Conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plate as well as preparation and application of conductive corrosion-resistant silver-doped titanium nitride coating

Abstract

The invention relates to the technical field of conductive corrosion-resistant coatings for metal bipolar plates of hydrogen fuel cells, and discloses a conductive corrosion-resistant silver-doped titanium nitride coating for a metal bipolar plate as well as preparation and application of the conductive corrosion-resistant silver-doped titanium nitride coating. The conductive corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate is formed by sequentially stacking a pure Ti transition layer, a silver-doped titanium nitride coating and a pure titanium nitride covering layer. According to the conductive corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate, silver can be stably and uniformly distributed in the titanium nitride coating, a conductive path is formed, the contact resistance of the coating is reduced, the titanium nitride coating forms a compact structure, the corrosion resistance and the surface hydrophobicity of the titanium nitride coating are enhanced, and the service life of the coating is prolonged. The surface contact resistance can reach 4.18 m omega.cm < 2 >, the corrosion current density can reach 0.59 mu A.cm < 2 >, the corrosion potential can reach 0.08 V, and the water contact angle can reach 106.70 degrees.

Description

Technical Field

[0001] The present invention relates to the technical field of conductive corrosion-resistant coatings for metal bipolar plates of hydrogen fuel cells, and in particular to a conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates, and a preparation method and application thereof. Background Art

[0002] Hydrogen fuel cells are known as the ultimate power source because their theoretical energy density is 100 times that of lithium-ion batteries and they are clean and environmentally friendly. After breakthroughs in key technologies that restrict hydrogen electrification, such as low-cost hydrogen production, high-density storage, and non-platinum catalysis, hydrogen fuel cells using hydrogen (H2) as a power source have demonstrated significant advantages such as long driving range and fast energy replenishment on a variety of vehicles.

[0003] Hydrogen fuel cells that use non-metallic materials such as graphite as bipolar plates can have plates that account for up to 50% of their volume and 70% of their mass. For a battery stack consisting of thousands of battery pairs, the high proportion of non-metallic bipolar plates in both volume and mass has become a difficulty for such batteries to compete for power sources for vehicles. In order to solve this problem, researchers began to explore the use of metal bipolar plates to replace non-metallic bipolar plates. By pressing out flow guide grooves on metal sheets less than 0.5 mm, they successfully achieved a significant reduction in the volume and mass of the battery stack. This method has become the best way to use fuel cells as power sources for vehicles and other vehicles.

[0004] However, the passivation film on the metal surface will increase the contact resistance. Even stainless steel materials cannot meet the corrosion resistance requirements for long-term service in a protonic acid environment. Therefore, how to reduce the volume and mass of the fuel cell stack while meeting the corrosion resistance requirements for long-term service in a protonic acid environment has become a technical problem that needs to be urgently solved by technical personnel in this field. Summary of the invention

[0005] The purpose of the present invention is to provide a conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates and its preparation and application. The conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates can reduce the volume and weight of the battery stack while meeting the corrosion resistance requirements for long-term service in a protonic acid environment.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] One of the technical solutions of the present invention:

[0008] A conductive, corrosion-resistant silver-doped titanium nitride coating for a metal bipolar plate is formed by sequentially stacking a pure Ti transition layer, a silver-doped titanium nitride coating and a pure titanium nitride covering layer.

[0009] Furthermore, the conductive corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate contains the following components in percentage by mass: N: 26.3% to 39.5%, Ti: 57.2% to 69.7%, Ag: 3.3% to 3.9%, and the remainder is unavoidable impurities.

[0010] The second technical solution of the present invention:

[0011] The method for preparing the conductive corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate comprises the following steps:

[0012] 1) Pretreatment of coating deposition: Plasma cleaning of the stainless steel substrate is performed by placing the stainless steel substrate in a magnetron sputtering vacuum chamber equipped with a Ti target and an Ag target;

[0013] 2) Depositing a pure Ti transition layer: using a Ti target as a sputtering source, magnetron sputtering a layer of pure Ti transition layer on the surface of the stainless steel substrate treated before coating deposition in step 1);

[0014] 3) Depositing a silver-doped titanium nitride coating: using a Ti target and an Ag target as sputtering sources, magnetron sputtering a layer of silver-doped titanium nitride coating on the surface of the pure Ti transition layer deposited in step 2);

[0015] 4) Deposition of a pure titanium nitride covering layer: Using a Ti target as a sputtering source, a pure titanium nitride covering layer is magnetron sputtered on the surface of the silver-doped titanium nitride coating deposited in step 3).

[0016] Furthermore, in step 1), the distance between the stainless steel substrate and the Ti target and the Ag target is 80 mm to 120 mm.

[0017] Furthermore, in step 1), the pressure in the vacuum chamber is ≤5.0×10 -3 Pa.

[0018] Furthermore, in step 1), the plasma cleaning temperature is 300-350° C. and the time is 20 min.

[0019] Furthermore, in step 1), the parameters of the plasma cleaning are: Ti target current 0.3A, Ag target current 0.01A, and substrate bias voltage increased from -100V to -400V.

[0020] Furthermore, in step 1), during the plasma cleaning, the stainless steel substrate needs to rotate at a constant speed of 8 r / min.

[0021] Furthermore, in step 2), the parameters of the magnetron sputtering are: Ti target current 1.8-2A, substrate bias voltage reduced from -120V to -90V.

[0022] Furthermore, in step 2), the temperature of the magnetron sputtering is 300° C., and the time is 5 to 10 minutes.

[0023] Furthermore, in step 2), during the magnetron sputtering, the stainless steel substrate needs to rotate at a constant speed of 8 r / min, and argon gas needs to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.1-0.5 Pa.

[0024] Furthermore, in step 3), the parameters of the magnetron sputtering are: Ti target current 2A, Ag target current 0.03A, substrate bias -60V.

[0025] Furthermore, in step 3), the temperature of the magnetron sputtering is 300° C. and the time is 60 to 80 minutes.

[0026] Furthermore, in step 3), during the magnetron sputtering, the stainless steel substrate needs to maintain a uniform rotation speed of 8 r / min, and argon and nitrogen need to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.1-0.5 Pa.

[0027] Furthermore, in step 4), the parameters of the magnetron sputtering are: Ti target current 2A, substrate bias -60V.

[0028] Furthermore, in step 4), the temperature of the magnetron sputtering is 300° C., and the time is 5 to 8 minutes.

[0029] Furthermore, in step 4), during the magnetron sputtering, the stainless steel substrate needs to maintain a uniform rotation speed of 8 r / min, and argon and nitrogen need to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.1-0.5 Pa.

[0030] The third technical solution of the present invention:

[0031] The above-mentioned conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates is used in metal bipolar plates.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] The conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates provided by the present invention can stably and evenly distribute silver in the titanium nitride coating to form a conductive path, reduce the contact resistance of the coating, form a dense structure of the titanium nitride coating, enhance the corrosion resistance and surface hydrophobicity of the titanium nitride coating, and the surface contact resistance can reach 4.18mΩ·cm 2 , the corrosion current density can reach 0.59μA·cm -2, the corrosion potential can reach 0.08V, and the water contact angle can reach 106.70°, which is beneficial to improve the self-cleaning ability and drainage efficiency of fuel cells during operation, and provide experimental support and basis for the development of fuel cell plates;

[0034] The conductive and corrosion-resistant silver-doped titanium nitride coating for a metal bipolar plate provided by the present invention can alleviate the sudden temperature rise of the substrate caused by thermal stress by lowering the substrate bias voltage to -60V, thereby improving the adhesion between the silver-doped titanium nitride coating and the stainless steel substrate;

[0035] The conductive, corrosion-resistant silver-doped titanium nitride coating for a metal bipolar plate provided by the present invention provides a strong thermal driving force for grain growth and its stability through the thermal activation effect brought about by the increase in deposition temperature, so that the self-formed nanocrystalline structure of Ag that does not react with N and Ti ions in the sputtering product is dispersed and evenly distributed in the titanium nitride coating with triangular pyramid grain accumulation, thereby realizing the preparation of a metal bipolar plate coating with both excellent conductive and corrosion-resistant properties and stable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0037] Figure 1 This is a surface morphology of the conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates prepared in Example 2 of the present invention;

[0038] Figure 2 This is the water contact angle of the conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates prepared in Example 2 of the present invention. DETAILED DESCRIPTION

[0039] Now, various exemplary embodiments of the present invention are described in detail, and this detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics and embodiments of the present invention. It should be understood that the terms described in the present invention are only for describing specific embodiments and are not used to limit the present invention.

[0040] In addition, for the numerical range in the present invention, it is understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between the intermediate value in any stated value or stated range and any other stated value or intermediate value in the range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0041] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0042] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to those skilled in the art. The present invention description and examples are exemplary only.

[0043] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0044] In the following embodiments, before using a stainless steel substrate to prepare a conductive corrosion-resistant silver-doped titanium nitride coating for a metal bipolar plate, the stainless steel substrate needs to be cleaned, specifically including the following steps:

[0045] The stainless steel substrate was placed in a solution containing a degreasing agent and ultrasonically cleaned for 8 minutes. The stainless steel substrate was then placed in deionized water, anhydrous ethanol and acetone in turn and ultrasonically cleaned for 5 minutes respectively. Finally, the stainless steel substrate was blown dry.

[0046] Example 1

[0047] A conductive, corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates

[0048] 1) Pretreatment of coating deposition: Plasma cleaning of the stainless steel substrate is performed by placing the stainless steel substrate in a magnetron sputtering vacuum chamber equipped with a Ti target and an Ag target;

[0049] Wherein, the distance between the stainless steel substrate and the Ti target and the Ag target is 90 mm;

[0050] The pressure in the vacuum chamber is 5.0×10 -3 Pa;

[0051] Wherein, the temperature of the plasma cleaning is 300°C and the time is 20 minutes;

[0052] The parameters of the plasma cleaning are as follows: Ti target current 0.3A, Ag target current 0.01A, substrate bias voltage increased from -100V to -400V;

[0053] During the plasma cleaning, the stainless steel substrate needs to rotate at a constant speed of 8 r / min;

[0054] 2) Depositing a pure Ti transition layer: using a Ti target as a sputtering source, magnetron sputtering a layer of pure Ti transition layer on the surface of the stainless steel substrate treated before coating deposition in step 1);

[0055] The parameters of the magnetron sputtering are: Ti target current 2A, substrate bias voltage reduced from -120V to -90V;

[0056] Wherein, the temperature of the magnetron sputtering is 300°C and the time is 10 minutes;

[0057] During the magnetron sputtering, the stainless steel substrate needs to rotate at a constant speed of 8 r / min, and argon gas needs to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.5 Pa;

[0058] 3) Depositing a silver-doped titanium nitride coating: using a Ti target and an Ag target as sputtering sources, magnetron sputtering a layer of silver-doped titanium nitride coating on the surface of the pure Ti transition layer deposited in step 2);

[0059] The parameters of the magnetron sputtering are: Ti target current 2A, Ag target current 0.03A, substrate bias -60V;

[0060] Wherein, the temperature of the magnetron sputtering is 300°C and the time is 80min;

[0061] During the magnetron sputtering, the stainless steel substrate needs to rotate at a constant speed of 8 r / min, and argon and nitrogen (argon 25 sccm, nitrogen 5 sccm) need to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.5 Pa;

[0062] 4) Depositing a pure titanium nitride covering layer: using a Ti target as a sputtering source, magnetron sputtering a pure titanium nitride covering layer on the surface of the silver-doped titanium nitride coating deposited in step 3);

[0063] The parameters of the magnetron sputtering are: Ti target current 2A, substrate bias -60V;

[0064] Wherein, the temperature of the magnetron sputtering is 300°C and the time is 8 minutes;

[0065] During the magnetron sputtering, the stainless steel substrate needs to maintain a uniform rotation speed of 8 r / min, and argon and nitrogen (argon 25 sccm, nitrogen 5 sccm) need to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.5 Pa.

[0066] After testing, the surface contact resistance of the conductive corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate prepared in Example 1 is 4.52 mΩ·cm 2 , the corrosion current density is 0.29μA·cm -2 , the corrosion potential is 0.05V, and the water contact angle is 91.24°.

[0067] After testing, the mass percentage of each component in the conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates prepared in Example 1 is shown in Table 1;

[0068] Table 1 Mass percentage of each component

[0069]

[0070] Example 2

[0071] A conductive, corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates

[0072] 1) Pretreatment of coating deposition: Plasma cleaning of the stainless steel substrate is performed by placing the stainless steel substrate in a magnetron sputtering vacuum chamber equipped with a Ti target and an Ag target;

[0073] Wherein, the distance between the stainless steel substrate and the Ti target and the Ag target is 90 mm;

[0074] The pressure in the vacuum chamber is 5.0×10 -3 Pa;

[0075] The plasma cleaning temperature is 350°C and the time is 20 minutes.

[0076] The parameters of the plasma cleaning are as follows: Ti target current 0.3A, Ag target current 0.01A, substrate bias voltage increased from -100V to -400V;

[0077] During the plasma cleaning, the stainless steel substrate needs to rotate at a constant speed of 8 r / min;

[0078] 2) Depositing a pure Ti transition layer: using a Ti target as a sputtering source, magnetron sputtering a layer of pure Ti transition layer on the surface of the stainless steel substrate treated before coating deposition in step 1);

[0079] The parameters of the magnetron sputtering are as follows: Ti target current 2A, substrate bias voltage reduced from -120V to -90V;

[0080] Wherein, the temperature of the magnetron sputtering is 350°C and the time is 10 minutes;

[0081] During the magnetron sputtering, the stainless steel substrate needs to rotate at a constant speed of 8 r / min, and argon gas needs to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.5 Pa;

[0082] 3) Depositing a silver-doped titanium nitride coating: using a Ti target and an Ag target as sputtering sources, magnetron sputtering a layer of silver-doped titanium nitride coating on the surface of the pure Ti transition layer deposited in step 2);

[0083] The parameters of the magnetron sputtering are: Ti target current 2A, Ag target current 0.03A, substrate bias -60V;

[0084] Wherein, the temperature of the magnetron sputtering is 350°C and the time is 80 minutes;

[0085] During the magnetron sputtering, the stainless steel substrate needs to rotate at a constant speed of 8 r / min, and argon and nitrogen (argon 25 sccm, nitrogen 5 sccm) need to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.5 Pa;

[0086] 4) Depositing a pure titanium nitride covering layer: using a Ti target as a sputtering source, magnetron sputtering a pure titanium nitride covering layer on the surface of the silver-doped titanium nitride coating deposited in step 3);

[0087] The parameters of the magnetron sputtering are: Ti target current 2A, substrate bias -60V;

[0088] Wherein, the temperature of the magnetron sputtering is 350°C and the time is 8 minutes;

[0089] During the magnetron sputtering, the stainless steel substrate needs to maintain a uniform rotation speed of 8 r / min, and argon and nitrogen (argon 25 sccm, nitrogen 5 sccm) need to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.5 Pa.

[0090] After testing, the surface contact resistance of the conductive corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate prepared in Example 2 is 4.18 mΩ·cm 2 , the corrosion current density is 0.59μA·cm -2 , the corrosion potential is 0.08V, and the water contact angle is 106.70°.

[0091] The surface morphology of the conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates prepared in Example 2 is as follows Figure 1 As shown;

[0092] Depend on Figure 1It can be seen that the conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates prepared in Example 2 has triangular pyramidal crystal particles on its surface, the titanium nitride particle size is about 40nm, and the nanoscale Ag particles are evenly embedded in the columnar crystals of titanium nitride, and no segregation and aggregation phenomenon between the columns is found;

[0093] The surface mobility of the adsorbed atoms increases with the decrease of the surface diffusion activation energy and the increase of the temperature of the stainless steel substrate. The temperature-increasing sputtering can significantly affect the surface morphology of the titanium nitride coating. The thermal activation energy promotes the uniformity of the nanoparticle size inside the silver-doped titanium carbide coating. This feature ensures the stability and conductivity of the coating.

[0094] The water contact angle of the conductive corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate prepared in Example 2 is as follows: Figure 2 As shown;

[0095] Depend on Figure 2 It can be seen that the water contact angle of the conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates prepared in Example 2 is 106.70°, indicating good hydrophobicity;

[0096] With the increase of deposition temperature, the deposited atoms are mainly diffused, the grain size composed of columnar structure tends to be uniform, defects are reduced, the boundary density between columns is higher, the flatness and roughness of the coating surface are determined by atomic diffusion, which is related to the size of the surface particles. In addition, the higher deposition temperature promotes the uniform and refined interface of TiN nanoparticles, so that the surface has fewer atoms with uncompensated bond energy exposed to the outside. Therefore, the reduction of coating surface energy is conducive to the increase of contact angle, which not only helps the transmission of electrons, but also facilitates the excretion of product water in the operation of fuel cells.

[0097] After testing, the mass percentage of each component in the conductive corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates prepared in Example 2 is shown in Table 2;

[0098] Table 2 Mass percentage of each component

[0099]

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A conductive, corrosion-resistant silver-doped titanium nitride coating for a metal bipolar plate, characterized in that: The conductive and corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate is formed by stacking a pure Ti transition layer, a silver-doped titanium nitride coating and a pure titanium nitride covering layer in sequence.

2. The conductive, corrosion-resistant silver-doped titanium nitride coating for a metal bipolar plate according to claim 1, characterized in that: The conductive corrosion-resistant silver-doped titanium nitride coating for the metal bipolar plate contains the following components in percentage by mass: N: 26.3% to 39.5%, Ti: 57.2% to 69.7%, Ag: 3.3% to 3.9%, and the remainder is unavoidable impurities.

3. A method for preparing a conductive, corrosion-resistant silver-doped titanium nitride coating for a metal bipolar plate as claimed in any one of claims 1 to 2, characterized in that: The following steps are involved: 1) Pretreatment of coating deposition: Plasma cleaning of the stainless steel substrate is performed by placing the stainless steel substrate in a magnetron sputtering vacuum chamber equipped with a Ti target and an Ag target; 2) Depositing a pure Ti transition layer: using a Ti target as a sputtering source, magnetron sputtering a layer of pure Ti transition layer on the surface of the stainless steel substrate after the pre-treatment of the coating deposition in step 1); 3) Depositing a silver-doped titanium nitride coating: using a Ti target and an Ag target as sputtering sources, magnetron sputtering a layer of silver-doped titanium nitride coating on the surface of the pure Ti transition layer deposited in step 2); 4) Deposition of a pure titanium nitride covering layer: Using a Ti target as a sputtering source, a pure titanium nitride covering layer is magnetron sputtered on the surface of the silver-doped titanium nitride coating deposited in step 3).

4. The preparation method according to claim 3, characterized in that: In step 1), the distance between the stainless steel substrate and the Ti target and the Ag target is 80 mm to 120 mm; the pressure in the vacuum chamber is ≤5.0×10 -3 Pa; the temperature of the plasma cleaning is 300-350°C, and the time is 20 minutes; the parameters of the plasma cleaning are: Ti target current 0.3A, Ag target current 0.01A, and substrate bias voltage increased from -100V to -400V; during the plasma cleaning, the stainless steel substrate needs to maintain a uniform rotation speed of 8r / min.

5. The preparation method according to claim 3, characterized in that: In step 2), the parameters of the magnetron sputtering are: Ti target current 1.8~2A, substrate bias voltage reduced from -120V to -90V; the temperature of the magnetron sputtering is 300°C, and the time is 5~10min; during the magnetron sputtering, the stainless steel substrate needs to maintain a uniform rotation speed of 8r / min, and argon gas needs to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.1~0.5Pa.

6. The preparation method according to claim 3, characterized in that: In step 3), the parameters of the magnetron sputtering are: Ti target current 2A, Ag target current 0.03A, substrate bias -60V; the temperature of the magnetron sputtering is 300°C, and the time is 60-80min; during the magnetron sputtering, the stainless steel substrate needs to maintain a uniform rotation speed of 8r / min, and argon and nitrogen need to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.1-0.5Pa.

7. The preparation method according to claim 3, characterized in that: In step 4), the parameters of the magnetron sputtering are: Ti target current 2A, substrate bias -60V; the temperature of the magnetron sputtering is 300°C, and the time is 5 to 8min; during the magnetron sputtering, the stainless steel substrate needs to maintain a uniform rotation speed of 8r / min, and argon and nitrogen need to be continuously introduced into the vacuum chamber to control the pressure in the vacuum chamber to be stable at 0.1 to 0.5Pa.

8. Use of the conductive, corrosion-resistant silver-doped titanium nitride coating for metal bipolar plates as claimed in any one of claims 1 to 2 in metal bipolar plates.

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