LAYER SYSTEM, BIPOLAR PLATE COMPRISING SUCH A LAYER SYSTEM, AND FUEL CELL PRODUCED THEREWITH

Abstract

A layer system (1) for coating a bipolar plate (2), including at least one cover layer (1a) made of tin oxide, wherein at least one metal oxide of the group comprising tantalum oxide, niobium oxide, titanium oxide, zirconium oxide, and hafnium oxide is homogenously dissolved in the tin oxide, and the electric conductivity of the cover layer (1a) is greater than or equal to 10.sup.2 S/cm. A bipolar plate (2, 2′) is also provided with an anode side and a cathode side, comprising a substrate (2a, 2a′) and such a layer system (1), and to a fuel cell (10) or an electrolyzer comprising such a bipolar plate (2, 2′).

Claims

1. A layer system (1) for coating a bipolar plate (2), comprising at least one cover layer (1a) made of tin oxide, characterized in that at least one metal oxide of the group comprising tantalum oxide, niobium oxide, titanium oxide, zirconium oxide and hafnium oxide is homogeneously dissolved in the tin oxide, and in that the electric conductivity of the cover layer (1a) is greater than or equal to 10.sup.2 S/cm.

2. The layer system (1) according to claim 1, characterized in that the cover layer (1a) is doped with iridium and/or ruthenium.

3. The layer system (1) according to claim 2, characterized in that the iridium and/or the ruthenium is present in the cover layer (1a) in a concentration in the range from 10.sup.−4 at % to 0.1 at %.

4. The layer system (1) according to one of the preceding claims, characterized in that an adhesive layer (1c) is also present in addition to the cover layer (1a), the adhesive layer (1c) having a layer thickness in the range from 1 nm to 300 nm.

5. The layer system (1) according to claim 4, characterized in that the adhesive layer (1c) is formed containing at least one element from the group comprising titanium, tantalum, niobium, zirconium and hafnium.

6. The layer system (1) according to claim 4 or 5, characterized in that between the cover layer (1a) and the adhesive layer (1c) there is arranged at least one intermediate layer (1b) of a metal carbide or at least one intermediate layer (1b) of a metal nitride or at least one intermediate layer (1b) of a metal boride or at least one intermediate layer (1b) comprising at least one metal carbide and at least one metal nitride or at least one metal carbide and at least one metal boride or at least one metal nitride and at least one metal boride or at least one metal carbide and at least one metal nitride and at least one metal boride or a combination of two or more such intermediate layers (1b).

7. The layer system (1) according to claim 6, characterized in that the metal carbide and/or the metal nitride and/or the metal boride has at least one metal from the group comprising titanium, tantalum, niobium, zirconium and hafnium.

8. The layer system (1) according to claim 7, characterized in that the at least one metal is present in a concentration in the range from 30 to 56 at % in the metal carbide and/or metal nitride and/or metal boride.

9. The layer system (1) according to one of claims 6 to 8, characterized in that the at least one intermediate layer (1b) contains boron.

10. The layer system (1) according to one of claims 1 to 9, characterized in that the cover layer (1a) is doped with fluorine.

11. The layer system (1) according to claim 10, characterized in that the cover layer (1a) is further doped with nitrogen and/or carbon.

12. A bipolar plate (2, 2′) having an anode side and a cathode side, comprising a substrate (2a, 2a′) and a layer system (1) according to one of claims 1 to 11, having a structure of the bipolar plate in the following order: substrate, in particular metallic substrate (2a, 2a′), gas diffusion layer (6, 6′), optional adhesive layer (1c), optional intermediate layer(s) (1b), cover layer (1a).

13. A fuel cell (10), in particular an oxygen-hydrogen fuel cell, or electrolyzer, comprising at least one bipolar plate (2, 2′) according to claim 12.

14. The fuel cell (10) according to claim 13, comprising at least one polymer electrolyte membrane (7).

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] FIGS. 1 to 5 are intended to explain, by way of example, a layer system according to the disclosure and a bipolar plate coated therewith and a fuel cell. In the figures:

[0061] FIG. 1 shows a bipolar plate having the layer system

[0062] FIG. 2 schematically shows a fuel cell system comprising a plurality of fuel cells

[0063] FIG. 3 shows a section III-III through the arrangement according to FIG. 1

[0064] FIG. 4 shows a section through two bipolar plates and a polymer electrolyte membrane according to FIG. 2 arranged therebetween; an

[0065] FIG. 5 shows a cross-section through a layer system in an enlarged illustration.

DETAILED DESCRIPTION

[0066] FIG. 1 shows a bipolar plate 2 with a layer system 1, which here has a metallic substrate or a metallic carrier plate 2a made of stainless steel. The layer system 1 covers the bipolar plate 2 at least on its cathode side. The layer system 1 has a total thickness in the range of 100 nm to 20 μm. The bipolar plate 2 has an inflow area 3a with openings 4 and an outlet area 3b with further openings 4′ which are used to supply a fuel cell with process gases and to remove reaction products from the fuel cell. The bipolar plate 2 also has a gas distribution structure 5 on each side, which is provided for contact with a polymer electrolyte membrane 7 (see FIG. 2).

[0067] FIG. 2 schematically shows a fuel cell system 100 comprising a plurality of fuel cells 10. Each fuel cell 10 comprises a polymer electrolyte membrane 7 which is adjacent to both sides of bipolar plates 2, 2′. The same reference symbols as in FIG. 1 indicate identical elements.

[0068] FIG. 3 shows a section III-III through the bipolar plate 2 according to FIG. 1. The same reference symbols as in FIG. 1 indicate identical elements. The carrier plate 2a, which is formed here from stainless steel, can be seen, which can be constructed in one part or in several parts. A gas diffusion layer 6 is arranged between the carrier plate 2a and the layer system 1. It can also be seen that a further anode-side coating 8 of the carrier plate 2a is provided. This can correspond to the layer system 1. Alternatively, a coating 8 can be provided which is designed according to DE 10 2016 202 372 A1. A further gas diffusion coating 6′ is located between the coating 8 and the carrier plate 2a. The gas diffusion coatings 6, 6′ are designed to be electrically conductive, and in particular are made of a fiber mat made of carbon material.

[0069] FIG. 4 shows a section through two bipolar plates 2, 2′ and a polymer electrolyte membrane 7 according to FIG. 2 arranged therebetween, which together form a fuel cell 10. The same reference symbols as in FIGS. 1 and 3 indicate identical elements. It can be seen that the layer system 1 of a first bipolar plate with carrier plate 2a as the cathode, and the coating 8 of a second bipolar plate with a further carrier plate 2a′ as the anode, are arranged adjacent to the polymer electrolyte membrane 7. The gas diffusion layers 6, 6′ can also be seen.

[0070] FIG. 5 shows a cross-section through the layer system 1 according to FIG. 1. It can be seen that a cover layer 1a, an intermediate layer 1b and an adhesive layer 1c are present. The adhesive layer 1c is located on a side B of the layer system 1 which is arranged facing the carrier plate 2a of the bipolar plate 2. The cover layer 1a is located on a side A of the layer system 1 which is arranged facing away from the carrier plate 2a of a bipolar plate 2. Alternatively, the layer system 1 can also have a plurality of intermediate layers 1b.

LIST OF REFERENCE SYMBOLS

[0071] 1 Layer system

[0072] 1a Cover layer

[0073] 1b Intermediate layer(s)

[0074] 1c Adhesive layer

[0075] 2, 2′ Bipolar plate

[0076] 2a, 2a′ Metallic substrate; carrier plate

[0077] 3a Inflow area

[0078] 3b Outlet area

[0079] 4, 4′ Opening

[0080] 5 Gas distribution structure

[0081] 6, 6′ Gas diffusion coating

[0082] 7 Polymer electrolyte membrane

[0083] 8 Coating

[0084] 10 Fuel cell

[0085] 100 Fuel cell system

[0086] A Side of the layer system 1 facing away from the carrier plate 2a

[0087] B Side of the layer system 1 facing the carrier plate 2a