Layer system, vacuum arrangement and method

Abstract

A layer system (300) and a method and a vacuum arrangement (400) for producing the layer system are disclosed, wherein the layer system (300) has: a carrier plate (102), which has one or more than one metal layer and is designed to provide at least one fluid flow channel (104, 106); and two carbon layers (302, 304) on the carrier plate (102), between which the one or more than one metal layer is arranged and which differ from one another in a resistance of the contact resistance (ICR) to electrochemical corrosion.

Description

[0001] Description

[0002] Layer system, vacuum arrangement and process

[0003] Various embodiments relate to a layer system, preferably for an electrochemical cell, such as a fuel cell, an electrolyzer or a redox flow battery, as well as a vacuum arrangement and a method for producing the layer system.

[0004] In general, fuel cells can be used to supply electrical energy. A fuel cell can comprise multiple (stacked) bipolar plates, with each bipolar plate fulfilling numerous functions, such as electrically connecting the cells, distributing gas across the surface of the bipolar plate, separating gases between adjacent cells, sealing them from the outside, cooling, etc. Various material systems can be used for this purpose, which can be advantageous for some of these functions but also disadvantageous for others. In addition to these functions of the bipolar plate, economics (e.g., manufacturing costs, operating costs, durability, efficiency) and associated properties of the bipolar plate, such as the weight of the bipolar plate, the volume of the bipolar plate, the cold-start capability of the bipolar plate, the corrosion resistance of the bipolar plate, etc., also play a role., play a crucial role. Traditionally, these properties vary depending on the structure of the bipolar plate, the established examples of which are graphite, carbon composite, or metal. The latter can optionally be coated for surface functionalization.

[0005] In this regard, it has been clearly recognized, among other things, that although carbon composite starting materials offer better properties under the corrosive conditions of an electrochemical cell, such as better corrosion resistance combined with low contact resistance, they are more difficult to produce, which often limits the production rate or at least its scaling. While the production of a bipolar plate made of metal (also referred to as a metal bipolar plate) is simpler and thus more easily scalable, which reduces manufacturing costs, the metal bipolar plate rarely meets high property requirements (e.g., high conductivity and / or low contact resistance) or under the corrosive conditions of an electrochemical cell, which limits the cell's lifetime.

[0006] To modify the properties of the metal bipolar plate, a coating can be used to protect its metallic surface from corrosion, inhibit the transfer of metal ions into the membrane, and provide low contact resistance. However, the resulting layered system has a large number of interrelated parameters due to the multitude of components and their properties, making it difficult to balance ensuring functionality with the cost-effectiveness of manufacturing in relation to the associated properties of the layered system.

[0007] According to various embodiments, aspects are provided that address the above dilemma. It has been recognized that the production of a bipolar plate with high quality and, at the same time, high cost-effectiveness of production can be facilitated if a metallic carrier plate is coated on both sides with a carbon layer and if these carbon layers differ from one another, for example in the resistance of their contact resistance (ICR) to electrochemical corrosion, the proportion of different modifications of the amorphous carbon and / or the layer thickness. Examples of such a carrier plate include: a half-plate made of stainless steel, which is optionally coated with a metallic intermediate layer (e.g., made of titanium, niobium and / or chromium); a half-plate made of titanium, which is not necessarily coated with such an intermediate layer; and / or a composite of several such half-plates.

[0008] Clearly, the aspects according to various embodiments, for example, two different carbon layers, offer more flexibility for the production of the layer system. For example, existing resources can be used to improve the one of the two carbon layers (e.g., on the outer side of the bipolar plate and / or on the cathode side of the bipolar plate) that is intended to meet the more stringent requirements. This makes it easier to produce a higher-quality layer system at the same cost or a layer system of equivalent quality at a lower cost.

[0009] In this context, it was recognized that the two sides of the carrier plate have different functions, which means that the requirements for the (e.g., chemical and / or physical) properties of the two sides differ, and that cost-effectiveness can be increased if these differences are addressed. These differences include the following two exemplary cases:

[0010] - The coating of the inside and outside of a multi-part bipolar plate (for example, by coating a metal strip or a half-plate on both sides), which comprises a composite of two carrier plates. The requirements for the outside of the bipolar plate include low contact resistance to the gas diffusion layer (also known as GDL) and high corrosion resistance to an acidic environment to prevent ion leakage and membrane damage. The requirements for the inside of the bipolar plate also include low contact resistance between the joined carrier plates of the bipolar plate, for example, if they are not welded together, but do not necessarily have to have high corrosion resistance, and possibly a reduction in ion leakage and extended maintenance cycles (ion exchangers);

[0011] - The coating of the anode and cathode sides of the bipolar plate. The anode side of the bipolar plate is exposed to less corrosive conditions (e.g., with regard to electrochemical potential and moisture) than the cathode side, so the corrosion resistance requirements of the anode side are lower than those of the cathode side.

[0012] In the latter case, for example, a gradient can occur along the fluid flow channel of the bipolar plate, resulting in different electrochemical conditions at the inlet and outlet of the fluid flow channel. Thus, at the start of the fuel cell, a hydrogen reaction can already occur at the inlet, while the anode side and the cathode side at the outlet of the bipolar plate are still exposed to air. This gradient can result in a voltage at the cathode side output of up to 1.4 volts (V) or, in some cases, up to 1.6 volts (V).

[0013] According to various embodiments, a metallic carrier plate can be coated on the top side and the bottom side with different carbon layers, each carbon layer ensuring the requirements for the (e.g. chemical and / or physical) properties of the corresponding side.

[0014] For example, the economic efficiency can be increased by producing the carbon layers using different physical or chemical vapor deposition processes, which differ from each other in the associated costs (manufacturing costs), e.g. operating costs, and / or with different layer thicknesses, which optimizes material consumption.

[0015] In an illustrative example, a more corrosion-resistant modification of amorphous carbon can be formed on the cathode side of a metallic bipolar plate, which has higher electrochemical requirements for corrosion resistance than the anode side, whereas a cost-effective carbon layer can be formed on the anode side of the metallic bipolar plate. Different modifications of amorphous carbon can result in different levels of corrosion resistance. The formation of a modification of amorphous carbon and thus the corrosion resistance can be influenced by selecting the type of PVD, examples of which include high-impulse magnetron sputtering (HiPIMS), arc evaporation, (e.g., DC) magnetron sputtering, or electron beam evaporation, which are associated with lower manufacturing costs compared to HiPIMS and arc evaporation.

[0016] The corrosion resistance of a layer (e.g., a carbon layer) is generally a function of a variety of properties (e.g., nature parameters) of the carbon layer. Examples include: the modification of the (e.g., amorphous) carbon in the layer (and / or the proportion of multiple modifications), the layer thickness, the orientation of the bonding planes of the carbon (also called basal planes) and / or graphene layers (e.g., texture), the microstructure (measurable via transmission electron microscopy) and bonding states (measurable via Raman spectrum), and / or the structuring (e.g., grain size). For information on the properties (e.g., nature parameters) of a carbon layer, see, among others, Robertson, John, et al. ("Diamond-like amorphous carbon," Materials science and engineering: R: Reports 37.4-6 (2002): 129-281); and WO 2010 061696 A1, JP 2022 059238 A, Ferrari and Robertson (PRB, Vol. 64, 075414, 2001).

[0017] These parameters can overlap to form a complex interplay that cannot always be expressed analytically or represented with sufficient accuracy by the numerical values ​​of these parameters. A less complex example is the layer thickness as a parameter, the increase of which increases the corrosion resistance of the layer. However, if other properties of the layer are varied, such as the proportion of different modifications of the amorphous carbon in the layer, it is no longer easy to estimate analytically based on the pure numerical values ​​whether the corrosion resistance of the layer is still dominated by the layer thickness or not.

[0018] Therefore, with regard to the corrosion resistance of the layer (e.g., a carbon layer), reference is made herein, among other things, to the contact resistance (also referred to as interfacial contact resistance, ICR for short) as an exemplary property of the layer, which is also simply referred to as the resistance of the contact resistance to corrosion or as contact electrical corrosion resistance. In this regard, the contact resistance can be understood as an exemplary property of the layer, which represents the (e.g., electrical) state of the layer and is based on the technological requirements of the layer for the operation of an electrochemical cell.

[0019] If a layer is exposed to a corrosive environment, the contact resistance of the layer system can increase, especially if the carbon layer is (almost) completely removed and an underlying surface, e.g. an intermediate layer (e.g. metallic) or a passivating non-conductive oxide layer, is gradually exposed. The greater the corrosion resistance of the layer, the slower the carbon layer corrodes, so that the increase in contact resistance also occurs later and / or is at least smaller. In principle, however, another property of the layer, for example an equivalent and / or electrical one, which represents the electrical state of the layer, can also be used, for which what is described herein for the contact resistance can then apply analogously.

[0020] The change in contact resistance (ICR) as a measure of the corrosion resistance of a coating can, for example, be expressed as a time period (from t=0 to t=Z) that begins (at t=0) when the coating is exposed to the corrosive environment and ends (at t=Z) when the contact resistance of the coating meets a criterion (also called resistance criterion). This criterion can, for example, represent that the coating has failed functionally, e.g., with regard to current transport and / or has lost its electrical conductivity. This resistance criterion can, for example, be met when the contact resistance reaches (e.g., exceeds) a threshold value S. The threshold value S can, for example, be k times the ICR(t=0), i.e., that ICR(t=Z)> ICR(t=0). The value of k can, for example, be 5 or more, e.g., 10 or more, e.g., 100 or more. However, the threshold value of the contact resistance can also be an absolute value, e.g.,10. 2 mQcm 2 or more, e.g. 10 3 mQcm 2 .

[0021] Here, reference is made to k=10 for the stability criterion, ie ICR(t=Z)=10 ICR(t=0), whereby the description can apply analogously to any other stability criterion.

[0022] Alternatively or additionally, examples of parameters for which the resistance criterion is fulfilled when they reach a threshold value S include: a mass loss of the layer; a corrosion rate of the layer; a corrosion current, an electrical power and / or energy imparted thereby (e.g. represented by an integral of the corrosion current).

[0023] Various examples are described below which relate to what is described herein and shown in the figures.

[0024] Example 1 is a layer system (e.g. for an electrochemical cell), comprising: a carrier plate (e.g. made of two parts, e.g. half plates, joined and / or metallic) which has one or more than one metallic layer and is configured to provide at least one (e.g. meander-shaped) fluid flow channel; and two carbon layers on the (e.g. outside of the) carrier plate, between which the one or more than one metallic layer is arranged, and which differ from each other, preferably in their corrosion resistance.

[0025] An exemplary implementation of the layer system from Example 1 can, for example, be a joined bipolar plate that addresses different electrochemical requirements on both sides. Another exemplary implementation of the layer system from Example 1 can, for example, be strip-shaped (e.g., comprising a metal strip as a layer) or a half-plate, wherein the carbon layer on the inside of the resulting bipolar plate is electrically conductive but may have lower corrosion resistance than the carbon layer on the outside of the resulting bipolar plate.

[0026] Example 2 is a layer system (e.g. for an electrochemical cell and / or according to Example 1), comprising: a carrier plate (e.g. joined from two parts and / or metallic) which has one or more than one metallic layer and is configured to provide at least one (e.g. meander-shaped) fluid flow channel (the carrier plate and / or layer, for example, having a trench); and two carbon layers on the carrier plate, between which the one or more than one metallic layer is arranged and which differ from one another in a time period (e.g. durability period) after which a (e.g. percentage) target proportion of the carbon layer is removed (e.g. a mass loss) in a corrosive medium (e.g. upon application of a voltage, for example of 1.4V or more).

[0027] Example 3 is a layer system (e.g. for an electrochemical cell and / or according to example 1 or 2), comprising: a carrier plate which has one or more than one metallic layer and is configured to provide at least one (e.g. meander-shaped) fluid flow channel; and two carbon layers on the carrier plate, between which the one or more than one metallic layer is arranged, which are electrically conductive and which differ from one another in a period of time (e.g. durability period), at the beginning of which the carbon layer is exposed to a corrosive environment (e.g. upon application of a voltage of, for example, 1.4 V or more) and at the end of which the carbon layer oxidizes and / or the layer system is no longer electrically conductive.For example, the carbon is oxidized and the resulting gas evaporates, so that the volume of the carbon layer decreases until the underlying surface (e.g., a metallic interlayer and / or a metallic substrate) is exposed, which itself forms a dielectric (and, e.g., passivating) oxide layer (e.g., titanium oxide in the case of titanium and / or chromium oxide in the case of stainless steel) that is a poor electrical conductor.

[0028] Example 4 is configured according to any one of examples 1 to 3, wherein for a first carbon layer of the two carbon layers, the time period (e.g., durability period) is at least twice as long as for a second carbon layer of the two carbon layers; and / or wherein the time period (e.g., durability period) is an oxidation period until complete dissolution of the carbon layer and / or the loss of electrical conductivity of the layer system.

[0029] Example 5 is configured according to any one of Examples 2 to 4, wherein the two carbon layers differ from each other in a corrosion rate.

[0030] Example 6 is configured according to any one of Examples 2 to 5, wherein the two carbon layers differ from one another in a proportion of one or more than one (e.g., crystalline and / or amorphous) carbon modification, a ratio of the proportions of different modifications of the amorphous carbon, and / or a layer thickness. For example, one of the two carbon layers may have a larger proportion of a first-type carbon modification than the other of the two carbon layers. Alternatively or additionally, one of the two carbon layers may have a larger ratio of the proportions of amorphous-type carbon modifications than the other of the two carbon layers.

[0031] Example 7 is configured according to any one of examples 1 or 6, wherein the sp 2 / sp 3 -hybridization ratio in a first carbon layer of the two carbon layers is greater than 90% and / or wherein the sp 2 / sp 3 - hybridization ratio in a second carbon layer of the two carbon layers is less than 10%.

[0032] Example 8 is configured according to any one of examples 1 or 7, wherein a first or more than one carbon layer of the two carbon layers has a (substantially) amorphous structure (e.g., aC) and / or is hydrogen-free.

[0033] Example 9 is configured according to any one of Examples 1 or 8, wherein the two carbon layers differ from each other in their crystallinity index and / or their orientation distribution function.

[0034] Example 10 is configured according to any one of examples 1 or 9, wherein the two carbon layers differ from each other in the time course of an electric current mediated by the electrochemical corrosion (also referred to as corrosion current) and / or the time integral of the corrosion current, for example until a point in time at which one of the two carbon layers is substantially completely corroded, e.g. eroded, by the electrochemical corrosion.

[0035] Example 11 is configured according to any one of Examples 1 to 10, wherein at least one layer of the one or more than one metallic layer (e.g., an intermediate layer and / or a half-sheet thereof) comprises (or consists of) titanium, niobium, and / or chromium.

[0036] Example 12 is configured according to any one of Examples 1 to 11, wherein the two carbon layers are electrically conductive.

[0037] Example 13 is configured according to any one of Examples 1 to 12, wherein the carbon of the two carbon layers is predominantly (ie, more than 50%, e.g., more than 80%) sp 2 -hybridized.

[0038] Example 14 is configured according to any one of Examples 1 to 13, wherein the two carbon layers differ from each other in a proportion of sp 2 -hybridized carbon (e.g. by about 5% or more, e.g. by about 10% or more, e.g. by about 20% or more, e.g. by about 50% or more).

[0039] Example 15 is configured according to any one of Examples 1 to 14, wherein the carrier plate is configured to provide at least two (e.g., meander-shaped) fluid flow channels. Example 16 is configured according to any one of Examples 1 to 15, wherein a first carbon layer of the two carbon layers is arranged directly on an upper side of the carrier plate, and wherein a second carbon layer of the two carbon layers is arranged directly on an underside (opposite the upper side) of the carrier plate. Alternatively or additionally, the first carbon layer of the two carbon layers or the second carbon layer of the two carbon layers may be part of a stack of multiple carbon layers.For example, the layer system may comprise two stacks of carbon layers (between which the one or more metallic layers are arranged), of which a first stack comprises the first carbon layer and a second stack comprises the second carbon layer.

[0040] Example 17 is a bipolar plate comprising the layer system according to any one of Examples 1 to 16.

[0041] Example 18 is a half-cell for a bipolar plate (e.g., a bipolar plate for a fuel cell or an electrolyzer) or for an electrode (e.g., an electrode of a redox flow battery), wherein the half-cell (also referred to as plate half or half-plate) comprises the layer system according to any one of Examples 1 to 16.

[0042] Example 19 is a use of the layer system according to any one of Examples 1 to 16 for producing an electrochemical cell (e.g., a fuel cell or an electrolyzer or a redox flow battery).

[0043] Example 20 is using a vacuum arrangement to produce the layer system according to any one of Examples 1 to 16.

[0044] Example 21 is a vacuum arrangement which is configured to produce the layer system according to one of Examples 1 to 16 (e.g. to transfer it in a vacuum and into the atmosphere, i.e. to discharge it).

[0045] Example 22 is configured according to any one of Examples 1 to 16, wherein the carrier plate has one or more than one metallic layer; a coating system configured to form a first carbon layer on an upper side of the carrier plate and to form a second carbon layer on an underside of the carrier plate (opposite the upper side); wherein the coating system is configured such that the first carbon layer and the second carbon layer differ from one another in a proportion of one or more than one modification of the amorphous carbon and / or the ratio of proportions of mutually different modifications of the amorphous carbon and / or a layer thickness when the layer system is discharged from the vacuum chamber system.

[0046] Example 23 is configured according to Example 22, wherein the coating system comprises at least one first coating device configured to form the first carbon layer and at least one second coating device configured to form the second carbon layer.

[0047] Example 24 is configured according to Example 23, wherein the at least one first coating device and the at least one second coating device are configured to form the first carbon layer and the second carbon layer by means of different vapor deposition methods and / or by means of different electrical (e.g. bias) voltages applied to the carbon layer and / or the carrier plate.

[0048] Example 25 is configured according to example 23 or 24, wherein the first coating device is configured to form the first carbon layer by means of evaporation (e.g., electron beam evaporation or arc evaporation) or high-impulse magnetron sputtering (HiPIMS), and the second coating device is configured to form the second carbon layer by means of (e.g.,DC) magnetron sputtering; or wherein the first coating device is configured to form the first carbon layer by means of HiPIMS, and the second coating device is configured to form the second carbon layer by means of arc evaporation; or wherein the first coating device is configured to form the first carbon layer by means of DC sputtering, and the second coating device is configured to form the second carbon layer by means of DC sputtering; and / or wherein the first coating device and the second coating device differ from one another in a bias voltage (e.g., applied to the substrate and / or the carbon layer).

[0049] Arc evaporation is more energy efficient and could be used for the thick layer, whereas HiPIMS is used for the thinner layer due to the poorer dynamic rate.

[0050] Example 26 is set up according to any one of examples 23 to 25, wherein the at least one first coating device and the at least one second coating device differ from one another in a proportion of one or more modifications of the amorphous carbon with which the carbon layer is formed, and / or in the proportion of mutually different modifications of the amorphous carbon with which the carbon layer is formed, and / or a rate (e.g. per distance of the transport path to which the carrier plate is exposed to the coating device) at which the carbon layer is formed, e.g. dynamic coating rate.

[0051] Example 27 is a method for producing a layer system (e.g. the layer system according to any one of Examples 1 to 16), the method comprising: controlling at least one first coating device for forming a first carbon layer on an upper side of a carrier plate, which has one or more than one metallic layer, in a vacuum; and controlling at least one second coating device for forming a second carbon layer on an underside (opposite the upper side) of the carrier plate in the vacuum; wherein the at least one first coating device and the at least one second coating device are controlled such that the first carbon layer and the second carbon layer differ from one another in the proportion of the modification(s) of the amorphous carbon and / or a layer thickness when the layer system is removed from the vacuum.

[0052] Example 28 is a method for producing a layer system (e.g. the layer system according to any one of Examples 1 to 16), the method comprising: forming a first carbon layer (e.g. directly) on an upper side of a carrier plate which has one or more than one metallic layer, in a vacuum; and forming a second carbon layer (e.g. directly) on an underside (opposite the upper side) of the carrier plate in the vacuum; wherein the first carbon layer and the second carbon layer are formed such that the first carbon layer and the second carbon layer differ from one another in the proportion of the modification(s) of the amorphous and / or a layer thickness when the layer system is removed from the vacuum.

[0053] Example 29 is configured according to any one of Examples 1 to 28, wherein the first carbon layer is formed at a first rate (e.g., dynamic deposition rate) and wherein the second carbon layer is formed at a second rate (e.g., dynamic deposition rate) different from the first rate.

[0054] Example 30 is configured according to any one of Examples 1 to 29, wherein the first carbon layer is graphitizing and the second carbon layer is non-graphitizing.

[0055] Example 31 is configured according to any one of Examples 1 to 30, wherein the two carbon layers differ from each other in a degree to which the bonding planes of the carbon are ordered (e.g., they may be ordered in one of the carbon layers and disordered in the other of the carbon layers).

[0056] Example 32 is configured according to any one of Examples 1 to 31, wherein the contact resistance resistance (ICR) to electrochemical corrosion comprises a duration of electrochemical corrosion for which the contact resistance is less than a threshold value, which is preferably several times the contact resistance at the onset of corrosion. Example 33 is configured according to any one of Examples 1 to 32, wherein the two carbon layers are provided as fabricated.

[0057] Example 34 is configured according to any one of Examples 1 to 33, wherein at least one layer of the one or more than one metallic layer (e.g., an intermediate layer and / or a half-sheet thereof) comprises (or consists of) titanium, niobium, and / or chromium.

[0058] Example 35 is configured according to any one of Examples 1 to 34, wherein the first carbon layer and the second carbon layer are electrically conductive.

[0059] Example 36 is configured according to any one of Examples 1 to 35, wherein the carbon atoms of the first carbon layer and the carbon atoms of the second carbon layer are predominantly (e.g., more than 80%) sp 2 -hybridized.

[0060] Example 37 is configured according to any one of Examples 1 to 36, wherein the first carbon layer and the second carbon layer differ from each other in a proportion of sp 2 -hybridized carbon atoms.

[0061] Example 38 is configured according to any one of Examples 1 to 37, wherein the carrier plate is configured to provide at least two (e.g., meander-shaped) fluid flow channels.

[0062] Example 39 is a computer program configured, when executed by a processor, to cause the processor to perform the method of any one of examples 27 to 38, e.g., by controlling a vacuum arrangement and / or one or more components thereof (e.g., coating device and / or transport device).

[0063] Example 40 is a computer-readable medium storing instructions configured, when executed by a processor, to cause the processor to perform the method of any of Examples 27 to 38, e.g., by controlling a vacuum arrangement and / or one or more components thereof (e.g., coating device and / or transport device).

[0064] Example 41 is a control device comprising: one or more than one processor configured to perform the method according to any one of examples 27 to 38, e.g., by controlling a vacuum arrangement and / or one or more than one component thereof (e.g., coating device and / or transport device).

[0065] Example 42 is a vacuum arrangement for producing a layer system (e.g., the layer system according to any one of Examples 1 to 16), the vacuum arrangement comprising: a vacuum chamber system (for providing a vacuum); a transport device providing a transport path through the vacuum chamber system for transporting the carrier plate along the transport path; the control device according to Example 41; at least one first coating device for forming the first carbon layer; and at least one second coating device for forming the second carbon layer.

[0066] Example 43 is any one of Examples 1 to 42, wherein each of the two carbon layers provides an electrical contact resistance; and wherein the two carbon layers differ from each other in an electrochemical corrosion resistance of the contact resistance (e.g., by about 10% or more, e.g., by about 25% or more, e.g., by about 50% or more, e.g., by about 75% or more); and / or wherein the two carbon layers differ from each other in a durability period of the contact resistance upon corrosion of the carbon layer (e.g., at a voltage of 1.2 V or more, e.g., 1.4 V or more, e.g., 1.6 V or more) and / or by about 10% or more (e.g., by about 25% or more, e.g., by about 50% or more, e.g., by about 75% or more). Example 44 is any one of Examples 1 to 43, wherein the carrier plate (e.g., the one or more than one layer) comprises at least one bipolar half-plate, e.g., one composed of two bipolar plate parts (e.g.,B. metal plates, then also called half-plates or bipolar half-plates) joined and / or metallic composite (e.g. a bipolar plate) or only one (e.g. monolithic) half-plate.

[0067] Example 45 is one of Examples 1 to 43, wherein the carrier plate (e.g. the one or more than one layer), e.g. for one or more than one carbon layer of the two carbon layers, has one or more than one (e.g. metallic) intermediate layer arranged between the at least one bipolar half-plate and the carbon layer, wherein the intermediate layer and the at least one bipolar half-plate differ from each other in a chemical composition and / or a layer thickness (e.g. the bipolar half-plate is thicker than the intermediate layer).

[0068] Example 46 is any one of Examples 1 to 45, wherein the two carbon layers differ from each other in a structuring and / or orientation of the modifications of the amorphous carbon (for example, even with the same proportion of the modifications of the amorphous carbon).

[0069] Example 47 is any one of Examples 1 to 46, wherein the two carbon layers differ from each other in a proportion of the modifications of the amorphous carbon (e.g., by about 10% or more, e.g., by about 25% or more, e.g., by about 50% or more, e.g., by about 75% or more).

[0070] Example 48 is any one of Examples 1 to 47, wherein the two carbon layers differ from each other in a layer thickness (e.g., by about 10% or more, e.g., by about 30% or more, e.g., by about 50% or more, e.g., by about 75% or more).

[0071] Example 49 is any one of Examples 1 to 48, wherein the fluid flow channel is meander-shaped and / or wherein the support plate has a trench-shaped cavity to provide the fluid flow channel.

[0072] Example 50 is any one of Examples 1 to 49, wherein each of the two carbon layers provides an electrical resistance (e.g., contact resistance), and wherein the corrosion resistance of the carbon layer is expressed as the time period at which the contact resistance upon corrosion of the carbon layer reaches (e.g., exceeds) a threshold value; wherein the threshold value is preferably 10 times the contact resistance before the onset of corrosion, a contact resistance of an oxide of the carrier plate, and / or 10 2 mQcm 2 is.

[0073] Example 51 is any one of Examples 1 to 50, wherein each of the two carbon layers has a proportion of sp 2- hybridized carbon of more than about 50%, e.g. than about 75%, e.g. than about 90%, e.g. than about 95%.

[0074] Example 52 is any one of Examples 1 to 51, wherein the two carbon layers differ from each other (e.g., by a factor of 5 or more, e.g., 10 or more) at a time after a period of electrochemical corrosion, preferably in their contact resistance after the electrochemical corrosion and / or in an integrated electrical current intensity (also referred to as corrosion current) for the duration of the electrochemical corrosion, which is imparted by the electrochemical corrosion. For example, the difference in resistance between the two carbon layers can be represented by the difference at that time.

[0075] Example 53 is one of Examples 1 to 52, wherein the electrochemical corrosion (e.g., its duration) ends when (e.g., only) one of the two carbon layers is used up (e.g., dissolved) and / or the electrochemical corrosion of (e.g., only) one of the two carbon layers stops.

[0076] Example 54 is any one of Examples 1 to 53, wherein the two carbon layers differ from each other (e.g., by a factor of 5 or more, e.g., 10 or more) at a time after electrochemical corrosion in a value; wherein the value indicates the contact resistance after electrochemical corrosion and / or the integrated electric current imparted by electrochemical corrosion for the duration of the electrochemical corrosion. For example, the difference in resistance between the two carbon layers can be represented by the difference at that time.

[0077] Example 55 is any one of Examples 1 to 54, wherein the formation of the first carbon layer is carried out by means of a first type of physical vapor deposition and the formation of the second carbon layer is carried out by means of a second type of physical vapor deposition, wherein the first type of physical vapor deposition and the second type of physical vapor deposition differ from one another, preferably in: an electrical voltage applied to the carrier plate during formation; a process (e.g. laser, plasma, arc, electron beam, etc.) by means of which a solid coating material is supplied to the vapor deposition; an electrical frequency, a duty cycle and / or electrical power by means of which the vapor deposition takes place; an ionization component and / or kinetic particle energy (e.g. of a gas phase) by means of which the vapor deposition takes place.A group of examples from which the first type of physical vapor deposition and the second type of physical vapor deposition are selected includes: direct current sputtering (also called DC sputtering); HiPIMS;.

[0078] Arc evaporation; magnetron sputtering (e.g., DC, bipolar, HiPIMS). For example, the first-type vapor deposition and the second-type physical vapor deposition may involve arc evaporation and differ in the bias voltage and / or by at least 50 volts applied to the substrate.

[0079] Example 56 is one of Examples 1 to 55, wherein the layer system or at least the two carbon layers are prefabricated.

[0080] Example 57 is any one of Examples 1 to 56, further configured according to any one of the appended claims.

[0081] It shows

[0082] Figure 1A shows a half-cell according to various embodiments in a schematic cross-sectional view or side view;

[0083] Figure 1 B shows a bipolar plate according to various embodiments in a schematic cross-sectional view or schematic side view;

[0084] Figure 2 shows a fuel cell according to various embodiments in a schematic cross-sectional view or schematic side view;

[0085] Figure 3 shows a layer system according to various embodiments in a schematic side view;

[0086] Figures 4A and 4B show an exemplary vacuum arrangement for producing a layer system according to various embodiments in a schematic top view or schematic side view;

[0087] Figures 5A and 5B show a measurement configuration according to various embodiments in a schematic side view; and

[0088] Figures 6A to 12 are various schematic diagrams for working examples according to various embodiments and for comparative examples thereto.

[0089] In the following detailed description, reference is made to the accompanying drawings, which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. In this regard, directional terminology such as "top," "bottom," "front," "back," "fore," "rear," etc., is used with reference to the orientation of the described figure(s). Since components of embodiments can be positioned in a number of different orientations, the directional terminology is for purposes of illustration and is in no way limiting. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention.It is understood that the features of the various exemplary embodiments described herein may be combined with one another unless specifically stated otherwise. The following detailed description is therefore not to be construed in a limiting sense, and the scope of the present invention is defined by the appended claims.

[0090] Throughout this description, the terms "connected," "attached," and "coupled" are used to describe both a direct and an indirect connection (e.g., resistive and / or electrically conductive, e.g., an electrically conductive connection), a direct or indirect connection, and a direct or indirect coupling. In the figures, identical or similar elements are provided with identical reference numerals where appropriate.

[0091] According to various embodiments, the term "coupled" or "coupling" can be understood in the sense of a (e.g., mechanical, hydrostatic, thermal, and / or electrical), e.g., direct or indirect, connection and / or interaction. For example, several elements can be coupled to one another along an interaction chain, along which the interaction can be exchanged, e.g., a fluid (then also referred to as fluidically coupled). For example, two coupled elements can exchange an interaction with one another, e.g., a mechanical, hydrostatic, thermal, and / or electrical interaction. A coupling of several vacuum components (e.g., valves, pumps, chambers, etc.) to one another can include fluidically coupling them. According to various embodiments, "coupled" can be understood in the sense of a mechanical (e.g., physical and / or physical) coupling, e.g.,by means of direct physical contact. A clutch can be configured to transmit a mechanical interaction (e.g., force, torque, etc.).

[0092] In the context of vacuum components (e.g., a pump, a chamber, a line, a valve, etc.), the term "coupled" or "coupling" can be understood in the sense of a connection to a common vacuum system. The components of the vacuum system can be configured to exchange a gas with each other via the coupling, whereby the coupling can be gas-separated from an external part of the vacuum system.

[0093] According to various aspects described herein, carbon layers are formed on a carrier plate. A carbon layer can be formed in a vacuum using a physical vapor deposition (PVD) or chemical vapor deposition (CVD) coating process.

[0094] An exemplary coating process for forming a carbon layer is sputtering. The term "sputtering" refers to the atomization of a material (also referred to as coating material or target material) using a plasma. The atomized components of the coating material (e.g., individual atoms and / or ions) are separated from one another and can be deposited elsewhere, for example, to form a layer (also referred to herein as layer formation). Sputtering can be carried out using a sputtering device, which can have one or more magnet systems (also referred to as a magnetron). The coating material can be provided by a sputtering target (also referred to as a target for short), which can be, for example, tubular (also referred to as a tubular target) or plate-shaped (also referred to as a plate target or planar target).To generate the plasma, a voltage (also called sputtering voltage) can be applied to the sputtering target (also referred to as the target for short), so that the sputtering target acts as a cathode. Even if the sputtering voltage is an alternating voltage, the term "cathode" is often retained.

[0095] For sputtering, the sputtering target can be placed in a vacuum chamber (also referred to simply as a processing chamber), allowing sputtering to take place in a vacuum. For this purpose, the ambient conditions (the process parameters) within the vacuum processing chamber (e.g., process pressure, temperature, gas composition, a magnetic field within the vacuum processing chamber, etc.) can be adjusted or controlled during sputtering.

[0096] The sputtering target can be attached to a sputtering target coupling within the magnetron. The sputtering target coupling can be rotatable, e.g., mounted on a pivot bearing, so that the sputtering target can be rotated by means of the sputtering target coupling. For example, the sputtering target coupling can be mounted on a pivot bearing. A media connection, e.g., a fluid line, can be arranged within the sputtering target coupling, by means of which a fluid, e.g., a coolant, can be supplied. For example, the sputtering target coupling can also be referred to as a rotary feedthrough.

[0097] There are different types of magnetron sputtering: In direct current (DC) magnetron sputtering, a direct voltage is applied between the sputtering target and the substrate to be coated. In radio frequency (RF) magnetron sputtering, a high-frequency alternating field is applied instead of the direct voltage. In high-impulse magnetron sputtering (HIPIMS), high-power pulses are applied to the sputtering target, allowing higher plasma densities to be achieved compared to DC and RF magnetron sputtering. Optionally, the coating process (e.g. magnetron sputtering), by means of which a carbon layer is formed, can be supported by applying a voltage to the substrate (also known as substrate bias voltage or bias voltage for short), to which the coating process is subjected. The bias voltage can clearly influence the properties of the carbon layer.

[0098] A "pulse" related to a physical quantity (e.g., power, then also referred to as a power pulse) can be understood as a temporal change of the quantity such that the value of the quantity increases (e.g., starting from an initial value, e.g., zero), exceeds a maximum (also referred to as a peak value), and then decreases again (e.g., to the initial value). The properties of the pulse are a function of the time dependence of the temporal change of the quantity. In a pulse, a value of the quantity can change over time from an initial value (e.g., base value) to a peak value (also referred to as the rising edge of the pulse) and then change over time from the peak value back to the initial value (also referred to as the falling edge of the pulse).

[0099] What has been described for sputtering as an exemplary coating process can apply analogously to a different type of physical vapor deposition (PVD) or chemical vapor deposition (CVD). In contrast to CVD, in PVD a solid material is first transferred into the gas phase (also referred to as the gaseous phase or vapor), and a layer is formed using this gas phase. In PVD, the gas phase of the target material can optionally be chemically reacted with a reactive gas to form a chemical compound, which is incorporated into the layer or forms it. During the chemical reaction in PVD, two or more materials are thus combined to form the chemical compound. In sputtering, the plasma-forming gas (e.g. argon) together with an optional reactive gas can form a process gas in which sputtering takes place. Reactive magnetron sputtering can, for example, be carried out using the reactive gas.

[0100] A plasma can be formed using a so-called working gas (also referred to as a plasma-forming gas). According to various embodiments, the working gas can comprise a gaseous material that is inert, in other words, that participates in few or no chemical reactions. A working gas can, for example, be defined by the target material used and be adapted to it. For example, a working gas can comprise a gas or a gas mixture that does not react with the target material to form a solid. The working gas can, for example, comprise a noble gas (e.g., helium, neon, argon, krypton, xenon, radon) or several noble gases. The plasma can be formed from the working gas, which, for example, essentially causes the sputtering of the target material. If a reactive gas is used, this can have a higher chemical reactivity than the working gas, e.g.,with respect to the target material. In other words, the atomized target material can react more quickly with the reactive gas (if present) (i.e., form more reaction product per unit time) than with the working gas (e.g., if it reacts chemically with the working gas at all). The reactive gas and the working gas can be supplied together or separately as a process gas (e.g., as a gas mixture), for example, by means of the gas supply device.

[0101] Another example of a coating process for forming a carbon layer is evaporation. Evaporation belongs to the class of thermal evaporation processes, which have in common that a material to be evaporated (here also referred to simply as the coating material) is heated to such an extent that it transforms into its gaseous state (e.g., by absorbing latent heat). This can (but does not necessarily have to) involve a melt of the material as an intermediate step. For example, it can evaporate from the melt or sublimate directly.

[0102] In electron beam evaporation, a high-energy, focused electron beam is directed at the target to evaporate the target material (as the coating material). The evaporated material spreads outward in a cone-shaped vapor jet and is then deposited on the substrate.

[0103] Evaporation can be carried out by means of an arc discharge (also referred to as arc evaporation or arcing). An arc discharge is a form of gas discharge in which the plasma formed is drawn together into a tube (or, descriptively, a thin thread, the so-called arc). Within the plasma tube formed in this way, high gas temperatures (e.g. in a range of approximately 5000 Kelvin to approximately 50,000 Kelvin), current intensities (e.g. in a range of approximately 2000 amperes or more) and gas pressures occur, by means of which the coating material is converted into the gaseous phase (also referred to as evaporation). The arc discharge and thus the plasma formation are usually of short duration, so that they occur in pulses.Arc evaporation must be distinguished from the process of cathode sputtering, in which the plasma is generated by a continuous glow discharge. Furthermore, instead of thermal evaporation, cathode sputtering primarily involves mechanical atomization of the material by large-area ion bombardment from the plasma, with the plasma being generated by the continuous glow discharge (e.g., at a voltage of less than 50 volts). Furthermore, in cathode sputtering, the pressure is increased.

[0104] In one variant of arc evaporation, a laser is used to control the ignition of the arc discharge, which locally stimulates the formation of a plasma (also known as laser-induced or laser-assisted arc discharge, or laser arcing). Here, the laser generates a very short pulsed plasma within the plasma chamber between the anode and the cathode (to ignite an initial plasma). This initial plasma, lasting a few 10 ns (nanoseconds) to 100 ns, is then amplified in pulse length and power by an arc discharge using an electrical (pulse) power source (e.g., a pulsed current source). The plasma thus formed lowers the impedance between the cathode and anode, so that a voltage applied between them leads to a discharge current through the plasma. In other words, a pulsed arc discharge can be excited using the laser.The laser is guided over the cathode using a mirror system, allowing the location of the arc discharge to be precisely adjusted. The laser influences the location of the ignition on the cathode, thus ensuring uniform, contact-free ablation of the target material.

[0105] A laser source is a device designed to generate a laser beam. A laser beam is understood to be a directed (e.g., collinear and / or collimated) propagation of electromagnetic waves, which is, for example, stimulated and / or coherent. The laser source can, for example, have an electromagnetic resonator, by means of which the stimulated emission of the laser beam occurs. In contrast to a continuous wave laser, a pulsed laser source generates pulsed laser radiation (also referred to as a laser pulse). The laser pulse can be generated by means of pulsed excitation or, for example, by means of a Q-switch in the laser itself. Examples of laser sources include gas lasers (e.g., carbon dioxide lasers) and solid-state lasers (e.g., semiconductor lasers).

[0106] Regarding coating processes for the production of carbon layers, reference is also made to the guideline of the Association of German Engineers (VDI) 3198.

[0107] Various aspects affect the properties of the produced carbon layer. Regarding the terminology used herein, reference is made to the VDI 2840 guideline. Carbon can generally be present in various carbon modifications: in one or more modifications of amorphous carbon (also referred to as amorphous carbon modifications or amorphous form) or in crystalline form, where the crystalline form comprises at least two carbon modifications (also referred to as crystalline carbon modifications or crystal modifications), namely diamond and graphite.

[0108] In general, modifications of amorphous carbon can differ from each other, for example, one or more than one of the following properties: in the proportion of sp 2 -hybridized carbon atoms, the proportion of sp 3 -hybridized carbon atoms, the sp 2 / sp 3 -ratio (also known as sp 2 / sp 3 -hybridization ratio), the orientation of the bond planes, microstructure, bond states, density, conductivity, and hardness. Reference is made to the guideline of the Association of German Engineers (VDI) 3198, standard VDI 2840, as well as to AC Ferrari and J. Robertson (Phys. Rev. B 64, 075414).

[0109] An example for the differentiation of different modifications of amorphous carbon is the standard VDI 2840 (or ISO 20523), where the differentiation is made, for example, based on the proportion of sp 2 - hybridized carbon, sp 3-hybridized carbon, the hydrogen content, and / or the proportion of one or more metallic additives. Alternatively or additionally, modifications of the amorphous carbon may differ from one another in the microstructure and / or the bonding states of the carbon, which may, for example, influence the resistance to electrochemical corrosion, without necessarily leading to other properties such as density, electrical conductivity, mechanical hardness, and / or sp 2 / sp 3 -ratio must correlate.

[0110] For example, an amorphous carbon layer described herein may have a hydrogen-free and / or amorphous structure (referred to as aC).

[0111] It is understood that a formed carbon layer can have a proportion of crystalline carbon modification and / or one or more than one proportion of amorphous carbon modification, wherein the carbon modifications can preferably differ from one another. If a carbon layer is referred to herein as amorphous (e.g. as having an amorphous structure), it is understood that it is essentially amorphous, e.g. having one or more than one modification of amorphous carbon. A carbon layer can be essentially amorphous if the proportion of amorphous carbon modification(s) is greater than 60% (e.g. greater than 70%, e.g. greater than 90%). Alternatively or additionally, a carbon layer can be essentially amorphous if the proportion of the crystalline carbon modification is less than 40% (e.g. less than 30%, e.g. less than 10%).

[0112] Two different carbon layers can, for example, alternatively or in addition to the difference in their proportion of amorphous carbon modification, differ from each other in a structuring and / or orientation (even with the same proportion of amorphous carbon modifications) of the carbon of the carbon layer. The carbon layers described herein can be electrically conductive. This can be necessary to ensure the function of the electrically conductive connection of a bipolar plate. Since a carbon layer with sp 2 - hybridized carbon atoms is electrically conductive and a carbon layer with sp 3 -hybridized carbon atoms is not electrically conductive, it is understood that all carbon layers described herein are predominantly (e.g. more than 80%, e.g. more than 90%, etc.) sp 2-hybridized carbon atoms. As described above with respect to carbon modification, it is understood that a carbon layer can contain both sp 2 -hybridized carbon atoms as well as sp 3 -hybridized carbon atoms. For example, a crystalline carbon layer with a diamond structure in which the carbon atoms are sp 3 -hybridized, also sp 2 -hybridized carbon atoms, since the carbon atoms at grain boundaries are often sp 2 - are hybridized. The hybridization of the carbon atoms can also be referred to as the bonding states of the carbon atoms or can specify them.

[0113] Qualitative differences in hybridization can be determined, for example, using Raman spectroscopy. A quantification of the proportion of sp 2 -hybridized carbon atoms and the proportion of sp 3-hybridized carbon atoms can be determined using electron energy loss spectroscopy (EELS) and / or nuclear magnetic resonance spectroscopy (NMR).

[0114] The basis for categorising amorphous carbon is provided by the standard VDI 2840 (or ISO 20523) and is based on the differentiation based on the proportions of the sp 2 or sp 3 -hybridization, hydrogen content, and / or various metallic additives. Furthermore, amorphous carbon can also vary in its microstructure and the respective bonding states, thus influencing, for example, the corrosion resistance of a carbon layer consisting of it, without this necessarily correlating directly with other commonly specified, tangible properties such as density, conductivity, hardness, sp2 / sp3 content.

[0115] Various aspects affect the thickness of carbon layers. The thickness of a carbon layer can be determined, for example, using X-ray reflection (XRR), microscopy (e.g., scanning electron microscopy and / or transmission electron microscopy), ellipsometry, ultrasound techniques, etc.

[0116] The term "control device" can be understood as any type of logic-implementing entity, which may, for example, comprise circuitry and / or a processor capable of executing software stored in a storage medium, firmware, or a combination thereof, and issuing instructions based thereon. The control device can, for example, be configured using code segments (e.g., software) to control the operation of a system (e.g., its operating point), e.g., a machine or a system, e.g., at least its kinematic chain.

[0117] Control can be understood as the intentional influencing of a system. The current state of the system (also referred to as the actual state) can be changed according to a specification (also referred to as the target state). The parameters explained here (also referred to as target parameters) of the target state can, for example, be implemented using code segments or be stored on a storage medium in some other way. Regulation can be understood as control, whereby a change in the state of the system is additionally counteracted by disturbances. Illustratively, the control system can have a forward-facing control path and thus clearly implement a sequential control that converts an input variable (e.g. the specification) into an output variable. However, the control path can also be part of a control loop, so that a closed-loop control is implemented.For control purposes, corresponding actuators of the system can be activated, which influence the actual state of the system. Examples of actuators include: a drive device (e.g., for providing torque), a valve (e.g., for controlling pressure), a switch (e.g., for closing a discharge path). The drive device can, for example, comprise a linear drive (e.g., a reciprocating piston) or an electric motor.

[0118] The term "actuator" (e.g., having an actuator and / or actuator) can be understood as a transducer configured to influence a state, a process (e.g., a coating process), or a device in response to actuation of the actuator. The actuator can convert a control signal supplied thereto (by means of which the actuation takes place) into mechanical movements and / or changes in physical quantities such as pressure or temperature. An electromechanical (also referred to as electromotive) actuator can, for example, be configured to convert electrical power into mechanical power (e.g., through movement) in response to actuation. An electrothermal actuator can, for example, be configured to convert electrical power into thermal power in response to actuation.An electrothermal actuator can, for example, be configured to convert electrical power into thermal power in response to the control. An electrical actuator can, for example, be configured to convert electrical energy into electrical energy (e.g., of a specific voltage, current, and / or power) in response to the control.

[0119] An actuator can be configured to influence the actual state (also referred to as the operating point) of the process (e.g., its manipulated variable), which is supplied by the actuator. This influence can be direct or indirect. For example, the manipulated variable and the controlled variable can differ from each other. The controlled variable (e.g., pressure) can then be a function of one or more manipulated variables (e.g., voltage).

[0120] With regard to the control of an actuator, reference is made, among other things, to the more easily understood manipulated variable and / or its control value, which is influenced by the actuator. What is described here can apply analogously to the controlled variable and / or its control value, which are fed to the actuator for control, and vice versa. The actuator acts as a converter, converting a control signal into the manipulated variable and / or its control value, so that the control value is a function of the control value. Modern actuators, for example, are provided as a complex assembly comprising an actuator and its own control device (also referred to as an actuator control device). The actuator control device can be configured to receive the control value as input using the control signal and to control the actuator according to the control value.The generation and transmission of the control variable then takes place within the actuator, so that the manipulated variable is fed to the actuator. Less complex actuators can only process the control variable as a control signal, so the control variable is fed to them for control.

[0121] More generally, an actuator can be controlled using a control signal, where the control signal can represent the manipulated variable and / or its manipulated value and / or the controlled variable and / or its controlled value. Alternatively or additionally, the control signal can contain instructions that specify how the manipulated variable and / or its manipulated value is to be changed (e.g., its relative change).

[0122] The term "processor," as used herein, can be understood as any type of entity that allows the processing of data or signals. The data or signals can, for example, be processed according to at least one (i.e., one or more than one) specific function performed by the processor. A processor can include or be formed from an analog circuit, a digital circuit, a mixed-signal circuit, a logic circuit, a microprocessor, a central processing unit (CPU), a graphics processing unit (GPU), a digital signal processor (DSP), a programmable gate array (FPGA), an integrated circuit, or any combination thereof. Any other type of implementation of the respective functions, which are described in more detail below, can also be understood as a processor or logic circuit.It is understood that one or more of the method steps described in detail herein may be executed (e.g., realized) by a processor through one or more specific functions performed by the processor. The processor may therefore be configured to perform one of the methods described herein or its components for information processing.

[0123] The term amorphous in relation to an object (e.g. material or body, such as a layer) is understood here as a non-crystalline and / or disordered nature of the object with regard to the arrangement of the atoms, which, for example, only have short-range order but no long-range order. Long-range order, i.e. a regular arrangement of atoms beyond their neighboring atoms, is characteristic of crystals. Regularly structured materials are called crystals. The crystallinity index (also referred to as crystallinity) and / or the orientation distribution function are often used as a measure of the proportion of long-range order. Related to a binary state model in which the atoms of the object are either crystalline or amorphous, which can serve as a first approximation, the crystallinity index indicates the ratio of the crystalline to the amorphous part of the object.

[0124] For more complex state models that consider a continuous transition between amorphous and crystalline, the crystallinity index indicates where the object lies in the transition between amorphous and crystalline, which makes it possible to compare two objects (e.g. layers) with regard to their nature, for example with regard to one or more than one of the following: the modification of the amorphous carbon (and / or the proportion thereof in the object), orientation of the bonding planes of the carbon and / or graphene layers, microstructure (measurable via transmission electron microscopy) and bonding states (measurable via Raman spectrum), and / or the structuring (e.g. grain size), if present.

[0125] Examples for determining the crystallinity index and / or the orientation distribution function are based on spectroscopy, e.g., using X-rays and / or nuclear magnetic resonance. A lower crystallinity index (significantly increasing amorphization) leads to the disappearance and / or broadening of peaks in the spectrum. This applies analogously to other measurement techniques, such as X-ray diffraction (XRD), transmission electron microscopy, electron backscattering (EBSD), and / or transmission Kikuchi diffraction (TKD).

[0126] With regard to the difference between two objects (e.g., two carbon layers) from each other, various parameters of the objects are discussed here. Examples include: electrical properties (e.g., contact resistance) and / or electrochemical resistance, their layer thickness, proportions, etc. In this regard, it can be understood that the difference between the two carbon layers from each other with regard to a parameter is greater than a fluctuation in the parameter within one of the carbon layers. Illustratively, the fluctuation of the parameter within an object (e.g., carbon layer) reflects the manufacturing-related fluctuation of the parameter. If the two objects differ from each other with regard to the parameter (also referred to as a parameter difference), this difference between the objects can be greater than the manufacturing-related fluctuation of the parameter.Alternatively or additionally, this difference is greater than a threshold value S, which indicates the usual manufacturing-related variation in the parameter, where S can, for example, be greater than approximately 1%, e.g., approximately 2.5%, e.g., approximately 5%, e.g., approximately 10%. For example, the parameter difference can be greater than approximately 20%, e.g., approximately 30%, e.g., approximately 50%.

[0127] The term "proportion" in relation to a material (e.g., a modification of carbon) of an object (e.g., layer) can be understood herein as a content variable, for example, based on the molar proportion (e.g., in at%), the mass proportion (e.g., in m%), and / or the volume proportion (e.g., in v%) of the material. The content information indicates the content of the material in the object, for example, the material proportion of the material in a mixture of the object. Analogously, information based on this can be understood, such as a ratio of proportions of different materials in the object and / or a ratio of a proportion of the same material in different objects (e.g., layers).

[0128] During electrochemical corrosion of a carbon layer, the carbon reacts, particularly with oxygen, to form a gaseous reaction product, which evaporates. During electrochemical corrosion, the carbon layer is converted into the gaseous reaction product, which evaporates (also referred to as dissolution of the carbon layer). Electrochemical corrosion of the carbon layer ends when the carbon in the carbon layer is consumed.

[0129] FIG.1A illustrates a half-cell 100 according to various embodiments in a schematic cross-sectional view or side view.

[0130] In general, the half-cell 100 can be a half-cell 100 for an electrochemical cell. The half-cell 100 can provide a positive electrode or a negative electrode of the electrochemical cell. The bipolar plate halves (also called half-plates) are also called anode or cathode plates because they face the anode or cathode in the membrane electrode assembly (MEA). A gas diffusion layer is located between them.

[0131] Depending on the application, an electrochemical cell may have two such half-cells (e.g. a first half-cell 100(1) and a second half-cell 100(2)).

[0132] In some embodiments, the electrochemical cell may be a galvanic cell. A galvanic cell may be an electrochemical power source that generates electrical energy through chemical reactions.

[0133] For example, the electrochemical cell can be the galvanic cell of a redox flow battery. In this case, a membrane can be arranged between the two half-cells.

[0134] For example, the electrochemical cell can be the galvanic cell of a fuel cell.

[0135] In other embodiments, the electrochemical cell can be an electrolysis cell. An electrolysis cell can be configured to produce one or more substances by applying electrical energy (e.g., a voltage). A device comprising the electrolysis cell can also be referred to as an electrolyzer. Unlike in a fuel cell, the conditions in the electrolyzer are reversed, i.e., the anode side (or at least the anode half-plate, e.g., its coating) is exposed to the more corrosive environment (e.g., a more intense electrochemical reaction, e.g., oxidation).

[0136] For example, the electrolyzer can be configured to decompose water into oxygen and hydrogen by applying a voltage. In the case of the electrolysis cell, the electrochemically more stable carbon layer can be used on the anode side, while a slightly less stable and / or less efficient carbon layer would suffice on the cathode side.

[0137] The half-cell 100 may include a carrier plate 102. The carrier plate 102 may include or consist of one or more metallic layers. In the context of this description, a metal (also referred to as a metallic material) may include (or be formed from) at least one metallic element (i.e., one or more metallic elements), e.g., at least one element from the following group of elements: copper (Cu), iron (Fe), titanium (Ti), nickel (Ni), silver (Ag), chromium (Cr), platinum (Pt), gold (Au), magnesium (Mg), aluminum (Al), zirconium (Zr), tantalum (Ta), molybdenum (Mo), tungsten (W), vanadium (V), barium (Ba), indium (In), calcium (Ca), hafnium (Hf), and / or samarium (Sm).

[0138] For example, the carrier plate 102 may comprise titanium, niobium, and / or chromium (e.g., consist essentially of titanium, niobium, and / or chromium), which improves the cell's properties. Preferably, the carrier plate 102 (or at least one or more layers) comprises or consists of titanium, niobium, and / or chromium.

[0139] A titanium substrate and / or a titanium interlayer on stainless steel inhibits the entry of iron ions into the cell's proton exchange membrane, thereby increasing the lifetime of the proton exchange membrane. Similarly, niobium and / or chromium can be used as an interlayer material, alternatively or in addition to titanium.

[0140] The carrier plate 102 can be configured to provide at least one fluid flow channel, e.g., by profiling (e.g., embossing) the carrier plate 102. The profile of the carrier plate 102 can, for example, have one or more than one (e.g., meandering) groove that provides the fluid flow channel. A fluid flow channel described herein can, for example, have a meandering course in the plane spanned by the direction 101 and the direction 103. "Meandering" in this context can be understood as meaning that the fluid flow channel (or at least the groove) extends longitudinally along a meandering (e.g., winding) path. For example, the fluid flow channel (or at least the groove) can extend back and forth several times between two edges of the carrier plate 102.

[0141] The support plate 102 may have a first section at which the fluid flow channel opens into an edge of the support plate 102. The support plate 102 may alternatively or additionally have a second section at which the fluid flow channel opens into an edge of the support plate 102. The first and / or second section clearly provide a connection section at which a fluid can be supplied to and / or removed from the fluid flow channel.

[0142] Below, various aspects of the half-cell 100 are described using a fuel cell as an example. It is understood that this is for illustrative purposes only, and the half-cell 100 may also be a half-cell of any other type of galvanic cell, such as a redox flow battery, or an electrolytic cell, such as an electrolytic cell for generating hydrogen.

[0143] In the exemplary example of the fuel cell, the support plate 102 may provide a reactant gas fluid flow channel 104 and a cooling medium fluid flow channel 106 (or at least a portion thereof).

[0144] In a fuel cell and in an electrolyzer, two half-cells (e.g., the first half-cell 100(1) and the second half-cell 100(2)) can be connected to each other to form a bipolar plate 110, as shown, for example, in FIG. 1B. Here, the first half-cell 100(1) can provide a positive electrode (e.g., cathode) of a first galvanic cell (in this case, the half-cell can also be referred to as a cathode plate), and the second half-cell 100(2) can provide a negative electrode (e.g., anode) of a second galvanic cell (in this case, the half-cell can also be referred to as an anode plate), or vice versa. This gives rise to the term bipolar plate, which indicates that there are two poles, a positive pole and a negative pole. In other words, one side of the bipolar plate faces the anode and the other side of the bipolar plate faces the cathode.

[0145] For example, the first reaction gas fluid flow channel 104(1) of the first half-cell 100(1) (configured as a cathode) can be configured to carry oxygen (e.g., as part of the air), and the second reaction gas fluid flow channel 104(2) of the second half-cell 100(2) (configured as an anode) can be configured to carry hydrogen. Furthermore, the water produced during the reaction can be removed by means of the fluid flow channel to provide the oxygen 100(1) to the bipolar plate (e.g., as water vapor). In some embodiments, the first half-cell 100(1) and the second half-cell 100(2) can be or have been detachably connected to form a bipolar plate 110. Reference herein to a carrier plate 102 can refer to a single half-cell 100 in this case. The half-cell 100 can then also be referred to as a plate half or half-plate.

[0146] In other embodiments, the first half-cell 100(1) and the second half-cell 100(2) may be or are non-releasably connected (e.g., welded together) to form a bipolar plate 110. Reference herein to a carrier plate 102 may refer to a bipolar plate 110 (consisting of two half-cells).

[0147] FIG. 2 shows a fuel cell 200 according to various embodiments in a schematic cross-sectional view or schematic side view. Several membrane electrode assemblies can be stacked in the fuel cell 200. A membrane 202 (e.g., comprising a proton exchange membrane) can be arranged between two adjacent bipolar plates 110.

[0148] Oxygen (e.g., as part of air) can be supplied to a membrane 202 via the first reaction gas fluid flow channel 104(1) of a first half-cell 100(1) of a bipolar plate (configured as a cathode), and hydrogen can be supplied to the membrane 202 via the second reaction gas fluid flow channel 104(2) of a second half-cell 100(2) of another bipolar plate (configured as an anode). This applies at least to the fuel cell. In the case of electrolysis, the cathode side is in contact with hydrogen, and water is provided on the anode side.

[0149] A fuel cell can generate electrical energy through the chemical reaction of oxygen and hydrogen (to form water). This chemical reaction can occur at any galvanic cell consisting of a membrane 202, the positive electrode (cathode) of a bipolar plate adjacent to the membrane 202, and the negative electrode (anode) of the other bipolar plate adjacent to the membrane 202.

[0150] It can be understood that the membrane 202 can also be provided as a membrane electrode assembly (MEA), for example, in a 3-layer configuration or a 5-layer configuration. The 3-layer configuration can comprise a catalyst-coated membrane, also called a catalyst-coated membrane (CCM). The 5-layer configuration comprises the following layers: GDL, 3-layer configuration, GDL.

[0151] The following reactions can occur:

[0152] Anode: 2H2(g) + 2H2O(I) 4H3O +(aq)+ 4e-

[0153] Cathode: O2(g) + 4H3O + (aq) + 4e~ 6H2O(I)

[0154] Overall reaction of the galvanic cell: 2H2(g)+O2(g) — > 2H2O(I) where (g) indicates a gaseous state, (I) a liquid state, and (aq) a state in aqueous solution.

[0155] This can lead to a direct electrical current flowing from the cathode to the anode. The electrical energy generated by the fuel cell can be the sum of the direct electrical current generated by all galvanic cells. Furthermore, heat can be generated, which can be dissipated via the cooling medium fluid flow channels 106.

[0156] In order to dissipate this direct electrical current, it may be necessary for the bipolar plate 110 (e.g. both half-cells) to be electrically conductive on their surface.

[0157] In some cases, the one or more than one metallic layer of the carrier plate 102 may form a passivating, electrically non-conductive boundary layer (e.g., a natural oxide layer), for example, the one or more than one metallic layer of the carrier plate 102 is a surface layer consisting, for example, of titanium, niobium, and / or chromium. To ensure the electrically conductive property (and thus the function of the bipolar plate), the bipolar plate and / or each half-cell 100(1), 100(2) may be coated on both sides with a carbon layer. Such a carbon layer may have a high electrical conductivity (e.g., above 10 5S / m). If a bipolar plate 110 (as carrier plate 102) is coated with carbon on both sides, one side of the bipolar plate 110 can be the cathode side and the (opposite) other side can be the anode side. If a half-cell 100 is coated with carbon on both sides, one side can be either a cathode side or an anode side and the other side can be a side exposed to the cooling medium.

[0158] Fluid flow channel 106. If such a half-cell 100 is coated with carbon on both sides, these can then be releasably joined to form a bipolar cell 110, wherein the carbon layer on the side facing the cooling medium fluid flow channel 106 can ensure the electrically conductive contact between the two half-cells.

[0159] FIG. 3 shows a layer system 300 according to various embodiments in a schematic side view. The layer system 300 can include the carrier plate 102.

[0160] The layer system 300 can have two carbon layers (directly) on the carrier plate 102, namely a first carbon layer 302 and a second carbon layer 304. The first carbon layer 302 can be arranged on a first side (e.g., a top side) of the carrier plate 102, and the second carbon layer 304 can be arranged on a second side (e.g., bottom side) of the carrier plate 102 opposite the first side. Consequently, the carrier plate 102 can be arranged between the first carbon layer 302 and the second carbon layer 304. Optionally, the carrier plate can have a coating, e.g., having one or more than one metallic intermediate layer, which is arranged between the carbon layers.

[0161] The first carbon layer 302 may have a first layer thickness 306. The carrier plate 102 may have a carrier plate layer thickness 308. The second carbon layer 304 may have a second layer thickness 310.

[0162] As explained herein, the carrier plate 102 can be either the half-cell 100 or the bipolar plate 110. Reference herein to two carbon layers 302, 304 on the carrier plate 102 can therefore include one of the following configurations:

[0163] - The support plate 102 is a half-cell 100. In this case, the half-cell 100 can be either a cathode-side half-cell or an anode-side half-cell. Consequently, the first carbon layer 302 can be a carbon layer on the cathode side or anode side of the half-cell 100, and the second carbon layer 304 can be a carbon layer on the side of the half-cell 100 facing the cooling medium fluid flow channel 106, or vice versa.

[0164] - The carrier plate 102 is a bipolar plate 10. In this case, the first carbon layer 302 can be a carbon layer on the cathode side of the bipolar plate 110 and the second carbon layer 304 can be a carbon layer on the anode side of the bipolar plate 110, or vice versa.

[0165] The use of carbon layers 302, 304 has numerous advantages. For example, bipolar plates in fuel cells are often coated with gold, which is significantly less expensive than carbon layers. Bipolar plates in electrolyzers (e.g., PEM electrolyzers) are often coated with platinum on the anode side and gold on the cathode side, which is significantly less expensive than carbon layers. Carbon layers also reduce the contact resistance (ICR) of the bipolar plates.

[0166] However, the oxidation reaction at the cathode of the fuel cell (e.g. in high potential ranges) can lead to oxidation of the carbon in the carbon layer (e.g. to CO2). The oxidation of the carbon can also be referred to as (chemical) corrosion of the carbon layer. DIN EN ISO 8044 (formerly DIN 50900) defines corrosion as the reaction of a metallic material with its environment, which causes a measurable change in the material and can impair the function of a metallic component or an entire system. The corrosion of the carbon layer can lead to a loss of the electrically conductive contact surface and consequently to a reduction in the efficiency of the fuel cell. The corrosion of the carbon layer can lead to decomposition of the carbon layer as a result of the oxidation of the carbon to carbon dioxide (CO2).It is understood that this may result in the electrically conductive property of the bipolar plate no longer being ensured.

[0167] Corrosion of the carbon layer can occur particularly during voltage peaks during cold start-ups of the fuel cell. These peak voltages can be approximately 1.4 volts (V) or, in some cases, even higher. For example, hydrogen at the cell inlet and air at the outlet on the anode side of the cell, or air / air at the cell outlet, can promote a local voltage peak of up to 1.4 V at the plate outlet on the cathode side. This value can be present at the catalyst layer, resulting in a slightly lower value at the bipolar plate.

[0168] Consequently, different requirements may be placed on the two carbon layers. The carbon layer on the cathode side may have the highest corrosion resistance requirements due to the oxidation reaction and the associated carbon corrosion. The carbon layer on the anode side may therefore have lower corrosion resistance requirements. If the carrier plate 102 is the half-cell 100, the carbon layer on the side facing the cooling medium fluid flow channel 106 may have lower corrosion resistance requirements than the carbon layer on the anode side due to its contact only with the cooling medium.

[0169] Therefore, the first carbon layer 302 and the second carbon layer 304 can differ from each other. Illustratively, the layer system 300 can be asymmetrical with respect to the two carbon layers 302, 304.

[0170] In general, the first carbon layer 302 and the second carbon layer 304 can differ from one another in terms of a period of time (e.g., durability period), after which the requirements for the carbon layer are no longer met. For example, the period of time can be a period of time after which a predefined (percentage) portion of the carbon layer is removed (e.g., a loss of mass) in a corrosive medium (e.g., when a voltage of, for example, 1.4 V is applied). For example, the period of time can be the durability period, after which the carbon layer is no longer electrically conductive in the corrosive medium (e.g., when a voltage of, for example, 1.4 V is applied). This can be achieved in two (combinable) ways: The first carbon layer 302 and the second carbon layer 304 can differ from one another in their corrosion resistance.In this way, the first carbon layer 302 and the second carbon layer 304 differ in the corrosion rate at which the carbon layer is decomposed. Thus, the carbon layer on the cathode side can have the lower corrosion rate and thus the highest corrosion resistance. Alternatively or additionally, the carbon layer 302 and the second carbon layer 304 can differ from one another in their layer thicknesses 306, 310. In this regard, it is understood that a carbon layer with a greater layer thickness, even with the same carbon modification, is associated with a longer period of time (e.g., resistance period) until the carbon layer is decomposed as a result of carbon corrosion. Thus, the carbon layer on the cathode side can have the greatest layer thickness.However, it is understood that if the carbon layer on the cathode side has a lower corrosion rate, the carbon layer on the cathode side may have a smaller layer thickness and the time it takes (e.g., durability period) for it to decompose may still be greater than the time it takes for the other carbon layer (e.g., the anode-side or fluid flow channel-side carbon layer). Corrosion resistance can be the ability of a material (e.g., its surface) to resist the destructive influence of corrosion over a predefined period of time (e.g., until the durability period). Corrosion resistance can be represented by a corrosion rate (also called erosion rate). The corrosion rate can indicate the rate of material change (e.g., material removal) (e.g., in mm per year; mm / a). It is understood that the nature of the corrosive medium can have a direct influence on this.

[0171] A higher corrosion resistance (e.g., a lower corrosion rate) of a carbon layer (e.g., the first carbon layer 302) compared to another carbon layer (e.g., the second carbon layer 304) can be achieved by the first carbon layer 302 having different proportions of amorphous carbon modifications than the second carbon layer 304. As explained herein, all carbon layers described herein can be electrically conductive and therefore their carbon atoms can be predominantly (e.g., more than 80%, more than 90%, etc.) 2 -hybridized.

[0172] Where reference is made herein to the corrosion resistance of a carbon layer, this may be electrochemical corrosion resistance.

[0173] Electrochemical corrosion resistance can be determined, for example, using a potentiostatic corrosion measurement. Electrochemical corrosion resistance can be measured, for example, by measuring the electrical conductivity of the carbon layer when a voltage (e.g., 1.4 V, 1.5 V, or 1.6 V, etc.) is applied in a corrosive medium (e.g., against a hydrogen standard electrode or an Ag / AgCl standard electrode, also known as an Ag / AgCl electrode or Ag / AgCl for short), for example, ex situ before and after corrosion, with the corrosion currents being recorded during corrosion. The longer the carbon layer remains electrically conductive, the longer the period for which its functionality is ensured.

[0174] Clearly, the first carbon layer 302 and the second carbon layer 304 can differ absolutely in a proportion of amorphous carbon modification. For example, a first amorphous proportion of the first carbon layer 302 can be greater by a predefined value than a second amorphous proportion of the second carbon layer 304. For example, a difference between the first amorphous proportion and the second amorphous proportion can be at least 2% (e.g., at least 5%). In particular, with the same proportion, 2 - hydrided carbon there are significant differences in corrosion resistance, for example resulting from different modifications of the amorphous carbon.

[0175] Optionally, the first carbon layer 302 and the second carbon layer 304 may differ from each other in a proportion of sp 2-hybridized carbon atoms. For example, the cathode-side first carbon layer 302 can have a larger proportion of sp 2 -hybridized carbon atoms than the opposite second carbon layer 304 to provide greater electrical conductivity.

[0176] In this case, the first layer thickness 306 of the first carbon layer 302 can be either greater than, less than, or equal to the second layer thickness 310 of the second carbon layer 304. According to various aspects, the proportion of crystalline carbon modification can be a proportion of graphite. In this case, the first carbon layer 302 can be a polycrystalline graphite layer.

[0177] In another embodiment, the first carbon layer 302 can be a layer stack composed of multiple carbon sublayers. In this case, at least the carbon sublayer can have a substantially crystalline structure on the surface. This is because the corrosion resistance at the surface of the first carbon layer 302 can be or can be increased. In yet another embodiment, both the first carbon layer 302 and the second carbon layer 304 can have a substantially amorphous structure (e.g., with a proportion greater than 90%). In this case, the first layer thickness 306 of the first carbon layer 302 can be greater than (e.g., at least twice as great as) the second layer thickness 310 of the second carbon layer 304.

[0178] As explained herein, the proportion of modifications of the amorphous carbon may depend on the coating process used to form the carbon layer. For example, the crystalline carbon layer may be formed using high-impulse magnetron sputtering (HiPIMS) or arc evaporation, and the amorphous carbon layer may be formed using (e.g., DC) magnetron sputtering or electron beam evaporation. Alternatively or additionally, the formation of a crystalline structure may be promoted using DC sputtering while applying a bias voltage to the substrate.

[0179] Therefore, according to various aspects, a vacuum arrangement can be used to produce the layer system 300. Consequently, this vacuum arrangement can be configured to produce the layer system 300. FIGS. 4A and 4B each show an exemplary vacuum arrangement for producing the layer system 300 according to various embodiments 400a, 400b in a schematic top view or schematic side view. It is understood that this is an exemplary implementation of a vacuum arrangement for producing the layer system 300.

[0180] The vacuum arrangement 400 can have a vacuum chamber. A vacuum chamber can be provided, for example, by means of a chamber housing in which one or more vacuum chambers can be provided. The chamber housing can be coupled, for example, to a pump arrangement, e.g., a vacuum pump arrangement, for providing a negative pressure or a vacuum (vacuum chamber housing), and can be configured so that it can withstand the effects of air pressure in the pumped-out state. The pump arrangement (comprising at least one vacuum pump, e.g., a high-vacuum pump, e.g., a turbomolecular pump) can make it possible to pump out part of the gas from the interior of the vacuum chamber. The or each vacuum chamber can optionally have a chamber lid that seals the interior of the vacuum chamber in a vacuum-tight manner.

[0181] The chamber housing, e.g. a vacuum chamber provided therein, may be arranged such that a negative pressure (ie a pressure less than atmospheric pressure) can be provided therein, e.g. a vacuum (ie a pressure less than 0.3 bar), e.g. a pressure in a range of about 10 mbar to about 1 mbar (in other words rough vacuum) or less, e.g. a pressure in a range of about 1 mbar to about 10 3 mbar (in other words fine vacuum) or less, e.g. a pressure in a range of approximately 10 3 mbar to approximately 10 7 mbar (in other words high vacuum) or less, e.g. a pressure less than high vacuum, e.g. less than about 10 7 mbar. Atmospheric pressure (e.g., 1 bar) can be the pressure acting on the chamber housing from the outside.

[0182] The vacuum arrangement 400 can, for example, be a continuous system. For this purpose, the vacuum arrangement 400 can comprise a vacuum chamber system with one or more vacuum chambers and a transport system 406 for transporting the carrier plate 102 (the half-cell 100 or the bipolar plate 110) through the one or more vacuum chambers. The transport system 406 can therefore provide a transport path through the vacuum chamber system for transporting the carrier plate 102 along the transport path.

[0183] The vacuum assembly 400 may include a first substrate transfer opening 402 for guiding the carrier plate 102 into the vacuum chamber system. The vacuum assembly 400 may include a second substrate transfer opening 404 for guiding the carrier plate 102 out of the vacuum chamber system. A plurality of processing areas 408 may be configured between the first substrate transfer opening 402 and the second substrate transfer opening 404. For example, one or more of the processing areas may each include one or more coating devices.

[0184] The vacuum arrangement 400 may include a coating system configured to form the first carbon layer 302 on a top surface of the carrier plate 102 and the second carbon layer 304 on a bottom surface of the carrier plate 102.

[0185] The coating system may include at least one first coating device 410(1) and at least one second coating device 412(1). The at least one first coating device 410(1) may be configured to form the first carbon layer 302.

[0186] In general, the at least one first coating device 410(1) and the at least one second coating device 412(1) can differ from one another in a type of coating method. FIG. 4A shows the vacuum arrangement 400 as an example for exactly one first coating device 410(1) and exactly one second coating device 412(1). FIG. 4B shows the vacuum arrangement 400 as an example for each processing area 408(n) having exactly one first coating device 410(1) and exactly one second coating device 412(1). It is understood that this is merely illustrative, and the number of first coating devices and second coating devices can be arbitrary.

[0187] For example, if the first carbon layer 302 is a substantially crystalline carbon layer, the at least one first coating device 410(1) may be a high-impulse magnetron sputtering (HiPIMS) or arc evaporation coating device, and the at least one second coating device 412(1) may be a (DC or high-frequency) magnetron sputtering or evaporation coating device to form the second carbon layer 304 as an amorphous carbon layer. In this way, the manufacturing costs for the second carbon layer 304 can be significantly reduced.

[0188] As explained herein, the first carbon layer 302 may be a layer stack of multiple carbon sublayers, and at least the carbon sublayer at the surface may have a substantially crystalline structure. For example, in this case, the at least one first coating device 410(1) may comprise multiple coating devices, and at least the last coating device, viewed in the transport direction, may then be a high-impulse magnetron sputtering (HiPIMS) or arc evaporation coating device. In this case, other coating devices of the at least one first coating device 410(1) could be a (DC or high-frequency) magnetron sputtering or evaporation coating device, which may further reduce manufacturing costs.

[0189] If both the first carbon layer 302 and the second carbon layer 304 are amorphous carbon layers, for example, the at least one first coating device 410(1) can be a coating device for evaporation, and the second coating device 412(1) can be a coating device for (DC or radio frequency) magnetron sputtering. In this case, the coating system can be configured to form the first carbon layer 302 and the second carbon layer 304 such that the first layer thickness 306 of the first carbon layer 302 is greater than the second layer thickness 310 of the second carbon layer 304.For this purpose, the at least one first coating device 410(1) can have a higher coating rate than the at least one second coating device 412(1) and / or the number of coating devices of the at least one first coating device 410(1) can be greater than the number of coating devices of the at least one second coating device 412(1). In this case, the second carbon layer 304 can be formed with significantly lower manufacturing costs than the first carbon layer 302. Clearly, according to various embodiments, the manufacturing costs for forming the half-cell 100 and / or bipolar plate 110 can be reduced, thus increasing cost-effectiveness.

[0190] In general, a (coating) rate can be specified as a rate per distance of the transport path in which the substrate is exposed to a coating device.

[0191] In continuous-flow systems, the rate at which the transported substrate (e.g., the carrier plate 102) is coated (also referred to as the coating rate) can be specified as the so-called dynamic coating rate (in nm / min), which is a function of the product of a layer thickness created by coating and a transport speed at which the substrate is transported, and thus provides more comparable values ​​for the coating rate for different scenarios. Therefore, in this case, the dynamic coating rate at which the first carbon layer 302 is formed can be greater than the dynamic coating rate at which the second carbon layer 304 is formed.

[0192] It is understood that the manufacturing of the layer system 300 can be carried out as a corresponding method (see, for example, Examples 27 to 37).

[0193] Below, exemplary implementations according to various embodiments and comparative examples are explained, particularly with regard to the contact electrical corrosion resistance of one or more carbon layers. In this regard, various implementations regarding requirements and for determining the contact electrical corrosion resistance (RES-ICR) are explained.

[0194] In an electrochemical cell, e.g., a fuel cell, peaks in the electrochemical voltage (also known as voltage overshoots) can occur to which the bipolar plate, e.g., its coating, is exposed. These voltage overshoots can occur, for example, when the fuel cell is started. If the coating of the bipolar plate contains carbon, e.g., in the case of a carbon layer, this voltage overshoot can promote corrosion of the coating, which reduces the service life of the coating and thus of the electrochemical cell. The more resistant the coating is to corrosion, for example, at least its properties (such as contact resistance), the longer the service life of the coating and thus of the electrochemical cell.

[0195] Requirements for RES-ICR

[0196] The contact resistance (ICR) of a layer is related to the contribution to the electrical resistance (e.g. resistance) of the layer that arises at the interface contacting the layer, through which the electrical current flows, conveyed by the layer. The contact resistance is related, for example, to one of the two opposite surfaces of the layer that are the closest apart (also referred to as layer thickness) when they are contacted. The contact resistance is a function of the electrical resistance (resistance) of these surfaces (also referred to as surface resistance of the layer), which contributes to the electrical resistance (resistance) of the layer when the electrical current flows through them, e.g. along the direction of the layer thickness.

[0197] The US Department of Energy (DoE) recommends test conditions and target values ​​to be achieved for the qualification of individual components for a polymer electrolyte fuel cell (PEM fuel cell), which a large part of the fuel cell market is based on. To determine the suitability of a configuration (e.g., bipolar plate and / or a coating of a metallic bipolar plate), its corrosion resistance and electrical conductivity (e.g., expressed by contact resistance) are essentially measured.

[0198] The specification for the contact resistance (ICR - interfacial contact resistance) between a bipolar plate and a gas diffusion layer (GDL), e.g. a carbon gas diffusion layer, is initially (e.g. as manufactured) and after corrosion (e.g. by exposure to a corrosive environment for a specified duration) a maximum of 10 milliohms times meters per square centimeter (mQcm 2). The contact between the bipolar plate and the gas diffusion layer can be achieved by pressing the latter at a target pressure of maximum 138 Newton per centimeter (N / cm 2 ), which corresponds approximately to the compression in a fuel cell. However, for better detection of differences in the ICR, this can also be done at a compression of a different value, e.g. 60 N / cm 2 , and / or by means of a contact against a contact terminal of the measuring setup.

[0199] The following refers to the corrosion resistance of the contact resistance (also referred to as RES-ICR).

[0200] Determining RES-ICR

[0201] Determining the corrosion resistance of an object, e.g., a layer (e.g., a carbon layer) or a layer system, can be done by detecting the galvanic current (also called corrosion current) and / or its change that flows during corrosion of the object when the object is exposed to a corrosive environment. The corrosive environment may include an electrical voltage (also called corrosion voltage) and / or an electrically conductive fluid (e.g., electrolyte) to which the object is exposed.

[0202] In this case, especially when specifying the corrosion potential, attention must be paid to the properties of the corrosive environment (e.g., reference electrode and / or electrolyte) (e.g., their standard potential) through which the corrosion current is mediated and / or to which the object is exposed. For example, the standard potential of a standard hydrogen electrode as a reference electrode is 0 V. The standard potential of a reference electrode made of AgCl / Ag (gold chloride / gold) is +0.22 V.

[0203] In general, the corrosion resistance of an object decreases with increasing corrosion voltage. For the example of a carbon layer, the corrosion current increases sharply from a corrosion voltage of 1 V against Ag / AgCl and is dominated by the oxidation of the carbon. If the corrosion voltage remains unchanged, the corrosion current flows until the carbon layer is completely oxidized and thus dissolved (also referred to as consumed). If a metal surface is exposed in the process, e.g. the surface of a carrier plate, this metal surface is subsequently oxidized. If the metal surface forms a stable metal oxide (e.g. chromium oxide or titanium oxide), this acts as a passivation, inhibiting corrosion and thus reducing the corrosion current. However, this metal oxide also inhibits the current flow of the electrochemical cell due to its low electrical conductivity, so that this impairs the functionality of the metallic carrier plate (e.g.as a bipolar plate) and the electrochemical cell fails.

[0204] In general, the dependence of the corrosion current on the corrosion voltage, and thus the threshold value of the corrosion voltage Uc (also called the threshold voltage) at which corrosion begins, as well as the time period Z (also called the resistance period) until the corrosion current drops, when corrosion stops due to the consumption of a layer, are reproducible and clearly measurable.

[0205] Below the threshold voltage, so-called creeping corrosion can occur in some cases. However, this occurs much more slowly and is therefore associated with a significantly lower corrosion current. Even in this case, the time period Z (also referred to as the resistance period) until the corrosion current drops, when creeping corrosion ceases due to the wear of a layer, can be measured reproducibly and clearly.

[0206] To compare the corrosion resistance of two coatings (e.g., carbon coatings), the influence of the same corrosive environment on one or more coating parameters (e.g., contact resistance) can be compared. In this case, the properties of the corrosive environment and thus the influencing factor of corrosion are identical, so the resistance duration of the coating parameter can serve as an exemplary measure of corrosion resistance. The description here can apply analogously to any other parameter that represents the influence of the corrosive environment on the coating, for example, the corrosion current, which is referred to below.

[0207] In an exemplary implementation, corrosion resistance is determined by measuring the corrosion current in an electrochemical cell. A solution containing sulfuric acid and small amounts of hydrofluoric acid (approximately 0.1 ppm) is used as the electrolyte (with a pH value of approximately 3), simulating the corrosive environment of a fuel cell containing sulfate and fluoride. The electrolyte is heated to the operating temperature of the electrochemical cell, for example, which can be approximately 80°C for a polymer electrolyte membrane fuel cell (LT-PEM-FC). Furthermore, an argon gas purge can be used to remove oxygen to simulate the anodic environment (performing potentiodynamic measurements, scanning over a wide potential range). Similarly, an oxygen gas purge can be used to simulate the cathodic environment (performing potentiostatic measurements, applying a constant voltage).The reference electrode is an Ag / AgCI electrode with saturated potassium chloride solution (KCI solution), whose self-potential is approximately 200 millivolts (mV).

[0208] The operating potential of a hydrogen-oxygen fuel cell is approximately 0.8 V. A threshold value Uc of the corrosion voltage, at which corrosion of a layer exposed to the operating potential begins, which is greater than the operating potential, inhibits corrosion of the layer during normal operation of the hydrogen-oxygen fuel cell. If gradual corrosion occurs, for example, at a corrosion voltage of 0.6 V against a reference electrode made of Ag / AgCl, the corrosion current normalized to the surface of the layer exposed to the corrosive environment should, according to the DoE, be less than 50 nanoamperes per square centimeter (nA / cm 2) in order to maintain an economical service life of the electrical cell. As already explained above, it has been recognized according to various embodiments that the corrosion current alone is not always suitable as a measure of corrosion resistance. In contrast, it has been recognized according to various embodiments that the highest possible electrical conductivity of the layer, which is dominated by the contact resistance, is favorable for the operation of the electrochemical cell. Against this background, the resistance of the contact resistance (ICR) to electrochemical corrosion (also referred to as contact electrical corrosion resistance) is preferred as a measure of the corrosion resistance of the layer, which increases when the resistance period is reached (e.g. by a factor k=5 or k=10).

[0209] This will be explained below.

[0210] Determining ICR

[0211] The actual contact resistance (actual ICR) of a layer system can be determined, for example, by means of a measurement in a so-called "through-plane resistance" (TPR) configuration (also referred to as TPR measurement), in which the reference current (source) flows through two contact terminals between which the layer system is arranged and which press against each other, e.g. with 60 N / cm 2 . Analogously, the actual contact resistance of a GDL can be measured individually in this way.

[0212] Fig. 5A and Fig. 5B illustrate various configurations 500a, 500b of an exemplary implementation of the TPR measurement (e.g., on a thin, metallic sample) in a schematic side view. "Source(+)" and "Source(-)" denote the points where the measuring current A is injected into the contact terminals 502 (e.g., made of gold), and "Sense(+)" and "Sense(-)" denote the points where the voltage U is detected, where the resistance R=U / A.

[0213] If the contact resistance between a layer system 504 and the gas diffusion layer GDL is to be determined, the following can apply:

[0214] R± = 2 ' RcDL-Zyl + RilGDL ilGDL = RI — 2 ■ RcDL-Cyl

[0215] ICR = Rsample-GDL = ^2 R[IGDL ~ ^GDL-Cyl

[0216] Here, R GDL-Zyi the contact resistance between contact terminal 502 and GDL, R nGDL the electrical bulk resistance of the GDL, R sa mpie-GDL the contact resistance between layer system (sample) and GDL, the resistance measured between sense(+) and between sense(-) when only the GDL is arranged between the contact terminals 502 (see configuration 500a), and R2 the resistance measured between sense(+) and between sense(-) when the GDL and the layer system 504 are arranged between the contact terminals (see configuration 500b). serves as a clear reference.

[0217] For example, R_sample (also called bulk resistance) of a thin metallic bipolar plate can be neglected, especially if the bipolar plate (e.g., its metal) is highly conductive. This applies analogously to the electrodes (e.g., made of gold) and / or the bulk resistance of the layer system.

[0218] The value of R GDL-Zyi can be determined individually in advance for each implementation of the TPR measurement, for example taking into account a GDL thickness variation.

[0219] An exemplary method for determining ICR comprises: multiple (e.g., twice) recording of R1, multiple (e.g., five) recording of R2, multiple (e.g., twice) recording of R1 (unloading between measurements), and averaging of R1 and R2. The GDL can be measured with at least 3 cycles at 60 N / cm 2 be pre-compressed and should be used for a maximum of 50 cycles.

[0220] In an analogous manner, only the layer system 504 can be arranged between the contact terminals 502 (see configuration 500a), whereby the above relations are then simplified to:

[0221] R1= 2 ■ ICR

[0222] As explained above, the contact terminals 502 can press against each other, for example with a pressure of 60 N / cm 2 . Care must be taken to ensure that the surface pressure of the contact terminals 502 is as homogeneous as possible.

[0223] Analogous to the RES-ICR, the dependence of the ICR of a coating on the duration of exposure to a corrosive environment can be determined. It is advantageous if the ICR is as independent as possible of the duration and severity of corrosion of the coating. In this case, the ICR is essentially invariant until the end of the resistance period, i.e., until the point in time at which corrosion ceases due to the wear of a coating.

[0224] In order to compare the contact electrical corrosion resistance of two layers (e.g. carbon layers), their properties in the same corrosive environment are compared. In this case, the properties of the corrosive environment and thus the influencing factors of corrosion are identical, so that the resistance time can be used as a measure of the corrosion resistance. However, it should be noted that in the case of two layers that differ greatly in their contact electrical corrosion resistance and thus their resistance time, it is not necessarily necessary to measure the resistance time of the more resistant layer. Rather, it may be sufficient to expose both layers to the corrosive environment for a duration that is longer than the resistance time of the less resistant layer and shorter than the resistance time of the more resistant layer.

[0225] Below, various working examples are explained for which the corrosion resistance, e.g., expressed as a resistance duration, was determined. Working examples 1 to 4: Difference in corrosion resistance due to layer thickness

[0226] Fig. 6A illustrates a diagram 600a in which the density of the corrosion current (in microamperes per square centimeter) is plotted schematically over time (in hours) for carbon layers that differ from each other only in their layer thickness, namely two carbon layers 602a with a layer thickness of x=<100 nanometers (nm) as working examples 1 and 2 and two carbon layers 602b with a layer thickness of y=4'X (in nm) as working examples 3 and 4.

[0227] The carbon coatings of working examples 1 to 4 were otherwise produced using the same coating parameters. During the measurement, the corrosive environment, in particular the corrosion voltage, was kept constant above the threshold value Uc, at which the dissolution or oxidation of the carbon coatings (e.g., their corrosion) begins. The corrosive environment was simulated using a reversible hydrogen electrode (RHE) as a reference electrode, to which a corrosion voltage of 1.8 V was applied, with the corrosion current being recorded potentiostatically for a period of 5 hours. This setup corresponds to a corrosion voltage of 1.6 V against a standard hydrogen electrode (SHE) as a reference electrode or a corrosion voltage of 1.4 V against Ag / AgCl as a reference electrode.

[0228] The diagram clearly shows how the durability period Z (the duration of dissolution of the carbon layer) is influenced by the layer thickness. The durability period Z1 of the two carbon layers 602a with a layer thickness of x=<100 nanometers (nm) is significantly shorter than the durability period Z2 (approximately 20 minutes) of the two carbon layers 602b with a layer thickness of y=4'X (e.g., in nm).

[0229] The corrosion current is initially very high and is dominated by carbon oxidation. Upon reaching the endurance period, the corrosion current decreases abruptly. This is due to the fact that the carbon in the carbon layer has been largely oxidized, exposing the underlying oxide layer of a metallic layer and participating in the electrochemical reaction. Since this oxide layer is significantly less reactive, a lower corrosion current is measured. After the endurance period, all working examples 1 to 4 have lost their initially high electrical conductivity.

[0230] In summary, the thicker carbon layer of working examples 3 and 4 is fully oxidized only at a later time, which maintains the electrical conductivity for a longer time, so that the lifetime of an electrochemical cell equipped with it is longer.

[0231] Working examples 5 to 10: Difference in corrosion resistance due to the coating process

[0232] The coating process influences the nature of the resulting carbon layer, including the proportion of crystalline carbon modification due to differences in the bonding states and / or the modification of the carbon in the carbon layer.

[0233] Fig. 6B illustrates a diagram 600b schematically plotting the corrosion current density (in microamperes per square centimeter) versus time (in hours) for carbon coatings that differ in the configuration of the coating process used to produce them. The coating processes are:

[0234] - Magnetron sputtering from the planar target (also called MS planar or MSp) as working example 5,

[0235] - Magnetron sputtering from the tube target (also called MS rotatable or MSr) as working example 6,

[0236] - Electron beam evaporation (also called EB) as working example 7,

[0237] - Laser-induced arc evaporation (also called LA) Working Example 8,

[0238] - atmospheric polymer coating (“Conductive Polymer”, also referred to as CP) as working example 9,

[0239] - Electroplated gold reference (also referred to as Au) as comparative example 1 , and

[0240] - Uncoated starting material 1.4404 or 316L (also referred to as 316L) as comparative example 2. The course of the corrosion current was recorded at a corrosion voltage of 1.2 V against Ag / AgCl as reference electrode for a duration of 10 hours.

[0241] After 10 hours, the carbon coatings of working examples 6 and 8 still exhibit sufficient electrical conductivity. For the carbon coatings of working examples 5 and 7, the ICR values ​​after 10 hours vary considerably, as their durability is close to 10 hours, so that some carbon coatings have already dissolved and others have not. However, the durability of the carbon coatings (e.g., working examples 5 and 7), which have a high corrosion current, is generally shorter than that of the carbon coatings (e.g., working examples 6 and 8), which have a lower corrosion current.

[0242] Fig. 7A illustrates various diagrams 700a, in which exemplary representatives of working examples 6 to 8 are shown together with the contact resistance after a potentiostatic measurement at 1.2 V vs. Ag / AgCl. Carbon layers with high corrosion resistance have an ICR < 1 mΩcm 2 (e.g. when pressed with 60 N / cm 2 ) after corrosion testing, while carbon coatings with low corrosion resistance have an ICR > 10 mQcm 2 have.

[0243] Below is a summary of the comparisons, with the ICR values ​​in mQcm 2 are specified.

[0244] Fig.7B illustrates a diagram 700b in which the density of the corrosion current (in microamperes per square centimeter) is plotted against time (in hours) for carbon films of Working Examples 6 and 8, each recorded at a corrosion voltage of 1.4 V against Ag / AgCl as a reference electrode for a duration of 10 hours.

[0245] It is evident that the corrosion of these carbon layers is favored by a corrosion voltage of 1.4 V, which simplifies the comparison between them. The first group, 802, represents coating systems whose ICR value after 10 hours at 1.4 V vs. Ag / AgCl is more than 100 mQcm 2 (at 60 N / cm 2 The second group 804 represents coating systems whose ICR value after 10 hours at 1.4 V vs. Ag / AgCI is less than 10 mQcm 2 amounts to.

[0246] Fig. 8A and Fig. 8B illustrate the corrosion process of two exemplary carbon layers in different schematic diagrams 800a and 800b, in which the corrosion current and the ICR (each in arbitrary units) are plotted against time t. The two carbon layers comprise a first carbon layer 1201 and a second carbon layer 1203, with the first carbon layer 1201 having greater resistance to electrochemical corrosion than the second carbon layer 1203.

[0247] This can be seen, for example, from the time course of the contact resistance (ICR), which increases more sharply for the second carbon layer 1203 in the range t=Z than for the first carbon layer 1201 and / or for t>Z is greater for the second carbon layer 1203 than for the first carbon layer 1201 (e.g., more than 5 or 10 times this). Z here denotes the durability of the second carbon layer 1203, at which its ICR changes abruptly. Furthermore, from the sudden increase in the contact resistance (ICR) at t=Z, it can be deduced that the second carbon layer 1203 is essentially completely corroded at t=Z. This can be seen alternatively or additionally from the time course of the corrosion current, the integral of which from t=0 to t=Z is greater for the second carbon layer 1203 in the range than for the first carbon layer 1201.The integral of the corrosion current of a carbon layer is a measure of the amount of material in the carbon layer that has already participated in electrochemical corrosion, for example, by undergoing chemical transformation. Analogously, based on the high corrosion current up to t=Z, it can be deduced that the second carbon layer 1203 corrodes faster than the first carbon layer 1201. The corrosion current of the first carbon layer 1201 quickly saturates to a very low value, indicating gradual corrosion. The corrosion current of the second carbon layer 1203 only reaches this value after it has almost completely corroded and, as a result, the underlying oxide layer is exposed, which dominates the temporal course of the corrosion current for t>Z.

[0248] It can be seen that the corrosion current can be used alternatively or in addition to the ICR as a measure of resistance to electrochemical corrosion, for example its integral up to t=Z.

[0249] In analogy, the time course of the corrosion current l(t <Z) einer Kohlenstoffschicht modelliert werden und auf dieser Grundlage der Zeitpunkt Z, an dem die elektrochemische Korrosion der Kohlenstoffschicht zum Erliegen kommt, ermittelt werden, beispielsweise anhand einer Angabe (z.B. Schichtdicke), welche die Menge an Kohlenstoff der Kohlenstoffschicht repräsentiert.

[0250] Fig. 12 illustrates the ICR values ​​of various working examples after electrochemical corrosion processes, for which the corrosion parameters are specified. "Initial" refers to the ICR value before electrochemical corrosion (e.g., as manufactured and / or at t=0). Otherwise, the corrosion voltage is given in volts (V) and the duration of corrosion (also referred to as corrosion duration) in hours (h).

[0251] Below is a summary of the comparisons, with the ICR values ​​in mQcm 2 are specified. DBMS references an unbalanced magnetron sputtering.

[0252] Further working examples are explained below, which relate to the influence of various parameters on corrosion resistance. As can be seen, a variation in the conditions (e.g., the measurement setup) under which corrosion resistance is determined does not represent a significant disturbance when comparing several layers (e.g., carbon layers) with each other in terms of their corrosion resistance. In other words, the property of two layers to differ in their corrosion resistance is invariant with a variation in the conditions (e.g., the measurement setup) under which corrosion resistance is determined. This applies analogously to the resistance criterion explained above.

[0253] Fig. 9A illustrates a diagram 900a in which the

[0254] Corrosion resistance, expressed as the resistance time Z, of a carbon layer over the layer thickness of the carbon layer for different corrosion voltages (e.g. 1.2 V, 1.4 V and 1.6 V against Ag / AgCl). For the resistance time Z, for example, the ICR(t=Z) of the carbon layer reaches 10 times the value of the initial ICR(t=O) as a resistance criterion. As can be seen, the increase in layer thickness leads to an increase in the measurable corrosion resistance regardless of the corrosion voltage used as the test voltage, which in this example represents an exemplary variation of the measurement configuration.

[0255] Fig.9B illustrates a diagram 900b in which the corrosion resistance, expressed as the durability time Z of the carbon layer, is schematically plotted as a function of the coating process and the layer thickness of the carbon layer for different corrosion voltages (e.g., 1.2 V, 1.4 V, and 1.6 V versus Ag / AgCl).

[0256] Fig. 10A illustrates a diagram 1000a schematically comparing the durability Z of two carbon layers K1 and K2 as a function of the pH value of the corrosive environment as an exemplary property to which the carbon layers K1, K2 are exposed, for various corrosion voltages KS (e.g., 1.2 V, 1.4 V, and 1.6 V versus Ag / AgCl). The carbon layer K1 exhibits greater (e.g., contact electrical) corrosion resistance, durability, than the carbon layer K2. For the durability Z, the ICR (t=Z) of the carbon layer, for example, reaches 10 times the value of the initial ICR (t=0) as a durability criterion.

[0257] Fig. 10B illustrates a diagram 1000b in which the durability period Z is schematically represented as a function of various corrosion voltages (e.g., 1.2 V, 1.4 V, and 1.6 V versus Ag / AgCl) for carbon coatings K1, K2, and K3 of varying corrosion resistance. For the durability period Z, for example, the ICR (t=Z) of the carbon coating reaches 10 times the initial ICR (t=0) as the durability criterion.

[0258] Fig. 11A and Fig. 11B illustrate the course of exemplary corrosion of a layer (e.g., carbon layer 302, 304) in a schematic diagram 1100a and 1100b, in which the corrosion current (l_korr) is plotted against time t for an exemplary working example. Depending on the electrical potential applied to the carbon layer 302, 304 (also referred to as corrosion voltage), an electrochemical reaction between the carbon layer 302, 304 and the reactants present in the electrolyte can be promoted. As long as this reaction proceeds, charge carriers Q are formed, the quantity of which can be determined by means of the measured corrosion current l(t) according to Faraday's first law via the corrosion current integral Q = f I(t)dt for any time interval [t1, t2] of the reaction course.The rate of this reaction is proportional to the corrosion current and occurs at least as long as the material required for the reaction (e.g., expressed as the amount of substance N[mol]) is present in its reaction-promoting structure. According to Faraday's second law, the charge carriers Q formed are proportional to the amount of substance N and the reaction charge number n. See also: Gunter Wittstock, Textbook of Electrochemistry, wiley-vch, 2023.

[0259] The reaction charge number n depends on the applied potential, which can enable different reactions with the reactants present in the electrolyte, generating a corresponding number n of electrons per reaction due to different oxidation states. The reaction then stops (e.g., is terminated) as soon as the material applied by the coating is consumed at time Z.This time Z depends on the amount of material in the carbon layer 302, 304 and the reaction rate, which are summarized in the corrosion current curve and can take on a temporal course depending on the circumstances, depending on whether (for example depending on the layer thickness and / or process) the carbon of the carbon layer 302, 304 is present in a stable (shown here as dotted lines) or a less stable modification, and / or the reaction is otherwise (at least temporarily) inhibited, for example if the surface exposed to the reaction reacts to form a reaction product that is electrochemically more stable and separates the material required for the reaction from the reaction.If the total amount of substance N present and the reaction charge number n are known, the maximum possible corrosion current integral Q_max can be determined until the carbon layer 302, 304 is consumed, assuming that only these defined reactions occur in the measuring cell. The time Z at which the reaction reaches the carrier plate 102 (e.g., a passivating layer of it) and thereby ceases is difficult to predict mathematically, but can be derived from the temporal progression of ICR and l_korr, which reflects the entire complexity of the layer system.

[0260] Various examples of an implementation in which a complex carbon layer is applied to a self-passivating corrosion barrier Ti, which itself does not react (e.g. if the carbon is used up), include:

[0261] - Carbon that is resistant to the corrosive environment in an electrochemical cell. This inhibits a reaction with the corrosive environment. For example, this can result in layer parameters (e.g., the surface), such as the contact resistance (ICR), remaining unchanged during cell operation. Under certain circumstances, contact with the electrolyte can also cause passivation (e.g., oxidation), which can, however, affect the ICR.

[0262] - If more carbon of a uniform corrosion resistance is present, which for example increases the thickness of the layer (also called layer thickness), this can prolong the duration of the reaction, ie the time until the reaction stops (see the working example EB).

[0263] - The coating (e.g., usually) exhibits coating properties that depend on the coating thickness, such as electrochemical resistance (e.g., corrosion resistance). This can, for example, be a function of the coating density and / or chemical composition (e.g., the proportion of foreign gas, etc.), but this is not necessarily the case. For example, the corrosion current may repeatedly increase and / or decrease over time (see Diagram 1100a), although this does not necessarily correlate with the time course of secondary surface properties such as ICR.

[0264] - The layer (e.g. carbon layer) contains so much material that the reaction consumes the electrolyte faster than the layer, so that the reaction stops without the layer being consumed.

[0265] In some cases, the time course of the corrosion current can be independent of the time course of the ICR. For example, as long as there is still sufficient conductive material present (ie at all times t <Z) kann davon ausgegangen werden, dass der ICR-Wert besser ist als der ICR der Trägerplatte (z.B. deren selbstpassivierenden Schicht), ohne dass ansonsten eine feste Relation zwischen der zeitlichen Veränderung von ICR-Wert und der zeitlichen Veränderung des Korrosionsstroms vorliegen muss.

[0266] For the evaluation of electrochemical resistance, the time Z alone is a good parameter. If two carbon layers have the same material quantity but differ in their electrochemical resistance, the reaction may proceed at different rates, meaning the reaction time until both layers have completely dissolved may be different. However, the integral of the corrosion current may be similar. Therefore, the temporal progression of the corrosion current or its integral may not always contain sufficient information to derive the (e.g., contact electrical) corrosion resistance of a layer.

[0267] An exemplary implementation for determining the corrosion resistance of several layers (e.g. carbon layers), which facilitates a reliable comparison of the layers with each other, can for example comprise:

[0268] - A target corrosion voltage, for example 1.2 V (or 1.4 V or 1.6 V) against Ag / AgCl, to which the layer is exposed;

[0269] - A desired contact surface with the layer which mediates the corrosion current, e.g. by means of a pressing of the layer with a contact terminal, wherein the pressing is carried out, for example, at a desired pressure (e.g. of 60 N / cm 2 or more); - A resistance criterion upon fulfilment of which corrosion is deemed to have ceased (e.g. target value of the corrosion current integral or target value of the ICR);

[0270] - Optionally, a guarantee corridor, in which it is proven that there is still a layer with certain properties left, and not only a layer is proven; - A parameter (e.g. the time until the corrosion resistance) whose value at the time when the

[0271] Corrosion is considered to be complete, is recorded and / or at least represents corrosion resistance.

Claims

Patent claims 1. Layer system (300), comprising: • a carrier plate (102) having one or more metallic layers and configured to provide at least one fluid flow channel (104, 106); and • two carbon layers (302, 304) on the carrier plate (102), each carbon layer providing an electrical contact resistance (ICR) and between which the one or more metallic layers are arranged, and • wherein the two carbon layers (302, 304) differ from each other in a resistance of the contact resistance (ICR) to electrochemical corrosion, and preferably in a proportion of one or more modifications of amorphous carbon and / or a layer thickness (306, 310).

2. Layer system (300) according to claim 1, wherein the one or more than one layer comprises at least one bipolar half-plate, preferably a composite joined from two bipolar half-plates.

3. Layer system (300) according to claim 1 or 2, wherein the resistance of the contact resistance (ICR) to electrochemical corrosion represents a duration of electrochemical corrosion for which the contact resistance is less than a threshold value, which is preferably several times the contact resistance at the beginning of the electrochemical corrosion.

4. Layer system (300) according to one of claims 1 to 3, wherein at least one layer of the one or more than one metallic layer comprises titanium, niobium and / or chromium.

5. Layer system (300) according to one of claims 1 to 4, wherein the two carbon layers (302, 304) differ from each other in a proportion of sp 2-hybridized carbon atoms and / or the proportion of one or more modifications of the amorphous carbon.

6. Layer system (300) according to claim 5, wherein the proportion of sp 2 -hybridized carbon atoms of the two carbon layers (302, 304) is greater than 75%.

7. Bipolar plate (110) which is provided by means of the layer system (300) according to one of claims 1 to 6.

8. Half cell (100) for a bipolar plate (110) or for an electrode of a redox flow battery, wherein the half cell (100) comprises the layer system (300) according to one of claims 1 to 6.

9. Use of the layer system (300) according to one of claims 1 to 6 for producing an electrochemical cell, preferably a galvanic cell or an electrolysis cell.

10. Using a vacuum arrangement (400) for producing the layer system (300) according to one of claims 1 to 6.

11. Vacuum arrangement (400) which is configured to produce the layer system (300) according to one of claims 1 to 6.

12. A method for producing a layer system (300), the method comprising: • Forming a first carbon layer (302) on a top surface of a carrier plate (102) having one or more metallic layers in a vacuum; and • forming a second carbon layer (304) on a bottom side of the carrier plate (102) in the vacuum; • wherein the first carbon layer (302) and the second carbon layer (304) are formed such that the first carbon layer (302) and the second carbon layer (304) differ from one another in a resistance of the contact resistance (ICR) to electrochemical corrosion, and preferably in the proportion of one or more modifications of amorphous carbon and / or a layer thickness (306, 310) when the layer system (300) is removed from the vacuum.

13. The method according to claim 12, wherein the formation of the first carbon layer is carried out by means of a physical vapor deposition of the first type and the formation of the second carbon layer is carried out by means of a physical vapor deposition of the second type, wherein the physical vapor deposition of the first type and the physical vapor deposition of the second type differ from each other, preferably in: • an electrical voltage applied to the carrier plate; and / or • a process by which a solid coating material is subjected to vapor deposition; • an electrical frequency, a duty cycle and / or electrical power by means of which the vapor deposition takes place; • an ionization component and / or kinetic particle energy by means of which the gas phase deposition takes place.

14. The method of claim 12 or 13, wherein the first carbon layer (302) is formed at a first rate and wherein the second carbon layer (304) is formed at a second rate different from the first rate. 15 A computer program which, when executed by a processor, is arranged to cause the processor to control a vacuum arrangement such that the method according to one of claims 12 to 14 is carried out by means of the vacuum arrangement.

16. A computer-readable medium storing instructions adapted, when executed by a processor, to cause the processor to control a vacuum arrangement such that the method according to any one of claims 12 to 14 is carried out by means of the vacuum arrangement. 17 Control device, comprising one or more than one processor which is configured to control a vacuum arrangement such that the method according to one of claims 12 to 14 is carried out by means of the vacuum arrangement.

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