Electrochemical cell layer for an electrochemical aggregate, and method for its production

Abstract

The invention relates to an electrochemical cell layer (100) for an electrochemical cell stack (10, 60), in particular a fuel cell stack (10) or an electrolysis cell stack (60), comprising a substrate (102) and a catalyst layer (106) provided on the substrate (102), wherein the catalyst layer (106) is formed as a catalyst layer (106) grown locally epitaxially on the substrate (102).

Description

[0001] The invention relates to an electrochemical cell layer and a method for producing an electrochemical cell layer. Furthermore, the invention relates to an electrochemical cell stack, an electrochemical assembly, and an electrochemical system. State of the art

[0002] In an electrolyzer of an electrolyzer unit (stationary or mobile), e.g., an electrolyzer system, e.g., a fuel cell vehicle, or an electrolyzer plant, water is electrochemically converted into hydrogen and oxygen using electrical energy, generating heat. - In a low-temperature polymer electrolyte fuel cell of a fuel cell unit (mobile or stationary), e.g., a fuel cell system, e.g., a fuel cell vehicle, two reactants of two operating media are electrochemically converted into electrical energy and heat.

[0003] The respective assembly can comprise at least one membrane electrode device, e.g., a membrane electrode assembly (MEA) with a PEM (proton exchange membrane) or an AEM (anion exchange membrane). Alternatively to the MEA, at least one electrode of a membrane electrode device can be arranged apart from and directly opposite a membrane on a fluid transport structure of the membrane electrode device. The assembly can be configured with a plurality of membrane electrode devices arranged in a stack and bipolar plates arranged between them, forming an electrochemical cell stack with a plurality of individual cells. Task

[0004] Efforts are constantly underway to improve fuel cell units and electrolyzer units and to make them more cost-effective in terms of materials, manufacturing costs, and / or maintenance costs. It is an object of the invention to provide an improved, particularly more cost-effective, cell stack layer for an electrochemical cell stack, in particular a fuel cell stack or an electrolysis cell stack. Disclosure of the invention

[0005] The object of the invention is achieved by means of an electrochemical cell layer and by a method for producing an electrochemical cell layer, each for an electrochemical cell stack; by means of an electrochemical cell stack, in particular a fuel cell stack or an electrolysis cell stack, for an electrochemical unit; and by means of an electrochemical unit, in particular a fuel cell unit or an electrolyzer unit, and an electrochemical system, in particular a fuel cell system or an electrolyzer system. Advantageous developments, additional features, and / or advantages of the invention emerge from the dependent claims and the following description.

[0006] The electrochemical cell layer according to the invention comprises a substrate and a catalyst layer provided on the substrate, wherein the catalyst layer is formed as a catalyst layer grown locally epitaxially on the substrate. The cell layer is particularly applicable to fuel cells and electrolyzers with PEM or AEM membranes, as well as to CO2 electrolyzers. The locally epitaxially grown catalyst layer provides a number of advantages for the electrical and / or chemical function of the cell layer.

[0007] For a particular catalyst layer material, this results in a longer durability or chemical stability of the catalyst layer (low-energy structure of the locally epitaxial catalyst layer). The electrical properties of the cell layer are improved, particularly with regard to electrical contact resistance. Furthermore, the growth of the catalyst layer allows for precise adjustment of its thickness over a wide range. Furthermore, it is possible to form the catalyst layer with different thicknesses in some areas, depending on the electrical, chemical, or even mechanical requirements of the cell stack.

[0008] A mediator layer can be arranged between the substrate and the catalyst layer, which is designed as a nucleation layer (seed layer) for the grown catalyst layer. Furthermore, the mediator layer can additionally or alternatively be designed as a commensurability layer, which enables crystal growth on the substrate as a substrate on which otherwise no or only limited crystal growth is possible.

[0009] The mediator layer as a nucleation layer is necessary, for example, when local epitaxial orientation between the substrate and the catalyst layer is not possible. And the mediator layer as a commensurability layer is necessary, for example, when no or only limited crystal growth of a material of the catalyst layer on the substrate is possible. Furthermore, a preferably amorphous bonding layer can be arranged between the substrate and the mediator layer. The mediator layer and / or the bonding layer can be constructed in such a way that interdiffusion between the substrate and the catalyst layer is significantly reduced.

[0010] The catalyst layer can continue a polycrystalline surface layer of the substrate locally epitaxially outwardly away from the substrate. Furthermore, the catalyst layer of the cell layer can be thicker in at least one region in which the catalyst layer is more susceptible to corrosion than in a region away from it. Furthermore, at least one third of the catalyst layer grown on the substrate can be formed as a locally epitaxial catalyst layer. Preferably, a minimum area proportion of the locally epitaxial catalyst layer compared to the entire catalyst layer is approximately 25%, approximately 30%, approximately 35%, approximately 40%, approximately 45%, approximately 50%, approximately 55%, approximately 60%, approximately 65%, approximately 70%, approximately 75%, or approximately 80%.

[0011] The locally epitaxial catalyst layer grown can be a thin film with an average layer thickness of less than, greater than or equal to approximately: 5nm, 10nm, 25nm, 50nm, 75nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1µm, 5µm, 10µm, 15µm, 20µm, 25µm, 30µm, 40µm, 50µm, 60µm, 70µm, 80µm, 90µm or 100µm. The substrate of the electrochemical cell layer can be a membrane, a fluid transport structure, a polar plate, or a polymer for the electrochemical cell stack.

[0012] The substrate as a membrane can be designed as a membrane of a membrane electrode assembly (MEA), e.g., as a CCM (Catalyst Coated PEM / AEM), particularly for a membrane electrode device. The substrate as a fluid transport structure can be designed, for example, as a structured or unstructured, metallic or non-metallic plate, sintered material, or paper. A fluid transport structure can be designed, in particular, as a transport layer, a transport sheet, a PTL, a GDL, a sintered metal element, a metallic sintered paper, a fiber element, a carbon sheet, a carbon paper, a flow structure, a flow field, etc. The substrate as a polar plate is designed, in particular, as a bipolar plate, but can of course also be designed as a monopolar plate. The substrate as a polymer can, for example, substitute for a conventional fluid transport structure.

[0013] In the method according to the invention for producing an electrochemical cell layer, a catalyst layer is provided on a substrate of the cell layer, wherein the production method is carried out such that the catalyst layer grows locally epitaxially on the substrate. The production method can be designed as a one-step process, wherein the catalyst layer grows locally epitaxially directly on the substrate. Alternatively, the production method can be designed as a two-step process, wherein first a mediator layer is provided on the substrate and subsequently the catalyst layer grows locally epitaxially on the mediator layer.Alternatively, the manufacturing process can be designed as a three-stage process, wherein first a preferably amorphous bonding layer is provided on the substrate, then a mediator layer is provided on the bonding layer and then the catalyst layer is grown locally epitaxially on the mediator layer.

[0014] The catalyst layer and / or the intermediary layer can be applied, for example, using (plasma-assisted) physical vapor deposition (PA-)PVD, (plasma-assisted) (metalorganic) chemical vapor deposition (PA-)(MO-)CVD, atomic layer deposition (ALD), electrodeposition, electron beam evaporation, thermal evaporation, thermal spraying, plasma spraying, or electrochemical deposition. The designations in parentheses refer to applicable extensions of the respective coating process and thus to subprocesses of a higher-level process group.

[0015] The manufacturing process can essentially comprise only the following steps: First, loading a manufacturing chamber with the substrate to be coated and in-situ cleaning of the substrate surface to be coated. In-situ cleaning can be achieved, in particular, by sputtering, e.g., with noble gases, reactive ion etching, etc. In the subsequent step, the substrate surface is coated with the catalyst layer, or with the mediator layer and the catalyst layer. In the latter case, the entire mediator layer is naturally produced first, and only subsequently does the catalyst layer grow on the mediator layer.

[0016] The electrochemical cell stack according to the invention comprises a plurality of stacked cell layers which form individual electrochemical cells of the cell stack, wherein preferably only anode-side and / or preferably only cathode-side electrochemical cell layers of the stacked cell layers of the cell stack have a locally epitaxial catalyst layer on a respective substrate, which locally epitaxially continues a particularly polycrystalline surface layer of the respective substrate or a respective mediator layer on the substrate.

[0017] The locally epitaxial catalyst layers can be grown on membranes, fluid transport structures, polar plates, or polymers of the cell stack, and / or directly adjacent to fluid transport structures, polar plates, polymers, or membranes. The locally epitaxial catalyst layers are arranged, in particular, between membranes and fluid transport structures and / or between membranes and polar plates, with the locally epitaxial catalyst layers being grown on the membranes, fluid transport structures, or polar plates.

[0018] The locally epitaxial catalyst layers can be mechanically detachably attached to membranes, fluid transport structures, or polar plates of the cell stack. Furthermore, the locally epitaxial catalyst layers can be grown integrally on the substrates of the fluid transport structures, polar plates, or membranes. Internal cohesion between a substrate and a respective catalyst layer is based exclusively on cohesion and adhesion. Amorphous bonding layers can preferably be arranged between the substrates and the mediator layers. The cell layers, preferably only on the anode side and / or preferably only on the cathode side, can be designed according to the invention (see above) and / or manufactured according to the invention (see also above).

[0019] The electrochemical unit or the electrochemical system according to the invention comprises at least one electrochemical cell stack and a control device for controlling and / or regulating operation of the cell stack, wherein electrochemical cell layers of the cell stack are designed according to the invention, electrochemical cell layers of the cell stack are manufactured according to the invention and / or the cell stack is designed according to the invention. Short description of the characters

[0020] The invention is explained in more detail below using exemplary embodiments with reference to the attached schematic and not-to-scale drawing. In the invention, a feature can be configured positively, i.e., present, or negatively, i.e., absent. In this specification, a negative feature is not explicitly explained as a feature unless it is important for the invention to be absent. This means that the invention actually made, and not one constructed by the prior art, consists in omitting this feature. The absence of a feature (negative feature) in an exemplary embodiment indicates that the feature may be optional (to a person skilled in the art). - In the merely exemplary and schematic figures (Fig.) of the drawing show: The Fig. 1 shows a simplified block diagram of an embodiment of a fuel cell unit with an electrochemical fuel cell stack for a fuel cell system of a fuel cell vehicle, the Fig. 2 shows a simplified block diagram of an embodiment of an electrolyzer unit with an electrochemical electrolysis cell stack for an electrolyzer system, e.g. an electrolyzer plant, the Fig. 3 and Fig. 4 highly schematized crystal structures of catalyst layers on substrates of electrochemical cell layers on the one hand according to the state of the art ( Fig. 3) and on the other hand according to the invention ( Fig. 4), and the Fig. 5 to 7 show highly schematic representations of epitaxial catalyst layers on a substrate ( Fig. 5), an intermediary layer of a substrate ( Fig. 6) and a mediator layer of a bonding layer of a substrate ( Fig. 7) each with an electrochemical cell layer. Embodiments of the invention

[0021] The invention is explained in more detail with reference to an electrochemical cell layer 100 and a manufacturing method of an electrochemical cell layer 100 for an electrochemical cell stack 10, 60 of an electrochemical unit 1, 51 (cf. also above and the Fig. 3 to 7). Here, the unit 1, 51 can be used as a fuel cell unit 1 (cf. Fig. 1) for a mobile or stationary fuel cell system, or also a stationary or mobile electrolyzer unit 51 (cf. Fig. 2) be trained for an electrolyzer system.

[0022] The drawings depict only those sections of the fuel cell system or electrolyzer system that are necessary for understanding the invention. Although the invention is described and illustrated in detail using preferred embodiments, the invention is not limited to the disclosed embodiments. Other variations may be derived therefrom without departing from the scope of the invention.

[0023] The Fig. 1 and Fig. 2 each show an electrochemical aggregate 1, 51 ( Fig. 1: Fuel cell unit 1, Fig. 2: Electrolyzer unit 51) according to a general embodiment, with at least one, in particular a plurality of, to form an electrochemical cell stack 10, 60 or a stack 10, 60 ( Fig. 1: Fuel cell stack 10, Fig. 2: Electrolysis cell stack 60) bundled electrochemical single cells 11, 61 ( Fig. 1: Single fuel cells 11, Fig. 2: Individual electrolysis cells 61), which are housed in a preferably fluid-tight stacked housing 16, 66.

[0024] Each individual cell 11, 61 comprises an electrode chamber 12, 62 formed as an anode chamber 12, 62 and an electrode chamber 13, 63 formed as a cathode chamber 13, 63, which are spatially and electrically separated from one another by a membrane or a membrane of an MEA. An electrically conductive fluid transport structure is arranged in the respective electrode chamber 12, 13; 62, 63, which is in fluid communication with a bipolar plate 17, 67 (see below). Alternatively, or in addition to an MEA with only one electrode, at least one electrode can also be provided away from the membrane on at least one fluid transport structure.

[0025] A membrane electrode device 15, 65 of the cell stack 10, 60 comprises a membrane or an MEA and fluid transport structures on its large-area sides. An individual fluid transport structure can comprise a transport layer, a transport layer, a PTL (porous transport layer), a GDL (gas diffusion layer), a sintered metal element, a metallic sintered paper, a fiber element, a carbon layer, a carbon paper, a flow structure and / or a flow field, etc. The fluid transport structures not explicitly shown in the drawing are arranged in the anode compartments 12 and the cathode compartments 13 of the cell stack 10, 60.

[0026] A bipolar plate 17, 67 is arranged between two directly adjacent membrane electrode devices 15, 15; 65, 65 including a respective anode compartment 12, 62 and a respective cathode compartment 13, 63, which serves, among other things, to supply / discharge media 3 / 4, 5 / 6, 7 / 8; 53 / 54, 56 for an anode compartment 12, 62 of a first individual cell 11, 61 or a cathode compartment 13, 63 of a directly adjacent second individual cell 11, 61 and, moreover, to create an electrically conductive connection between these individual cells 11, 11; 61, 61. - The cathode compartments 13, 63 and, if applicable, their common inflow area or their actual electrodes form a cathode 39, 89, and the anode compartments 12, 62 and, if applicable, their common inflow area or their actual electrodes form an anode 29, 79 of the cell stack 10, 60.

[0027] In principle, the membranes of the cell stack 10, 60 can comprise PEMs (proton exchange membranes) or AEMs (anion exchange membranes). PEMs are preferred for a fuel cell stack 10, and AEMs or PEMs are preferred for an electrolysis cell stack 60. In addition to the fuel cell unit 1 or the electrolyzer unit 51, the fuel cell system or electrolyzer system comprises peripheral system components, such as a control unit, which can be one of the fuel cell system or electrolyzer system itself, etc.

[0028] The following explanations only concern the electrochemical unit 1 as a fuel cell unit 1, e.g. according to the Fig. 1. - To supply the electrochemical cell stack 10 as fuel cell stack 10 with its actual operating media 3 (anode operating medium, actual fuel), 5 (cathode operating medium, usually air), the fuel cell unit 1 has an anode supply 20 and a cathode supply 30.

[0029] The anode supply 20 preferably comprises: a fuel reservoir 23 for the anode operating medium 3 (flowing in); an anode supply path 21 (medium path 21) with a pressure reducer, a shut-off valve, and / or a metering valve 27 (for example), as well as a jet pump 24 (jet pump 24, ejector 24); an anode exhaust gas path 22 (medium path 22) for an anode exhaust gas medium 4 (flowing out, usually into the environment 2); a fuel recirculation path 25 with a fluid conveying device 26 located therein; optionally, a water separator, preferably with a water tank.

[0030] The cathode supply 30 preferably comprises: a cathode supply path 31 (medium path 31) for the cathode operating medium 5 (flowing in, usually from the environment 2), with a fluid conveying device 33; a cathode exhaust gas path 32 (medium path 32) for a cathode exhaust gas medium 6 (flowing out, usually into the environment 2), preferably with a turbine 34, in particular for the fluid conveying device 33; a humidity exchanger 36, in particular a gas-to-gas humidifier 36; optionally a cathode-side stack bypass 35 (wastegate 35) between the cathode supply path 31 and the cathode exhaust gas path 32, with a bypass valve 37; optionally a water separator, preferably with a water tank.

[0031] The fuel cell unit 1 further comprises, in particular, a cooling medium supply 40 of a thermal system, through which the fuel cell stack 10 can be integrated into a cooling circuit for temperature control, preferably by means of its bipolar plates 17 (cooling medium paths 43). The cooling medium supply 40 comprises a cooling medium inlet path 41 and a cooling medium outlet path 42. The cooling medium 7 (inflowing) and 8 (outflowing) circulating in the cooling medium supply 40 are preferably conveyed by means of at least one cooling medium conveying device 44.

[0032] The following explanations concern only the electrochemical unit 51 as electrolyzer unit 51, e.g. according to the Fig. 2. - To supply the electrochemical cell stack 60 as electrolysis cell stack 60 with, for example, mildly alkaline water 53 as a supply medium 53, the electrolyzer unit 51 has a medium supply 70. And to remove the media 54, 56 of the cell stack 60, the electrolyzer unit 51 has a media removal 80.

[0033] The medium supply 70 preferably comprises: a medium reservoir 73 for the supply medium 53 (flowing in), a supply path 71 (medium path 71) and a conveying device 76 on / in the supply path 71. - The media removal 80 has at least one disposal path 81 (medium path 81) for a disposal medium 54 or a disposal medium 54 with oxygen back into the medium reservoir 73, optionally with a gas separator for oxygen, and / or in another direction (shown in dashed lines), e.g. into the environment 2.

[0034] A product medium 56 of the electrolyzer unit 51, i.e., the produced hydrogen 56, is transported away through a product medium path 82 of the media removal 80. A gas / liquid separator 83 with a valve 84 can be inserted in the product medium path 82 to separate the disposal medium 54 in the product medium path 82. The disposal medium 54 separated in the gas / liquid separator 83 can be conveyed back into the medium reservoir 73 or in another direction, e.g., into the environment 2, possibly by gravity. The produced hydrogen 56 can be stored, for example, in a hydrogen storage unit 90, wherein the product medium path 82 can flow directly into the hydrogen storage unit 90. Another method of transporting the hydrogen 56 away is, of course, possible.

[0035] Depending on the embodiment of the electrolyzer unit 51, a media guide in the cell stack 60 can be designed differently. In this case, it is possible to provide a temperature control system that differs from an electrochemical function of the cell stack 60, in particular water cooling, or to implement the temperature control system together with the electrochemical function of the cell stack 60.

[0036] In membrane electrode devices 65 with AEMs, it is possible to set up a supply of the supply medium 53, possibly exclusively on the anode side (dotted arrow at anode 79), in addition to an anode- and cathode-side supply, possibly also as a cooling medium. Furthermore, in membrane electrode devices 65 with PEMs, it is possible to set up a supply of the supply medium 53, possibly exclusively on the cathode side (dotted arrow at cathode 89), in addition to an exclusively on the anode side (dotted arrow at cathode 89).

[0037] The Fig. 4 to 7 each show an electrochemical cell layer 100, the substrate 102 of which is designed as a membrane 102, a fluid transport structure 102, a polar plate 102 (cf. above the bipolar plate 17, 67), a polymer 102, etc. for the electrochemical cell stack 10, 60. The substrate 102 has a polycrystalline surface (possibly due to an intermediary layer 104), as in the Fig. 4, wherein on the substrate 102 ( Fig. 5) or indirectly ( Fig. 6 and Fig. 7) a catalyst layer 106 is provided.

[0038] Furthermore, the Fig. 3 shows an electrochemical cell layer 101 according to the prior art, wherein the catalyst layer 107 of the cell layer 101 continues the polycrystalline surface of its substrate 102 in a polycrystalline manner. This means that a crystal direction (hatching) of the substrate 102 in a surface depth range (i.e., with respect to the Fig. 3 upwards or downwards) is not correlated with a crystal direction within the catalyst layer 107; ie, the crystal direction within the catalyst layer 107 is arbitrary with respect to the crystal direction in the surface region of the substrate 102.

[0039] The Fig. 4 now shows a catalyst layer 106 with a defined crystal structure by epitaxial orientation directly on / at the polycrystalline surface of the substrate 102 (see Fig. 5) or on / at an intermediary layer 104 on the substrate 102 (see Fig. 6 and Fig. 7). The mediator layer 104 can be formed as a nucleation layer 104 (seed layer 104) and / or a commensurability layer 104 (see above). Such a mediator layer 104 can be used in particular when the substrate 102 is formed as a membrane 102 or polymer 102. Furthermore, a preferably (amorphous) bonding layer 103 can be arranged between the substrate 102 and the mediator layer 104.

[0040] The catalyst layer 106 grown locally epitaxially on the substrate 102 epitaxially continues the polycrystalline surface layer of the substrate 102 or the mediator layer 104 not only randomly at one point, but as an entire layer in significant regions. In these significant regions, the polycrystalline surface layer of the substrate 102 or the mediator layer 104 continues epitaxially. A manufacturing process for the cell layer 100 is naturally carried out such that the catalyst layer 106 grows locally epitaxially on the substrate 102.

[0041] In summary, epitaxial growth allows for the adjustment of a defined crystal structure and stoichiometry, and thus material properties, in particular chemical stability, of the catalyst layer 106. Catalyst materials with more than one metastable crystal structure or stoichiometry can be reproducibly grown in a defined state over an entire relevant area of ​​the substrate 102, and thus the electrochemical properties of the cell layer 100 can be largely adjusted. This leads to a controllable adjustment of the stability and activity of the locally epitaxially grown catalyst layer 106 by controlling the crystal structure and stoichiometry.

[0042] The mediator layer 104 allows incompatible crystal structures of substrate 102 and catalyst layer 106 to be combined ( Fig. 6 and Fig. 7). In this case, the mediator layer 104 may be made of a different crystalline material than the crystalline material of the substrate 102 and one of the catalyst layer 106 ( Fig. 6). This other crystalline material may be required between a crystal structure and a polarity of the substrate 102 and the material to be grown for the catalyst layer 106 in order to adjust a crystal structure, an orientation, and / or intended nanostructures of the catalyst layer 106.

[0043] Furthermore, the preferably amorphous bonding layer 103 ( Fig.7) followed by the optional mediator layer 104 for the local epitaxial growth of a crystal structure, an orientation, and / or intended nanostructures of the catalyst layer 106. - In addition, the bonding layer 103 and / or the mediator layer 104 can be designed such that interdiffusion between the substrate 102 and the catalyst layer 106 is reduced by more than approximately 5%, 10%, 20%, 30%, 40%, 50%, or 60%.

Claims

[1] Electrochemical cell layer (100) for an electrochemical cell stack (10, 60), in particular a fuel cell stack (10) or an electrolysis cell stack (60), comprising a substrate (102) and a catalyst layer (106) provided on the substrate (102), characterized by , that the catalyst layer (106) is formed as a catalyst layer (106) grown locally epitaxially on the substrate (102). [2] Electrochemical cell layer (100) according to the preceding claim, characterized by , that between the substrate (102) and the catalyst layer (106) a mediator layer (104) is arranged, which is designed as a nucleation layer (104) for the grown catalyst layer (106), and / or the mediator layer (104) is further formed as a commensurability layer (104) which enables crystal growth on the substrate (102) as a substrate on which otherwise no or only conditional crystal growth is possible. [3] Electrochemical cell layer (100) according to the preceding claim, characterized by that a preferably amorphous bonding layer (103) is arranged between the substrate (102) and the mediator layer (104), and / or the mediator layer (104) and / or the bonding layer (103) is constituted in such a way that interdiffusion between the substrate (102) and the catalyst layer (106) is significantly reduced. [4] Electrochemical cell layer (100) according to one of the preceding claims, characterized by , that: • the catalyst layer (106) is a polycrystalline surface layer of the substrate (102) which continues locally epitaxially outwards from the substrate (102), • the catalyst layer (106) of the cell layer (100) is thicker in at least one region in which the catalyst layer (106) is more susceptible to corrosion than in a region away from it, and / or • the catalyst layer (106) grown on the substrate (102) is formed as a locally epitaxial catalyst layer (106) over at least one third. [5] Electrochemical cell layer (100) according to one of the preceding claims, characterized by that the grown locally epitaxial catalyst layer (106) is a thin film with an average layer thickness of less than, greater than or equal to approximately: 5nm, 10nm, 25nm, 50nm, 75nm, 100nm, 150nm, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 600nm, 700nm, 800nm, 900nm, 1µm, 5µm, 10µm, 15µm, 20µm, 25µm, 30µm, 40µm, 50µm, 60µm, 70µm, 80µm, 90µm or 100µm. [6] Electrochemical cell layer (100) according to one of the preceding claims, characterized bythat the substrate (102) is designed as a membrane, a fluid transport structure, a polar plate (17, 67) or a polymer for the electrochemical cell stack (10, 60). [7] Method for producing an electrochemical cell layer (100) for an electrochemical cell stack (10, 60), in particular a fuel cell stack (10) or an electrolysis cell stack (60), wherein a catalyst layer (106) is provided on a substrate (102) of the cell layer (100), characterized by that the manufacturing process is carried out in such a way that the catalyst layer (106) grows locally epitaxially on the substrate (102). [8] Manufacturing process according to the preceding claim, characterized by that the manufacturing process is designed as a one-stage process, wherein the catalyst layer (106) grows locally epitaxially directly on the substrate (102), or the manufacturing process is designed as a two-stage process, wherein firstly a mediator layer (104) is provided on the substrate (102) and subsequently the catalyst layer (106) grows locally epitaxially on the mediator layer (104), or the manufacturing process is designed as a three-stage process, wherein firstly a preferably amorphous bonding layer (103) is provided on the substrate (102), subsequently a mediator layer (104) is provided on the bonding layer (103) and subsequently the catalyst layer (106) grows locally epitaxially on the mediator layer (104). [9] Manufacturing method according to one of the preceding claims, characterized by that the manufacturing process essentially only comprises the following steps Loading a production chamber with the substrate (102) to be coated and in-situ cleaning of the surface of the substrate (102) to be coated, and Coating the surface of the substrate (102) with the catalyst layer (106), or with the mediator layer (104) and the catalyst layer (106). [10] Electrochemical cell stack (10, 60), in particular fuel cell stack (10) or electrolysis cell stack (60), for an electrochemical unit (1, 51), in particular a fuel cell unit (1) or an electrolyzer unit (51), wherein the cell stack (10, 60) comprises a plurality of stacked cell layers which form individual electrochemical cells (11, 51) of the cell stack (10, 60), characterized by , that anode-side and / or cathode-side, electrochemical cell layers (100) of the stacked cell layers of the cell stack (10, 60), on a respective substrate (102), have a locally epitaxial catalyst layer (106) which locally epitaxially continues a particularly polycrystalline surface layer of the respective substrate (102) or of a respective mediator layer (104) on the substrate (102). [11] Electrochemical cell stack (10, 60) according to the preceding claim, characterized by that the locally epitaxial catalyst layers (106) are grown on membranes, fluid transport structures, polar plates (17, 67) or polymers of the cell stack (10, 60), and / or are immediately adjacent to fluid transport structures, polar plates (17, 67), polymers or membranes. [12] Electrochemical cell stack (10, 60) according to one of the preceding claims, characterized by , that: • the locally epitaxial catalyst layers (106) are mechanically detachably attached to membranes, fluid transport structures or polar plates (17, 67) of the cell stack (10, 60), • the locally epitaxial catalyst layers (106) are grown integrally on the substrates (102) of the fluid transport structures, polar plates (17, 67) or membranes, • preferably amorphous bonding layers (103) are arranged between the substrates (102) and the mediator layers (104), and / or • the anode-side and / or cathode-side cell layers (100) are designed and / or manufactured according to one of the preceding claims. [13] Electrochemical unit (1, 51), in particular fuel cell unit (1) or electrolyzer unit (51), or electrochemical system, in particular fuel cell system or electrolyzer system, with at least one electrochemical cell stack (10, 60) and a control device for controlling and / or regulating operation of the cell stack (10, 60), characterized by , that electrochemical cell layers (100) of the cell stack (10, 60) are designed according to one of the preceding claims, electrochemical cell layers (100) of the cell stack (10, 60) are manufactured according to one of the preceding claims and / or the cell stack (10, 60) is designed according to one of the preceding claims.

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