Solid polymer fuel cell and water electrolysis device

Abstract

Provided are a solid polymer fuel cell and a water electrolysis device which each include: a membrane / electrode / gas diffusion layer assembly (MEGA) comprising a solid polymer electrolyte membrane, catalyst layers bonded to both surfaces of the solid polymer electrolyte membrane, and a gas diffusion layer disposed on the outer side of each catalyst layer; and a deterioration inhibitor added to any portion of the MEGA. The deterioration inhibitor includes a complex comprising an Fe ion and ligands coordinated thereto. The ligands include 1,10-phenanthroline-5,6-dione and / or a derivative thereof. The content of the deterioration inhibitor is preferably 0.0001-10.0 mol%.

Description

Polymer electrolyte fuel cells and water electrolysis devices

[0001] The present invention relates to a polymer electrolyte fuel cell and a water electrolysis device, and more particularly to a polymer electrolyte fuel cell and a water electrolysis device containing an additive that has the effect of suppressing degradation of a solid polymer electrolyte.

[0002] A polymer electrolyte fuel cell includes a membrane electrode assembly (MEA) in which catalyst layers are bonded to both sides of an electrolyte membrane. A gas diffusion layer is usually disposed on the outside of the catalyst layer. A laminate of the MEA and the gas diffusion layer is also called a membrane-electrode-gas diffusion layer assembly (MEGA). Furthermore, a current collector (separator) equipped with a gas flow path is disposed on the outside of the gas diffusion layer. A polymer electrolyte fuel cell usually includes a structure (stack) in which a plurality of unit cells each consisting of such a MEGA and current collector are stacked. A polymer electrolyte membrane (PEM) water electrolysis device has a similar structure to a polymer electrolyte fuel cell, although its usage differs from that of a polymer electrolyte fuel cell.

[0003] The electrolyte contained in MEGA is said to be attacked and deteriorated by radicals generated directly by the direct reaction or electrochemical reaction between oxygen and hydrogen, or by radicals generated via hydrogen peroxide. In solid polymer fuel cells and PEM-type water electrolysis devices, radical attack is known to increase the resistance of the electrolyte membrane, increase cross-leakage, and shorten the lifespan due to thinning. Furthermore, degradation products generated by radical attack may poison the catalyst, resulting in a decrease in electrolysis performance and cell performance.

[0004] Therefore, various proposals have been made to solve this problem. For example, Patent Document 1 discloses a solid polymer electrolyte containing tungsten oxide formed by a hydrolysis method. This document describes that: (A) tungsten oxide functions as a catalyst for decomposing hydrogen peroxide, and (B) by using the hydrolysis method, nanometer-order tungsten oxide can be dispersed almost uniformly throughout the solid polymer electrolyte.

[0005] Patent Document 2 discloses a solid polymer electrolyte membrane obtained by applying a liquid composition containing a sulfonic acid group-containing fluorocarbon polymer and cerium oxide onto a substrate using a die coater and drying the composition. The document also describes that cerium oxide has the effect of suppressing degradation of the polymer due to hydrogen peroxide or peroxide radicals.

[0006] Patent Document 3 discloses: (a) an electrolyte membrane obtained by mixing bathophenanthroline, Ce(NO3)3.6H2O, and a perfluorosulfonic acid (PFSA) ionomer dispersion and casting the mixture; (b) an electrolyte membrane obtained by mixing 1,10-phenanthroline-5-amino, MnO2, and a PFSA ionomer dispersion and casting the mixture; and (c) an electrolyte membrane obtained by mixing 1,10-phenanthroline, MnO2, and a PFSA ionomer dispersion and casting the mixture.

[0007] The document states that: (A) a proton-conducting composite polymer electrolyte containing a metal-ligand complex can be obtained by this method; (B) an electrolyte membrane containing a metal-ligand complex made of (Ce)(bathophenanthroline) or (Mn)(1,10-phenanthroline-5-amino) exhibits higher performance than a Nafion (registered trademark) 875 membrane containing no degradation inhibitor; and (C) an electrolyte membrane containing a metal-ligand complex made of (Mn)(1,10-phenanthroline) exhibits lower performance than a Nafion (registered trademark) 875 membrane containing no degradation inhibitor.

[0008] To improve the durability of polymer electrolyte fuel cells, it is important to suppress the degradation of the electrolyte membrane. Therefore, various degradation inhibitors have been proposed. Among these, tungsten oxide and cerium oxide have the effect of suppressing the degradation of the electrolyte membrane, as described in Patent Documents 1 and 2. However, when tungsten oxide is added to the electrolyte membrane, components eluted from the tungsten oxide may migrate to the cathode side and poison the electrode catalyst on the cathode side.

[0009] Furthermore, when the degradation inhibitor is a cationic material, the cationic component of the degradation inhibitor may undergo ion exchange with protons of acid groups in the electrolyte membrane or catalyst layer ionomer, resulting in a decrease in the proton conductivity of the electrolyte. A decrease in proton conductivity can cause a decrease in fuel cell performance. In particular, when cerium oxide is added to the electrolyte membrane, cerium ions may be eluted from the cerium oxide. Because cerium ions have a large valence, the conductivity of the electrolyte membrane decreases significantly when they are ion-exchanged with protons of acid groups in the electrolyte membrane. Meanwhile, as described in Patent Document 3, certain metal-ligand complexes are known to have the effect of improving the durability of fuel cells. However, in order to suppress electrolyte membrane degradation, a degradation inhibitor that is highly effective in smaller amounts is desired.

[0010] Patent No. 4326271 International Publication No. 2020 / 116645 U.S. Patent No. 09172107

[0011] An object of the present invention is to provide a polymer electrolyte fuel cell and a water electrolysis device containing a novel deterioration inhibitor that is highly effective in smaller amounts.

[0012] In order to solve the above problems, the solid polymer fuel cell according to the present invention comprises a membrane-electrode-gas diffusion layer assembly (MEGA) in which catalyst layers are bonded to both sides of a solid polymer electrolyte membrane and a gas diffusion layer is disposed on the outer side of the catalyst layers, and a degradation inhibitor added to any part of the MEGA, wherein the degradation inhibitor includes a complex in which a ligand is coordinated to an Fe ion, and the ligand includes 1,10-phenanthroline-5,6-dione and / or a derivative thereof.

[0013] The water electrolysis device according to the present invention comprises: a membrane-electrode-gas diffusion layer assembly (MEGA) in which catalyst layers are bonded to both sides of a solid polymer electrolyte membrane and a gas diffusion layer is disposed on the outer side of the catalyst layers; and a degradation inhibitor added to any part of the MEGA, wherein the degradation inhibitor includes a complex in which a ligand is coordinated to an Fe ion, and the ligand includes 1,10-phenanthroline-5,6-dione and / or a derivative thereof.

[0014] Complexes in which certain phenanthroline-based ligands are coordinated to Fe ions have the effect of eliminating substances that cause membrane degradation (HO, OH, H). This is thought to be because complexes in which certain phenanthroline-based ligands are coordinated to Fe ions have an oxidation-reduction potential of 0.75 V (vs. RHE) or higher and 1.8 V (vs. RHE) or lower. Complexes with such oxidation-reduction potentials are capable of electron transfer (redox) reactions with substances that cause membrane degradation, and it is thought that the electron transfer reaction eliminates the substances that cause membrane degradation. Therefore, adding a small amount of such complexes as a degradation inhibitor to any part of the MEGA can improve the durability of solid polymer fuel cells and water electrolysis devices.

[0015] F after durability test of the cells obtained in Example 1 and Comparative Examples 1 to 3 - F after durability tests of the cells obtained in Example 2 and Comparative Examples 4 to 6 - Emissions.

[0016] [Configuration 1] A solid polymer fuel cell comprising: a membrane-electrode-gas diffusion layer assembly (MEGA) in which catalyst layers are bonded to both sides of a solid polymer electrolyte membrane and gas diffusion layers are disposed on the outer sides of the catalyst layers; and a degradation inhibitor added to any part of the MEGA, wherein the degradation inhibitor includes a complex in which a ligand is coordinated to an Fe ion, and the ligand includes 1,10-phenanthroline-5,6-dione and / or a derivative thereof.

[0017] [Configuration 2] The polymer electrolyte fuel cell according to Configuration 1, wherein the content of the degradation inhibitor is 0.0001 mol % or more and 10.0 mol % or less, wherein the "content of the degradation inhibitor" refers to the ratio (= n1 × 100 / n0) of the number of moles of coordinating atoms contained in the ligand (n1) to the number of moles of acid groups (n0) contained in the solid polymer electrolyte membrane and the catalyst layer ionomer.

[0018] [Configuration 3] A water electrolysis device comprising: a membrane-electrode-gas diffusion layer assembly (MEGA) in which catalyst layers are bonded to both sides of a solid polymer electrolyte membrane and gas diffusion layers are disposed on the outer sides of the catalyst layers; and a degradation inhibitor added to any part of the MEGA, wherein the degradation inhibitor includes a complex in which a ligand is coordinated to an Fe ion, and the ligand includes 1,10-phenanthroline-5,6-dione and / or a derivative thereof.

[0019] [Configuration 4] The water electrolysis device according to Configuration 3, wherein the content of the deterioration inhibitor is 0.0001 mol % to 10.0 mol %, inclusive, wherein the "content of the deterioration inhibitor" refers to the ratio (=n1 × 100 / n0) of the number of moles of coordinating atoms (n1) contained in the ligand to the number of moles of acid groups (n0) contained in the solid polymer electrolyte membrane and the catalyst layer ionomer.

[0020] An embodiment of the present invention will be described in detail below. [1. Polymer Electrolyte Fuel Cell] A polymer electrolyte fuel cell according to the present invention comprises a membrane-electrode-gas diffusion layer assembly (MEGA) in which catalyst layers are bonded to both sides of a solid polymer electrolyte membrane and gas diffusion layers are disposed on the outer sides of the catalyst layers, and a degradation inhibitor is added to any part of the MEGA.

[0021] [1.1. MEGA] A "membrane electrode assembly (MEA)" refers to an assembly in which an anode catalyst layer is bonded to one surface of an electrolyte membrane and a cathode catalyst layer is bonded to the other surface. A "membrane-electrode-gas diffusion layer assembly (MEGA)" refers to a laminate in which an anode gas diffusion layer and a cathode gas diffusion layer are disposed on the outer sides of the anode catalyst layer and the cathode catalyst layer of the MEA, respectively. In the present invention, the materials of the components constituting the MEGA are not particularly limited, and an optimum material can be used depending on the purpose.

[0022] [1.1.1. Electrolyte Membrane] Examples of materials for the electrolyte membrane include Nafion (registered trademark), Flemion (registered trademark), Aquivion (registered trademark), and Aciplex (registered trademark).

[0023] [1.1.2. Catalyst Layer] The catalyst layer is usually made of a composite of an electrode catalyst and a catalyst layer ionomer. The electrode catalyst usually includes a support and catalyst particles (active species) supported on the surface of the support. Note that the electrode catalyst may also consist of only catalyst particles.

[0024] The material of the catalyst particles is not particularly limited as long as it has hydrogen oxidation reaction activity or oxygen reduction reaction activity, and examples of the material of the catalyst particles include: (a) noble metals (Pt, Au, Ag, Pd, Rh, Ir, Ru, Os), (b) alloys containing two or more noble metal elements, and (c) alloys containing one or more noble metal elements and one or more base metal elements (e.g., Fe, Co, Ni, Cr, V, Ti, etc.).

[0025] Examples of the support material include: (a) solid carbon such as carbon black; (b) porous carbon such as mesoporous carbon; and (c) SnO2, non-stoichiometric titanium oxide (TiO x ) and other conductive metal oxides or composite metal oxides.

[0026] Examples of materials for the catalyst layer ionomer include: (a) perfluorocarbon sulfonic acid polymers such as Nafion (registered trademark), Flemion (registered trademark), Aciplex (registered trademark), and Aquivion (registered trademark); and (b) high oxygen permeable ionomers (HOPI).

[0027] Here, the term "highly oxygen-permeable ionomer" refers to a polymer compound containing an acid group and a cyclic structure within its molecular structure. The highly oxygen-permeable ionomer has a high oxygen permeability coefficient due to the cyclic structure within its molecular structure. Therefore, when this ionomer is used as an ionomer, the oxygen transfer resistance at the interface with the catalyst particle becomes relatively small. In other words, the "highly oxygen-permeable ionomer" refers to an ionomer whose oxygen permeability coefficient is higher than that of perfluorocarbon sulfonic acid polymers, such as Nafion (registered trademark).

[0028] Examples of highly oxygen-permeable ionomers include: (a) electrolyte polymers containing perfluorocarbon units having an aliphatic ring structure and acid group units having perfluorosulfonic acid in the side chain, (b) electrolyte polymers containing perfluorocarbon units having an aliphatic ring structure and acid group units having perfluoroimide in the side chain, and (c) electrolyte polymers containing units in which perfluorosulfonic acid is directly bonded to perfluorocarbons having an aliphatic ring structure (see References 1 to 4). [Reference 1] JP 2003-036856 A [Reference 2] WO 2012 / 088166 A [Reference 3] JP 2013-216811 A [Reference 4] JP 2006-152249 A

[0029] [1.1.3. Gas Diffusion Layer] A gas diffusion layer typically includes a substrate and a water-repellent layer formed on the surface of the substrate. Examples of materials for the substrate include carbon fiber nonwoven fabric, carbon paper, carbon cloth, and porous metal sintered compacts. The water-repellent layer typically comprises a composite of conductive particles and water-repellent particles.

[0030] [1.2. Degradation Inhibitor] [1.2.1. Materials] In the present invention, the degradation inhibitor includes a complex in which a ligand is coordinated to an Fe ion. The ligand includes at least 1,10-phenanthroline-5,6-dione and / or a derivative thereof. Here, the term "derivative" refers to a 1,10-phenanthroline-5,6-dione in which at least one of the 2-, 3-, 4-, 7-, 8-, and 9-positions is substituted with one or more functional groups selected from the group consisting of a hydroxyl group, a nitro group, an amino group, a carboxyl group, a carbonyl group, a methyl group, a methoxy group, a fluoro group, a chloro group, a bromo group, a sulfo group, a nitrile group, and a phenyl group.

[0031] The ligand coordinated to one Fe ion may consist solely of 1,10-phenanthroline-5,6-dione and / or a derivative thereof, or may additionally contain other ligands. Furthermore, the deterioration inhibitor may consist solely of Complex A containing 1,10-phenanthroline-5,6-dione and / or a derivative thereof as a ligand, or may be a mixture of Complex A and Complex B containing neither 1,10-phenanthroline-5,6-dione nor a derivative thereof as a ligand.

[0032] Examples of other ligands include (a) 1,10-phenanthroline, and (b) compounds in which a substituent has been added to 1,10-phenanthroline at a position other than the 1-, 2-, 9-, or 10-position. Examples of (b) include 5-methyl-1,10-phenanthroline, 4,7-dimethyl-1,10-phenanthroline, 5,6-dimethyl-1,10-phenanthroline, 5-amino-1,10-phenanthroline, 4,7-dimethoxy-1,10-phenanthroline, and 4,7-dihydroxy-1,10-phenanthroline.

[0033] [1.2.2. Addition Site] In the present invention, the addition site of the degradation inhibitor is not particularly limited. For example, the degradation inhibitor may be added to any one of the electrolyte membrane, catalyst layer, water-repellent layer, and gas diffusion layer substrate, or may be added to two or more of them.

[0034] [1.2.3. Content] The "content of degradation inhibitor" refers to the ratio (=n1 × 100 / n0) of the number of moles of coordinating atoms (n1) contained in the ligand to the number of moles of acid groups (n0) contained in the solid polymer electrolyte membrane and the catalyst layer ionomer. The "coordinating atom" refers to an atom contained in the ligand that can be directly bonded to the central atom of the complex.

[0035] If the content of the deterioration inhibitor is too low, it becomes difficult to suppress electrolyte degradation due to radicals. Therefore, the content of the deterioration inhibitor is preferably 0.0001 mol% or more. The content is more preferably 0.001 mol% or more, 0.01 mol% or more, 0.1 mol% or more, or 0.5 mol% or more. On the other hand, adding more than the necessary amount of deterioration inhibitor does not make a difference in effect and is of no practical benefit. Therefore, the content of the deterioration inhibitor is preferably 10.0 mol% or less. The content is more preferably 8.0 mol% or less, 6.0 mol% or less, 4.0 mol% or less, or 2.0 mol% or less.

[0036] [2. Water Electrolysis Apparatus] The water electrolysis apparatus according to the present invention includes a membrane-electrode-gas diffusion layer assembly (MEGA) in which catalyst layers are bonded to both sides of a solid polymer electrolyte membrane and gas diffusion layers are disposed on the outer sides of the catalyst layers, and a degradation inhibitor is added to any part of the MEGA.

[0037] The material of the catalyst particles used in the water electrolysis device is not particularly limited as long as it has hydrogen generation reaction activity or oxygen generation reaction activity. Examples of materials for catalyst particles having hydrogen generation reaction activity include: (a) noble metals (Pt, Au, Ag, Pd, Rh, Ir, Ru, Os), (b) alloys containing two or more noble metal elements, and (c) alloys containing one or more noble metal elements and one or more base metal elements (e.g., Fe, Co, Ni, Cr, V, Ti, etc.).

[0038] Examples of materials for catalyst particles having oxygen generating reaction activity include metal oxides, such as iridium oxide, ruthenium oxide, cobalt oxide, nickel oxide, iron oxide, and composite oxides of these.

[0039] Other aspects of the structure of the water electrolysis device are the same as those of the polymer electrolyte fuel cell, and therefore a description thereof will be omitted.

[0040] [3. Manufacturing Method of Polymer Electrolyte Fuel Cell] The polymer electrolyte fuel cell according to the present invention can be manufactured by: (a) adding a degradation inhibitor to at least one of the electrolyte membrane, catalyst layer, and gas diffusion layer; (b) bonding catalyst layers to both sides of the electrolyte membrane to form an MEA; (c) arranging gas diffusion layers on both sides of the MEA to form an MEGA; and (d) arranging separators on both sides of the MEGA. In this case, the method of adding the degradation inhibitor is not particularly limited, and it is preferable to use an optimal method depending on the addition location. In the following description of the addition method, the term "degradation inhibitor" refers to (a) a complex or (b) a mixture of Fe ions and a ligand.

[0041] Methods for adding a deterioration inhibitor to an electrolyte membrane include, for example, (a) a method of casting a solution in which a solid polymer electrolyte and a deterioration inhibitor are dispersed to obtain an electrolyte membrane, (b) a method of applying a solution containing a deterioration inhibitor to the surface of an electrolyte membrane that does not contain a deterioration inhibitor, and (c) a method of immersing an electrolyte membrane that does not contain a deterioration inhibitor in a solution containing a deterioration inhibitor.

[0042] Methods for adding a deterioration inhibitor to a catalyst layer include, for example, (a) a method of applying a catalyst ink containing an electrode catalyst, a catalyst layer ionomer, and a deterioration inhibitor to the surface of a substrate and drying it, (b) a method of applying a solution containing a deterioration inhibitor to the surface of a catalyst layer that does not contain a deterioration inhibitor, and (c) a method of immersing a catalyst layer that does not contain a deterioration inhibitor in a solution containing a deterioration inhibitor.

[0043] Methods for adding a degradation inhibitor to a gas diffusion layer include, for example, (a) a method of applying a water-repellent layer paste containing conductive particles, water-repellent particles, and a degradation inhibitor to the surface of a substrate and drying it; (b) a method of applying a solution containing a degradation inhibitor to the MEA-side surface (surface of the water-repellent layer) of a gas diffusion layer that does not contain a degradation inhibitor; and (c) a method of immersing a gas diffusion layer that does not contain a degradation inhibitor in a solution containing a degradation inhibitor.

[0044] Furthermore, during the manufacturing process of a polymer electrolyte fuel cell, Fe ions may be mixed into the MEGA due to unavoidable circumstances. If Fe ion mixing is expected, it is possible to add only a ligand to any part of the MEGA. The ligand added to any part of the MEGA forms a complex with the Fe ions mixed into the MEGA due to unavoidable circumstances. Even such a complex functions as a degradation inhibitor.

[0045] [4. Manufacturing Method of Water Electrolysis Device] The water electrolysis device has a structure similar to that of a polymer electrolyte fuel cell, except for the material of the catalyst particles. Therefore, the water electrolysis device can be manufactured by the same method as that of a polymer electrolyte fuel cell. Other aspects of the manufacturing method of the water electrolysis device are the same as those of the polymer electrolyte fuel cell, and therefore will not be described again.

[0046] [5. Action] Complexes in which certain phenanthroline-based ligands are coordinated to Fe ions have the effect of eliminating substances that cause membrane degradation (HO, OH, H). This is thought to be because complexes in which certain phenanthroline-based ligands are coordinated to Fe ions have an oxidation-reduction potential of 0.75 V (vs. RHE) or higher and 1.8 V (vs. RHE) or lower. Complexes with such oxidation-reduction potentials are capable of electron transfer (redox) reactions with substances that cause membrane degradation, and it is thought that the electron transfer reaction eliminates the substances that cause membrane degradation. Therefore, adding a small amount of such complexes as a degradation inhibitor to any part of the MEGA can improve the durability of solid polymer fuel cells and water electrolysis devices.

[0047] (Example 1, Comparative Examples 1 to 3) [1. Preparation of Samples] [1.1. Preparation of Electrolyte Membrane Containing Degradation Inhibitor] A Nafion (registered trademark) solution (solid content: 21.5 mass%, Ew: 1000) was used as the ionomer solution for forming the electrolyte membrane and catalyst layer.

[0048] The additives used were: (a) none (Comparative Example 1), (b) Ce ions (Comparative Example 2), (c) 1,10-phenanthroline (phen) (Comparative Example 3), or (d) 1,10-phenanthroline-5,6-dione (phen-dione) (Example 1). Table 1 shows the structure, redox species, and redox potential of each additive.

[0049]

[0050] The ionomer solution and additives were mixed in a sample bottle. The amount of Ce ions added was 4.4 mol% of the amount of sulfonic acid groups in the ionomer. The amount of other additives added was 1.5 mol% of the amount of sulfonic acid groups in the ionomer. This ionomer solution was hand-coated onto a PET film and then dried at 140°C in air to produce an electrolyte membrane with a thickness of approximately 30 μm.

[0051] [1.2. Cell Fabrication] Platinum-supported carbon was dispersed in an ionomer solution to obtain a catalyst ink. This catalyst ink was applied to a PET film and dried to obtain a catalyst layer. The platinum weight of the catalyst layer was 0.2 mg / cm. 2 The obtained catalyst layers were thermally transferred to both sides of an electrolyte membrane at 140°C to obtain a membrane electrode assembly (MEA). The electrode area of ​​the MEA was 4 cm 2 The effective electrode area is 3.24 cm 2 Furthermore, the MEA was sandwiched between paper gas diffusion layers (GDLs) with water-repellent layers to form a cell.

[0052] [2. Test Method] [2.1. Break-in Operation] The above cell was subjected to break-in operation under the following conditions.

[0053] [Break-in] Cell temperature: 80.0°C Humidity: Anode 20% RH, Cathode 122% RH Gas: Anode (H2, 1.0 L / min), Cathode (Air, 2.0 L / min) Back pressure: 50 kPa Measurement conditions: 0.1 V (9 min) + OCV (1 min), 6 cycles

[0054] 2.2 Initial Power Generation Performance The initial power generation performance of the cell after the break-in was evaluated under the following conditions.

[0055] [Evaluation of power generation performance] Cell temperature: 80.0°C Humidity: 80% RH at both electrodes (bubbler temperature 52.9°C) or 30% RH at both electrodes (same 74.6°C) Gas: anode (H2, 1.0 L / min), cathode (air, 2.0 L / min) Back pressure: 0 kPa Measurement conditions: OCV-0.1 V-OCV, 0.02 V / s, 5 cycles

[0056] [2.3. Durability Test] After evaluating the initial power generation performance, the cell was subjected to an open circuit voltage (OCV) retention durability test under the following conditions.

[0057] [OCV durability test] Cell temperature: 95.0°C Humidity: 30% RH at both electrodes (bubbler temperature was 65°C at both electrodes) Gas: anode (H2, 0.3 L / min), cathode (air, 0.3 L / min) Back pressure: 133 kPa at both electrodes Durability time: 90 hours Collection of discharged water: Water was collected at 24, 48, 72, and 90 hours after the start of the durability test.

[0058] [2.4.F - Calculation of Discharge Amount] After the durability test, the cells were again subjected to a break-in operation, and then the power generation performance was evaluated. The conditions for the break-in operation and the evaluation of power generation performance were the same as those described above. After a predetermined time had elapsed since the start of the durability test and after the durability test, the water discharged from the cells was collected, and the fluoride ions (F - ) was quantified by ion chromatography. - The amount is integrated and the integrated value is set as "F - emissions."

[0059] [3. Results] FIG. 1 shows the F of the cells obtained in Example 1 and Comparative Examples 1 to 3 after the durability test. - The following can be seen from Figure 1: (1) Comparative Example 1, which contains no additives, has the lowest F content among the evaluated samples. - The emissions are the highest, and the F - The discharge rate is 608 μg / cm 2This is thought to be due to the fact that Fe ions were mixed into the cell as contaminants from the raw materials, film formation process, cell fabrication process, and piping during performance evaluation. - The increase in discharged amount is thought to be due to the fact that radical species were generated from hydrogen peroxide due to the influence of Fe ions mixed in the cell, and the radical species deteriorated the electrolyte membrane.

[0060] (2) In Comparative Examples 2 and 3 and Example 1, in which additives were added, F was lower than that in Comparative Example 1. - In addition, in Comparative Example 3 and Example 1, the amount of additives contained was about one-third of that in Comparative Example 2, but the amount of F discharged was significantly reduced compared to Comparative Example 1. - The amount of emissions was significantly reduced. - The discharge amount was 1 / 4 or less of that in Comparative Example 2.

[0061] (3) The electrolyte membranes obtained in Comparative Example 3 and Example 1 turned red immediately after membrane formation. Furthermore, when the electrolyte membranes obtained in Comparative Example 3 and Example 1 were analyzed after durability testing, iron ions were detected. These results are believed to indicate that the additive and the Fe ions mixed in the cell formed a complex. The complexes of Fe ions with 1,10-phenanthroline or 1,10-phenanthroline-5,6-dione all have an oxidation-reduction potential of 0.75 V (vs. SHE) or more and 1.8 V (vs. SHE) or less. Therefore, it is believed that the complex reacts with the causative substances of membrane degradation (mainly OH) and eliminates the causative substances.

[0062] (4) Example 1 is F - This is thought to be because the complex of Fe ions and 1,10-phenanthroline-5,6-dione has the best compatibility with the causative substance in terms of electron density overlap, and is highly reactive with the causative substance.

[0063] (Example 2, Comparative Examples 4 to 6) [1. Preparation of Samples] [1.1. Preparation of Electrolyte Membrane Containing Degradation Inhibitor] A Nafion (registered trademark) solution (solid content: 21.5 mass%, Ew: 1000) was used as the ionomer solution for forming the electrolyte membrane and catalyst layer.

[0064] The additives used were: (a) none (Comparative Example 4), (b) Ce ions (Comparative Example 5), (c) 1,10-phenanthroline (phen) (Comparative Example 6), or (d) 1,10-phenanthroline-5,6-dione (phen-dione) (Example 2).

[0065] The ionomer solution, additive, and iron (II) sulfate were mixed in a sample bottle. The amount of Ce ions added was 4.4 mol% of the amount of sulfonic acid groups in the ionomer. The amounts of 1,10-phenanthroline and 1,10-phenanthroline-5,6-dione added were each 1.5 mol% of the amount of sulfonic acid groups in the ionomer. The amount of iron (II) sulfate (i.e., Fe ions) added was 0.5 mol% of the sulfonic acid groups in the ionomer. This ionomer solution was hand-coated onto a PET film and then dried at 140°C in air to produce an electrolyte membrane with a thickness of approximately 30 μm.

[0066] [1.2. Cell Fabrication] A cell was fabricated in the same manner as in Example 1.

[0067] [2. Test Method] In the same manner as in Example 1, F - The amount of emissions was measured.

[0068] [3. Results] FIG. 2 shows the F after durability tests of the cells obtained in Example 2 and Comparative Examples 4 to 6. - 2 shows that Example 2 and Comparative Example 6 have a lower F than Comparative Examples 4 and 5. - This is thought to be because, in Comparative Examples 4 and 5, the Fe ions added to the electrolyte membrane function as a radical generation source, whereas in Example 2 and Comparative Example 6, at least a portion of the Fe ions form complexes with ligands, and the complexes function as degradation inhibitors.

[0069] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various modifications are possible within the scope of the gist of the present invention.

[0070] The polymer electrolyte fuel cell according to the present invention can be used as an in-vehicle power source, a small stationary generator, etc. The water electrolysis device according to the present invention can be used as a hydrogen generation device and / or an oxygen generation device.

Claims

1. A polymer electrolyte fuel cell comprising: a membrane-electrode-gas diffusion layer assembly (MEGA) in which catalyst layers are bonded to both sides of a solid polymer electrolyte membrane and a gas diffusion layer is disposed on the outer side of the catalyst layers; and a degradation inhibitor added to any part of the MEGA, wherein the degradation inhibitor includes a complex in which a ligand is coordinated to an Fe ion, and the ligand includes 1,10-phenanthroline-5,6-dione and / or a derivative thereof.

2. The polymer electrolyte fuel cell according to claim 1, wherein the content of the degradation inhibitor is 0.0001 mol% or more and 10.0 mol% or less, wherein the "content of the degradation inhibitor" refers to the ratio (=n1 × 100 / n0) of the number of moles of coordinating atoms contained in the ligand (n1) to the number of moles of acid groups (n0) contained in the solid polymer electrolyte membrane and the catalyst layer ionomer.

3. A water electrolysis device comprising: a membrane-electrode-gas diffusion layer assembly (MEGA) in which catalyst layers are bonded to both sides of a solid polymer electrolyte membrane and gas diffusion layers are disposed on the outer sides of the catalyst layers; and a degradation inhibitor added to any part of the MEGA, wherein the degradation inhibitor includes a complex in which a ligand is coordinated to an Fe ion, and the ligand includes 1,10-phenanthroline-5,6-dione and / or a derivative thereof.

4. The water electrolysis device according to claim 3, wherein the content of the deterioration inhibitor is 0.0001 mol % or more and 10.0 mol % or less, wherein the "content of the deterioration inhibitor" refers to the ratio (= n1 × 100 / n0) of the number of moles of coordinating atoms contained in the ligand (n1) to the number of moles of acid groups (n0) contained in the solid polymer electrolyte membrane and the catalyst layer ionomer.

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