Coated metallic component for an electrolysis cell

Abstract

The present invention relates to a metallic component (1), preferably a bipolar plate and / or a porous transport layer for an electrolysis cell comprising a substrate (2) and a galvanic corrosion protection coating (4), wherein the corrosion protection coating (4) comprises a tin-based dispersion.

Description

[0001] The present invention relates to a metallic component, preferably a porous transport layer and / or a bipolar plate, for an electrolysis cell.

[0002] Hydrogen can be produced from water in electrolysis cells via electrolysis.

[0003] An electrolysis cell comprises two half-cells: an anodic half-cell and a cathodic half-cell, with both half-cells connected by a membrane. Each half-cell has a bipolar plate that contacts a gas diffusion layer or porous transport layer. The gas diffusion layer or porous transport layer forms an electrode or is electrically contacted to an electrode through which a voltage is applied to an electrolyte solution. The resulting ion flow through the electrolyte solution creates an ion current from one half-cell to the other, with hydrogen or oxygen being deposited at the respective electrodes.

[0004] The cell reactions for hydrogen and oxygen formation, for example in an acidic environment, are as follows: Anode H2O → 2H + + 1 / 2 O2 + 2e - , E> 1, 2V Kathode 2H + + 2e - → H2, E=0V

[0005] Spatial separation of the cell reactions is made possible by the aforementioned membrane, which allows ionic transport through the electrolysis cell. In the case of anion exchange membrane electrolysis (AEM water electrolysis), this is achieved through the use of a hydroxide ion-conducting membrane. In the case of proton exchange membrane electrolysis (PEM electrolysis), this is achieved through the use of a proton-conducting membrane.

[0006] The electrolysis cells are typically connected in series in so-called stacks. Each electrolyzer can have a large number of stacks.

[0007] The lifespan of PEM-based water electrolyzers is significantly limited by the release of cations (e.g., Fe) and the associated membrane damage. Furthermore, the bipolar plates, gas diffusion layers, or porous transport layers can also be damaged by exposure to cathodic or anodic potentials and the corresponding reactants such as H₂ or O₂.

[0008] It is known to use PVD (physical vapor deposition) coatings for corrosion protection of stainless steel components in PEM electrolysis cells. Common PVD coatings include, for example, Au, TiN, TiN / C, TaN, or SnO2 / F. However, these do not provide the necessary efficient corrosion protection at the high potentials in PEM electrolysis. For example, while Ti does form a stable oxide layer, a detrimental increase in interfacial resistance is subsequently observed.

[0009] WO 2017 / 140293 discloses a multilayer PVD coating with a nitrided Ti-Nb intermediate layer and an applied Ir-C or Ir-Ru-C-based layer. However, due to the PVD process, pores and defects in the layer are unavoidable, which creates the risk of pitting and microcracking in the coating. This can adversely affect corrosion protection. Furthermore, the production of such coatings is expensive due to the use of precious metals.

[0010] Against this background, the use of electroplating is well-established, enabling the creation of dense coatings. Approaches focus on the use of dispersion coatings, which employ a corrosion-resistant metallic matrix and a dispersion. This combination allows for the production of coatings with specific mechanical and electrical properties.

[0011] EP 3336942 A1 discloses a metal sheet for forming a separator for a polymer electrolyte fuel cell. The metal sheet has a two-layer coating consisting of island-applied NiP and an electrochemically deposited film of TiN with dispersed Ni3Sn2.

[0012] WO 2023 / 274441 A1 discloses a galvanic coating approach for an electrochemical cell, wherein a metallic substrate comprises a two-layer corrosion protection layer consisting of an adhesive layer of Ni or Cu, and a second layer of an alloy comprising at least two of the elements Sn, Cu, Ni, Ag, Zn, Bi, Sb, Co, Mn or W.

[0013] Starting from the known state of the art, it is an object of the present invention to provide an improved metallic component, preferably a bipolar plate and / or a porous transport layer, for an electrolysis cell.

[0014] The problem is solved by a metallic component for an electrolysis cell having the features of claim 1. Advantageous further developments are described in the dependent claims, the description and the figures.

[0015] Accordingly, a metallic component, preferably a bipolar plate and / or a porous transport layer, is proposed for an electrolysis cell, comprising a substrate and an electroplated corrosion protection coating. According to the invention, the electroplated corrosion protection coating comprises a tin-based dispersion.

[0016] The porous transport layer can be a gas diffusion layer and / or a macroporous layer and / or a microporous layer and / or a sintered body.

[0017] A gas diffusion layer enables the transport of media (gaseous or liquid) between the individual half-cells in the electrolysis cell. A macroporous layer is porous on a macroscopic scale, with the pore size, for example, in the micrometer to nanometer range. A macroporous layer also includes expanded metal layers with a pore size in the millimeter to nanometer range, as well as combinations of macroporous layers with different properties. The layers exhibit different properties, for example, if they differ in terms of pore size and / or porosity and / or manufacturing process. For instance, a titanium fiber structure can be applied to a multilayer expanded metal layer, forming a macroscopic layer together with it. A sintered body is, more generally, a body produced by sintering.

[0018] A tin-based dispersion can mean that a tin matrix is ​​provided into which a disperse is incorporated. However, a tin base can also mean that the mixture for an electroplating process consists largely of tin. Furthermore, a tin base can indicate that the bonding processes are geared towards tin, and the other substances in the dispersion preferentially bond to tin or via an intermediary.

[0019] The layer is applied using an electroplating process, resulting in particularly dense corrosion protection layers.

[0020] The Sn-based corrosion protection coating can prevent anodic and cathodic corrosion in particular.

[0021] For example, the proposed corrosion protection coating is corrosion-resistant at anode voltages up to over 2V, at temperatures between 60°C and 80°C, and in acidic and fluoride-containing environments (pH 0-5) saturated with O2.

[0022] The proposed corrosion protection coating also exhibits high electrical conductivity at the coating level, as well as low contact resistance and a low wetting voltage. In particular, the contact resistance of the proposed corrosion protection coating is 100 N / cm. 2 less than 20mΩcm 2 .

[0023] Furthermore, the proposed corrosion protection coating is based on precious metal-free materials, enabling the use of a particularly cost-effective and scalable deposition technique. The metallic components coated with the proposed corrosion protection coating are also resistant to cathode-side hydrogen embrittlement.

[0024] The substrate may include or consist of austenitic and / or non-austenitic steels, or titanium or titanium alloys.

[0025] In particular, the substrate may comprise or consist of stainless steel 1.4404, 1.4301, 1.4571 or 1.4401.

[0026] The tin base of the corrosion protection coating can be metallic or oxide-based.

[0027] One advantage of the oxide coating is that corrosion protection can be achieved through passivation during the deposition process. For example, SnO2 is generated directly by the deposition process, eliminating the need for downstream processing steps.

[0028] In the non-oxide variant, SnO2 can be selectively generated through a downstream process, such as heat treatment or pickling. The SnO2 passivation layer only occurs in the interface region, and overall, simplified electroplating is possible.

[0029] The corrosion protection coating may additionally include Ni and / or TiO2 and / or NbO2 and / or TaO2 and / or RuO2.

[0030] For example, electroplating of layer systems as oxides is possible in the forms SnO2 with NbO2, Nb2O5, SnO2 with RuO2, and SnO2 with TaO2. These combinations enable electroplated nickel-free coatings as corrosion protection coatings.

[0031] The corrosion protection coating may also include carbon (C).

[0032] In particular, carbon can be present in the form of graphite or graphite fibers. Generally, the graphite particles can be up to 5 µm or 10 µm in size and blend into the dispersion.

[0033] The use of carbon dispersions allows for the creation of conductive pathways through the layer, resulting in low contact resistance. The carbon also increases the coating's ductility, making it more resistant to mechanical indentation and associated cracking. The preferred carbon concentration is in the range of 10–35 wt.%.

[0034] The corrosion protection coating may additionally include B4C and / or SiC and / or WC and / or TiN and / or TiO2 and / or BN and / or WS2 and / or MoS2 and / or B-doped diamond.

[0035] The other dispersants mentioned are compounds that achieve increased corrosion resistance (SiC, WC, TiO2, WS2, NbO2, Nb2O5), improved mechanical properties (SiC, B4C, TiN, WC, BN, MoS2, and B-doped diamond), or improved electrical properties (TiN, WS2, MoS2, and B-doped diamond). The use of TiO2 in combination with graphite is preferred. These additional dispersants may be necessary to tailor the coating properties to specific requirements and should therefore be included in the analysis.

[0036] The corrosion protection coating may include additional additives designed to increase the stability of the material composition of the corrosion protection coating.

[0037] Stability here can refer to (electro-)chemical stability, but also to mechanical stability, for example of carbon particles or fibers.

[0038] In particular, the formation of agglomerates in the dispersions during deposition can be prevented by additional additives. This allows for a more homogeneous application of the corrosion protection coatings. For example, surfactants can be used to keep the sometimes fine particles of the dispersions in a stable chemical state.

[0039] In particular, the additives can also be catalytically active elements of electrolysis.

[0040] Regarding its use as a coating for porous transport layers, the catalytically active function in contact with the electrode can be advantageous. A preferred catalytic element could be, for example, ruthenium, platinum, iridium, or palladium, with the additives comprising one or more of these elements. These can be used, for example, in the final deposition step to activate the surface.

[0041] The corrosion protection coating can have a thickness between 3µm and 20µm, preferably a thickness between 6µm and 10µm.

[0042] Corrosion protection coatings of this size are particularly stable and dense, and therefore offer a particularly high level of corrosion protection.

[0043] The metallic component may have an intermediate layer comprising Ni or Sn.

[0044] The intermediate layer is positioned between the substrate and the corrosion protection coating. This intermediate layer primarily serves as an adhesion promoter, bonding the corrosion protection coating to the substrate.

[0045] The intermediate layer can be, in particular, a Sn coating or an SnNi alloy.

[0046] The thickness of the intermediate layer can be less than 500 nm. A particularly good adhesion can be achieved through the appropriately designed intermediate layer and its small thickness.

[0047] Another aspect of the invention is an electrolysis cell with a metallic component, preferably a bipolar plate and / or a porous transport layer, with the proposed corrosion protection coating. The corrosion protection coating enables long and reliable operation of the electrolysis cell.

[0048] Preferred further embodiments of the invention are explained in more detail by the following description of the figure. This shows: Fig. 1 A schematic representation of the layer structure of the bipolar plate.

[0049] Preferred embodiments are described below with reference to the figure. Identical, similar, or equivalent elements in the different figures are designated with identical reference numerals, and repeated descriptions of these elements are sometimes omitted to avoid redundancy.

[0050] In Fig. Figure 1 schematically shows a first embodiment of a metallic component 1, for example a bipolar plate and / or a porous transport layer, for an electrolysis cell, which has a substrate 2, an intermediate layer 3 and a corrosion protection coating 4.

[0051] In this embodiment, the substrate 2 is made of 1.4404 stainless steel, onto which an approximately 100 nm thick tin layer is applied as an intermediate layer 3 to promote adhesion. The corrosion protection coating 4 applied to the intermediate layer 3 comprises, in this embodiment, a tin base, as well as carbon and TiO2, with a thickness of approximately 8 µm.

[0052] In a second possible embodiment of the metallic component 1, for example a bipolar plate and / or a porous transport layer, the substrate 2 is again made of 1.4404 stainless steel, onto which an approximately 100 nm thick tin layer is applied as an intermediate layer 3. In this embodiment, the corrosion protection coating 4 comprises a base of SnO2, as well as C and NbO2, or Nb2O5, wherein the layer thickness is preferably between 6 µm and 10 µm.

[0053] In a third possible embodiment of the metallic component 1, for example a bipolar plate and / or a porous transport layer, the substrate 2 is again made of 1.4404 stainless steel, onto which a coating comprising Ni and / or Sn is applied as an adhesion-promoting intermediate layer 3. In this embodiment, the corrosion protection coating 4 comprises a Sn base with Ni and C.

[0054] The thickness of the corrosion protection coating 4 can range from 3 µm to 20 µm. With a preferred thickness of 8 µm, for example, very low contact resistances can be achieved, in particular contact resistances of less than 20 mΩ / cm. 2 at 100N / cm 2 Contact pressure can be achieved. Furthermore, electrolytic coating can achieve an electrolyte-tight deposition.

[0055] In a fourth possible embodiment of metallic component 1, for example a bipolar plate and / or a porous transport layer, the material of the substrate 2 is an austenitic stainless steel, onto which a coating comprising Ni and / or Sn is applied as an intermediate layer 3.

[0056] In this embodiment, the corrosion protection coating 4 comprises a Sn base with C.

[0057] Where applicable, all individual features shown in the exemplary embodiments can be combined and / or exchanged without leaving the scope of the invention. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2017 / 140293

[0009] EP 3336942 A1

[0011] WO 2023 / 274441 A1

[0012]

Claims

[1] Metallic component (1), preferably a bipolar plate and / or a porous transport layer, for an electrolysis cell, comprising a substrate (2) and a galvanic corrosion protection coating (4), characterized by that the anti-corrosive coating (4) comprises a Sn-based dispersion. [2] Metallic component (1) according to the preceding claim, characterized by that the porous transport layer is a gas diffusion layer. [3] Metallic component (1) according to one of the preceding claims, characterized by that the porous transport layer is a macroporous layer and / or a sintered body. [4] Metallic component (1) according to one of the preceding claims, characterized by that the substrate (2) comprises or consists of austenitic and / or non-austenitic steels, or the substrate (2) comprises or consists of titanium or titanium alloys. [5] Metallic component (1) according to one of the preceding claims, characterized bythat the Sn base of the corrosion protection coating (4) is metallic or oxidic. [6] Metallic component (1) according to one of the preceding claims, characterized by that the corrosion protection coating (4) additionally comprises Ni and / or TiO2 and / or NbO2 and / or Nb2O5 and / or TaO2 and / or RuO2. [7] Metallic component (1) according to one of the preceding claims, characterized by that the corrosion protection coating (4) additionally comprises C. [8] Metallic component (1) according to one of the preceding claims, characterized by that the corrosion protection coating (4) additionally comprises B4C and / or SiC and / or WC and / or TiN and / or TiO2 and / or BN and / or WS2 and / or MoS2 and / or B-doped diamond. [9] Metallic component (1) according to one of the preceding claims, characterized bythat the corrosion protection coating (4) comprises additives which are designed to increase the stability of the material composition of the corrosion protection coating (4), wherein the additives are in particular catalytically active elements. [10] Metallic component (1) according to one of the preceding claims, characterized by that the corrosion protection coating (4) has a thickness between 3µm and 20µm, preferably a thickness between 6µm and 10µm. [11] Metallic component (1) according to one of the preceding claims, characterized by an intermediate layer (3) arranged between the substrate (2) and the corrosion protection coating (4), wherein the intermediate layer (3) comprises Ni or Sn. [12] Metallic component (1) according to one of the preceding claims, characterized by that the thickness of the intermediate layer (3) is less than 500nm. [13] Electrolysis cell with a metallic component (1), preferably a bipolar plate and / or a porous transport layer according to one of the preceding claims.

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