Coated metal component for an electrolysis cell

Abstract

The present invention relates to a metal component (1), preferably a bipolar plate and / or a porous transport layer for an electrolysis cell comprising a substrate (2) and a galvanic anti-corrosion coating (4), wherein the anti-corrosion coating (4) comprises a dispersion based on Sn, wherein an intermediate layer (3) is arranged between the substrate (2) and the anti-corrosion coating (4), wherein the intermediate layer (3) comprises Ni or Sn and the thickness of the intermediate layer (3) is less than 500nm.

Description

[0001] Description

[0002] Coated metallic component for an electrolysis cell

[0003] The present invention relates to a metallic component, preferably a porous transport layer and / or a bipolar plate, for an electrolysis cell.

[0004] The production of hydrogen from water can be achieved in electrolytic cells via electrolysis.

[0005] An electrolysis cell comprises two half-cells, namely an anodic half-cell and a cathodic half-cell, with both half-cells being joined by a membrane. Each half-cell has a bipolar plate which contacts a gas diffusion layer or porous transport layer, with the gas diffusion layer or the porous transport layer forming an electrode or being electrically contacted to an electrode through which a voltage is applied to an electrolyte solution. The ion flow through the electrolyte solution caused in this way ultimately causes an ion current to flow from one half-cell to the other half-cell, with hydrogen or oxygen being deposited at the respective electrodes.

[0006] The cellular reactions of hydrogen and oxygen formation, for example in acidic environments, are:

[0007] Anode H20 2H+ + 1 / 2 02+ 2e~ , E>1 , 2V

[0008] Cathode 2H+ + 2e~ H2, E=0V

[0009] Spatial separation of the cell reactions is made possible by the membrane mentioned above, which permits 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. The electrolysis cells are typically connected in series in so-called stacks. Each electrolyzer can have a large number of stacks.

[0010] The lifetime 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, the gas diffusion layers, or the porous transport layers can also be damaged by exposure to cathodic or anodic potentials and the corresponding reactants such as H2 or O2.

[0011] It is known to use PVD coatings ("physical vapor deposition") for corrosion protection of stainless steel elements in PEM electrolysis cells. Examples of well-known PVD coatings include Au, TiN, TiN / C, TaN, or SnCt / E.

[0012] However, these do not provide the necessary efficient corrosion protection at the high potentials used in PEM electrolysis. For example, although Ti forms a stable oxide layer, a disadvantageous increase in interfacial resistance is observed.

[0013] WO 2017 / 140293 discloses a multilayer PVD coating with a nitridic Ti-Nb intermediate layer and an Ir-C- or Ir-Ru-C-based layer deposited thereon. However, due to the PVD process, pores and defects in the layer cannot be avoided, creating the risk of pitting or microcracks in the coating. This can adversely affect corrosion protection. Furthermore, the production of such coatings is cost-intensive due to the use of precious metals.

[0014] Against this background, the use of electroplated coatings is known, which can be used to create dense coatings. Approaches focus on the use of dispersion coatings, which combine a corrosion-resistant metallic matrix and a disperse material. This combination makes it possible to provide coatings with specific mechanical and electrical properties.

[0015] 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 of island-shaped NiP and an electrochemically deposited film of TiN with dispersed Ni3Sn2.

[0016] WO 2023 / 274441 A1 discloses a galvanic layer approach for an electrochemical cell, wherein a metallic substrate comprises a two-layer corrosion protection layer consisting of an adhesion 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.

[0017] DE 102022112319 A1 relates to a component for an electrochemical cell comprising a metal substrate and a layer system applied at least partially to the metal substrate by electroplating.

[0018] Starting from the known prior 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.

[0019] The object is achieved by a metallic component for an electrolysis cell having the features of claim 1. Advantageous further developments emerge from the subclaims, the description, and the figures.

[0020] Accordingly, a metallic component, preferably a bipolar plate and / or a porous transport layer, is proposed for an electrolysis cell, comprising a substrate and a galvanic corrosion protection coating. According to the invention, the galvanic corrosion protection coating comprises a Sn-based dispersion. 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.

[0021] A gas diffusion layer enables media transport (gaseous or liquid) in the electrolysis cell between the individual half-cells. A macroporous layer is porous on a macroscopic size scale, with the size of the pores being, for example, in the micrometer to nanometer range. A macroporous layer also includes expanded metal layers with pore sizes in the millimeter to nanometer range, as well as a combination of macroporous layers of different characteristics. The layers have different characteristics, for example, if they differ in terms of pore size and / or porosity and / or manufacturing process. For example, a Ti fiber structure can be applied to a multi-layer expanded metal layer and together with this form a macroscopic layer. A sintered body is, in general terms, a body produced by sintering.

[0022] A Sn-based dispersion can mean that a Sn matrix is ​​provided into which a dispersant is introduced. However, a Sn-based dispersion can also mean that the mixture for a galvanic coating consists predominantly of Sn. A Sn-based dispersion can also mean that the bonding processes are directed toward Sn, and the other substances in the dispersion preferentially bond to Sn or, through an intermediary, with Sn.

[0023] The layer is applied using a galvanic coating process, which creates particularly dense corrosion protection layers.

[0024] The Sn-based anti-corrosive coating can prevent, in particular, anodic and cathodic corrosion. For example, the proposed anti-corrosive coating is corrosion-resistant at anode voltages above 2V, at temperatures between 60 °C and 80 °C, and in acidic and fluoride-containing environments (pH 0-5) saturated with O2.

[0025] The proposed anti-corrosive coating also exhibits high electrical conductivity in the coating plane, as well as low contact resistance and low wetting voltage. In particular, the contact resistance of the proposed anti-corrosive coating is 100N / cm 2 less than 20mQcm 2 .

[0026] Furthermore, the proposed corrosion protection coating is based on precious metal-free materials, allowing for 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.

[0027] The substrate may comprise or consist of austenitic and / or non-austenitic steels or may comprise or consist of titanium or titanium alloys.

[0028] In particular, the substrate may comprise or consist of stainless steel 1 . 4404 , 1 . 4301 , 1 . 4571 or 1 . 4401 .

[0029] The Sn base of the corrosion protection coating can be metallic or oxide.

[0030] An advantage of the oxide design is that corrosion protection can be achieved through passivation during the deposition process. For example, SnO2 is generated directly by the deposition process, so no subsequent processing steps are required.

[0031] In the non-oxide variant, SnO2 can be selectively produced through a downstream process, such as heat treatment or pickling. The SnO2 passivation layer occurs only in the interface area, and overall, simplified electroplating is possible.

[0032] The corrosion protection coating may additionally comprise Ni and / or TiCt and / or NbCt and / or TaCt and / or RuCt.

[0033] For example, the electrodeposition of coating systems as oxides in the forms SnÜ2 with NbÜ2, Nb2Os, SnÜ2 with RUO2, and SnÜ2 with TaO2 is possible. These combinations enable electrodeposited Ni-free coatings as corrosion protection coatings.

[0034] The anti-corrosive coating may additionally comprise carbon (C).

[0035] In particular, carbon can be present in the form of graphite or graphite fibers. In general, the graphite particles can be up to 5 or 10 pm in size and can be incorporated into the dispersion.

[0036] By using carbon dispersants, conductive paths can be created through the coating, resulting in low contact resistance. The carbon also increases the ductility of the coating and makes it more resistant to mechanical indentation and associated cracking. The preferred carbon concentration is in the range of 10-35 wt.%.

[0037] The corrosion protection coating may additionally comprise B4C and / or SiC and / or WC and / or TiN and / or ÜO2 and / or BN and / or WS2 and / or M0S2 and / or B-doped diamond.

[0038] The other dispersants mentioned are compounds that achieve increased corrosion resistance (SiC, WC, TiO2, WS2, NbÜ2, Nb2Os) or improved mechanical properties (SiC, B4C, TiN, WC, BN, M0S2 and B-doped diamond) or improved electrical properties (TiN, WS2, M0S2, B-doped diamond). The preferred method is TiCd in combination with graphite. The other dispersants may be necessary to tailor the coating properties according to requirements and should therefore be included.

[0039] The anti-corrosive coating may comprise additional additives designed to increase the stability of the material composition of the anti-corrosive coating.

[0040] Stability here can be understood as (electro-)chemical stability, but also as mechanical stability, for example of carbon particles or fibers.

[0041] In particular, additional additives can prevent the formation of agglomerates in the dispersants during deposition. This allows for a more homogeneous application of the corrosion protection coatings. For example, additives in the form of surfactants can be used to keep the sometimes fine particles of the dispersants in a stable chemical state.

[0042] In particular, the additives can also be catalytically active elements in electrolysis.

[0043] With regard to use as a coating for porous transport layers, the catalytically active function in contact with the electrode can be advantageous. A preferred catalytic element can be, for example, ruthenium, platinum, iridium, or palladium, whereby the additives can comprise one or more of these elements. These can, for example, be used in the final deposition step to activate the surface.

[0044] The anti-corrosive coating can have a thickness between 3 and 20 pm, preferably between 6 and 10 pm. Anti-corrosive coatings dimensioned in this way are particularly stable and dense and therefore offer particularly high levels of corrosion protection.

[0045] According to the invention, the metallic component has an intermediate layer, wherein the intermediate layer comprises Ni or Sn.

[0046] The intermediate layer is positioned between the substrate and the corrosion protection coating. The intermediate layer serves primarily as an adhesion promoter to bond the corrosion protection coating to the substrate.

[0047] The intermediate layer can in particular be a Sn coating or a SnNi alloy.

[0048] According to the invention, the thickness of the intermediate layer is less than 500 nm. The appropriately designed intermediate layer and its low thickness allow for particularly good adhesion.

[0049] A further 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 anti-corrosive coating. The anti-corrosive coating enables long and reliable operation of the electrolysis cell.

[0050] Preferred further embodiments of the invention are explained in more detail by the following description of the figures. In this figure:

[0051] Figure 1 is a schematic representation of a layer structure of the bipolar plate.

[0052] Preferred embodiments are described below with reference to the figures. Identical, similar, or equivalent elements in the various figures are provided with identical reference symbols, and a repeated description of these elements is partially omitted to avoid redundancies.

[0053] 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 an anti-corrosion coating 4.

[0054] In this embodiment of the invention, the material of the substrate 2 is 1.4404 stainless steel, to which an approximately 10 μm thick Sn layer is applied as an intermediate layer 3 to promote adhesion. The anti-corrosive coating 4 applied to the intermediate layer 3 comprises, in this embodiment, an Sn base, as well as C and TiCt, the layer thickness of the anti-corrosive coating 4 being approximately 8 μm.

[0055] In a second embodiment of the metallic component 1 according to the invention, for example a bipolar plate and / or a porous transport layer, the material of the substrate 2 is again 1.4404 stainless steel, to which an approximately 10 μm thick Sn layer is applied as an intermediate layer 3. In this embodiment, the corrosion protection coating 4 comprises a base of SnCt, as well as C and NbCp, or Nb2Os, the layer thickness preferably being between 6 μm and 10 μm.

[0056] In a third possible embodiment of the metallic component 1, for example a bipolar plate and / or a porous transport layer, the material of the substrate 2 is again 1.4404 stainless steel, to which a coating comprising Ni and / or Sn is applied as an adhesion-promoting intermediate layer 3. In this embodiment, the anti-corrosion coating 4 comprises an Sn base with Ni and C.

[0057] The layer thickness of the corrosion protection coating 4 can be between 3 pm and 20 pm. With a preferred layer thickness of 8 pm, for example, very low contact resistances can be achieved, in particular contact resistances of less than 20 mOhm cm. 2 at 100N / cm 2 contact pressure can be achieved. In addition, electrolytic coating can achieve an electrolyte-tight deposition.

[0058] 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, to which a coating comprising Ni and / or Sn is applied as an intermediate layer 3.

[0059] In this embodiment, the corrosion protection coating 4 comprises a Sn base with C .

[0060] Where applicable, all individual features shown in the embodiments can be combined and / or exchanged without departing from the scope of the invention.

Claims

Patent 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 anti-corrosion coating (4), wherein the anti-corrosion coating (4) comprises a Sn-based dispersion, characterized in that an intermediate layer (3) is arranged between the substrate (2) and the anti-corrosion coating (4), wherein the intermediate layer (3) comprises Ni or Sn and the thickness of the intermediate layer (3) is less than 500 nm.

2. Metallic component (1) according to the preceding claim, characterized in that the porous transport layer is a gas diffusion layer.

3. Metallic component (1) according to one of the preceding claims, characterized in 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 in 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 in that 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 in that the corrosion protection coating (4) additionally contains Ni and / or TiCt and / or NbO2and / or Nb2O5 and / or TaO2and / or RUO2.

7. Metallic component (1) according to one of the preceding claims, characterized in that the corrosion protection coating (4) additionally comprises C.

8. Metallic component (1) according to one of the preceding claims, characterized in 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 in that the anti-corrosive coating (4) comprises additives which are designed to increase the stability of the material composition of the anti-corrosive coating (4), wherein the additives are in particular catalytically active elements.

10. Metallic component (1) according to one of the preceding claims, characterized in that the corrosion protection coating (4) has a thickness between 3pm and 20pm, preferably a thickness between 6pm and 10pm.

11. 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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