii) providing said organic solvent different from said dispersant; iii) providing said anionic conductive polymer; iv) providing said particles; v) dissolving said anionically conductive polymer in said organic solvent to obtain a solution of said anionically conductive polymer; vi) suspending the particles in the dispersant to obtain a suspension; vii) adding said solution to said suspension The method of claim 8, wherein the

13. 1. An electrochemically active layer structure comprising a substrate and at least a two-phase coating applied thereto, said coating comprising an anionically conductive polymer as a first phase and particles comprising an electrocatalytically active material as a second phase, said second phase being dispersed within said first phase; The anionic conductive polymer has structural formula (I): 【Transformation 5】 (Wherein, X is C １ and C ２ is a component containing a positively charged nitrogen atom bonded to a C ３ and C ４ and contains at least one aromatic six-membered ring bonded directly to one of the oxygen atoms. The aromatic six-membered ring may be one or more halogens and / or one or more C １ - C ４ - may be substituted with an alkyl group. Structural formula (II): 【Transformation 6】 (Wherein, X is C １ and C ２ is a component containing a positively charged nitrogen atom bonded to a C ３ and C ４ and contains at least one aromatic six-membered ring bonded directly to one of the oxygen atoms. The aromatic 6-membered ring may have the same or different C １ - C ４ may be substituted with an alkyl group. and structural formula (III): 【Transformation 7】 (wherein X is a ketone group or a sulfone group. Z is an entity that includes at least one tertiary carbon atom and at least one aromatic six-membered ring, said aromatic six-membered ring being directly bonded to one of the two oxygen atoms. Y is a component containing at least one positively charged nitrogen atom, said nitrogen atom being bonded to said component Z. Electrochemically active layer structure having at least one structure selected from the group comprising:

14. The anion conductive polymer is represented by the following structural formula (IVa) to structural formula (IVd): 【Transformation 8】 (In the formula, M ａ and M ｂ is a natural number from 1 to 500, preferably from 5 to 250, and the aromatic ring is １ - C ４ may be further substituted by an alkyl group. The electrochemically active layer structure of claim 13 , represented by at least one of:

15. 14. An electrochemically active layer structure according to claim 13, obtainable by a method according to any one of claims 8, 9 or 10.

16. 14. An electrochemical cell comprising at least one electrochemically active layer structure according to claim 13.

17. A method for producing hydrogen and oxygen by electrochemical splitting of water, comprising filling the electrochemical cell of claim 16 with an aqueous electrolyte having a pH of 7 to 15.

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