KR20100128361A - Bipolar plate coated with titanium oxynitride for fuel cell and method of manufacturing the same - Google Patents

Abstract

PURPOSE: A bipolar plate for a fuel cell is provided to improve corrosion resistance and performance of a fuel battery by comprising a titanium oxide film. CONSTITUTION: A bipolar plate(35,40) for a fuel cell comprises stainless steel and a titanium oxide layer containing titanium 43-44%, nitrogen 44-45%, and oxygen 12-14% applied on the surface of the stainless steel. A method for manufacturing the bipolar plate for a fuel cell comprises the steps of: loading a chamber containing mixed gas including oxygen, nitrogen and argon on a substrate; and coating the surface of the substrate with a titanium oxynitride film while injecting oxygen 0.2 sccm.

Description

Bipolar plate coated with titanium oxynitride for fuel cell and method of manufacturing the same}

The present disclosure generally relates to a separator for a fuel cell and a method for manufacturing the same, and more particularly, to a separator for a fuel cell coated with titanium nitride and a method for manufacturing the same.

In general, a fuel cell is a power generation device that generates electrical energy from hydrogen energy. Such fuel cells are phosphate type (Phosphoric Acid Fuel Cell, PAFC), molten carbonate type (MCFC), solid oxide type (SOFC), and polymer solid electrolyte fuel cell depending on the type of electrolyte. Polymer Electrolyte Membrane Fuel Cell, PEMFC).

Among them, Polymer Electrolyte Membrane Fuel Cells (PEMFCs) generally have a membrane electrode assembly with electrodes / catalyst layers in which chemical reactions occur on both sides of an electrolyte membrane to which hydrogen ions move. A gas diffusion layer (GDL) which distributes the reaction gases evenly and transfers the generated electricity, a gasket and a fastening mechanism for maintaining the tightness and proper tightness of the reaction gases and the cooling water, It consists of a bipolar plate through which gases and cooling water move.

Among these, the separator serves to block the hydrogen gas and the oxygen gas as the reaction gas from being mixed with each other, electrically connect the membrane electrode assembly, and support the membrane electrode assembly to maintain the shape of the fuel cell. Therefore, it must have a structure so compact that the two gases are not mixed, have excellent electrical conductivity for the role of the conductor, and have sufficient mechanical strength for the role of the support. Separator also accounts for a significant portion of the total cost of a molecular solid electrolyte fuel cell, so it must be inexpensive and suitable for the fuel cell operating environment.

In general, graphite having excellent electrical conductivity and chemical stability is mainly used as a material of the separator, and is usually manufactured by machining. Graphite has high electrical conductivity and stable chemical properties in acidic electrolyte solutions. However, graphite has good tensile strength and ductility, so it breaks well. Graphite needs to have a predetermined thickness to be used as a separator. Accordingly, the volume and weight of the fuel cell are increased, and the efficiency and output of the fuel cell per unit weight or unit volume are lowered. In addition, the processing cost of graphite is also high.

In order to overcome this disadvantage of graphite, attempts have been made to use metal materials as separators. The metal has sufficient mechanical strength, excellent workability, and low material and processing costs. It also has the advantage of reducing the thickness of the separator. However, when a metal material is used as the separator, corrosion occurs in the electrolyte solution to contaminate the electrode and the electrolyte, electrical conductivity is reduced due to corrosion products on the surface, and metal ions penetrate into the polymer electrolyte membrane due to corrosion. There is a problem of lowering the movement of hydrogen ions.

The present invention provides a separator coated with titanium nitrate.

The present invention provides a method for producing a separator coated with titanium nitrate.

According to one embodiment of the invention, the separator for fuel cell comprises stainless steel and 43-45% titanium, 43-45% nitrogen, 11-13% oxygen and 3-4% carbon coated on the stainless steel surface. Titanium oxynitride film.

According to one embodiment of the present invention, a method of manufacturing a separator for a fuel cell is provided. The substrate is loaded into a chamber containing a mixed gas containing oxygen, nitrogen and argon. The titanium oxynitride film is coated on the surface of the substrate while injecting 0.2 sccm of oxygen.

Coating the titanium nitride oxide film may be sputtering using an inductively coupled plasma.

The titanium oxynitride film is coated on the separator of the fuel cell. Titanium oxynitride improves the corrosion resistance of the fuel cell separator.

Hereinafter, with reference to the accompanying drawings will be described embodiments of the present invention; However, this is not intended to limit the present invention to a specific disclosed form, it should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention. The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise.

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art. Terms such as those defined in the commonly used dictionaries should be construed as having meanings consistent with the meanings in the context of the related art and shall not be construed in ideal or excessively formal meanings unless expressly defined in this application. Do not.

1 is a cross-sectional view of one cell included in a fuel cell.

Referring to FIG. 1, a cell includes a membrane electrode assembly 10, a gas diffusion layers 25 and 30 formed on the membrane electrode assembly 10, and separator plates 35 and 40 formed on the gas diffusion layers 25 and 30. ). A plurality of cells may be stacked to form a stack.

The membrane electrode assembly 10 generates electricity through an oxidation reaction of a fuel and a reduction reaction of an oxidant. The membrane electrode assembly 10 includes an electrolyte membrane 5, a cathode 15 and an anode 20 formed on both sides of the electrolyte membrane. The negative electrode 15 and the positive electrode 20 may include platinum, ruthenium, osmium, palladium and alloys thereof. In addition, the cathode 15 and the anode 20 may include a transition metal. An oxidation reaction of the fuel occurs at the cathode 15 and a reduction reaction of the oxidant occurs at the anode 20.

The electrolyte membrane 5 transfers hydrogen ions generated by oxidation of the fuel from the cathode 15 to the anode 20, separates the cathode 15 and the anode 20, and the fuel or oxidant flows therebetween. To prevent them. The electrolyte membrane 5 may be used all conventionally used ion transport materials. For example, the polymer resin which has ion exchange groups, such as a sulfonic acid group, a carboxylic acid group, a phosphoric acid group, a phosphonic acid group, and derivatives thereof, is mentioned. As another example, a fluorine polymer, a benzimidazole polymer, a polyimide polymer, a polyetherimide polymer, a polyphenylene sulfide polymer, a polysulfone polymer, a polyether sulfone polymer, a polyether ketone polymer, a polyether Ether ketone-based polymers or polyphenylquinoxane-based polymers;

The gas diffusion layers 25 and 30 deliver fuel or oxidant delivered from the separator plates 35 and 40 to the cathode 15 and the anode 20. As the gas diffusion layers 25 and 30, all conductive materials commonly used may be used. For example, the gas diffusion layers 25 and 30 include carbon cloth, carbon paper and carbon felt.

The separator plates 35 and 40 include a metal coated with titanium nitride oxide (TiN _x O _y ). As the metal to which titanium nitride is coated, stainless steel, for example, commercial 316L stainless steel can be used. In another aspect, the separators 35 and 40 may be considered to be coated with a material in which oxygen is doped with titanium oxide (TiN) in stainless steel. However, the present invention is not limited thereto, and aluminum alloys, titanium alloys, and / or nickel alloys may be used.

Comparative example

The 316L stainless steel substrate was deposited using an inductively coupled plasma (ICP). The titanium nitride film was deposited on both sides of a 316L stainless steel substrate. An ICP was generated by applying an RF power of about 13.56 MHz with a power of about 400 W (8.77 W / cm 2). Prior to deposition, the stainless steel substrate was cleaned using ultrasound in acetone and ethanol solution for about 20 minutes. The deposition was performed under conditions of a mixed gas of argon and nitrogen at a pressure of 10 mTorr or less. Prior to supplying argon and nitrogen, the base pressure was maintained inside the chamber at a vacuum of 6 × 10 ⁻⁷ Torr.

Experimental Example 1

A titanium oxynitride film was deposited on a 316L stainless steel substrate using an inductively coupled plasma (ICP). The titanium oxynitride film was deposited on both sides of a 316L stainless steel substrate. An ICP was generated by applying an RF power of about 13.56 MHz with a power of about 400 W. Prior to deposition, the stainless steel substrate was cleaned using ultrasound in acetone and ethanol solution for about 20 minutes. The deposition was performed under conditions of a mixed gas of argon, nitrogen and oxygen at a pressure of 10 mTorr or less. At this time, oxygen was introduced into the process chamber at a flow rate of about 0.2 sccm during the deposition process. Prior to supplying argon, nitrogen and oxygen, the base pressure was maintained inside the chamber at a vacuum of 6 × 10 ⁻⁷ Torr.

Experimental Example 2

A titanium oxynitride film was deposited on a 316L stainless steel substrate using an inductively coupled plasma (ICP). The titanium oxynitride film was deposited on both sides of a 316L stainless steel substrate. An ICP was generated by applying an RF power of about 13.56 MHz with a power of about 400 W. Prior to deposition, the stainless steel substrate was cleaned using ultrasound in acetone and ethanol solution for about 20 minutes. The deposition was performed under conditions of a mixed gas of argon, nitrogen and oxygen at a pressure of 10 mTorr or less. At this time, oxygen was introduced into the process chamber at a flow rate of about 0.4 sccm during the deposition process. Prior to supplying argon, nitrogen and oxygen, the base pressure was maintained inside the chamber at a vacuum of 6 × 10 ⁻⁷ Torr.

Experimental Example 3

A titanium oxynitride film was deposited on a 316L stainless steel substrate using an inductively coupled plasma (ICP). The titanium oxynitride film was deposited on both sides of a 316L stainless steel substrate. An ICP was generated by applying an RF power of about 13.56 MHz with a power of about 400 W. Prior to deposition, the stainless steel substrate was cleaned using ultrasound in acetone and ethanol solution for about 20 minutes. The deposition was performed under conditions of a mixed gas of argon, nitrogen and oxygen at a pressure of 10 mTorr or less. At this time, during the deposition process, oxygen was introduced into the process chamber at a flow rate of about 0.6 sccm. Prior to supplying argon, nitrogen and oxygen, the base pressure was maintained inside the chamber at a vacuum of 6 × 10 ⁻⁷ Torr.

Experimental Example 4

A titanium oxynitride film was deposited on a 316L stainless steel substrate using an inductively coupled plasma (ICP). The titanium oxynitride film was deposited on both sides of a 316L stainless steel substrate. An ICP was generated by applying an RF power of about 13.56 MHz with a power of about 400 W. Prior to deposition, the stainless steel substrate was cleaned using ultrasound in acetone and ethanol solution for about 20 minutes. The deposition was performed under conditions of a mixed gas of argon, nitrogen and oxygen at a pressure of 10 mTorr or less. At this time, during the deposition process, oxygen was introduced into the process chamber at a flow rate of about 0.8 sccm. Prior to supplying argon, nitrogen and oxygen, the base pressure was maintained inside the chamber at a vacuum of 6 × 10 ⁻⁷ Torr.

2A to 2E are graphs illustrating atomic concentrations of Comparative Examples and Experimental Examples 1 to 4, respectively, measured by Auger Electron Spectroscopy.

Referring to FIG. 2A, the composition ratio of the TiN film according to the comparative example is 46-48% titanium, 47-49% nitrogen, and 7-8% oxygen. Oxygen was not introduced during the formation of the TiN film according to the comparative example, but it was found that oxygen in the air penetrated the TiN film.

Referring to Figure 2b, the composition ratio of the TiNO film according to Experimental Example 1 is 43-44% titanium, 44-45% nitrogen, 12-14% oxygen.

Referring to Figure 2c the composition ratio of the TiNO film according to Experimental Example 2 is 42-43% titanium, 39-40% nitrogen, 18-19% oxygen.

Referring to FIG. 2D, the composition ratio of the TiNO film according to Experimental Example 3 is 32-33% titanium, 31-32% nitrogen, and 37-38% oxygen.

Referring to FIG. 2E, the composition ratio of the TiNO film according to Experimental Example 4 is 30-31% titanium, 28-29% nitrogen, and 42-43% oxygen.

Although not shown as a composition ratio, the film prepared according to Comparative Examples and Experimental Examples 1 to 4 may contain a trace amount of carbon, which is determined to be infiltrated by natural carbon.

The interfacial contact resistance (ICR) of Comparative Examples and Experimental Examples 1 to 4 was measured. 3 is a cross-sectional view showing a method of measuring the interfacial contact resistance of Comparative Examples and Experimental Examples 1 to 4.

Referring to FIG. 3, after the carbon papers 105 and 110 are disposed on the upper and lower portions of the specimen 100, the copper plates are plated with gold on the lower portions of the carbon paper 105 and 110 that do not contact the specimen 100. The interfacial contact resistance of the specimen 100 was measured by applying voltage and current while applying pressure to (115, 120). At this time, the applied pressure was about 150 N / cm 2. Experimental method was carried out by Davies method.

Figure 4 is a graph showing the interfacial contact resistance of the membrane coated membrane prepared according to Comparative Examples and Experimental Examples 1 to 4.

Referring to FIG. 4, the interface resistance of the specimen in which the titanium nitride film was deposited on 316L stainless steel was about 2.5 m 2 cm 2. The interface resistance of the specimen in which the titanium oxynitride film was deposited on the stainless steel while injecting oxygen at a flow rate of 0.2 sccm was about 2.5 m 2 cm 2. The interface resistance of the titanium oxynitride film deposited on the stainless steel while injecting oxygen at a flow rate of 0.4 sccm slightly increased than about 2.5 m 2 cm 2. However, the specimens in which the titanium oxynitride film was deposited on the stainless steel while injecting oxygen at a flow rate of 0.6 sccm had an interface resistance slightly higher than about 5.0 mΩcm2. The interfacial resistance of the deposited specimen was about 17.5 mΩcm 2.

FIG. 5 shows the Potentiodynamic Polarization Curve of uncoated 316L stainless steel, Comparative Examples and Experimental Examples 1 to 4 in an air bubbled atmosphere in 0.1 NH ₂ SO ₄ + 2 ppm HF solution. It is a graph. FIG. 6 shows the displacement polarization curves of uncoated 316L stainless steel, Comparative Examples and Experimental Examples 1 to 4 in a bubbling atmosphere using hydrogen gas at a temperature of 80 degrees in a 0.1 NH ₂ SO ₄ + 2 ppm HF solution. It is a graph showing (Potentiodynamic Polarization Curve).

5 and 6, bubbled with air means that the corrosion resistance of the specimen in the anode atmosphere was measured. By bubbling with hydrogen, we mean the corrosion resistance of the specimen in the cathode atmosphere. Compared with 316L stainless steel without coating, Comparative Examples and Experimental Examples 1 to 4 showed excellent corrosion resistance. In particular, Experimental Example 1 in which the titanium nitride film was coated on 316L stainless steel while injecting oxygen of about 0.2 sccm showed the most excellent corrosion resistance. Experimental Example 1 The corrosion current density of the specimen was 0.6 vs SCE (SaturatedCalomel Electrode) of 2.7 × 10 ⁻⁶ Acm ⁻² . The corrosion current density of the comparative example was 0.6 × SCE of 8 × 10 ⁻⁶ Acm ⁻² .

FIG. 7 is a graph showing a potentiostatic polarization curve of specimens of uncoated 316L stainless steel, Comparative Examples and Experimental Examples 1 to 4, measured in an anode atmosphere. FIG. 8 is a graph showing a potentiostatic polarization curve of specimens of uncoated 316L stainless steel, Comparative Examples and Experimental Examples 1 to 4 measured in a cathode atmosphere.

The potentiometric polarization measurement was measured for 10 minutes at -0.1V in the cathode atmosphere and 0.6V in the anode atmosphere.

7 and 8, Comparative Examples and Experimental Examples 1 to 4 exhibited a low current density of about 2.0 × 10 ⁻⁶ Acm ⁻² in the anode atmosphere. In the cathode atmosphere, Experimental Example 1 and Experimental Example 2 showed a negative current density because the corrosion potential was -0.1V or more. This means that the titanium nitride oxide film of Experimental Example 1 and Experimental Example 2 functions as a corrosion preventing film. In Experimental Example 3 and Experimental Example 4, a positive current was observed.

As can be seen from the interfacial contact resistance, the displacement potential polarization curve, and the potential potential polarization curve of Comparative Examples and Experimental Examples 1 to 4, the titanium oxynitride layer may be coated on the stainless steel as compared with the conventional titanium nitride layer on the stainless steel. In this case, there was no change in electrical conductivity, but the corrosion resistance increased and the interface contact resistance decreased. In particular, when the titanium oxynitride film was coated while injecting oxygen at a flow rate of 0.2 sccm, that is, in case of Experimental Example 1 containing 12-14% of oxygen, the interfacial contact resistance was the lowest as compared with the excellent corrosion resistance. Could know. In other words, in terms of corrosion resistance, the titanium oxynitride film has excellent characteristics, and considering the interfacial contact resistance, when the titanium oxynitride film is coated while injecting oxygen at a flow rate of 0.2 sccm, that is, containing 12-14% oxygen Experimental Example 1 has the best characteristics.

In Experimental Example 1, a titanium oxynitride film was coated on 316L stainless steel while injecting 0.2 sccm of oxygen to form a titanium oxynitride film containing 12-14% of oxygen. Can vary depending on the flow rate of the gas. Regardless of the titanium oxynitride coating process, the titanium oxynitride film having a composition ratio of titanium 43-44%, nitrogen 44-45%, and oxygen 12-14% is coated on 316L stainless steel to be used as a separator of a fuel cell. It means the best effect.

It is possible to improve the performance of the fuel cell by coating titanium nitride film on the separator for fuel cell to improve corrosion resistance.

Although the present invention has been described with reference to preferred embodiments, the present invention is not limited by such embodiments. Those skilled in the art will be able to make various modifications and alternative techniques from the scope and concept of the invention. Therefore, the scope of the present invention should be defined and protected by the following claims and their equivalents.

The invention will be better understood when read in conjunction with the accompanying drawings. While examples of preferred drawings have been shown to illustrate the invention, it should be understood that the invention is not limited to the precise arrangements and instrumentalities shown in the drawings.

1 is a cross-sectional view of one cell included in a fuel cell.

2A to 2E are atomic concentrations measured using Auger Electron Spectroscopy of membranes according to Comparative Examples and Experimental Examples 1 to 4, respectively.

 3 is a cross-sectional view showing a method for measuring the interfacial contact resistance of 316L stainless steel coated with a film according to Comparative Examples and Experimental Examples 1 to 4.

4 is a graph showing 316L stainless steel interface contact resistance coated with a film according to Comparative Examples and Experimental Examples 1 to 4.

FIG. 5 shows the Potentiodynamic Polarization Curve of uncoated 316L stainless steel, Comparative Examples and Experimental Examples 1 to 4 in an air bubbled atmosphere in 0.1 NH ₂ SO ₄ + 2 ppm HF solution. It is a graph.

FIG. 6 shows the displacement polarization curves of uncoated 316L stainless steel, Comparative Examples and Experimental Examples 1 to 4 in a bubbling atmosphere using hydrogen gas at a temperature of 80 degrees in a 0.1 NH ₂ SO ₄ + 2 ppm HF solution. It is a graph showing (Potentiodynamic Polarization Curve).

FIG. 7 is a graph showing a potentiostatic polarization curve of specimens of uncoated 316L stainless steel, Comparative Examples and Experimental Examples 1 to 4, measured in an anode atmosphere.

FIG. 8 is a graph showing a potentiostatic polarization curve of specimens of uncoated 316L stainless steel, Comparative Examples and Experimental Examples 1 to 4 measured in a cathode atmosphere.

Claims (3)

Stainless steel; And Separation plate for a fuel cell comprising a titanium oxynitride film comprising 43-44% titanium, 44-45% nitrogen, 12-14% oxygen coated on the stainless steel surface. Loading the substrate into a chamber containing a mixed gas comprising oxygen, nitrogen and argon; And A method of manufacturing a separator for a fuel cell, comprising coating a titanium oxynitride film on the surface of the substrate while injecting 0.2 sccm of oxygen. The method of claim 2, wherein the coating of the titanium nitride oxide film is sputtering using an inductively coupled plasma.

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