WO2017170066A1

WO2017170066A1 - Cell for solid polymer fuel cell, and solid polymer fuel cell stack

Info

Publication number: WO2017170066A1
Application number: PCT/JP2017/011554
Authority: WO
Inventors: 樽谷　芳男
Original assignee: 新日鐵住金株式会社
Priority date: 2016-03-29
Filing date: 2017-03-22
Publication date: 2017-10-05
Also published as: JP6278157B1; JPWO2017170066A1

Abstract

A cell 10 for a solid polymer fuel cell and equipped with an anode-side cell constituent member 11 and a cathode-side cell constituent member 12, wherein: the anode-side cell constituent member 11 comprises a ferritic stainless steel material, and the cathode-side cell constituent member 12 comprises a stainless steel material; the ferritic stainless steel material which constitutes the anode-side cell constituent member 11 has a chemical composition in which the Sn content is 0.02-2.50%, by mass%, and has a precipitate therein which contains a finely dispersed and precipitated M₂B boride; part of the precipitate projects from the surface of the ferritic stainless steel material; and the stainless steel material constituting the cathode-side cell constituent member 12 has a chemical composition in which the Sn content is less than 0.02%, by mass%.

Description

Polymer polymer fuel cell and polymer electrolyte fuel cell stack

The present invention relates to a polymer electrolyte fuel cell and a polymer electrolyte fuel cell stack.

Fuel cells are cells that generate direct current using hydrogen and oxygen, and are roughly classified into solid electrolyte type, molten carbonate type, phosphoric acid type, and solid polymer type. Each type is derived from the constituent material of the electrolyte part constituting the basic part of the fuel cell.

Currently, fuel cells that have reached the commercial stage include a phosphoric acid type operating near 200 ° C. and a molten carbonate type operating near 650 ° C. With the progress of recent technological development, solid polymer type that operates near room temperature and solid electrolyte type that operates at 700 ° C. or more are attracting attention as compact power supplies for automobiles or home use.

FIG. 1 is an explanatory view showing the structure of a solid polymer fuel cell, FIG. 1 (a) is an exploded view of a fuel cell (single cell), and FIG. 1 (b) is a perspective view of a fuel cell stack. is there.

As shown in FIGS. 1 (a) and 1 (b), the fuel cell stack 1 is an assembly of single cells. In the single cell, as shown in FIG. 1A, a fuel electrode film (anode) 3 is laminated on one surface of a solid polymer film 2, and an oxidant electrode film (cathode) 4 is laminated on the other surface. The separators 5a and 5b are stacked.

As a typical solid polymer membrane 2, there is a fluorine ion exchange resin membrane having a hydrogen ion (proton) exchange group.

The fuel electrode film 3 and the oxidant electrode film 4 each include a diffusion layer and a catalyst layer provided on the surface of the diffusion layer on the solid polymer film 2 side. The diffusion layer is made of carbon paper or carbon cloth composed of carbon fibers, and the catalyst layer is made of a particulate platinum catalyst, graphite powder, and a fluororesin having hydrogen ion (proton) exchange groups. The catalyst layers of the fuel electrode film 3 and the oxidant electrode film 4 are in contact with the fuel gas or the oxidizing gas that has permeated the diffusion layer.

A fuel gas (hydrogen or hydrogen-containing gas) A is flowed from a flow path 6 a provided in the separator 5 a and hydrogen is supplied to the fuel electrode film 3. Further, an oxidizing gas B such as air is flowed from the flow path 6b provided in the separator 5b, and oxygen is supplied. The supply of these gases causes an electrochemical reaction to generate DC power.

The functions required of the polymer electrolyte fuel cell separator are (1) a function as a “flow path” for uniformly supplying fuel gas in the surface on the fuel electrode side, and (2) water generated on the cathode side as fuel. Functions as a "flow path" that efficiently discharges the battery together with carrier gas such as air and oxygen after reaction from the battery, and (3) a single cell that maintains low electrical contact resistance and good electrical conductivity as an electrode over a long period of time A function as an electrical “connector” between them, and (4) a function as a “partition wall” between an anode chamber of one cell and a cathode chamber of an adjacent cell in adjacent cells.

So far, various studies have been made on the base material of the separator that exhibits the above functions. Materials used for the separator are roughly divided into metal-based materials and carbon-based materials.

As a carbon-based material, the application of carbon plate materials to separators has been intensively studied at the laboratory level. However, the carbon plate material has a problem that it is easily broken, and further has a problem that the machining cost for flattening the surface and the machining cost for forming the gas flow path are very high. Each of these is a major problem, and it has been difficult to commercialize fuel cells.

Among the carbons, the thermally expansive graphite processed product is remarkably inexpensive, and is thus attracting the most attention as a material for polymer electrolyte fuel cell separators. However, it is necessary to deal with stricter dimensional accuracy, deterioration of organic resin with age, which occurs during the application of fuel cells, carbon corrosion that progresses under the influence of battery operating conditions, and when fuel cells are assembled and in use. Problems such as unexpected cracking accidents that occur in Japan are still issues to be solved.

As an attempt to examine the application of graphite-based materials, attempts have been made to apply stainless steel to separators for the purpose of cost reduction.

For example, Patent Document 1 discloses a fuel cell separator made of a metal member and directly plated with gold on a contact surface with an electrode of a unit cell. Examples of the metal member include stainless steel, aluminum, and nickel-iron alloy, and SUS304 is used as the stainless steel.

In the invention described in Patent Document 1, since the separator is gold-plated, the contact resistance between the separator and the electrode is reduced, and conduction of electrons from the separator to the electrode is improved. Is supposed to grow.

Further, Patent Document 2 discloses a polymer electrolyte fuel cell in which a separator made of a metal material in which a passive film formed on the surface is easily generated by the atmosphere is used. Stainless steel and titanium alloy are mentioned as metal materials.

In the invention described in Patent Document 2, there is always a passive film on the surface of the metal used for the separator, and the water generated in the fuel cell is less likely to be chemically attacked by the metal surface. It is said that the degree of ionization is reduced and the decrease in the electrochemical reactivity of the fuel cell is suppressed. Further, it is said that the surface contact resistance value is reduced by removing the passive film at the portion in contact with the electrode film of the separator and forming a noble metal layer.

However, even if a metal material such as stainless steel having a passive film on the surface as disclosed in Patent Documents 1 and 2 is used as it is for a separator, corrosion resistance is not sufficient and metal elution occurs and is supported by eluted metal ions. Catalyst performance deteriorates. In addition, since the contact resistance of the separator is increased by corrosion products such as Cr—OH or Fe—OH generated after elution, the separator made of a metal material is subjected to precious metal plating such as gold plating that is not costly. This is the current situation.

Under such circumstances, stainless steel having excellent corrosion resistance that can be applied as a separator without being subjected to expensive surface treatment has been proposed.

Patent Document 3 discloses stainless steel suitable as a separator for a solid oxide fuel cell. Patent Documents 4 and 5 disclose a polymer electrolyte fuel cell including a separator made of ferritic stainless steel.

Patent Document 6 discloses a ferritic stainless steel for a separator of a polymer electrolyte fuel cell containing 0.01 to 0.15% by mass of C in the steel and depositing Cr-based carbides, and a solid high A molecular fuel cell is disclosed. Patent Document 7 discloses an austenitic stainless steel for a separator of a polymer electrolyte fuel cell containing 0.015 to 0.2% C and 7 to 50% Ni and depositing Cr carbide in steel. Steel is shown.

Patent Document 8 discloses that among M ₂₃ C ₆ type, M ₄ C type, M ₂ C type, MC type carbide metal inclusions and M ₂ B type boride inclusions having conductivity on a stainless steel surface. Stainless steel for separators of polymer electrolyte fuel cells in which one or more of the above are dispersed and exposed is disclosed, and by mass%, C: 0.15% or less, Si: 0.01 to 1.5% , Mn: 0.01 to 1.5%, P: 0.04% or less, S: 0.01% or less, Cr: 15 to 36%, Al: 0.001 to 6%, N: 0.035% A ferritic stainless steel is described that contains the following, the Cr, Mo, and B contents satisfying 17% ≦ Cr + 3 × Mo−2.5 × B, and the balance being Fe and inevitable impurities.

Patent Document 9, the surface of the stainless steel by corrosion by the acidic aqueous solution, M ₂₃ C ₆ type having conductivity in its surface, M 4 _C type, M 2 _C type, MC type carbide-based metal inclusions and M ₂ shows a method for producing a stainless steel material for a separator of a polymer electrolyte fuel cell in which one or more of B-type boride-based metal inclusions are exposed, and in mass%, C: 0.15% or less, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.04% or less, S: 0.01% or less, Cr: 15 to 36%, Al: 0.001 ~ 1%, B: 0 ~ 3.5%, N: 0.035% or less, Ni: 0 ~ 5%, Mo: 0 ~ 7%, Cu: 0 ~ 1%, Ti: 0 ~ 25 × (C % + N%), Nb: 0 to 25 × (C% + N%), and the content of Cr, Mo and B is 17% ≦ Cr + 3 × Mo− Has satisfied .5 × B, ferritic stainless steel is disclosed that the balance Fe and impurities.

Further, Patent Document 10 discloses that an M ₂ B type boride-based metal compound is exposed on the surface, and when the anode area and the cathode area are each 1, the area where the anode is in direct contact with the separator, and A solid polymer fuel cell is shown in which the area where the cathode is in direct contact with the separator is from 0.3 to 0.7, and M ₂₃ C ₆ type having conductivity on the stainless steel surface. , M ₄ C type, M ₂ C type, MC type carbide based metal inclusions and M ₂ B type boride type inclusions are disclosed.

In Patent Document 10, stainless steel constituting the separator is, by mass%, C: 0.15% or less, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.04% or less, S: 0.01% or less, Cr: 15 to 36%, Al: 0.2% or less, B: 3.5% or less (excluding 0%), N: 0.035% Hereinafter, Ni: 5% or less, Mo: 7% or less, W: 4% or less, V: 0.2% or less, Cu: 1% or less, Ti: 25 × (C% + N%) or less, Nb: 25 × It is shown that it is a ferritic stainless steel material that is (C% + N%) or less and the content of Cr, Mo, and B satisfies 17% ≦ Cr + 3 × Mo−2.5 × B.

Patent Documents 11 to 15 disclose an austenitic stainless clad steel material in which M ₂ B type boride conductive metal deposits are exposed on the surface and a method for manufacturing the same.

In Patent Document 16, C: 0.08% or less, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.035% or less, S: 0.01% Hereinafter, Cr: 17 to 36%, Al: 0.001 to 0.2%, B: 0.0005 to 3.5%, N: 0.035% or less, containing Ni, Mo, Cu if necessary, And the Cr, Mo, and B contents satisfy 17% ≦ Cr + 3Mo−2.5B, the chemical composition is composed of the balance Fe and impurities, and B in the steel precipitates as M ₂ B type boride-based metal inclusions. A fuel cell comprising a separator made of ferritic stainless steel is disclosed.

In Patent Document 17, for example, C: 0.2% or less, Si: 2% or less, Mn: 3% or less, Al: 0.001% or more and 6% or less, P: 0.06% or less, S: 0 0.03% or less, N: 0.4% or less, Cr: 15% to 30%, Ni: 6% to 50%, B: 0.1% to 3.5%, balance Fe and impurities An austenitic stainless steel material for a separator of a polymer electrolyte fuel cell having a chemical composition and having a conductive material made of M ₂ B type boride metal inclusions is disclosed.

In Patent Document 18, C: 0.02% or less, Si: 0.15% or less, Mn: 0.3 to 1%, P: 0.04% or less, S: 0.003% or less, Cr: 20 -25%, Mo: 0.5-2%, Al: 0.1% or less, N: 0.02% or less, Nb: 0.001-0.5%, and 2.5 <Mn / (Si + Al) <8.0 is contained, and as optional elements, Ti: 0.5% or less, V: 0.5% or less, Ni: 2% or less, Cu: 1% or less, Sn: 1% or less, B: 0.0. 005% or less, Mg: 0.005% or less, Ca: 0.005% or less, W: 1% or less, Co: 1% or less, Sb: 0.5% or less, and the balance Fe and A ferritic stainless steel sheet having a chemical composition comprising impurities and having an oxide film having good electrical conductivity at high temperatures is disclosed.

In Patent Document 19, C: 0.001 to 0.03%, Si: 0.01 to 2%, Mn: 0.01 to 1.5%, P: 0.005 to 0.05%, S: 0.0001 to 0.01%, Cr: 16 to 30%, N: 0.001 to 0.03%, Al: more than 0.8% to 3%, Sn: 0.01 to 1%, the balance being Fe And a ferritic stainless steel sheet having a chemical composition comprising impurities and having a small amount of Sn added to improve oxidation resistance and high-temperature strength.

In Patent Document 20, C: 0.01% or less, Si: 0.01 to 0.20%, Mn: 0.01 to 0.30%, P: 0.04% or less, S: 0.01% Hereinafter, Cr: 13 to 22%, N: 0.001 to 0.020%, Ti: 0.05 to 0.35%, Al: 0.005 to 0.050%, Sn: 0.001 to 1% Also disclosed is a ferritic stainless steel having a chemical composition consisting of Fe and impurities in the balance and containing Sn to improve the corrosion resistance by modifying the passive film.

However, in spite of these many proposals, the application of stainless steel as the material for the polymer electrolyte fuel cell separator requires that the cathode electrode side catalyst support be generated when starting the polymer electrolyte fuel cell after the suspension. The major issue of carbon corrosion remains.

Specifically, when hydrogen gas, which is a fuel gas, is introduced to the anode electrode side in a state where the oxidizing gas (air) is filled on the anode electrode side at the time of startup, the anode electrode side and the cathode electrode side are unsteady. Transient phenomena occur. This excessive phenomenon is a phenomenon in which an instantaneous cell potential rise occurs on the cathode electrode side, and the cathode electrode-supported carbon is consumed. Consumption of the cathode electrode side catalyst-supporting carbon inevitably causes a decrease in catalyst function.

To date, as a countermeasure, the anode volume side volume is reduced to shorten the gas replacement time, or the fuel gas (hydrogen) flow rate at startup is increased so that the gas replacement proceeds in a short time. Devising the channel design has been done. Further, introduction of fuel gas (hydrogen) into the anode electrode side in a pressurized state is also performed.

In addition, a resistor that short-circuits the anode and cathode sides is also installed for each cell. However, as the number of cells increases, system control becomes significant, making the fuel cell system expensive. It causes the battery efficiency to drop.

As described above, the consumption of the cathode-supported catalyst-supporting carbon at the time of starting the polymer electrolyte fuel cell is a big issue in order to ensure the long-term durability of the polymer electrolyte fuel cell and reduce the performance degradation. .

Patent Document 21 discloses an invention in which a gas sensing layer is interposed inside a cell of a polymer electrolyte fuel cell, between an anode flow field plate and an anode catalyst layer. The gas sensing layer includes, for example, semiconductor oxide nanostructures less than about 30 nanometers. The semiconductor oxide nanostructure is composed of titanium oxide, tin oxide, zinc oxide, zirconium oxide, and combinations thereof. The gas sensing layer reduces electrical resistance when contacted with hydrogen gas and increases electrical resistance when contacted with oxygen-containing gas to protect the cell from corrosion when O ₂ remains in the anode channel. .

That is, when oxygen is still present in the anode when the polymer electrolyte fuel cell is started, the electric resistance of the gas sensing layer in contact with oxygen is high, and the cell reaction at this site is suppressed, leading to electrode deterioration. Chemical reaction is suppressed.

After that, when hydrogen continues to flow and air is expelled from the anode, the gas sensing layer comes into contact with hydrogen and the electric resistance decreases, and the original cell reaction proceeds. In other words, the gas sensing layer has an electrical property that causes a decrease in battery performance caused by an induced voltage between the anode and the cathode through an MEA (Membrane Electrode Assembly) composed of a gas diffusion layer, a polymer film, and a catalyst layer. Suppress chemical reactions.

Patent Document 21 further discloses SnO ₂ as tin oxide and TiO ₂ nanotubes as titanium oxide. The gas sensing layer can be formed by coating on a gas diffusion layer or bipolar plate and heat treatment at 200-400 ° C. to improve adhesion, physical vapor deposition on the bipolar plate, chemical Deposition methods such as vapor deposition and electrodeposition are disclosed. It is also disclosed to convert the nanostructured semiconductor oxide into a gas sensing layer using known techniques such as electrochemical etching or acid corrosion of these metal films.

Japanese Patent Laid-Open No. 10-228914 Japanese Patent Laid-Open No. 08-180883 JP 2000-239806 A JP 2000-294255 A JP 2000-294256 A JP 2000-303151 A JP 2000-309854 A JP 2003-193206 A JP 2001-214286 A JP 2002-151111 A JP 2004-71319 A JP 2004-156132 A JP 2004-306128 A JP 2007-1118025 A JP 2009-215655 A JP 2000-328205 A JP 2010-140886 A JP 2014-031572 A JP 2012-172160 A JP 2009-174036 A JP2015-128064A

The technological development so far is in the above situation, but when starting the solid molecular fuel cell, the fuel gas (for example, air) remains in the anode electrode side inside the fuel cell (for example, air) Corrosion of carbon (for example, catalyst-supporting carbon) and separator on the cathode electrode side that occurs when hydrogen is introduced to the anode electrode side cannot be sufficiently reduced.

The present invention solves the above-mentioned problem, and at the time of starting the solid molecular fuel cell, the fuel gas is introduced into the anode electrode side while the oxidizing gas remains inside the anode electrode side of the fuel cell. It is an object of the present invention to provide a polymer electrolyte fuel cell, which can reduce corrosion of carbon and separator on the cathode electrode side, and a polymer electrolyte fuel cell stack including the same.

The present invention has been made in order to solve the above-mentioned problems, and has the following gist and a polymer electrolyte fuel cell stack and a polymer electrolyte fuel cell stack.

(1) A cell for a polymer electrolyte fuel cell comprising an anode electrode side cell constituent member and a cathode electrode side cell constituent member,
The anode electrode side cell constituent member includes a ferritic stainless steel material, and the cathode electrode side cell constituent member includes a stainless steel material,
The ferritic stainless steel material contained in the anode electrode side cell constituent member has a chemical composition of mass% and Sn content of 0.02 to 2.50%, and
In the ferritic stainless steel material, there are precipitates containing M ₂ B type boride finely dispersed and precipitated,
A part of the precipitate protrudes from the surface of the ferritic stainless steel material,
The stainless steel material contained in the cathode electrode side cell constituent member has a chemical composition in which the Sn content is less than 0.02% by mass%.
Solid polymer fuel cell.

(2) The precipitate that the ferritic stainless steel material included in the anode electrode side cell constituent member has,
A composite precipitate in which M ₂ B type boride is used as a precipitation nucleus and M ₂₃ C ₆ type Cr-based carbide is precipitated on the surface thereof;
A part of the composite precipitate protrudes from the surface of the ferritic stainless steel material,
The polymer electrolyte fuel cell according to (1) above.

(3) The stainless steel material included in the cathode electrode side cell constituent member is:
In the stainless steel material, having a precipitate containing M ₂ B type boride finely dispersed and precipitated,
A part of the precipitate protrudes from the surface of the stainless steel material.
The polymer electrolyte fuel cell according to the above (1) or (2).

(4) The deposit that the stainless steel material included in the cathode electrode side cell constituent member has,
A composite precipitate in which M ₂ B type boride is used as a precipitation nucleus and M ₂₃ C ₆ type Cr-based carbide is precipitated on the surface thereof;
A part of the composite precipitate protrudes from the surface of the stainless steel material.
The polymer electrolyte fuel cell according to (3) above.

(5) The stainless steel material included in the cathode electrode side cell constituent member is:
It has a corrosion-resistant plating layer with conductivity on the surface,
The polymer electrolyte fuel cell according to the above (1) or (2).

(6) The polymer electrolyte fuel cell according to any one of (1) to (5) is provided.
Solid polymer fuel cell stack.

According to the present invention, at the time of starting the solid molecular fuel cell, the cathode electrode is caused by the fuel gas being introduced into the anode electrode side while the oxidizing gas remains inside the anode electrode side of the fuel cell. It is possible to obtain a polymer electrolyte fuel cell, and a polymer electrolyte fuel cell stack including the same, which can reduce corrosion of carbon and separator on the side.

1A and 1B are explanatory views showing the structure of a solid polymer fuel cell. FIG. 1A is an exploded view of a fuel cell (single cell), and FIG. 1B is a perspective view of a fuel cell stack. is there. FIG. 2 is a schematic cross-sectional view of a polymer electrolyte fuel cell. FIG. 3 is a photograph showing the shape of the separator used in the example.

The present inventor has found that the metal of MEA composed of a diffusion layer, a polymer membrane, and a catalyst layer has little metal elution from the separator surface even when used for a long time as a separator of a polymer electrolyte fuel cell for many years. We have been devoted to the development of stainless steel materials that can suppress the progress of ion contamination and hardly deteriorate the performance of the catalyst and polymer membrane.

FIG. 2 is a schematic cross-sectional view of the polymer electrolyte fuel cell 10. The polymer electrolyte fuel cell 10 includes an MEA 20 in which catalyst layers 17 and 18 and

diffusion layers

15 and 16 are provided on both sides of a polymer membrane 19, respectively, and an anode electrode side cell configuration provided on both sides of the MEA 20 respectively. A member 11 and a cathode electrode side cell constituting member 12. Between the MEA 20 and the anode electrode side cell constituent member 11 and the cathode electrode side cell constituent member 12, an anode electrode side fuel gas channel 13 and a cathode electrode side gas channel 14 are provided, respectively.

As described above, the polymer electrolyte fuel cell is started in a state where the anode electrode side fuel gas passage 13 is filled with air. FIG. 2 schematically illustrates a chemical reaction that proceeds inside the solid polymer fuel cell 10 at the time of startup. With reference to FIG. 2, a transient phenomenon that occurs inside the polymer electrolyte fuel cell 10 at the time of startup will be described in more detail.

When hydrogen is introduced into the anode electrode side fuel gas channel 13 side in the air atmosphere, the air on the anode electrode side fuel gas channel 13 side is replaced with hydrogen. However, there is a large volume on the anode electrode side fuel gas flow path 13 side in the polymer electrolyte fuel cell 10 including the pipe and the manifold portion. Since the introduced gas flow rate and gas flow rate are limited, a certain amount of time (for example, several seconds) is unavoidably required until the air is completely expelled by hydrogen.

That is, at the time of start-up, a boundary portion is generated between the hydrogen flowing into the anode electrode side fuel gas passage 13 and the remaining air. Then, on the surface of the catalyst layer 17 on the anode electrode side in the vicinity of the boundary portion, an instantaneous catalyst surface reaction with air and hydrogen proceeds, and local H ⁺ deficiency occurs.

As a result, a local battery is formed inside the cell, and an induced voltage exceeding 1.4 V is instantaneously generated between the anode electrode side cell constituent member 11 and the cathode electrode side cell constituent member 12 via the MEA 20. The chemical reactions involved in local battery formation are as follows.

(I) Reaction at the catalyst layer 17 on the anode side (instantaneous catalyst surface reaction)
O ₂ + 4H ⁺ + 4e ⁻ → 2H ₂ O (i)
(II) Reaction at the catalyst layer 18 on the cathode side C + 2H ₂ O → 4H ⁺ + 4e ⁻ + CO ₂ (ii)
2H ₂ O → 4H ⁺ + 4e ⁻ + O ₂ (iii)

Reaction (i) is a reaction in which the remaining air generates H ⁺ deficiency, and is a transient reaction at the time of start-up that proceeds in the catalyst layer 17 on the anode electrode side. Reaction (ii) is a C exhaustion reaction that proceeds on the catalyst layer 18 side on the cathode side. Furthermore, the reaction (iii) is a water splitting reaction (oxidation reaction) for compensating for the H ⁺ deficiency that proceeds on the catalyst layer 18 side on the cathode side.

As these reactions (i) to (iii) progress, the catalyst-carrying carbon is consumed (corroded) in the cathode-side catalyst layer 18 and the cathode-electrode-side cell component 12 is further corroded. In particular, the corrosion of the catalyst-carrying carbon directly leads to a decrease in fuel cell performance. In addition, since the corrosion of the catalyst-supporting carbon is an irreversible reaction, it causes a cumulative decrease in fuel cell performance.

As the internal volume of the fuel cell system increases, the H ⁺ deficiency state in the anode electrode side fuel gas passage 13 occurs for a longer time, and the corrosion of the catalyst-supporting carbon in the catalyst layer 18 on the cathode electrode side becomes apparent. It becomes easy to change.

As described above, it is important to reduce the corrosion amount of the catalyst-supporting carbon and the cell constituent members by suppressing the formation of the local battery that occurs when the solid polymer fuel cell 10 is started.

By the way, in the conventional polymer electrolyte fuel cell, it is assumed that the same material is used for the anode electrode side cell constituent member and the cathode electrode side cell constituent member. This is because the use of different materials is expected to increase the manufacturing cost, and it has been considered that there is no need to use different materials in the first place.

However, the present inventor has intensively studied without being bound by such premise. That is, it was examined to apply a material that exhibits the performance required in each environment for the anode electrode side cell constituent member and the cathode electrode side cell constituent member.

In particular, the anode-side cell component member has excellent surface corrosion resistance in addition to low surface contact resistance during normal operation and excellent electrical conductivity (contact electrical resistance). It is desirable to be high and to suppress the formation of local batteries. Then, this inventor examined the steel material which has such performance, As a result, it came to obtain the following knowledge.

(A) M ₂ B type boride finely dispersed in the steel material and projecting on the surface (hereinafter sometimes simply referred to as “M ₂ B”) is formed on the surface of the stainless steel covered with a passive film. By functioning as a “passage (conductive path)”, the contact electric resistance of the steel surface is remarkably improved.

(B) By including Sn in the steel, Sn dissolved in the mother phase is subjected to acid solution treatment that is performed in advance or gentle mother phase dissolution that occurs during operation of the fuel cell. In addition, the surface of M ₂ B is concentrated as metallic tin or tin oxide. This significantly suppresses the elution of metal ions from the parent phase and M ₂ B.

(C) Metal tin and tin oxide concentrated on the surface of the parent phase and M ₂ B have semiconducting properties. The electrical conductivity of metal tin or tin oxide varies depending on the oxygen potential of the gas atmosphere to be exposed (hereinafter referred to as “oxygen concentration”). Specifically, the lower the oxygen concentration, the more the electrical conductivity. Become good. Therefore, the contact electrical resistance of the steel material surface increases when the oxygen concentration of the atmosphere to which the steel material surface is exposed is high as in air, and decreases when the oxygen concentration is extremely low as in a hydrogen atmosphere.

(D) That is, the metal tin or tin oxide covering the M 2 _B, upon startup of a solid polymer fuel cell, the oxygen concentration is subjected to high ambient electrical conductivity has decreased, M ₂ The function of B as a conductive path is suppressed. As a result, the surface contact resistance value of the steel material is increased only at the time of start-up, and the local battery reaction that occurs transiently is suppressed.

(E) On the other hand, the cathode electrode side cell constituent member is used in an oxidizing atmosphere even during normal operation. Therefore, when a stainless steel material containing Sn is applied to the cathode electrode side cell constituent member, the surface of the mother phase is inferior in conductivity due to the dissolution of the mother phase (corrosion) that proceeds extremely slowly during operation. To become. As a result, the contact electrical resistance increases and the battery output decreases.

(F) As a result of the above, the present inventors applied a stainless steel material containing a predetermined amount of Sn and a precipitate containing M ₂ B protruding from the surface as the anode electrode side cell constituent member, and the Sn content As a result, we have developed a polymer electrolyte fuel cell using a stainless steel material with reduced carbon as a cathode component. And it has been found that the polymer electrolyte fuel cell including the same can suppress a decrease in battery performance due to consumption of the cathode electrode-side catalyst-supporting carbon even when the anode electrode side is started from an oxidizing atmosphere (air).

The present invention has been made based on the above findings. Hereinafter, each requirement of the present invention will be described in detail.

Referring to FIG. 2, the polymer electrolyte fuel cell 10 includes an anode electrode-side cell component 11 and a cathode electrode-side cell component 12. Each will be described in detail.

In the present invention, the “cell constituent member” is a separator or a current plate. The separator is sometimes called a bipolar plate. The rectifying plate is a member for rectifying or distributing fuel gas or oxidizing gas, and is sometimes referred to as a porous plate, fin, or mesh.

1. Anode electrode side cell constituent member The anode electrode side cell constituent member 11 includes a ferritic stainless steel material described below. In addition, it is preferable that the member used for the surface part of a gas flow path at least among the anode electrode side cell structural members 11 is comprised by the ferritic stainless steel material mentioned later.

1-1. Chemical composition of ferritic stainless steel material The reasons for limitation of each element are as follows. In the following description, “%” for the content means “% by mass”.

The ferritic stainless steel material contained in the anode electrode side cell constituent member 11 has an Sn content of 0.02 to 2.50%. The reason why the Sn content is limited to the above range will be described later.

The chemical composition of the ferritic stainless steel material is as follows: C: 0.001 to 0.15%, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.00. 035% or less, S: 0.01% or less, Cr: 22.5-35.0%, Mo: 0.01-6.0%, Ni: 0.01-6.0%, Cu: 0.01 -1.0%, N: 0.035% or less, V: 0.01-0.35%, B: 0.5-1.0%, Al: 0.001-6.0%, Sn: 0 0.02 to 2.50%, REM: 0 to 0.1%, Nb: 0 to 0.35%, Ti: 0 to 0.35%, and the balance: Fe and impurities, represented by the following formula (iv) Is preferably satisfied.
20.0 ≦ Cr + 3 × Mo−2.5 × B-17 × C ≦ 45.0 (iv)
However, each element symbol in a formula means content (mass%) of each element contained in steel materials.

Here, “impurities” are components mixed by various factors such as melting raw materials, additive elements, scraps, and manufacturing processes used when industrially producing steel materials, and are allowed within a range that does not adversely affect the present invention. Means what will be done.

Further, the above-mentioned ferritic stainless steel materials include the following two types of ferritic stainless steel materials.

(A) C: 0.001% or more and less than 0.020%, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.035% or less, S: 0.0. 01% or less, Cr: 22.5 to 35.0%, Mo: 0.01 to 6.0%, Ni: 0.01 to 6.0%, Cu: 0.01 to 1.0%, N: 0.035% or less, V: 0.01 to 0.35%, B: 0.5 to 1.0%, Al: 0.001 to 6.0%, Sn: 0.02 to 2.50%, REM: 0 to 0.1%, Nb: 0 to 0.35%, Ti: 0 to 0.35%, and the balance: Fe and impurities, satisfying the following formula (v): Ferritic stainless steel material .
20.0 ≦ Cr + 3 × Mo−2.5 × B ≦ 45.0 (v)

(B) C: 0.020 to 0.15%, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.035% or less, S: 0.01% Hereinafter, Cr: 22.5-35.0%, Mo: 0.01-6.0%, Ni: 0.01-6.0%, Cu: 0.01-1.0%, N: 0.00. 035% or less, V: 0.01 to 0.35%, B: 0.5 to 1.0%, Al: 0.001 to 6.0%, Sn: 0.02 to 2.50%, REM: A ferritic stainless steel material that is 0 to 0.1%, and the balance is Fe and impurities, and satisfies the following formula (iv).
20.0 ≦ Cr + 3 × Mo−2.5 × B-17 × C ≦ 45.0 (iv)

C: 0.001 to 0.15%
C depends on the structure and composition of the parent phase, particularly the Cr content in the steel, but steel as Cr-based M ₂₃ C ₆ type Cr-based carbide (hereinafter sometimes simply referred to as “M ₂₃ C ₆ ”). May precipitate out. By setting the C content to 0.001% or more, M ₂₃ C ₆ is precipitated and the contact resistance characteristics are improved. On the other hand, if C is contained excessively, the productivity is remarkably deteriorated. Therefore, the C content is set to 0.001 to 0.15%.

When Cr-based carbides such as M ₂₃ C ₆ are not used, by suppressing the C content low, it is possible to prevent deterioration of corrosion resistance due to sensitization, improve room temperature toughness, and improve productivity. become. Sensitization can be easily confirmed by a sulfuric acid-copper sulfate corrosion test specified in JIS G 0575. When intergranular corrosion occurs, it becomes impossible to maintain the corrosion resistance in the polymer electrolyte fuel cell, so it is preferable to suppress sensitization. On the other hand, if the C content is extremely reduced, the scouring time becomes longer and the scouring cost increases. For this reason, C content is good also as 0.001% or more and less than 0.020%. In this case, the C content is preferably 0.0015% or more, and preferably less than 0.010%.

In addition, when a Cr-based carbide such as M ₂₃ C ₆ is actively used, the C content may be 0.020 to 0.15%. In this case, the C content is preferably 0.030% or more, and preferably 0.14% or less.

Si: 0.01 to 1.5%
Si is a deoxidizing element as effective as Al in mass-produced steel. When the Si content is less than 0.01%, not only deoxidation becomes unstable, but also the amount of Al added increases and the production cost increases. Also, steel surface flaws are likely to occur. On the other hand, if the Si content exceeds 1.5%, the moldability deteriorates. Therefore, the Si content is set to 0.01 to 1.5%. The Si content is preferably 0.05% or more, and more preferably 0.1% or more. Moreover, it is preferable that Si content is 1.2% or less, and it is more preferable that it is 1.0% or less.

Mn: 0.01 to 1.5%
Mn has an effect of fixing S in steel as a Mn-based sulfide, and has an effect of improving hot workability. On the other hand, if the Mn content exceeds 1.5%, the adhesion of the high-temperature oxide scale formed on the surface during heating during production is reduced, and scale peeling that causes surface roughness is likely to occur. Therefore, the Mn content is set to 0.01 to 1.5%. The Mn content is preferably 0.05% or more, and more preferably 0.1% or more. Further, the Mn content is preferably 1.2% or less, and more preferably 1.0% or less.

P: 0.035% or less P is a harmful impurity element along with S. If the P content exceeds 0.035%, the productivity decreases. Therefore, the P content is 0.035% or less.

S: 0.01% or less S is an impurity element extremely harmful to corrosion resistance. For this reason, S content shall be 0.01% or less. Depending on the coexisting elements in steel and the amount of S in steel, S is mostly precipitated as Mn-based sulfides, Fe-based sulfides, or composite non-metallic precipitates with these composite sulfides and oxides. is doing.

In the polymer electrolyte fuel cell separator environment, any non-sulfide sulfide precipitate of any composition will act as a starting point for corrosion to some extent, but it will maintain the passive film and elute metal ions. Harmful to suppression. The S content of ordinary mass-produced steel is more than 0.005% to around 0.008%, but in order to suppress the harmful effects described above, the S content should be 0.003% or less. Preferably, it is 0.002% or less, more preferably less than 0.001%. The lower the S content, the better. It is possible to make the S content less than 0.001% at an industrial mass production level with a slight increase in production cost if the current refining technology is used.

Cr: 22.5-35.0%
Cr is an element having an action of ensuring the corrosion resistance of the base material. The higher the Cr content, the higher the corrosion resistance. Also, in order to precipitate M _{2 B} in the steel material, it is necessary to include Cr. On the other hand, if the Cr content exceeds 35.0%, production on a mass production scale becomes difficult. Therefore, the Cr content is 22.5 to 35.0%.

In addition, by precipitation of M ₂ B, the Cr concentration that contributes to the improvement of the corrosion resistance in the matrix phase may be lower than the Cr concentration in the molten steel stage, and the corrosion resistance may be lowered. In order to ensure corrosion resistance inside the polymer electrolyte fuel cell with a C content of 0.001% or more and less than 0.020%, it is preferable to satisfy the following formula (v).
20.0 ≦ Cr + 3 × Mo−2.5 × B ≦ 45.0 (v)

Also, Cr is a necessary element when M ₂₃ C ₆ is deposited. By precipitation of M ₂ B and M ₂₃ C ₆ , the Cr concentration that contributes to improving the corrosion resistance in the matrix may be lower than the Cr concentration at the molten steel stage, and the corrosion resistance may be lowered. The C content is 0.020 to 0.15%, and in order to ensure the corrosion resistance inside the polymer electrolyte fuel cell, it is preferable to satisfy the following formula (iv).
20.0 ≦ Cr + 3 × Mo−2.5 × B-17 × C ≦ 45.0 (iv)

Mo: 0.01 to 6.0%
Mo has an effect of improving the corrosion resistance in a small amount as compared with Cr. Further, even if Mo is eluted, the influence on the performance of the catalyst supported on the anode and cathode is relatively small. This is thought to be because the eluted Mo exists as molybdate ions, which are anions, so that the influence of inhibiting the proton conductivity of the fluorine-based ion exchange resin membrane having a hydrogen ion (proton) exchange group is small. .

However, if Mo is contained in an amount exceeding 6.0%, it is difficult to avoid precipitation of intermetallic compounds such as sigma phase during the production, and production is difficult due to the problem of steel embrittlement. Mo is an expensive additive element. Therefore, the Mo content is set to 0.01 to 6.0%. The Mo content is preferably 0.05% or more, and preferably less than 5.0%.

Ni: 0.01 to 6.0%
Ni is an element that improves corrosion resistance and toughness. However, if the Ni content exceeds 6.0%, it becomes difficult to obtain a ferrite single phase structure even if heat treatment is applied industrially. Therefore, the Ni content is set to 0.01 to 6.0%. The Ni content is preferably 0.03% or more.

Cu: 0.01 to 1.0%
Cu is inevitably mixed in by 0.01% or more from the melting raw material. Although it is possible to dissolve at less than 0.01%, the production cost increases. If the Cu content exceeds 1.0%, hot workability will be reduced, and it will be difficult to ensure mass productivity. Therefore, the Cu content is set to 0.01 to 1.0%. Cu needs to be dissolved in the matrix. When dispersed as a metal-based precipitate, it becomes a starting point for corrosion in the fuel cell, resulting in a decrease in cell performance. The Cu content is preferably 0.02% or more, and preferably 0.8% or less.

N: 0.035% or less N is an element that is contained in steel as an impurity and deteriorates room temperature toughness. Therefore, the N content is 0.035% or less. Industrially, the N content is desirably 0.007% or less. However, excessively reducing the N content results in a significant increase in melting costs. For this reason, it is preferable that N content is 0.001% or more, and it is more preferable that it is 0.002% or more.

V: 0.01 to 0.35%
V is not an intentionally added element, but is unavoidably contained in a Cr source used as a melting raw material during mass production. V improves the room temperature toughness of ferritic stainless steel, albeit slightly. For this reason, the V content is set to 0.01 to 0.35%. The V content is preferably 0.03% or more, and preferably 0.30% or less.

B: 0.5 to 1.0%
When B is added at the molten steel stage, almost all of it precipitates as M ₂ B due to the eutectic reaction at the time of solidification. M ₂ B precipitated and dispersed in the steel material and exposed to the surface improves the surface conductivity and also serves as a precipitation nucleus for controlling the precipitation of M ₂₃ C ₆ . If the B content is less than 0.5%, the amount of M ₂ B deposited is small and it is difficult to ensure the surface conductivity. On the other hand, if the content exceeds 1.0%, the ductility is remarkably lowered and it becomes difficult to produce a steel material. Therefore, the B content is 0.5 to 1.0%. The B content is preferably 0.5% or more, and preferably 0.85% or less.

Al: 0.001 to 6.0%
In addition to being a ferrite forming element, Al is an effective deoxidizing element. Since B, which is essential, is an element having a strong binding force with oxygen in the molten steel, it is necessary to sufficiently reduce the oxygen concentration in the molten steel by Al deoxidation. Therefore, it is necessary to contain 0.001% or more of Al. On the other hand, when an amount of Al exceeding 6.0% is contained, an aluminum oxide film having poor conductivity is easily generated on the steel material surface, and the manufacturing cost increases. Therefore, the Al content is made 0.001 to 6.0%. The Al content is preferably 0.01% or more, and preferably 5.5% or less.

Sn: 0.02 to 2.50%
Sn is dissolved in the matrix phase by adding it as an alloy element in the molten steel stage. As described above, Sn dissolved in the mother phase is not only the surface of the mother phase but also M _{2 due to the} acid solution treatment performed in advance or the gentle mother phase dissolution that occurs during the operation of the fuel cell. The surface of B is also concentrated as metallic tin or tin oxide. Metal tin and tin oxide have semiconducting properties, and the surface contact resistance value in an oxidizing atmosphere is about 2 to 3 times the surface contact resistance value in a non-oxidizing atmosphere. Get higher. This action exerts an action of suppressing a local cell reaction that occurs transiently at the time of starting the polymer electrolyte fuel cell.

If the Sn content is less than 0.02%, such an effect may not be stably obtained. On the other hand, if the Sn content exceeds 2.50%, the productivity may decrease. Therefore, the Sn content is 0.02 to 2.50%. The Sn content is preferably 0.05% or more, and preferably 1.0% or less.

REM: 0 to 0.1%
Since REM (rare earth element) has an effect of improving hot manufacturability, it may be contained as necessary. However, excessive inclusion leads to an increase in manufacturing cost. Therefore, the REM content is 0.1% or less. The REM content is preferably 0.05% or less. In order to obtain the above effect, the REM content is preferably 0.001% or more, and more preferably 0.005% or more.

Here, in the present invention, REM refers to a total of 17 elements of Sc, Y and lanthanoid, and the content of REM means the total content of these elements. The lanthanoid is industrially added in the form of misch metal.

Nb: 0 to 0.35%
Ti: 0 to 0.35%
Nb and Ti are C and N stabilizing elements in steel. That is, Nb and Ti form carbides and nitrides in the steel. Therefore, in particular, when the C content is 0.001% or more and less than 0.020%, one or two of these may be contained as necessary. The contents of Ti and Nb are both 0.35% or less. The Nb and Ti contents are preferably 0.30% or less. In order to acquire said effect, it is preferable to contain 0.001% or more of 1 type or 2 types of Nb and Ti. Further, Nb is preferably contained so that the (Nb / C) value is 3.0 to 25.0, and Ti is contained so that the {Ti / (C + N)} value is 3.0 to 25.0. .

1-2. Precipitate in Ferritic Stainless Steel Material Ferritic stainless steel material included in anode electrode side cell constituting member 11 has a precipitate containing M ₂ B finely dispersed and precipitated in the steel material. This precipitate may further include a composite precipitate in which M ₂₃ C ₆ is precipitated on the surface using M ₂ B as a precipitation nucleus. Note that M in M ₂₃ C ₆ is Cr, Cr, Fe, or the like, and a part of C may be substituted with B. M in M ₂ B is Cr, Cr, Fe, or the like, and a part of B may be substituted with C.

A part of the precipitate protrudes from the surface of the steel material. M ₂ B or M ₂₃ C ₆ protruding from the surface of the steel material functions as a conductive path and has an effect of reducing contact resistance.

Even when M ₂ B and M ₂₃ C ₆ are projected from the surface of the steel material, a passive film (oxide film) is formed on the surface of these precipitates. However, the Cr concentration in M ₂ B and M ₂₃ C ₆ is higher than the Cr concentration in the matrix. In addition, the thickness of the passive film formed on the surface of M ₂ B or M ₂₃ C ₆ is thinner than the passive film covering the matrix surface. Therefore, these deposits are excellent in electronic conductivity and function as a conductive path.

There is a concern that M ₂ B protruding from the surface of the steel material may fall off. However, since M ₂ B is a metal precipitate, it is metal-bonded to the parent phase and does not fall off. Moreover, M ₂ B is a large and very hard precipitate. Therefore, it is mechanically crushed in each process of hot forging, hot rolling, and cold rolling, and is uniformly dispersed.

M ₂ B has electrical conductivity and is a very large metal precipitate even when crushed. Therefore, a sufficient function as a conductive path can be obtained even with M ₂ B alone. However, M ₂₃ C ₆ is more excellent in conductivity than M ₂ B. Therefore, by depositing M ₂₃ C ₆ excellent in conductivity on the surface of M ₂ B which is large and dispersed in a large amount, a composite precipitate having large and excellent conductivity is dispersed and exists. A more desirable surface state can be obtained as a steel material used for the pole-side cell constituent member.

Here, M ₂ B is precipitated by a eutectic reaction that proceeds at the end of solidification. Therefore, it has the characteristics that the composition is uniform and is extremely stable thermally. There is no re-dissolution, re-precipitation, or component change due to the thermal history in the manufacturing process of the steel material.

On the other hand, although M ₂₃ C ₆ depends on the C content in the steel, a part or all of it is dissolved in the heating process and re-precipitated on the surface of M ₂ B in the subsequent cooling process. That is, by performing a heat treatment in which appropriate heating and cooling conditions are set, it is possible to obtain a composite precipitate in which M ₂₃ C ₆ is precipitated on the surface using M ₂ B as a precipitation nucleus.

2. Cathode pole side cell constituent member The cathode pole side cell constituent member 12 includes a stainless steel material described below. In addition, it is preferable that the member used for at least the surface part of a gas flow path among the cathode electrode side cell structural members 12 is comprised by the stainless steel material mentioned later.

2-1. Chemical composition of stainless steel material The stainless steel material contained in the cathode electrode side cell constituent member 12 limits the Sn content to less than 0.02%. The reason why the Sn content is limited to the above range will be described later.

The chemical composition of the above stainless steel material is as follows: C: 0.001 to 0.2%, Si: 0.01 to 1.5%, Mn: 0.01 to 2.5%, P: 0.035% Hereinafter, S: 0.01% or less, Cr: 16.0-35.0%, Mo: 0-7.0%, Ni: 0.01-50.0%, Cu: 0.01-3.0 %, N: 0.001 to 0.4%, V: 0 to 0.35%, B: 0.5 to 1.0%, Al: 0.001 to 6.0%, W: 0 to 4. 0%, Sn: less than 0.02%, REM: 0 to 0.1%, Nb: 0 to 0.35%, Ti: 0 to 0.35%, and the balance: Fe and impurities. iv) It is preferable to satisfy the formula.
20.0 ≦ Cr + 3 × Mo−2.5 × B-17 × C ≦ 45.0 (iv)

The above stainless steel material may be a ferritic stainless steel material or an austenitic stainless steel material. Examples of the ferritic stainless steel material include the following two types of ferritic stainless steel materials, and examples of the austenitic stainless steel material include the following one type of austenitic stainless steel material. Each chemical composition will be described in detail.

In addition, since the directivity is recognized in the formability of the steel material that is a rolled material when it has a two-phase structure of a ferrite phase and an austenite phase, a duplex stainless steel material is a cell for a polymer electrolyte fuel cell. It is not suitable as a component.

(C) C: 0.001% or more and less than 0.020%, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.035% or less, S: 0.0. 01% or less, Cr: 22.5 to 35.0%, Mo: 0.01 to 6.0%, Ni: 0.01 to 6.0%, Cu: 0.01 to 1.0%, N: 0.035% or less, V: 0.01 to 0.35%, B: 0.5 to 1.0%, Al: 0.001 to 6.0%, Sn: less than 0.02%, REM: 0 A ferritic stainless steel material that is 0.1%, Nb: 0-0.35%, Ti: 0-0.35%, and the balance: Fe and impurities, satisfying the following formula (v).
20.0 ≦ Cr + 3 × Mo−2.5 × B ≦ 45.0 (v)

(D) C: 0.020 to 0.15%, Si: 0.01 to 1.5%, Mn: 0.01 to 1.5%, P: 0.035% or less, S: 0.01% Hereinafter, Cr: 22.5-35.0%, Mo: 0.01-6.0%, Ni: 0.01-6.0%, Cu: 0.01-1.0%, N: 0.00. 035% or less, V: 0.01 to 0.35%, B: 0.5 to 1.0%, Al: 0.001 to 6.0%, Sn: less than 0.02%, REM: 0 to 0 1% and the balance: ferritic stainless steel material that is Fe and impurities and satisfies the following formula (iv).
20.0 ≦ Cr + 3 × Mo−2.5 × B-17 × C ≦ 45.0 (iv)

(E) C: 0.005 to 0.20%, Si: 0.01 to 1.5%, Mn: 0.01 to 2.5%, P: 0.035% or less, S: 0.01% Hereinafter, Cr: 16.0 to 30.0%, Mo: 0 to 7.0%, Ni: 7.0 to 50.0%, Cu: 0.01 to 3.0%, N: 0.001 to 0.4%, V: 0.3% or less, B: 0.5 to 1.0%, Al: 0.001 to 0.2%, Sn: less than 0.02%, balance: Fe and impurities An austenitic stainless steel material that satisfies the following formula (vi).
24.0 ≦ Cr + 3 × Mo−2.5 × B−17 × C ≦ 45.0 (vi)

2-2. Chemical composition of ferritic stainless steel C: 0.001 to 0.15%
C may precipitate in steel as M ₂₃ C ₆ mainly composed of Cr, although it depends on the structure and composition of the parent phase, particularly the Cr content in the steel. By setting the C content to 0.001% or more, M ₂₃ C ₆ is precipitated and the contact resistance characteristics are improved. On the other hand, if C is contained excessively, the productivity is remarkably deteriorated. Therefore, the C content is set to 0.001 to 0.15%.

When Cr-based carbides such as M ₂₃ C ₆ are not used, by suppressing the C content low, it is possible to prevent deterioration of corrosion resistance due to sensitization, improve room temperature toughness, and improve productivity. become. On the other hand, if the C content is extremely reduced, the scouring time becomes longer and the scouring cost increases. For this reason, C content is good also as 0.001% or more and less than 0.020%. In this case, the C content is preferably 0.0015% or more, and preferably less than 0.010%.

V: 0.01 to 0.35%
V is not an element intentionally added, but is unavoidably contained in a Cr source used as a melting raw material during mass production. V improves the room temperature toughness of ferritic stainless steel, albeit slightly. For this reason, the V content is set to 0.01 to 0.35%. The V content is preferably 0.03% or more, and preferably 0.30% or less.

Sn: Less than 0.02% As described above, the cathode electrode side cell constituent member is used in an oxidizing atmosphere even during normal operation. Therefore, when a stainless steel material containing Sn is applied to the cathode electrode side cell constituent member, tin oxide having poor conductivity becomes thicker on the surface of the parent phase and the like. When the Sn content is 0.02% or more, the increase in the contact electric resistance becomes remarkable, and the battery output decreases. For this reason, Sn content shall be less than 0.02%. The Sn content is preferably 0.015% or less. The Sn content may be at the impurity level.

2-3. Chemical composition of austenitic stainless steel C: 0.005 to 0.20%
C is an austenite phase stabilizing element. If the C content is less than 0.005%, the austenite phase becomes unstable and sensitization is likely to occur, and the corrosion resistance due to sensitization is liable to be lowered, and the normal temperature toughness is lowered and productivity is lowered. On the other hand, if C is contained excessively, the productivity is remarkably deteriorated. Therefore, the C content is set to 0.005 to 0.20%. The C content is preferably 0.015% or more. The C content is preferably 0.15% or less, and more preferably 0.025% or less.

Si: 0.01 to 1.5%
Si is a deoxidizing element as effective as Al in mass-produced steel. When the Si content is less than 0.01%, not only deoxidation becomes unstable, but also the amount of Al added increases and the production cost increases. Steel surface flaws are also likely to occur. On the other hand, if the Si content exceeds 1.5%, the moldability deteriorates. Therefore, the Si content is set to 0.01 to 1.5%. The Si content is preferably 0.05% or more, and more preferably 0.1% or more. Moreover, it is preferable that Si content is 1.2% or less, and it is more preferable that it is 1.0% or less.

Mn: 0.01 to 2.5%
Mn has an effect of fixing S in steel as a Mn-based sulfide, and has an effect of improving hot workability. If the Mn content is less than 0.01%, the above effect cannot be obtained. On the other hand, when the Mn content exceeds 2.5%, the adhesion of the high-temperature oxide scale formed on the surface during heating during production is reduced, and scale peeling that causes surface roughness is likely to occur. Therefore, the Mn content is set to 0.01 to 2.5%. The Mn content is preferably 0.05% or more, and more preferably 0.1% or more. Moreover, it is preferable that Mn content is 1.0% or less, and it is more preferable that it is 0.6% or less.

P: 0.035% or less P is a harmful impurity element along with S. If the P content exceeds 0.035%, the productivity decreases. Therefore, the P content is 0.035% or less. From the viewpoint of manufacturability, the P content is preferably 0.030% or less.

Cr: 16.0-30.0%
Cr is an element having an action of ensuring the corrosion resistance of the base material. The higher the Cr content, the higher the corrosion resistance. Also, in order to precipitate M _{2 B} in the steel material, it is necessary to include Cr. On the other hand, since Cr is a ferrite-forming element, if the Cr content exceeds 30.0%, it is necessary to contain a large amount of Ni, which is an austenite-forming element, in order to stabilize the austenite phase. The decrease becomes noticeable. Therefore, the Cr content is 16.0 to 30.0%.

In addition, Cr is a necessary element also when M ₂₃ C ₆ is deposited. By precipitation of M ₂ B and M ₂₃ C ₆ , the Cr concentration that contributes to improving the corrosion resistance in the matrix may be lower than the Cr concentration at the molten steel stage, and the corrosion resistance may be lowered. In order to ensure corrosion resistance inside the polymer electrolyte fuel cell, it is preferable to satisfy the following formula (vi).
24.0 ≦ Cr + 3 × Mo−2.5 × B−17 × C ≦ 45.0 (vi)

Mo: 0 to 7.0%
Mo has an effect of improving the corrosion resistance in a small amount as compared with Cr. Since the inside of the polymer electrolyte fuel cell is a severe environment as a corrosive environment, Mo may be contained if necessary. Further, even if Mo is eluted, the influence on the performance of the catalyst supported on the anode and cathode is relatively small. This is thought to be because the eluted Mo exists as molybdate ions, which are anions, so that the influence of inhibiting the proton conductivity of the fluorine-based ion exchange resin membrane having a hydrogen ion (proton) exchange group is small. .

However, if Mo is contained in an amount exceeding 7.0%, it is difficult to avoid precipitation of intermetallic compounds such as sigma phase during the production, and production is difficult due to the problem of steel embrittlement. Mo is an expensive additive element. Therefore, the Mo content is 7.0% or less. The Mo content is preferably 6.5% or less. In order to acquire the said effect, it is preferable that Mo content is 0.5% or more.

Ni: 7.0 to 50.0%
Since Ni is an austenite forming element, it is contained by 7.0% or more. However, since Ni is an expensive element, if it is contained in excess of 50.0%, the moldability deteriorates and it becomes unsuitable for processing as a structural member, and the production cost increases, so that the polymer electrolyte fuel cell It becomes difficult to apply as a cell structure member. Therefore, the Ni content is 7.0 to 50.0%.

Cu: 0.01 to 3.0%
Since Cu is an austenite forming element, it is contained in an amount of 0.01% or more. However, if the Cu content exceeds 3.0%, the corrosion resistance may decrease. Therefore, the Cu content is set to 0.01 to 3.0%. Cu needs to be dissolved in the matrix. When dispersed as a metal-based precipitate, it becomes a starting point for corrosion in the fuel cell, resulting in a decrease in cell performance. The Cu content is preferably 0.02% or more, and preferably less than 0.8%.

N: 0.001 to 0.4%
Since N is the cheapest austenite forming element, 0.001% or more is contained. However, when the N content exceeds 0.4%, the manufacturability is remarkably lowered and the thin plate workability is also remarkably lowered. Therefore, the N content is set to 0.001 to 0.4%. The N content is preferably 0.002% or more, and preferably 0.1% or less.

V: 0.3% or less V is inevitably contained in a Cr source added as a melting raw material used in mass production. V does not need to be added intentionally, but excessive reduction of the content causes an increase in cost. Therefore, the V content is 0.3% or less.

Al: 0.001 to 0.2%
Al is added at the molten steel stage as a deoxidizing element. Since B, which is essential, is an element having a strong binding force with oxygen in the molten steel, it is necessary to sufficiently reduce the oxygen concentration in the molten steel by Al deoxidation. Therefore, the Al content is set to 0.001 to 0.2%.

2-4. Precipitate in stainless steel material The stainless steel material contained in the cathode electrode side cell constituting member 12 may have a precipitate containing M ₂ B finely dispersed and precipitated in the steel material, if necessary. Further, this precipitate may further include a composite precipitate in which M ₂₃ C ₆ is precipitated on its surface with M ₂ B as a precipitation nucleus. And when it has said precipitate, the one part protrudes from the surface of steel materials. M ₂ B or M ₂₃ C ₆ protruding from the surface of the steel material functions as a conductive path and has an effect of reducing contact resistance.

2-5. Corrosion-resistant plating layer on the surface of the stainless steel material The stainless steel material included in the cathode electrode side cell constituting member 12 may have a corrosion-resistant plating layer having conductivity on the surface of the steel material, if necessary. By having a corrosion-resistant plating layer on the steel material surface, the contact resistance is greatly reduced. Examples of the corrosion resistant plating layer include a gold plating layer.

3. Manufacturing Method There are no particular restrictions on the manufacturing conditions of the ferritic stainless steel material included in the anode electrode side cell constituent member 11 and the stainless steel material included in the cathode electrode side cell constituent member 12. For example, it can manufacture by performing a hot rolling process, an annealing process, a cold rolling process, and a final annealing process in order with respect to steel which has said chemical composition.

In the hot rolling process, it is preferable to adjust the crystal grain size and control the precipitation of M ₂₃ C ₆ by utilizing the phase transformation of α phase and γ phase at high temperature. Specifically, the crystal grain size and the intragranular precipitates can be controlled by controlling so as to have an α-γ two-phase structure during rolling.

Subsequently, it is desirable to roughen the surface so that precipitates protrude from the steel surface as necessary. Although there is no particular limitation on the roughening treatment method, pickling (etching) treatment is most excellent in mass productivity. In particular, an etching process in which an aqueous ferric chloride solution is sprayed is preferable.

The spray etching process using a high-concentration ferric chloride aqueous solution is widely used as an etching process for stainless steel, and the processing liquid after use can be reused. In general, the spray etching process using a high concentration ferric chloride aqueous solution is often performed as a local thinning process or a through-drilling process after the masking process. Used in the cutting process for

The spray etching process will be described in more detail. The ferric chloride solution used is a very concentrated acid solution. The ferric chloride solution concentration is quantified by the Baume degree, which is an indication measured with a Baume hydrometer. The etching treatment for surface roughening may be performed by dipping in a stationary state or flowing ferric chloride solution, but it is desirable to roughen the surface by spray etching. This is because it is possible to control the etching depth, the etching rate, and the degree of surface roughening efficiently and accurately in production on an industrial scale. The spray etching process can be controlled by the pressure discharged from the nozzle, the amount of liquid, the liquid flow velocity (linear flow velocity) on the surface of the etching material, the spray hit angle, and the liquid temperature.

It is desirable that the ferric chloride solution to be applied has a low copper ion concentration and Ni concentration in the liquid, but there is no problem in purchasing and using industrial products that are generally distributed in Japan. The concentration of the ferric chloride solution used is 40 to 51 ° in terms of Baume degree. If the concentration is less than 40 °, the tendency to perforate corrosion becomes strong and is not suitable for surface roughening. On the other hand, if it exceeds 51 °, the etching rate is remarkably slow, and the deterioration rate of the liquid is also fast. It is not suitable as a roughening solution for the surface of the core material of a polymer electrolyte fuel cell separator that needs to be mass-produced.

The ferric chloride solution concentration is more preferably 42 to 46 ° in terms of Baume degree. The temperature of the ferric chloride solution is preferably 20 to 60 ° C. When the temperature decreases, the etching rate decreases, and when the temperature increases, the etching rate increases. When the temperature is high, the liquid deterioration proceeds in a short time.

The degree of liquid deterioration can be continuously quantitatively evaluated by measuring the natural potential of a platinum plate immersed in a ferric chloride solution. As a simple method of recovering the liquid capacity when the liquid deteriorates, there is a method of adding a new liquid or exchanging the whole liquid with a new liquid. Further, chlorine gas may be blown.

After etching with ferric chloride solution, immediately clean the surface with a large amount of clean water. This is because the surface deposit (precipitate) derived from the ferric chloride solution diluted with the washing water is washed away. Spray cleaning that increases the flow velocity on the surface of the material is desirable, and it is also desirable to use cleaning that immerses in running water for a while after spray cleaning.

As described above, in the ferritic stainless steel material included in the anode electrode side cell constituting member 11, Sn dissolved in the matrix phase is preliminarily metal tin or oxidized on the surface of the matrix phase and the surface of the precipitate. It is desirable to concentrate it as tin.

During cleaning and the subsequent drying process, various metal chlorides and hydroxides adhering to the surface change to a more stable metal or its oxide in the atmosphere. Sn is concentrated as metal tin or tin oxide on the steel material surface and the precipitate surface protruding from the steel material surface. All of them have electrical conductivity and exhibit semiconductor characteristics by being concentrated on the surface.

After the surface roughening treatment with the ferric chloride aqueous solution, spray washing using a sulfuric acid aqueous solution or immersion treatment may be further performed. Since the ferric chloride solution used in the previous step has a very low pH and a high flow rate, metallic tin and tin oxide are in a state where surface concentration is difficult. However, for example, spray cleaning or immersion treatment using a sulfuric acid aqueous solution of less than 20% is slower than the liquid flow rate (linear flow rate) on the etching material surface in spray cleaning with ferric chloride solution, or close to standing. When carried out in the state, surface enrichment of tin oxide is promoted.

The concentration of sulfuric acid solution to be applied varies depending on the corrosion resistance of the material to be treated. When soaked, the concentration is adjusted so as to be corrosive enough to start to generate bubbles on the surface. Concentration conditions that generate violent bubbles with corrosion are undesirable. This is because the above-mentioned metal or its oxide may interfere with concentration on the surface, and there is a possibility that the function of lowering the contact resistance immediately after application of the polymer electrolyte fuel cell may be reduced.

Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to these examples.

The material (steel material) used for the anode electrode side separator and the cathode electrode side separator is any one of steel materials 1 to 6 shown in Table 1. Steel materials 1 to 6 are all bright annealing specification (BA specification) cold rolled stainless steel coil materials, with a plate thickness of 0.126 mm and a coil width of 240 mm. The molding process was performed using a dedicated progressive die and a general-purpose 250-ton press.

FIG. 3 is a photograph showing the shape of the separator used in the example. The separator channel is a serpentine type with three parallel channels, the channel width is 1 mm, and the depth is 0.7 mm. A separator having the same shape was inverted and arranged on the cathode side and the anode side to constitute a polymer electrolyte fuel cell. The effective reaction area as a cell is 100 cm ² .

As the MEA, a commercially available integrated MEA in which a catalyst layer was provided on both sides of a polymer membrane and carbon paper was applied as a diffusion layer was used. Platinum catalyst supported amount of anode side 0.05 mg / cm ^2, a cathode-side 0.4 mg / cm ^2.

In steel materials 1 to 5, M ₂ B was dispersed in the steel. In the steel materials 2 and 4, M ₂₃ C ₆ was further deposited on the surface of the dispersed M ₂ B. In steel materials 2 and 4, there was almost no M ₂ B precipitated alone, and M ₂₃ C ₆ precipitated alone was an amount that could not be easily confirmed.

Thereafter, ferrous chloride aqueous solution spray etching treatment for adjusting the surface roughness was performed on the steel materials 1 to 6 described above. The amount of welding is 8 μm on each side, and the plate thickness after spray etching is 0.11 mm.

Furthermore, the steel material 6 was provided with conductive corrosion-resistant plating having an average weight per unit area of 20 nm by gold plating in a cyan bath.

By adjusting the surface roughness, M ₂ B precipitated in the steel in steel materials 1, 3 and 5, and M ₂₃ C ₆ was precipitated on the surface in steel materials 2 and 4 with M ₂ B as a precipitation nucleus. A part of each of the composite precipitates, M ₂₃ C ₆ , protruded from the steel surface.

Immediately after spray etching, the substrate was washed with a clean acid solution and water. Thereby, in the steel materials 1 and 2 containing Sn in the steel, a composite precipitate in which M ₂₃ C ₆ is precipitated on the surface of the parent phase and M ₂ B and M ₂ B as precipitation nuclei, and M None of the surface of ₂₃ C _6, metallic tin and tin oxide is in a state of covering thin surface.

The surface roughness was adjusted by the concentration of the ferric chloride solution, the liquid temperature, the spray speed (linear flow velocity on the plate surface), and the spray treatment time. Specifically, spray treatment was performed using a ferric chloride aqueous solution having a Baume degree of 43 degrees and a temperature of 35 ° C. The spray discharge pressure was 2 kg / cm ² and the spray time was about 40 seconds.

In order to construct the cell, an EPDM gasket and a PEN film having tackiness were used. After integration as a cell, it was confirmed after assembly as a fuel cell that there was no leakage of hydrogen gas and cooling water.

The fuel cell evaluation operation equipment used in the examples was manufactured by combining commercially available equipment. In the fuel cell evaluation operation facility, a gas retention tank having an internal volume of 50 ml was provided which was directly connected to the anode electrode side gas inlet and the anode electrode side gas outlet of the fuel cell stack to keep the gas temperature from decreasing. This corresponds to a capacity 10 times the set hydrogen gas flow rate at startup.

In addition, a three-way solenoid valve is provided in the piping in front of the entry side tank so that the gas can be instantaneously switched from air to hydrogen and from hydrogen to air in the anode side supply gas to the fuel cell. This makes it possible to reproduce the H ⁺ deficiency state that occurs on the anode electrode side when the fuel cell is activated.

Immediately after switching the three-way solenoid valve, the air in the gas retention tank installed at the anode electrode side gas inlet is replaced with hydrogen gas over a period of 10 to 20 seconds. During this time, the anode electrode flows into the anode electrode side in the cell. The hydrogen concentration in the side gas also decreases because it flows in diluted with the air in the residence tank installed at the anode electrode side gas inlet, and gradually increases with the progress of the hydrogen gas replacement in the residence tank. It becomes.

On the other hand, on the anode electrode side outlet side of the cell, the anode electrode side gas after the reaction in the battery is further diluted by the air in the gas retention tank installed on the outlet side. Although the reaction area of the cell used in this example is small and the internal volume in the flow path is small, the gas retention tank is connected to the anode gas electrode side gas inlet and the anode gas electrode side gas outlet for about 20 seconds. It is possible to reproduce the transient in-cell conditions at the time of starting the battery.

The fuel cell is assembled in a single-cell configuration. When starting up, nitrogen gas replacement is performed on both the anode and cathode sides, including the inside of the piping, and then air is introduced into the anode and hydrogen is introduced into the cathode. Introduced and started the battery reaction.

The gas flow rate was kept constant such that hydrogen was 300 cc / min and air was constant at 600 cc / min and the current density was constant at 0.1 A / cm ² .

Performance evaluation was performed by measuring the degree of cell voltage decrease and cell resistance increase, and the amount of MEA film metal contamination after the end of operation. The amount of MEA film metal contamination indicates the degree of corrosion of the separator. Specifically, the amounts of Fe, Cr, Ni, Sn and Pt were quantified. However, since the amounts of Cr, Ni, Sn, and Pt were small, the amount of Fe was used as an indicator of the degree of corrosion of the separator.

When the amount of Fe contaminated with the MEA film increases, the film degradation of the polymer film progresses due to the Fenton reaction accompanied by the generation of hydrogen peroxide, and the elution of the Pt catalyst progresses to deteriorate the MEA film performance. If the operation time becomes longer and the polymer membrane is perforated, it becomes difficult to continue the operation of the fuel cell. In this example, no perforation occurred.

The electric cell resistance value during operation as a battery was measured with a resistance meter (MODEL 3565) manufactured by Tsuruga Electric Co., Ltd. The displayed cell resistance value is an AC impedance value at a frequency of 1 kHz according to the four-terminal method.

The increase in the cell resistance value indicates an increase in the polymer film resistance value, and is an index for confirming the dry and wet state of the MEA during battery operation and the decrease in MEA film performance. When the cell resistance value starts to increase greatly exceeding 2 mΩ, it indicates that the deterioration of MEA is progressing.

Table 2 summarizes the types of steel materials used for the anode-side and cathode-side separators of each cell and the measurement results described above.

As shown in Table 2, in this example, the cell resistance value after the operation is less than 1 mΩ, and it can be judged that the deterioration of the polymer film itself is hardly a problem.

In addition, when the cell voltage is compared and examined in detail, there is no difference in performance between the example and the comparative example in the cell voltage values after 100 hours and 2000 hours after the start of operation, and it is inevitable in the fuel cell operation. It was confirmed that the cell voltage performance was in the range of deterioration.

For this reason, the present embodiment does not introduce air to the anode electrode side while hydrogen is filled on the anode electrode side, and the set current value during operation is constant, and the battery is not paused or started. In the example environment, it can be seen that there is no difference in performance degradation due to the separator material. That is, the effect of the polymer electrolyte fuel cell according to the present invention could not be confirmed under the constant current operation environment in which air does not enter the anode side. In the result of quantitative determination of the amount of Fe ions in MEA after the operation was completed, an increase in the amount of Fe ions accompanying the operation could not be confirmed.

In Example 2, mode operation (repeated operation under a certain condition) was performed. At the first start-up, both the anode electrode side and the cathode electrode side were replaced with nitrogen gas, including the inside of the pipe, and then hydrogen was introduced into the anode electrode side and air was introduced into the cathode electrode side to start battery operation. During the entire evaluation time, air is not introduced to the anode side during operation.

However, in this example, in order to experimentally reproduce the potential increase that occurs at the time of starting the actual polymer electrolyte fuel cell, the cell voltage (constant) is 1.0 V from the outside while the anode side remains in the hydrogen atmosphere. Was set in the mode for voltage loading on the cell using the electronic load device.

Specific operation modes are: (s1) cell voltage 1.0 V (constant) holding operation for 20 seconds, (s2) holding operation for 5 minutes at a current density of 0.1 A / cm ² , (s3) current density of 0.2 A / cm 3 min holding operation at cm ² , (s4) 3 min holding operation at a current density of 0.3 A / cm ² , (s5) 5 min holding operation at a current density of 0.4 A / cm ² , and (s6) open circuit It is a repetition of 6 steps of holding for 20 seconds in a state (a state where no load is applied to the battery by an external power source).

The gas flow rate was 300 cc / min of hydrogen and 600 cc / min of air per current density of 0.1 A / cm ² . When the set current density is 0.4 A / cm ² , the set flow rates are 1200 cc / min for hydrogen and 2400 cc / min for air. In applying this separator, the optimum flow rate is determined to compensate for the most stable operation.

In the step of maintaining the open circuit state and maintaining the cell voltage of 1.0 V (constant), hydrogen gas was flowed at a flow rate of 300 cc / min. The battery operating temperature was 68 ° C. The cell voltage of 1.0 V is a cell voltage increase value confirmed as the main stack when hydrogen gas is introduced in a state where the anode electrode is filled with air. In stainless steel, it is an electric potential range called a overpassive region, and is a potential environment in which the passive film formed on the stainless steel surface changes into a stable overpassive film in the overpassive region. It can be regarded as an environment in which metal elution is likely to proceed due to surface coating changes. The evaluation operation time is 1000 hours, and the number of mode repetitions is 3600 cycles.

Table 3 summarizes the types of steel materials used for the anode and cathode electrode separators of each cell and the measurement results.

Since the cell voltage drop is larger than the cell voltage 100 hours after the start of operation in the constant current holding operation at 0.1 A / cm ² shown in Example 1, the MEA performance drop is caused under this mode operation condition. Can be confirmed.

However, the cell voltage after 1000 hours is almost the same as after 100 hours, and no significant cell voltage drop has occurred. It can be determined that the cell performance is stable. The Fe ion concentration in the MEA after the operation was also less than 100 ppb, and it was judged that the Fe ion concentration was not reached so as to promote performance degradation.

In Example 3, mode operation (repeated operation under a certain condition) was performed in a pattern similar to Example 2. However, at the first start-up, after performing nitrogen gas substitution on both the anode electrode side and the cathode electrode side including the inside of the pipe, the battery operation was started after introducing air into both the anode electrode side and the cathode electrode side.

In addition, in order to reproduce the potential increase that occurs at the start of an actual polymer electrolyte fuel cell in the laboratory, the three-way solenoid valve is switched during the open circuit maintenance mode so that air is supplied to the anode-side hydrogen atmosphere. The gas was replaced by hydrogen to air (flow rate 2400 cc / min, held for 20 seconds), and then the three-way solenoid valve was switched to introduce hydrogen gas to the anode electrode side at a flow rate of 300 cc / min. The 1.0 V (constant) load by the electronic load device from the outside is an operation for improving the reproducibility of the condition setting.

Specific operation modes are: (s1) cell voltage 1.0 V (constant) holding operation (20 seconds), (s2) holding operation at a current density of 0.1 A / cm ² for 5 minutes, (s3) current density 0. 3 min holding operation at 2 A / cm ² , (s4) 3 min holding operation at a current density of 0.3 A / cm ² , (s5) 5 min holding operation at a current density of 0.4 A / cm ² , and (s6 ) Repetition of holding for 20 seconds in an open circuit state (a state where no load is applied to the battery by an external power source). The evaluation operation time is 1000 hours, and the number of mode repetitions is 3600 cycles.

Table 4 summarizes the types of steel materials used for the anode-side and cathode-side separators of each cell and the measurement results.

The performance difference is not clear at 100 hours after the start of operation, but is clear at the cell voltage and cell resistance value after 1000 hours. If the cell voltage is 0.75 V or higher, it is judged that the performance is good. Test No. of the present invention example using a ferritic stainless steel material containing Sn only for the separator on the anode side. In 75-78 and 81-84, the performance degradation is small, and it can be judged that it is preferable as a combination of separator materials.

On the other hand, test No. of a comparative example using Sn-containing ferritic stainless steel material for both the anode electrode side and cathode electrode side separators. In 73, 74, 79 and 80, the increase in cell resistance is clear. It is judged that the elution (corrosion) of the stainless steel substrate and the generation of tin oxide that inevitably proceed on the cathode electrode side, which is an oxidizing atmosphere, are remarkable, and the surface contact resistance is increased. Even in the disassembly after the evaluation, tin oxide adhesion was significant on the cathode electrode separator surface including the MEA surface (diffusion layer).

Also, test No. of a comparative example using a stainless steel material not containing Sn for the separator on the anode electrode side. From 85 to 101, a clear cell voltage drop was confirmed.

Comparative test No. Although the performance of 102 was inferior to that in the case where the anode side separator material did not contain Sn, the cell voltage drop was relatively small. It can be determined that the cell voltage drop is relatively small due to the effect of gold plating applied to the cathode side.

On the other hand, test No. of the comparative example. 103-108, test no. Compared to 102, the cell voltage drop is larger. In the gold plating process, it is judged that there is an influence of the matrix corrosion from the plating defects that inevitably remain. It can be judged that galvanic corrosion from plating defects has progressed.

The superiority or inferiority can also be confirmed from the MEA analysis results after the evaluation. However, the battery performance deterioration due to the polymer film deterioration has not yet become apparent, and it has been determined that the cell voltage decrease due to the catalyst performance deterioration due to the carbon corrosion on the cathode side is the main.

According to this example, under the environment of the cycle operation in which air enters the anode electrode side, there is a difference in performance deterioration due to the separator material, and the effect of the present invention was confirmed.

1 Fuel Cell Stack 2 Solid Polymer Electrolyte Membrane 3 Fuel Electrode Membrane (Anode)
4 Oxidant electrode membrane (cathode)
5a, 5b Separator 6a, 6b Channel 10 Solid polymer fuel cell 11 Anode electrode side cell component 12 Cathode electrode side cell component 13 Anode electrode side fuel gas channel 14 Cathode electrode

side gas channel

15, 16 Diffusion Layers 17 and 18 Catalyst layer 19 Polymer membrane 20 MEA

Claims

A polymer electrolyte fuel cell cell comprising an anode electrode side cell component and a cathode electrode cell component,
The anode electrode side cell component is made of a ferritic stainless steel material, and the cathode electrode side cell component is made of a stainless steel material,
The ferritic stainless steel material constituting the anode electrode side cell constituent member has a chemical composition in mass% and Sn content of 0.02 to 2.50%, and
In the ferritic stainless steel material, there are precipitates containing M 2 B type boride finely dispersed and precipitated,
A part of the precipitate protrudes from the surface of the ferritic stainless steel material,
The stainless steel material constituting the cathode electrode side cell constituting member has a chemical composition in which the Sn content is less than 0.02% by mass%.
Solid polymer fuel cell.
The precipitate that the ferritic stainless steel material constituting the anode electrode side cell constituent member has,
A composite precipitate in which M 2 B type boride is used as a precipitation nucleus and M 23 C 6 type Cr-based carbide is precipitated on the surface thereof;
A part of the composite precipitate protrudes from the surface of the ferritic stainless steel material,
The polymer electrolyte fuel cell according to claim 1.
The stainless steel material constituting the cathode electrode side cell constituting member is:
In the stainless steel material, having a precipitate containing M 2 B type boride finely dispersed and precipitated,
A part of the precipitate protrudes from the surface of the stainless steel material.
The polymer electrolyte fuel cell according to claim 1 or 2.
The precipitate that the stainless steel material constituting the cathode electrode side cell constituting member has,
A composite precipitate in which M 2 B type boride is used as a precipitation nucleus and M 23 C 6 type Cr-based carbide is precipitated on the surface thereof;
A part of the composite precipitate protrudes from the surface of the stainless steel material.
The polymer electrolyte fuel cell according to claim 3.
The stainless steel material constituting the cathode electrode side cell constituting member is:
It has a corrosion-resistant plating layer with conductivity on the surface,
The polymer electrolyte fuel cell according to claim 1 or 2.
The solid polymer fuel cell is provided with the cell according to any one of claims 1 to 5.
Solid polymer fuel cell stack.