JP4574149B2 - Electrolyte membrane electrode assembly for polymer electrolyte fuel cell and polymer electrolyte fuel cell - Google Patents
Electrolyte membrane electrode assembly for polymer electrolyte fuel cell and polymer electrolyte fuel cell Download PDFInfo
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- 239000003792 electrolyte Substances 0.000 title claims description 111
- 239000012528 membrane Substances 0.000 title claims description 104
- 239000000446 fuel Substances 0.000 title claims description 61
- 239000005518 polymer electrolyte Substances 0.000 title claims description 33
- KRHYYFGTRYWZRS-UHFFFAOYSA-M Fluoride anion Chemical compound [F-] KRHYYFGTRYWZRS-UHFFFAOYSA-M 0.000 claims description 88
- 239000003054 catalyst Substances 0.000 claims description 54
- 229910052760 oxygen Inorganic materials 0.000 claims description 32
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 30
- 239000001301 oxygen Substances 0.000 claims description 30
- 229910052751 metal Inorganic materials 0.000 claims description 20
- 239000002184 metal Substances 0.000 claims description 20
- -1 fluoride ions Chemical class 0.000 claims description 18
- 239000007864 aqueous solution Substances 0.000 claims description 15
- 239000000243 solution Substances 0.000 claims description 14
- 150000003839 salts Chemical class 0.000 claims description 12
- 230000002378 acidificating effect Effects 0.000 claims description 10
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 10
- 239000002253 acid Substances 0.000 claims description 9
- 150000002910 rare earth metals Chemical class 0.000 claims description 9
- 229910052723 transition metal Inorganic materials 0.000 claims description 9
- 239000007789 gas Substances 0.000 claims description 8
- 229920000642 polymer Polymers 0.000 claims description 8
- 150000003624 transition metals Chemical class 0.000 claims description 8
- 150000002978 peroxides Chemical class 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 7
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims description 5
- 239000001257 hydrogen Substances 0.000 claims description 5
- 229910052739 hydrogen Inorganic materials 0.000 claims description 5
- 230000007062 hydrolysis Effects 0.000 claims description 5
- 238000006460 hydrolysis reaction Methods 0.000 claims description 5
- 230000001590 oxidative effect Effects 0.000 claims description 3
- 239000003513 alkali Substances 0.000 claims description 2
- 239000002737 fuel gas Substances 0.000 claims description 2
- 239000007800 oxidant agent Substances 0.000 claims description 2
- CUPFNGOKRMWUOO-UHFFFAOYSA-N hydron;difluoride Chemical compound F.F CUPFNGOKRMWUOO-UHFFFAOYSA-N 0.000 claims 1
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 58
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 23
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 17
- 238000000034 method Methods 0.000 description 16
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 description 15
- 230000006866 deterioration Effects 0.000 description 14
- 229910052731 fluorine Inorganic materials 0.000 description 13
- 239000011737 fluorine Substances 0.000 description 13
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 12
- 238000009792 diffusion process Methods 0.000 description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 11
- 229910052799 carbon Inorganic materials 0.000 description 10
- 239000002243 precursor Substances 0.000 description 8
- 230000007797 corrosion Effects 0.000 description 7
- 238000005260 corrosion Methods 0.000 description 7
- 229910052697 platinum Inorganic materials 0.000 description 7
- 238000006243 chemical reaction Methods 0.000 description 6
- 238000000354 decomposition reaction Methods 0.000 description 6
- 239000000463 material Substances 0.000 description 6
- 239000007769 metal material Substances 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 238000003487 electrochemical reaction Methods 0.000 description 5
- 238000005868 electrolysis reaction Methods 0.000 description 5
- 238000004519 manufacturing process Methods 0.000 description 5
- 229910021645 metal ion Inorganic materials 0.000 description 5
- 229920001343 polytetrafluoroethylene Polymers 0.000 description 5
- 239000004810 polytetrafluoroethylene Substances 0.000 description 5
- 239000011734 sodium Substances 0.000 description 5
- 239000004215 Carbon black (E152) Substances 0.000 description 4
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 4
- 239000003575 carbonaceous material Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 239000004744 fabric Substances 0.000 description 4
- 229930195733 hydrocarbon Natural products 0.000 description 4
- 150000002430 hydrocarbons Chemical class 0.000 description 4
- 229920006254 polymer film Polymers 0.000 description 4
- 239000005871 repellent Substances 0.000 description 4
- 150000003460 sulfonic acids Chemical class 0.000 description 4
- QTBSBXVTEAMEQO-UHFFFAOYSA-N Acetic acid Chemical compound CC(O)=O QTBSBXVTEAMEQO-UHFFFAOYSA-N 0.000 description 3
- 229910015475 FeF 2 Inorganic materials 0.000 description 3
- 229920000557 Nafion® Polymers 0.000 description 3
- DNIAPMSPPWPWGF-UHFFFAOYSA-N Propylene glycol Chemical compound CC(O)CO DNIAPMSPPWPWGF-UHFFFAOYSA-N 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 3
- 150000002222 fluorine compounds Chemical class 0.000 description 3
- 229910052500 inorganic mineral Inorganic materials 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 3
- 239000011707 mineral Substances 0.000 description 3
- 229910052700 potassium Inorganic materials 0.000 description 3
- 238000010248 power generation Methods 0.000 description 3
- 238000006722 reduction reaction Methods 0.000 description 3
- 230000002940 repellent Effects 0.000 description 3
- 238000003980 solgel method Methods 0.000 description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 description 2
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 description 2
- ZLMJMSJWJFRBEC-UHFFFAOYSA-N Potassium Chemical compound [K] ZLMJMSJWJFRBEC-UHFFFAOYSA-N 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
- 238000007606 doctor blade method Methods 0.000 description 2
- 238000011156 evaluation Methods 0.000 description 2
- 150000004820 halides Chemical group 0.000 description 2
- 238000007731 hot pressing Methods 0.000 description 2
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000007774 longterm Effects 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 238000002156 mixing Methods 0.000 description 2
- 150000004965 peroxy acids Chemical class 0.000 description 2
- 239000011148 porous material Substances 0.000 description 2
- 239000011591 potassium Substances 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000002829 reductive effect Effects 0.000 description 2
- 229910052708 sodium Inorganic materials 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- SDTMFDGELKWGFT-UHFFFAOYSA-N 2-methylpropan-2-olate Chemical compound CC(C)(C)[O-] SDTMFDGELKWGFT-UHFFFAOYSA-N 0.000 description 1
- QTBSBXVTEAMEQO-UHFFFAOYSA-M Acetate Chemical compound CC([O-])=O QTBSBXVTEAMEQO-UHFFFAOYSA-M 0.000 description 1
- 229920003934 Aciplex® Polymers 0.000 description 1
- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 1
- 229910016509 CuF 2 Inorganic materials 0.000 description 1
- 229920003935 Flemion® Polymers 0.000 description 1
- 229910005690 GdF 3 Inorganic materials 0.000 description 1
- 229910017768 LaF 3 Inorganic materials 0.000 description 1
- 229910002651 NO3 Inorganic materials 0.000 description 1
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 description 1
- MUBZPKHOEPUJKR-UHFFFAOYSA-N Oxalic acid Chemical compound OC(=O)C(O)=O MUBZPKHOEPUJKR-UHFFFAOYSA-N 0.000 description 1
- 239000004642 Polyimide Substances 0.000 description 1
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 1
- 239000004809 Teflon Substances 0.000 description 1
- 229920006362 Teflon® Polymers 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- 150000001340 alkali metals Chemical class 0.000 description 1
- 150000001447 alkali salts Chemical class 0.000 description 1
- 239000012670 alkaline solution Substances 0.000 description 1
- 125000003118 aryl group Chemical group 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 150000001732 carboxylic acid derivatives Chemical class 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000004523 catalytic cracking Methods 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 239000008139 complexing agent Substances 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000002788 crimping Methods 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- SHZIWNPUGXLXDT-UHFFFAOYSA-N ethyl hexanoate Chemical compound CCCCCC(=O)OCC SHZIWNPUGXLXDT-UHFFFAOYSA-N 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 125000001153 fluoro group Chemical group F* 0.000 description 1
- 229920002313 fluoropolymer Polymers 0.000 description 1
- 125000000524 functional group Chemical group 0.000 description 1
- 238000010574 gas phase reaction Methods 0.000 description 1
- 229910052736 halogen Inorganic materials 0.000 description 1
- 150000002367 halogens Chemical group 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 238000010030 laminating Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 229910000510 noble metal Inorganic materials 0.000 description 1
- QGLKJKCYBOYXKC-UHFFFAOYSA-N nonaoxidotritungsten Chemical compound O=[W]1(=O)O[W](=O)(=O)O[W](=O)(=O)O1 QGLKJKCYBOYXKC-UHFFFAOYSA-N 0.000 description 1
- 239000003960 organic solvent Substances 0.000 description 1
- 238000006864 oxidative decomposition reaction Methods 0.000 description 1
- 150000003009 phosphonic acids Chemical class 0.000 description 1
- 229920001721 polyimide Polymers 0.000 description 1
- 229920005597 polymer membrane Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 230000002250 progressing effect Effects 0.000 description 1
- OGHBATFHNDZKSO-UHFFFAOYSA-N propan-2-olate Chemical compound CC(C)[O-] OGHBATFHNDZKSO-UHFFFAOYSA-N 0.000 description 1
- 239000012495 reaction gas Substances 0.000 description 1
- 230000002787 reinforcement Effects 0.000 description 1
- 229910001925 ruthenium oxide Inorganic materials 0.000 description 1
- WOCIAKWEIIZHES-UHFFFAOYSA-N ruthenium(iv) oxide Chemical compound O=[Ru]=O WOCIAKWEIIZHES-UHFFFAOYSA-N 0.000 description 1
- 239000012266 salt solution Substances 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
- 229910001220 stainless steel Inorganic materials 0.000 description 1
- 239000010935 stainless steel Substances 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 125000000542 sulfonic acid group Chemical group 0.000 description 1
- 125000002128 sulfonyl halide group Chemical group 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- TXEYQDLBPFQVAA-UHFFFAOYSA-N tetrafluoromethane Chemical compound FC(F)(F)F TXEYQDLBPFQVAA-UHFFFAOYSA-N 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910001428 transition metal ion Inorganic materials 0.000 description 1
- 229910001930 tungsten oxide Inorganic materials 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
Classifications
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/30—Hydrogen technology
- Y02E60/50—Fuel cells
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- Inert Electrodes (AREA)
- Fuel Cell (AREA)
Description
本発明は、固体高分子型燃料電池に関し、特に固体高分子型燃料電池に用いられる電解質膜電極接合体に関する。 The present invention relates to a polymer electrolyte fuel cell, and more particularly to an electrolyte membrane electrode assembly used in a polymer electrolyte fuel cell.
ガスの電気化学反応により電気を発生させる燃料電池は、発電効率が高く、排出されるガスがクリーンで環境に対する影響が極めて少ない。そのため、近年、発電用、低公害の自動車用電源等、種々の用途が期待されている。 A fuel cell that generates electricity by an electrochemical reaction of gas has high power generation efficiency, clean gas discharged, and extremely little influence on the environment. Therefore, in recent years, various uses such as power generation and low-pollution automobile power supplies are expected.
なかでも、固体高分子型燃料電池は、８０℃程度の低温で作動させることができ、大きな出力密度を有する。固体高分子型燃料電池は、通常、プロトン導電性のある高分子膜を電解質とする。電解質となる高分子膜の両側にそれぞれ燃料極、酸素極となる一対の電極が設けられ電解質膜電極接合体（ＭＥＡ）が構成される。この電解質膜電極接合体をセパレータで挟持した単セルが発電単位となる。そして、水素や炭化水素等の燃料ガスを燃料極に、酸素や空気等の酸化剤ガスを酸素極にそれぞれ供給し、ガスと電解質と電極との三相界面における電気化学反応により発電を行う。 Among them, the polymer electrolyte fuel cell can be operated at a low temperature of about 80 ° C. and has a large output density. In general, a polymer electrolyte fuel cell uses a polymer film having proton conductivity as an electrolyte. A pair of electrodes each serving as a fuel electrode and an oxygen electrode are provided on both sides of the polymer film serving as an electrolyte to form an electrolyte membrane electrode assembly (MEA). A single cell in which the electrolyte membrane electrode assembly is sandwiched between separators serves as a power generation unit. Then, a fuel gas such as hydrogen or hydrocarbon is supplied to the fuel electrode, and an oxidant gas such as oxygen or air is supplied to the oxygen electrode, and power is generated by an electrochemical reaction at the three-phase interface between the gas, the electrolyte, and the electrode.
しかし、固体高分子型燃料電池は、長期間の運転により、電池性能が低下してしまうという問題を有する。電池性能の低下の原因としては、例えば、電解質膜や電極の劣化が挙げられる。加えて、セパレータや、燃料電池システムを構成する配管、マニホールド等に用いられる金属材料の腐食が挙げられる。金属材料が腐食すると、溶出した金属イオンが、電解質膜や電極を構成する高分子中のスルホン酸基のプロトンとイオン交換する。これにより、電解質膜のプロトン導電性が阻害され、抵抗が増加する。また、電極における電気化学反応も阻害される。 However, the polymer electrolyte fuel cell has a problem that the battery performance is deteriorated by long-term operation. As a cause of the decrease in battery performance, for example, deterioration of an electrolyte membrane or an electrode can be mentioned. In addition, corrosion of metal materials used for separators, piping constituting a fuel cell system, manifolds, and the like can be given. When the metal material is corroded, the eluted metal ions are ion-exchanged with protons of sulfonic acid groups in the polymer constituting the electrolyte membrane and the electrode. Thereby, the proton conductivity of the electrolyte membrane is inhibited, and the resistance increases. Moreover, the electrochemical reaction in an electrode is also inhibited.
通常、固体高分子型燃料電池の運転時には、酸素極において、水素と酸素とから水が生成される。しかし、運転条件等によっては、酸素極における酸素の還元が２電子反応で止まってしまい、過酸化水素（Ｈ2Ｏ2）が生成されることがある。生成された過酸化水素は、例えば、金属イオン等の存在下でラジカル分解する。その過酸化水素ラジカルにより、電解質膜や電極が損傷を受け劣化すると考えられる。 Usually, when the polymer electrolyte fuel cell is operated, water is generated from hydrogen and oxygen at the oxygen electrode. However, depending on the operating conditions, the reduction of oxygen at the oxygen electrode may be stopped by a two-electron reaction, and hydrogen peroxide (H 2 O 2 ) may be generated. The generated hydrogen peroxide undergoes radical decomposition in the presence of, for example, metal ions. The hydrogen peroxide radical is thought to damage and deteriorate the electrolyte membrane and the electrode.
過酸化水素による電解質膜等の劣化を抑制し、燃料電池の耐久性を向上させる試みとして、例えば、酸化マンガン、酸化ルテニウム、酸化タングステン等の酸化物を、電解質膜や電極に含有させることが提案されている（例えば、特許文献１、２参照。）。 As an attempt to suppress deterioration of electrolyte membranes due to hydrogen peroxide and improve the durability of fuel cells, for example, it is proposed to include oxides such as manganese oxide, ruthenium oxide, tungsten oxide in electrolyte membranes and electrodes (For example, refer to Patent Documents 1 and 2).
一方、特許文献３には、電極の撥水性を向上させるという観点から、カーボン材料からなる電極基体の表面に撥水性フッ化物被膜を形成する方法が示されている。
しかしながら、上記特許文献１、２に示された手法では、含有させる酸化物として、資源量が少なく高価な金属を用いるため、実用性、コストの面で問題がある。また、固体高分子型燃料電池の運転時には、通常、その内部は８０℃程度の高温下、酸性雰囲気等の過酷な環境となる。上記酸化物は、高温かつ酸性の条件で溶出し易く、耐久性が低いという問題がある。 However, the methods disclosed in Patent Documents 1 and 2 have problems in terms of practicality and cost because they use an expensive metal with a small amount of resources as the oxide to be contained. Further, when the polymer electrolyte fuel cell is operated, the inside thereof is usually a severe environment such as an acidic atmosphere at a high temperature of about 80 ° C. The oxides have a problem that they are easily eluted under high temperature and acidic conditions and have low durability.
一方、特許文献３に示された方法では、カーボン材料の表面にフッ化カーボン層、あるいはフルオロカーボン系ポリマー層を形成して、該カーボン材料に撥水性を付与しているにすぎない。また、特許文献３には、過酸化水素のラジカル化を抑制するという思想は全くない。 On the other hand, in the method disclosed in Patent Document 3, a carbon fluoride layer or a fluorocarbon polymer layer is formed on the surface of the carbon material to impart water repellency to the carbon material. Patent Document 3 does not have any idea of suppressing radicalization of hydrogen peroxide.
固体高分子型燃料電池の多くは、電解質膜として、炭化水素系材料あるいはフッ素系材料からなる高分子膜を用いる。従来、フッ素系電解質膜は、過酸化水素によりほとんど損傷を受けないと考えられてきた。したがって、上記特許文献１、２においても、炭化水素系電解質膜について検討がなされている。しかし、本発明者は、種々の検討を重ねた結果、フッ素系電解質膜であっても、過酸化水素により損傷を受ける場合があるという知見を得た。この場合、過酸化水素によりＣ−Ｆ結合が分解されるため、フッ酸等が生じるおそれもある。 Many of the polymer electrolyte fuel cells use a polymer membrane made of a hydrocarbon material or a fluorine material as an electrolyte membrane. Conventionally, it has been considered that a fluorine-based electrolyte membrane is hardly damaged by hydrogen peroxide. Therefore, also in the said patent documents 1, 2, examination is made about the hydrocarbon type electrolyte membrane. However, as a result of various studies, the present inventor has obtained knowledge that even a fluorine-based electrolyte membrane may be damaged by hydrogen peroxide. In this case, since the C—F bond is decomposed by hydrogen peroxide, hydrofluoric acid or the like may be generated.
本発明は、このような実状に鑑みてなされたものであり、電池内で生成された過酸化水素を分解して無害化することにより、長期間運転した場合でも電池性能の低下が少ない固体高分子型燃料電池を提供することを課題とする。また、そのような固体高分子型燃料電池を構成し得る電解質膜電極接合体を提供することを課題とする。 The present invention has been made in view of such a situation, and by decomposing and detoxifying hydrogen peroxide generated in the battery, the solid content can be reduced even when operated for a long period of time. It is an object to provide a molecular fuel cell. It is another object of the present invention to provide an electrolyte membrane electrode assembly that can constitute such a polymer electrolyte fuel cell.
本発明の固体高分子型燃料電池用電解質膜電極接合体は、イオン導電性を有する電解質膜と、該電解質膜の両側に設けられた一対の電極と、からなり、該電解質膜および該一対の電極の少なくとも一つに過酸化物を分解する高温かつ酸性の条件で難溶性のフッ化物であって、希土類金属のフッ化物または遷移金属のフッ化物を含むことを特徴とする。 An electrolyte membrane electrode assembly for a polymer electrolyte fuel cell of the present invention comprises an electrolyte membrane having ionic conductivity and a pair of electrodes provided on both sides of the electrolyte membrane, and the electrolyte membrane and the pair of electrodes At least one of the electrodes is a fluoride that is hardly soluble under high-temperature and acidic conditions for decomposing peroxide, and includes a fluoride of a rare earth metal or a fluoride of a transition metal .
本発明の電解質膜電極接合体（以下、適宜「ＭＥＡ」と称す。）では、電解質膜の両側にそれぞれ燃料極、酸素極となる一対の電極が配置される。よって、本発明のＭＥＡでは、電解質膜、燃料極、酸素極の少なくとも一つに、難溶性フッ化物が含まれる。難溶性フッ化物がそれらの二つ以上に含まれる場合には、より過酸化物の分解効果が高くなる。 In the electrolyte membrane electrode assembly of the present invention (hereinafter referred to as “MEA” where appropriate), a pair of electrodes that respectively serve as a fuel electrode and an oxygen electrode are disposed on both sides of the electrolyte membrane. Therefore, in the MEA of the present invention, a sparingly soluble fluoride is contained in at least one of the electrolyte membrane, the fuel electrode, and the oxygen electrode. When the hardly soluble fluoride is contained in two or more of them, the decomposition effect of the peroxide becomes higher.
上述したように、固体高分子型燃料電池の運転時には、その内部環境は、高温下、酸性雰囲気となる。よって、含有されるフッ化物には、高温かつ酸性の条件で溶出し難いことが要求される。本発明のＭＥＡに含まれるフッ化物は、難溶性のフッ化物であるため、高温かつ酸性の条件でも比較的安定で、溶出し難い。一般に、高温でのフッ化物の溶解度は、室温での溶解度とほとんど変わらないと考えられる。なかには、高温での溶解度が室温での溶解度よりも低下するフッ化物もある。これは、フッ化物が高温で加水分解し、表面に難溶性の塩基性塩あるいは酸化物を生成するためである。本明細書では、室温における水１００ｇへの溶解量が１０ｇ以下の場合を「難溶性」とする。前述したように、固体高分子型燃料電池の運転時の温度である８０℃〜１００℃では、フッ化物の溶解度は室温における値とほぼ同じか、小さくなる。よって、室温における水１００ｇへのフッ化物の溶解量が１０ｇ以下であれば、実用上充分な耐久性を有すると考えられる。 As described above, when the polymer electrolyte fuel cell is operated, the internal environment is an acidic atmosphere at a high temperature. Therefore, the contained fluoride is required to be difficult to elute under high temperature and acidic conditions. Since the fluoride contained in the MEA of the present invention is a sparingly soluble fluoride, it is relatively stable even under high temperature and acidic conditions and is difficult to elute. In general, the solubility of fluoride at high temperature is considered to be almost the same as the solubility at room temperature. Some fluorides have lower solubility at high temperatures than at room temperature. This is because the fluoride is hydrolyzed at a high temperature to form a slightly soluble basic salt or oxide on the surface. In this specification, the case where the amount dissolved in 100 g of water at room temperature is 10 g or less is defined as “slightly soluble”. As described above, at a temperature of 80 ° C. to 100 ° C., which is the operating temperature of the polymer electrolyte fuel cell, the solubility of fluoride is substantially the same as or lower than the value at room temperature. Therefore, if the amount of fluoride dissolved in 100 g of water at room temperature is 10 g or less, it is considered to have practically sufficient durability.
加えて、本発明のＭＥＡに含まれる難溶性フッ化物は、過酸化水素等の過酸化物の分解能が高い。以下、一例として、過酸化水素の分解について説明する。 In addition, the sparingly soluble fluoride contained in the MEA of the present invention has a high resolution of peroxides such as hydrogen peroxide. Hereinafter, decomposition of hydrogen peroxide will be described as an example.
過酸化水素は、式（１）、（２）に示すように、遷移金属イオン（Ｍn+／Ｍ(n+1)+）の存在下でラジカル分解する。
ＨＯＯＨ ＋ Ｍ(n+1)+ → ＨＯＯ・ ＋ Ｈ+ ＋ Ｍn+ ・・・（１）
ＨＯＯＨ ＋ Ｍn+ → ＨＯ・ ＋ ＯＨ- ＋ Ｍ(n+1)+ ・・・（２）
難溶性フッ化物は、このように過酸化水素がラジカル分解する前に、過酸化水素を、式（３）に示すように還元分解するか、あるいは式（４）に示すように酸化分解する。
Ｈ2Ｏ2 ＋ ２Ｈ+ ＋ ２ｅ- → ２Ｈ2Ｏ ・・・（３）
Ｈ2Ｏ2 → Ｏ2 ＋ ２Ｈ+ ＋ ２ｅ- ・・・（４）
なお、難溶性フッ化物の表面では、式［（３）＋（４）］より、式（５）に示すように、２分子の過酸化水素が衝突して、水と酸素とに分解する、いわゆる接触分解反応となる。
２Ｈ2Ｏ2 → ２Ｈ2Ｏ ＋ Ｏ2 ・・・（５）
このように、運転中に生成された過酸化水素は、ラジカル化する前に難溶性フッ化物により分解されるため、過酸化水素ラジカルによるフッ素系材料等の分解や低分子量化は抑制される。その結果、電解質膜や電極の劣化が抑制される。また、セパレータや、燃料電池システムを構成する配管、マニホールド等に移動する過酸化水素が減少するため、それら金属材料の腐食も抑制される。
Hydrogen peroxide undergoes radical decomposition in the presence of transition metal ions (M n + / M (n + 1) + ) as shown in formulas (1) and (2).
HOOH + M (n + 1) + → HOO · + H + + M n + ··· (1)
HOOH + M n + → HO · + OH − + M (n + 1) + (2)
Before the hydrogen peroxide is radically decomposed in this way, the hardly soluble fluoride is subjected to reductive decomposition as shown in the formula (3) or oxidative decomposition as shown in the formula (4).
H 2 O 2 + 2H + + 2e − → 2H 2 O ... (3)
H 2 O 2 → O 2 + 2H + + 2e − (4)
On the surface of the hardly soluble fluoride, from the formula [(3) + (4)], as shown in the formula (5), two molecules of hydrogen peroxide collide and decompose into water and oxygen. This is a so-called catalytic cracking reaction.
2H 2 O 2 → 2H 2 O + O 2 (5)
Thus, since hydrogen peroxide generated during operation is decomposed by the hardly soluble fluoride before radicalization, decomposition of the fluorine-based material and the like due to hydrogen peroxide radicals and reduction in molecular weight are suppressed. As a result, deterioration of the electrolyte membrane and the electrode is suppressed. Moreover, since the hydrogen peroxide which moves to a separator, piping, a manifold, etc. which comprise a fuel cell system reduces, corrosion of these metal materials is also suppressed.
ここで、金属材料の腐食について説明する。金属Ｍが２価で溶出する腐食反応は、式（６）で示される。
Ｍ → Ｍ2+ ＋ ２ｅ- ・・・（６）
一方、過酸化水素の存在下では、過酸化水素が式（７）に示すように腐食の還元反応を担う。
Ｈ2Ｏ2 ＋ ２Ｈ+ ＋ ２ｅ- → ２Ｈ2Ｏ ・・・（７）
したがって、ＭＥＡにて過酸化水素を分解し、ＭＥＡの外部へ移動する過酸化水素を少なくすることで、金属材料の腐食を効果的に抑制することができる。
Here, the corrosion of the metal material will be described. The corrosion reaction in which the metal M elutes in divalent is represented by the formula (6).
M → M 2+ + 2e - ··· (6)
On the other hand, in the presence of hydrogen peroxide, hydrogen peroxide is responsible for the corrosion reduction reaction as shown in equation (7).
H 2 O 2 + 2H + + 2e − → 2H 2 O ... (7)
Therefore, corrosion of the metal material can be effectively suppressed by decomposing hydrogen peroxide with the MEA and reducing the amount of hydrogen peroxide that moves to the outside of the MEA.
本発明の固体高分子型燃料電池は、上記本発明の電解質膜電極接合体を備えることを特徴とする。すなわち、本発明の固体高分子型燃料電池では、運転時に過酸化水素が生成しても、過酸化水素は難溶性フッ化物により速やかに分解される。そのため、運転時における電解質膜や電極の劣化が少なく、長期間運転した場合でも電池性能の低下は少ない。 A polymer electrolyte fuel cell according to the present invention includes the above-described electrolyte membrane electrode assembly according to the present invention. That is, in the polymer electrolyte fuel cell of the present invention, even if hydrogen peroxide is generated during operation, the hydrogen peroxide is rapidly decomposed by the hardly soluble fluoride. For this reason, there is little deterioration of the electrolyte membrane and the electrode during operation, and there is little decrease in battery performance even when operated for a long period of time.
本発明の電解質膜電極接合体は、電解質膜および一対の電極の少なくとも一つに過酸化物を分解する難溶性フッ化物を含む。そのため、運転中に生成された過酸化水素は、難溶性フッ化物により速やかに分解され無害化される。したがって、本発明の電解質膜電極接合体を備えた固体高分子型燃料電池では、電極や電解質膜の劣化が少なく、長期間運転した場合でも電池性能の低下は少ない。 The electrolyte membrane electrode assembly of the present invention contains a sparingly soluble fluoride that decomposes peroxide in at least one of the electrolyte membrane and the pair of electrodes. Therefore, the hydrogen peroxide generated during operation is quickly decomposed and rendered harmless by the hardly soluble fluoride. Therefore, in the polymer electrolyte fuel cell provided with the electrolyte membrane electrode assembly of the present invention, there is little deterioration of the electrode and the electrolyte membrane, and even when the battery is operated for a long time, the battery performance is hardly lowered.
以下に、本発明の固体高分子型燃料電池用電解質膜電極接合体および固体高分子型燃料電池の実施形態を説明する。なお、本発明の固体高分子型燃料電池用電解質膜電極接合体および固体高分子型燃料電池は、下記の実施形態に限定されるものではない。本発明の固体高分子型燃料電池用電解質膜電極接合体および固体高分子型燃料電池は、本発明の要旨を逸脱しない範囲において、当業者が行い得る変更、改良等を施した種々の形態にて実施することができる。 Hereinafter, embodiments of the electrolyte membrane electrode assembly for a polymer electrolyte fuel cell and the polymer electrolyte fuel cell of the present invention will be described. In addition, the electrolyte membrane electrode assembly for polymer electrolyte fuel cells and the polymer electrolyte fuel cell of the present invention are not limited to the following embodiments. The electrolyte membrane electrode assembly for a polymer electrolyte fuel cell and the polymer electrolyte fuel cell of the present invention are in various forms that have been modified or improved by those skilled in the art without departing from the gist of the present invention. Can be implemented.
〈固体高分子型燃料電池用電解質膜電極接合体〉
本発明の固体高分子型燃料電池用電解質膜電極接合体は、イオン導電性を有する電解質膜と、該電解質膜の両側に設けられた一対の電極と、からなり、該電解質膜および該一対の電極の少なくとも一つに過酸化物を分解する難溶性フッ化物を含む。
<Electrolyte membrane electrode assembly for polymer electrolyte fuel cell>
An electrolyte membrane electrode assembly for a polymer electrolyte fuel cell of the present invention comprises an electrolyte membrane having ionic conductivity and a pair of electrodes provided on both sides of the electrolyte membrane, and the electrolyte membrane and the pair of electrodes At least one of the electrodes includes a sparingly soluble fluoride that decomposes the peroxide.
難溶性フッ化物としては、希土類金属および遷移金属の少なくとも一種を含むフッ化物を用いる。それらのフッ化物の一種を単独で用いてもよく、また二種以上を混合して用いてもよい。希土類金属を含む難溶性フッ化物には、例えば、ＣｅＦ３、ＬａＦ３、ＧｄＦ３等が挙げられる。また、遷移金属を含む難溶性フッ化物には、例えば、ＦｅＦ２、ＦｅＦ２・４Ｈ２Ｏ、ＦｅＦ３、ＦｅＦ３・３Ｈ２Ｏ、Ｌｉ３ＦｅＦ６、ＬｉＦｅ２Ｆ６、ＮａＦｅＦ３、Ｎａ３ＦｅＦ６、ＫＦｅＦ３、ＫＦｅＦ４、Ｋ２ＦｅＦ５、Ｋ２ＦｅＦ５・Ｈ２Ｏ、Ｋ３ＦｅＦ６、ＣｓＦｅＦ３、ＴｉＦ４、Ｎａ２ＴｉＦ６、Ｋ２ＴｉＦ６、Ｋ２ＴｉＦ６・Ｈ２Ｏ、ＣａＴｉＦ６、ＳｒＴｉＦ６、ＢａＴｉＦ６、ＺｒＦ４、Ｎａ５ＺｒＦ９、ＣｒＦ３、Ｋ３ＣｒＦ６、ＮｉＦ２、ＣｕＦ２、ＭｎＦ２、ＭｎＦ３・３Ｈ２Ｏ、ＹＦ３等が挙げられる。特に、酸に対する溶解度が小さく、過酸化水素の分解能を長期間安定して発揮できるという理由から、難溶性フッ化物としてＣｅＦ３を用いることが望ましい。 The sparingly soluble fluoride, Ru with a fluoride containing at least one rare earth metal and transition metal. One of these fluorides may be used alone, or two or more thereof may be mixed and used. Examples of the hardly soluble fluoride containing rare earth metal include CeF 3 , LaF 3 , GdF 3 and the like. Examples of the hardly soluble fluoride containing a transition metal include FeF 2 , FeF 2 .4H 2 O, FeF 3 , FeF 3 .3H 2 O, Li 3 FeF 6 , LiFe 2 F 6 , NaFeF 3 , and Na 3. FeF 6 , KFeF 3 , KFeF 4 , K 2 FeF 5 , K 2 FeF 5 · H 2 O, K 3 FeF 6 , CsFeF 3 , TiF 4 , Na 2 TiF 6 , K 2 TiF 6 , K 2 TiF 6 · H 2 O, CaTiF 6, SrTiF 6 , BaTiF 6, ZrF 4, Na 5 ZrF 9, CrF 3, K 3 CrF 6, NiF 2, CuF 2, MnF 2, MnF 3 · 3H 2 O, YF 3 , and the like . In particular, CeF 3 is desirably used as the sparingly soluble fluoride because it has a low solubility in acid and can stably exhibit the resolution of hydrogen peroxide for a long period of time.
難溶性フッ化物としては、天然に鉱物として存在するフッ化物を用いてもよく、人工的に合成したフッ化物を用いてもよい。鉱物には、例えば、希土類金属Ｒを含む螢石（Ｃａ、Ｒ）Ｆ2等が挙げられる。鉱物は、安価であるが、使用に際して不純物の精製および粉砕等が必要となる。一方、人工的に合成したフッ化物は、純度が高く、合成の際に粒度の調整も可能であるため好適である。また、人工的に合成した後、高温でエージングし、結晶性を高めたフッ化物は、より溶出し難く好適である。 As the sparingly soluble fluoride, a fluoride naturally existing as a mineral may be used, or an artificially synthesized fluoride may be used. Examples of the mineral include meteorite (Ca, R) F 2 containing a rare earth metal R. Minerals are inexpensive, but need to be purified and pulverized for impurities. On the other hand, an artificially synthesized fluoride is preferable because it has high purity and can be adjusted in particle size during synthesis. Further, a fluoride which has been artificially synthesized and then aged at a high temperature to improve crystallinity is preferable because it is more difficult to elute.
含有される難溶性フッ化物の粒子径は、特に限定されるものではない。但し、難溶性フッ化物の粒子径が小さすぎると、酸性条件で溶出し易くなり長期間の安定性という観点で問題となる。よって、難溶性フッ化物の粒子径は０．０５μｍ以上であることが望ましい。一方、難溶性フッ化物の粒子径が大きすぎると、分散性が低下する。よって、難溶性フッ化物の粒子径は５μｍ以下であることが望ましい。 The particle diameter of the hardly soluble fluoride to be contained is not particularly limited. However, if the particle diameter of the sparingly soluble fluoride is too small, it is easy to elute under acidic conditions, which causes a problem in terms of long-term stability. Therefore, the particle diameter of the hardly soluble fluoride is desirably 0.05 μm or more. On the other hand, if the particle diameter of the sparingly soluble fluoride is too large, the dispersibility is lowered. Therefore, the particle size of the hardly soluble fluoride is desirably 5 μm or less.
難溶性フッ化物は、電解質膜、燃料極、酸素極の少なくとも一つに含まれる。例えば、難溶性フッ化物を電解質膜に含有させる場合、難溶性フッ化物の含有割合を、電解質膜の全体重量を１００ｗｔ％とした場合の０．１ｗｔ％以上とすることが望ましい。０．１ｗｔ％未満の場合には、過酸化物を分解する効果が小さいからである。０．５ｗｔ％以上とするとより好適である。一方、プロトン導電性を考慮すると、難溶性フッ化物の含有割合を５ｗｔ％以下とすることが望ましい。１ｗｔ％以下とするとより好適である。 The hardly soluble fluoride is contained in at least one of the electrolyte membrane, the fuel electrode, and the oxygen electrode. For example, when the hardly soluble fluoride is contained in the electrolyte membrane, the content ratio of the hardly soluble fluoride is preferably 0.1 wt% or more when the total weight of the electrolyte membrane is 100 wt%. This is because when the amount is less than 0.1 wt%, the effect of decomposing peroxide is small. More preferably, it is 0.5 wt% or more. On the other hand, considering proton conductivity, it is desirable that the content ratio of the hardly soluble fluoride is 5 wt% or less. More preferably, it is 1 wt% or less.
一般に、燃料極および酸素極は、それぞれ、触媒層と拡散層とから構成される。触媒層は、電気化学反応の反応場であり、カーボンに担持された白金等の触媒と固体高分子電解質とを含む。拡散層は、触媒層への反応ガスの供給と、触媒層との間で電子の授受を行う役割を果たし、カーボンクロス等の多孔質材料からなる。よって、例えば、難溶性フッ化物を電極の触媒層に含有させる場合、難溶性フッ化物の含有割合を、カーボンに担持された白金触媒（以下、「Ｐｔ／Ｃ触媒」と表す。）の重量を１００ｗｔ％とした場合の０．２ｗｔ％以上とすることが望ましい。０．２ｗｔ％未満の場合には、過酸物を分解する効果が小さいからである。０．５ｗｔ％以上とするとより好適である。一方、電極における電気化学的反応への影響を考慮すると、難溶性フッ化物の含有割合を１０ｗｔ％以下とすることが望ましい。５ｗｔ％以下とするとより好適である。 In general, the fuel electrode and the oxygen electrode are each composed of a catalyst layer and a diffusion layer. The catalyst layer is a reaction field for electrochemical reaction, and includes a catalyst such as platinum supported on carbon and a solid polymer electrolyte. The diffusion layer serves to supply a reaction gas to the catalyst layer and exchange electrons with the catalyst layer, and is made of a porous material such as carbon cloth. Therefore, for example, when a hardly soluble fluoride is contained in the catalyst layer of the electrode, the content of the hardly soluble fluoride is the weight of a platinum catalyst supported on carbon (hereinafter referred to as “Pt / C catalyst”). It is desirable to set it to 0.2 wt% or more with respect to 100 wt%. This is because when the amount is less than 0.2 wt%, the effect of decomposing the peracid is small. More preferably, it is 0.5 wt% or more. On the other hand, considering the influence on the electrochemical reaction in the electrode, it is desirable that the content ratio of the hardly soluble fluoride is 10 wt% or less. More preferably, it is 5 wt% or less.
また、難溶性フッ化物を電極の拡散層に含有させる場合、難溶性フッ化物の含有割合を、拡散層を構成する多孔質材料の重量を１００ｗｔ％とした場合の０．２ｗｔ％以上とすることが望ましい。０．２ｗｔ％未満の場合には、過酸物を分解する効果が小さいからである。１ｗｔ％以上とするとより好適である。一方、拡散層の撥水性低下による生成水の排出性能低下を抑制するという観点から、難溶性フッ化物の含有割合を１０ｗｔ％以下とすることが望ましい。５ｗｔ％以下とするとより好適である。なお、触媒層と拡散層とが一体となり電極を構成するような場合には、難溶性フッ化物の含有割合は、上記触媒層に固定する場合に準ずればよい。 In addition, when the hardly soluble fluoride is contained in the diffusion layer of the electrode, the content ratio of the hardly soluble fluoride is 0.2 wt% or more when the weight of the porous material constituting the diffusion layer is 100 wt%. Is desirable. This is because when the amount is less than 0.2 wt%, the effect of decomposing the peracid is small. More preferably, it is 1 wt% or more. On the other hand, it is desirable that the content ratio of the sparingly soluble fluoride is 10 wt% or less from the viewpoint of suppressing a decrease in the discharge performance of generated water due to a decrease in water repellency of the diffusion layer. More preferably, it is 5 wt% or less. In the case where the catalyst layer and the diffusion layer are integrated to form an electrode, the content ratio of the hardly soluble fluoride may be the same as that in the case of fixing to the catalyst layer.
難溶性フッ化物は、電解質膜、燃料極、酸素極のいずれに含まれていてもよい。生成した過酸化水素を速やかに分解するという観点から、難溶性フッ化物を酸素極に含有させることが望ましい。また、電解質膜の劣化、およびフッ酸等の生成を効果的に抑制するという観点から、難溶性フッ化物を電解質膜に含有させることが望ましい。難溶性フッ化物を、電解質膜および酸素極の両方に含有させるとより好適である。また、電極が触媒層と拡散層とから構成される場合、難溶性フッ化物を拡散層に含有させると、過酸化水素のＭＥＡ外部への移動を抑制することができ、燃料電池システムを構成する配管等の金属材料の腐食を効果的に抑制することができる。 The hardly soluble fluoride may be contained in any of the electrolyte membrane, the fuel electrode, and the oxygen electrode. From the viewpoint of promptly decomposing generated hydrogen peroxide, it is desirable to contain a hardly soluble fluoride in the oxygen electrode. Further, from the viewpoint of effectively suppressing the deterioration of the electrolyte membrane and the generation of hydrofluoric acid and the like, it is desirable to contain a hardly soluble fluoride in the electrolyte membrane. More preferably, the hardly soluble fluoride is contained in both the electrolyte membrane and the oxygen electrode. Further, when the electrode is composed of a catalyst layer and a diffusion layer, when the hardly soluble fluoride is contained in the diffusion layer, the movement of hydrogen peroxide to the outside of the MEA can be suppressed, and the fuel cell system is configured. Corrosion of metal materials such as piping can be effectively suppressed.
難溶性フッ化物を電解質膜、電極へ含有させる方法は、特に限定されるものではない。例えば、粉末状の難溶性フッ化物を電解質膜等へ混合する、あるいは、ゾルゲル法により電解質膜等へ固定する等の方法等が挙げられる。ゾルゲル法は、難溶性フッ化物の微粒子を、電解質膜等に均一に分散させることができるため好適である。以下、各方法について具体的に説明する。 The method for incorporating the hardly soluble fluoride into the electrolyte membrane and the electrode is not particularly limited. For example, a method of mixing a powdery poorly soluble fluoride into an electrolyte membrane or the like, or fixing it to the electrolyte membrane or the like by a sol-gel method, etc. The sol-gel method is preferable because fine particles of hardly soluble fluoride can be uniformly dispersed in an electrolyte membrane or the like. Each method will be specifically described below.
（１）混合法
（ａ）電解質膜
粉末状の難溶性フッ化物を電解質膜となる高分子に混練し、その高分子を成膜して電解質膜とすればよい。
(1) Mixing method (a) Electrolyte membrane A powdery hardly soluble fluoride may be kneaded with a polymer to be an electrolyte membrane, and the polymer is formed into an electrolyte membrane.
（ｂ）電極
電極の触媒層に含有させる場合、触媒層を形成するための触媒インクに、粉末状の難溶性フッ化物を混合すればよい。具体的には、粉末状の難溶性フッ化物と、電極触媒と、バインダーとなる高分子とを、水やアルコール等の溶媒に分散させて触媒インクを調製すればよい。
(B) Electrode When contained in the catalyst layer of the electrode, a powdery hardly soluble fluoride may be mixed with the catalyst ink for forming the catalyst layer. Specifically, a catalyst ink may be prepared by dispersing a powdery hardly soluble fluoride, an electrode catalyst, and a polymer as a binder in a solvent such as water or alcohol.
電極の拡散層に含有させる場合、例えば、拡散層となるカーボンクロス等の表面に、粉末状の難溶性フッ化物を含む撥水層を形成すればよい。具体的には、まず、粉末状の難溶性フッ化物、炭素粉末等の導電性物質、ポリテトラフルオロエチレン（ＰＴＦＥ）等の撥水剤、必要に応じて界面活性剤等を、水またはアルコール等の揮発性溶媒と混合してペーストを生成する。次いで、そのペーストをドクターブレード法、スプレー法等によりカーボンクロス等の表面に塗布、乾燥して撥水層を形成すればよい。 When it is contained in the diffusion layer of the electrode, for example, a water repellent layer containing a powdery hardly soluble fluoride may be formed on the surface of carbon cloth or the like that becomes the diffusion layer. Specifically, first, a powdery hardly soluble fluoride, a conductive material such as carbon powder, a water repellent such as polytetrafluoroethylene (PTFE), a surfactant as necessary, water, alcohol, etc. To produce a paste. Next, the paste may be applied to the surface of carbon cloth or the like by a doctor blade method, a spray method, or the like, and dried to form a water repellent layer.
（２）ゾルゲル法
本方法では、電解質膜、あるいは電極の触媒層内電解質に、難溶性フッ化物を析出させて固定する。例えば、電解質膜等を、難溶性フッ化物を構成する希土類金属および遷移金属の少なくとも一種を含む金属塩を水に溶解した金属塩水溶液、あるいは希土類金属および遷移金属の少なくとも一種を含む金属の有機錯体を有機溶媒に溶解した有機錯体溶液に浸漬し、その後、フッ化物イオンを含む酸溶液またはアルカリ溶液と接触させて加水分解すればよい。
(2) Sol-gel method In this method, a hardly soluble fluoride is deposited and fixed on the electrolyte membrane or the electrolyte in the catalyst layer of the electrode. For example, an electrolyte membrane or the like, an aqueous metal salt solution in which a metal salt containing at least one kind of rare earth metal and transition metal constituting a sparingly soluble fluoride is dissolved in water, or an organic complex of a metal containing at least one kind of rare earth metal and transition metal May be immersed in an organic complex solution dissolved in an organic solvent, and then contacted with an acid solution or an alkali solution containing fluoride ions for hydrolysis.
ここで、上記金属塩としては、水への溶解度が高い塩として、硝酸塩、硫酸塩、塩化物、酢酸塩、シュウ酸塩等を用いればよい。上記金属の有機錯体としては、該金属のｔ−ブトキサイド、エチルヘキサネート、オクタンジオネート、イソプロポキサイド等を用いればよい。また、フッ化物イオンを含む酸溶液としては、ＫＨＦ2等の酸性フッ化物の水溶液、フッ化水素酸等を用いればよい。フッ化物イオンを含むアルカリ溶液としては、ナトリウム、カリウム、アンモニウム等のフッ化物の水溶液を用いればよい。なかでも、フッ化水素酸を用いることが望ましい。フッ化水素酸を用いると、フッ化物の生成と、金属イオンによりイオン交換された電解質基の酸型への変換とを同時に行うことができる。 Here, as the metal salt, nitrate, sulfate, chloride, acetate, oxalate, or the like may be used as a salt having high solubility in water. As the metal organic complex, t-butoxide, ethylhexanate, octanedionate, isopropoxide, or the like of the metal may be used. As the acid solution containing fluoride ions, an aqueous solution of acidic fluoride such as KHF 2 , hydrofluoric acid, or the like may be used. As the alkaline solution containing fluoride ions, an aqueous solution of fluoride such as sodium, potassium, or ammonium may be used. Of these, it is desirable to use hydrofluoric acid. When hydrofluoric acid is used, it is possible to simultaneously generate fluoride and convert the electrolyte group ion-exchanged with metal ions into an acid form.
金属塩水溶液、有機錯体溶液への浸漬、その後の加水分解の際には、必要に応じて、加熱してもよい。特に、金属塩水溶液を用いる場合には、酢酸、クエン酸等の錯化剤を加えるとよい。 In the case of immersion in a metal salt aqueous solution or an organic complex solution, and subsequent hydrolysis, heating may be performed as necessary. In particular, when a metal salt aqueous solution is used, a complexing agent such as acetic acid or citric acid may be added.
また、電解質膜等の前駆体を、上記金属塩水溶液あるいは有機錯体溶液に浸漬し、加水分解してもよい。本方法は、電解質膜等の前駆体から電解質膜等への変換と、難溶性フッ化物の固定とを同時に進行させるため効率的である。ここで、電解質膜等の前駆体とは、電解質膜等の電解質基が電解質基前駆体に置換されたものをいう。また、電解質基前駆体とは、加水分解により容易に電解質基に変換可能な官能基をいう。電解質基前駆体の具体例として、スルホニルハライド基（−ＳＯ2Ｘ：Ｘはハロゲン元素、以下同じ。）等のハライド基、−ＳＯ3Ｍ（Ｍはアルカリ金属元素、以下同じ。）等のアルカリ金属塩等が挙げられる。 Further, a precursor such as an electrolyte membrane may be immersed in the metal salt aqueous solution or the organic complex solution and hydrolyzed. This method is efficient because the conversion from the precursor such as the electrolyte membrane to the electrolyte membrane and the like and the fixing of the hardly soluble fluoride proceed simultaneously. Here, a precursor such as an electrolyte membrane refers to a material in which an electrolyte group such as an electrolyte membrane is replaced with an electrolyte group precursor. The electrolyte group precursor means a functional group that can be easily converted into an electrolyte group by hydrolysis. Specific examples of the electrolyte group precursor include halide groups such as a sulfonyl halide group (—SO 2 X: X is a halogen element, the same shall apply hereinafter), and alkalis such as —SO 3 M (M is an alkali metal element, the same applies hereinafter). A metal salt etc. are mentioned.
電解質膜等の前駆体をアルカリ性の金属塩水溶液等に浸漬すると、例えば、ハライド基は加水分解されアルカリ金属塩となる（−ＳＯ2Ｘ→−ＳＯ3Ｍ）。次いで、フッ化物イオンを含む酸溶液と接触させることにより、電解質基前駆体は酸型に変換され電解質基となる（−ＳＯ3Ｍ→−ＳＯ3Ｈ）。 When a precursor such as an electrolyte membrane is immersed in an alkaline metal salt aqueous solution or the like, for example, the halide group is hydrolyzed to become an alkali metal salt (—SO 2 X → —SO 3 M). Then, by contact with an acid solution including fluoride ions, the electrolyte group precursor is converted to acid form the electrolyte group (-SO 3 M → -SO 3 H ).
（３）電解法
本方法では、ＭＥＡを電解用電極の少なくとも一方として、フッ化物イオンを含む溶液中で通電することにより、該ＭＥＡの表面に難溶性フッ化物を析出させ、固定する。フッ化物イオンを含む溶液としては、ＫＨＦ2等の酸性フッ化物の水溶液、フッ化水素酸、ケイフッ化水素酸、ホウフッ化水素酸、ナトリウム、カリウム、アンモニウム等のフッ化物の水溶液を用いればよい。また、ＭＥＡには、予め電極触媒層の触媒等に、難溶性フッ化物を構成する希土類金属および遷移金属の少なくとも一種を含む金属を含有させておく。そして、フッ化物イオンを含む溶液を電気分解することにより、溶液中のフッ化物イオンと、ＭＥＡから溶出した金属イオン（Ｒn+）とが、［Ｒn+＋ｎＦ-→ＲＦn］のごとくアノード側で反応し、難溶性フッ化物が生成する。
(3) Electrolytic method In this method, the MEA is used as at least one of the electrodes for electrolysis, and a current is passed in a solution containing fluoride ions to deposit and fix a poorly soluble fluoride on the surface of the MEA. As the solution containing fluoride ions, an aqueous solution of an acidic fluoride such as KHF 2, or an aqueous solution of a fluoride such as hydrofluoric acid, silicohydrofluoric acid, borohydrofluoric acid, sodium, potassium, or ammonium may be used. In the MEA, a metal containing at least one of a rare earth metal and a transition metal constituting a sparingly soluble fluoride is previously contained in the catalyst of the electrode catalyst layer. Then, by electrolyzing the solution containing fluoride ions, the fluoride ions in the solution and the metal ions (R n + ) eluted from the MEA are on the anode side as [R n + + nF − → RF n ]. Reacts to produce sparingly soluble fluoride.
本方法では、電解用電極の両方をＭＥＡとしてもよく、電解用電極の一方をＭＥＡとしてもよい。電解用電極の一方をＭＥＡとした場合には、他方の電解用電極として、チタン、白金、カーボン等を用いればよい。なお、使用するＭＥＡは、電解質膜の両面に電極が形成されている態様の他、電解質膜の片面に電極が形成されている態様であってもよい。通常、電極は、拡散層と触媒層とから構成される。しかし、本方法では、固体高分子電解質の劣化を効果的に抑制するという観点から、触媒層のみが形成されたＭＥＡを使用することが望ましい。この場合、ＭＥＡにおける触媒層の表面に、難溶性フッ化物が析出し、固定される。 In this method, both of the electrodes for electrolysis may be MEA, and one of the electrodes for electrolysis may be MEA. When one of the electrodes for electrolysis is MEA, titanium, platinum, carbon, or the like may be used as the other electrode for electrolysis. The MEA to be used may be an aspect in which electrodes are formed on one side of the electrolyte membrane in addition to an aspect in which electrodes are formed on both sides of the electrolyte membrane. Usually, the electrode is composed of a diffusion layer and a catalyst layer. However, in this method, it is desirable to use MEA in which only the catalyst layer is formed from the viewpoint of effectively suppressing deterioration of the solid polymer electrolyte. In this case, a hardly soluble fluoride is deposited and fixed on the surface of the catalyst layer in the MEA.
（４）気相反応法
本方法では、ＭＥＡにおける電極触媒層の触媒等に、予め、難溶性フッ化物を構成する希土類金属および遷移金属の少なくとも一種を含む金属、その酸化物等を含有させておき、該ＭＥＡにフッ素ガスあるいはフッ化水素ガスを吹き付けることにより、金属等とフッ素とを反応させ、難溶性フッ化物を生成させる。
(4) Gas phase reaction method In this method, the catalyst of the electrode catalyst layer in MEA is preliminarily made to contain a metal containing at least one kind of rare earth metal and transition metal constituting the sparingly soluble fluoride, its oxide, and the like. Then, by spraying fluorine gas or hydrogen fluoride gas on the MEA, metal or the like reacts with fluorine to generate a hardly soluble fluoride.
本発明のＭＥＡは、難溶性フッ化物を電解質膜、電極へ含有させる点を除いて、通常の方法に従って作製することができる。例えば、まず、酸素極用および燃料極用の各触媒インクを、それぞれＰＴＦＥ製シートの表面に塗布、乾燥し、該シート表面に各電極の触媒層を形成する。続いて、シート表面に形成された各電極の触媒層を、電解質膜の両表面にそれぞれホットプレス等により圧着する。圧着後、シートのみを剥離する。これにより、電解質膜の一方の表面には、酸素極を構成する触媒層が、他方の表面には燃料極を構成する触媒層が形成される。最後に、拡散層となるカーボンクロス等を両極それぞれの触媒層の表面にホットプレス等により圧着し、ＭＥＡとすればよい。 The MEA of the present invention can be produced according to a usual method except that a hardly soluble fluoride is contained in the electrolyte membrane and the electrode. For example, first, each catalyst ink for oxygen electrode and fuel electrode is applied to the surface of a PTFE sheet and dried to form a catalyst layer for each electrode on the sheet surface. Subsequently, the catalyst layer of each electrode formed on the sheet surface is pressure-bonded to both surfaces of the electrolyte membrane by hot pressing or the like. After crimping, only the sheet is peeled off. As a result, a catalyst layer constituting the oxygen electrode is formed on one surface of the electrolyte membrane, and a catalyst layer constituting the fuel electrode is formed on the other surface. Finally, a carbon cloth or the like serving as a diffusion layer may be pressure-bonded to the surfaces of the catalyst layers of both electrodes by hot pressing or the like to form an MEA.
なお、本発明のＭＥＡでは、電解質膜の種類は特に限定されるものではない。例えば、全フッ素系スルホン酸膜、全フッ素系ホスホン酸膜、全フッ素系カルボン酸膜、含フッ素炭化水素系グラフト膜、全炭化水素系グラフト膜、全芳香族膜等を用いることができる。また、ＰＴＦＥ、ポリイミド等の補強材を含む、機械的特性を強化した複合高分子膜を用いてもよい。特に、耐久性等を考慮した場合には、全フッ素系の高分子膜を用いることが望ましい。なかでも、電解質としての性能が高いという理由から、全フッ素系スルホン酸膜を用いることが望ましい。全フッ素系スルホン酸膜の一例として、「ナフィオン」（登録商標、デュポン社製）、「アシプレックス」（登録商標、旭化成株式会社製）、「フレミオン」（登録商標、旭硝子株式会社製）等が挙げられる。 In the MEA of the present invention, the type of electrolyte membrane is not particularly limited. For example, a perfluorinated sulfonic acid film, a perfluorinated phosphonic acid film, a perfluorinated carboxylic acid film, a fluorinated hydrocarbon-based graft film, a perhydrocarbon-based graft film, a wholly aromatic film, or the like can be used. Moreover, you may use the composite polymer film which strengthened mechanical characteristics containing reinforcement materials, such as PTFE and a polyimide. In particular, in consideration of durability and the like, it is desirable to use a perfluorinated polymer film. Among these, it is desirable to use a perfluorinated sulfonic acid membrane because of its high performance as an electrolyte. Examples of perfluorinated sulfonic acid membranes include “Nafion” (registered trademark, manufactured by DuPont), “Aciplex” (registered trademark, manufactured by Asahi Kasei Corporation), “Flemion” (registered trademark, manufactured by Asahi Glass Co., Ltd.), etc. Can be mentioned.
〈固体高分子型燃料電池〉
本発明の固体高分子型燃料電池は、上記本発明の電解質膜電極接合体を備える。例えば、本発明の電解質膜電極接合体を、セパレータを介して複数個積層させて構成すればよい。電解質膜電極接合体を挟持するセパレータとしては、集電性能が高く、酸化水蒸気雰囲気下でも比較的安定な焼成カーボン、成形カーボンや、ステンレス材料の表面に貴金属や炭素材料を被覆したもの等を用いればよい。
<Solid polymer fuel cell>
The polymer electrolyte fuel cell of the present invention includes the above-described electrolyte membrane electrode assembly of the present invention. For example, what is necessary is just to comprise the electrolyte membrane electrode assembly of this invention by laminating | stacking two or more through a separator. As a separator for sandwiching an electrolyte membrane electrode assembly, a fired carbon, a molded carbon, or a stainless steel material coated with a noble metal or a carbon material, which has high current collecting performance and is relatively stable even in an oxidizing water vapor atmosphere, is used. That's fine.
上記実施形態に基づいて、種々の難溶性フッ化物を含む電解質膜を製造し、その耐久性を評価した。また、酸素極の触媒層に難溶性フッ化物としてＣｅＦ3を含むＭＥＡを作製した。作製したＭＥＡを用いて電池反応を行い、電解質膜および電極の劣化の程度を調査した。以下、順に説明する。 Based on the said embodiment, the electrolyte membrane containing various hardly soluble fluoride was manufactured, and the durability was evaluated. In addition, an MEA containing CeF 3 as a sparingly soluble fluoride in the catalyst layer of the oxygen electrode was produced. A battery reaction was performed using the produced MEA, and the degree of deterioration of the electrolyte membrane and the electrode was investigated. Hereinafter, it demonstrates in order.
〈難溶性フッ化物を含む電解質膜の製造および耐久性評価〉
（１）難溶性フッ化物を含む電解質膜の製造
下記表１に示す各金属塩のＣｅ3+等の陽イオン濃度が０．０１Ｍである種々の金属塩水溶液を１００ｍｌ準備した。準備した各金属塩水溶液に、全フッ素系スルホン酸膜（７．２ｃｍ×７．２ｃｍ、厚さ４５μｍ、本製造過程では、以下単に「膜」と称す。）を９０℃にて１時間浸漬し、金属イオンを膜に吸着させた。膜をイオン交換水で洗浄した後、０．１Ｍのフッ化水素酸に９０℃にて１時間浸漬し、加水分解した。その後、膜をイオン交換水で数回洗浄し、種々の難溶性フッ化物が固定された膜（実施例１〜６）を得た。
<Manufacture and durability evaluation of electrolyte membrane containing sparingly soluble fluoride>
(1) Production of Electrolyte Membrane Containing Refractory Fluoride 100 ml of various metal salt aqueous solutions having a cation concentration of 0.01 M such as Ce 3+ of each metal salt shown in Table 1 below were prepared. A perfluorinated sulfonic acid membrane (7.2 cm × 7.2 cm, thickness 45 μm, hereinafter simply referred to as “membrane” in this production process) is immersed in each prepared metal salt aqueous solution at 90 ° C. for 1 hour. , Metal ions were adsorbed on the membrane. The membrane was washed with ion-exchanged water, and then immersed in 0.1 M hydrofluoric acid at 90 ° C. for 1 hour for hydrolysis. Thereafter, the membrane was washed several times with ion-exchanged water to obtain membranes (Examples 1 to 6) on which various hardly soluble fluorides were fixed.
（２）耐久性の評価
製造した各電解質膜を、ＰＴＦＥ製の密封容器中にて、１ｗｔ％の過酸化水素と１４ｐｐｍの鉄イオン（Ｆｅ2+）とを含む水溶液（２００ｍｌ）に浸漬し、１００℃に加熱して２４時間保持した。該水溶液を冷却した後、水溶液中に溶出したフッ化物イオン（Ｆ-）の濃度を測定した。Ｆ-濃度の測定は、イオン選択性電極（オリオン社製）を用いた。Ｆ-濃度は、各電解質膜の劣化の程度を示す指標となる。なお、比較のため、難溶性フッ化物が固定されていない同種の電解質膜（比較例１）を、上記同様の水溶液に浸漬し、Ｆ-濃度を測定した。結果を表１に示す。
(2) Durability Evaluation Each manufactured electrolyte membrane was immersed in an aqueous solution (200 ml) containing 1 wt% hydrogen peroxide and 14 ppm iron ions (Fe 2+ ) in a sealed container made of PTFE, Heat to 100 ° C. and hold for 24 hours. After the aqueous solution was cooled, the concentration of fluoride ions (F − ) eluted in the aqueous solution was measured. For the measurement of F − concentration, an ion selective electrode (manufactured by Orion) was used. The F − concentration is an index indicating the degree of deterioration of each electrolyte membrane. For comparison, an electrolyte membrane of the same kind (Comparative Example 1) to which hardly soluble fluoride is not fixed was immersed in the same aqueous solution as described above, and the F − concentration was measured. The results are shown in Table 1.
表１に示すように、難溶性フッ化物が固定された実施例１〜６の電解質膜では、従来の比較例１の電解質膜と比較して、Ｆ-濃度は小さくなった。特に、実施例１（ＣｅＦ3）、実施例５（ＦｅＦ2）の電解質膜におけるＦ-濃度は小さかった。これより、難溶性フッ化物を含む電解質膜は、過酸化水素およびＦｅ2+の存在下でも分解され難く、劣化し難いことがわかった。 As shown in Table 1, in the electrolyte membranes of Examples 1 to 6 to which the hardly soluble fluoride was fixed, the F − concentration was smaller than that of the conventional electrolyte membrane of Comparative Example 1. In particular, the F − concentration in the electrolyte membranes of Example 1 (CeF 3 ) and Example 5 (FeF 2 ) was small. From this, it was found that the electrolyte membrane containing the hardly soluble fluoride is hardly decomposed even in the presence of hydrogen peroxide and Fe 2+ , and hardly deteriorates.
〈ＭＥＡの作製および劣化調査〉
（１）ＭＥＡの作製
酸素極の触媒層にＣｅＦ3を含むＭＥＡを作製した。まず、酸素極の触媒層を形成するための酸素極用触媒インクを調製した。０．５ｇのＰｔ／Ｃ触媒（白金担持率６０ｗｔ％）に、０．０２５ｇのＣｅＦ3粉末を加え、さらに、蒸留水２．０ｇ、エタノール２．５ｇ、プロピレングリコール１．０ｇ、ナフィオン溶液（２２ｗｔ％、デュポン社製）０．９ｇを、この順に加えた。そして、超音波ホモジナイザーで分散させてＣｅＦ3を含む触媒インクを調製した。
<Production and degradation investigation of MEA>
(1) Production of MEA An MEA containing CeF 3 in the catalyst layer of the oxygen electrode was produced. First, an oxygen electrode catalyst ink for forming an oxygen electrode catalyst layer was prepared. 0.025 g of CeF 3 powder is added to 0.5 g of Pt / C catalyst (platinum loading 60 wt%), and further, 2.0 g of distilled water, 2.5 g of ethanol, 1.0 g of propylene glycol, Nafion solution (22 wt. %, Manufactured by DuPont) was added in this order. Then, a catalyst ink containing CeF 3 was prepared by dispersing with an ultrasonic homogenizer.
次に、燃料極の触媒層を形成するための燃料極用触媒インクを調製した。ＣｅＦ3粉末を加えない点、および燃料極触媒には、白金の含有割合が３０ｗｔ％であるＰｔ／Ｃ触媒を用いた点以外は、上記酸素極用触媒インクの調製と同様の方法で、燃料極用触媒インクを調製した。 Next, a fuel electrode catalyst ink for forming a fuel electrode catalyst layer was prepared. The fuel was prepared in the same manner as in the preparation of the oxygen electrode catalyst ink, except that no CeF 3 powder was added, and a Pt / C catalyst having a platinum content of 30 wt% was used as the fuel electrode catalyst. An electrode catalyst ink was prepared.
調製した酸素極用触媒インク、および燃料極用触媒インクを、それぞれテフロン（登録商標、デュポン社製）製のシート表面に、ドクターブレード法により塗布した。その後、室温で真空乾燥して溶媒を除去し、シート表面に各電極の触媒層を形成した。なお、酸素極の触媒層では、単位面積あたりの白金量を、０．５〜０．６ｍｇ／ｃｍ2とした。また、燃料極の触媒層では、単位面積あたりの白金量を０．２ｍｇ／ｃｍ2とした。各触媒層が形成されたシートを３６ｍｍ角に切り出した後、燃料極の触媒層が形成されたシートを、ナフィオン１１２（商品名、デュポン社製）膜の一方の表面に、また、酸素極の触媒層が形成されたシートを電解質膜の他方の表面に、圧力約４．９ＭＰａ、温度約１２０℃でホットプレスした。その後、シートのみを剥離して、電解質膜の両側に、酸素極触媒層、燃料極触媒層がそれぞれ形成されたＭＥＡを得た。 The prepared oxygen electrode catalyst ink and fuel electrode catalyst ink were each applied to the surface of a sheet made of Teflon (registered trademark, manufactured by DuPont) by a doctor blade method. Thereafter, the solvent was removed by vacuum drying at room temperature, and a catalyst layer of each electrode was formed on the sheet surface. In the catalyst layer of the oxygen electrode, the platinum amount per unit area was set to 0.5 to 0.6 mg / cm 2 . In the catalyst layer of the fuel electrode, the amount of platinum per unit area was 0.2 mg / cm 2 . After the sheet on which each catalyst layer is formed is cut into a 36 mm square, the sheet on which the fuel electrode catalyst layer is formed is placed on one surface of a Nafion 112 (trade name, manufactured by DuPont) membrane, The sheet on which the catalyst layer was formed was hot-pressed on the other surface of the electrolyte membrane at a pressure of about 4.9 MPa and a temperature of about 120 ° C. Thereafter, only the sheet was peeled off to obtain an MEA in which an oxygen electrode catalyst layer and a fuel electrode catalyst layer were formed on both sides of the electrolyte membrane.
（２）電解質等の劣化調査
作製したＭＥＡを、小型（電極面積１３ｃｍ2）の固体高分子型燃料電池セルに組み込んだ。すなわち、ＭＥＡの両側に、ガス流路が形成されたカーボン製のセパレータを配置して、それをＳＵＳ製の支持体で保持した。そして、酸素極に加湿した空気を、燃料極に加湿した水素をそれぞれ供給して、固体高分子型燃料電池を２４時間作動させた。空気および水素の加湿温度は９０℃、流量は１００ｍｌ／ｍｉｎ、電池の作動温度は９０℃とした。電池作動中に、酸素極および燃料極から排出された水を回収した。回収水中のフッ化物イオン（Ｆ-）濃度を、イオンクロマト装置ＰＩＡ−１０００（株式会社島津製作所製）にて測定し、フッ素排出速度（μｇ／（ｃｍ2・ｈｒ））を求めた。フッ素排出速度は、単位時間、単位電極面積当たりの排出フッ素量であり、各電極からの回収水の量と、回収水中のＦ-濃度とから算出される。フッ素排出速度は、電解質膜および電極の劣化の程度を示す指標となる。つまり、フッ素排出速度が大きいほど、電解質膜等の劣化が進行していることを示す。
(2) Investigation of deterioration of electrolyte, etc. The produced MEA was incorporated into a small (electrode area 13 cm 2 ) solid polymer fuel cell. That is, carbon separators with gas flow paths formed on both sides of the MEA were placed and held by a SUS support. Then, humidified air was supplied to the oxygen electrode, and humidified hydrogen was supplied to the fuel electrode, and the polymer electrolyte fuel cell was operated for 24 hours. The humidification temperature of air and hydrogen was 90 ° C., the flow rate was 100 ml / min, and the operating temperature of the battery was 90 ° C. During the battery operation, water discharged from the oxygen electrode and the fuel electrode was collected. The concentration of fluoride ions (F − ) in the recovered water was measured with an ion chromatograph PIA-1000 (manufactured by Shimadzu Corporation), and the fluorine discharge rate (μg / (cm 2 · hr)) was determined. The fluorine discharge rate is the amount of fluorine discharged per unit time and unit electrode area, and is calculated from the amount of recovered water from each electrode and the F − concentration in the recovered water. The fluorine discharge rate is an index indicating the degree of deterioration of the electrolyte membrane and the electrode. In other words, it indicates that the deterioration of the electrolyte membrane or the like is progressing as the fluorine discharge rate is higher.
測定の結果、ＣｅＦ3を含むＭＥＡのフッ素排出速度は、０．４μｇ／（ｃｍ2・ｈｒ）となった。これに対して、ＣｅＦ3を含まない点以外は同様に構成された従来のＭＥＡでは、フッ素排出速度は０．８μｇ／（ｃｍ2・ｈｒ）と２倍になった。これより、ＣｅＦ3を含むＭＥＡでは、電解質膜および電極の劣化が抑制されたことがわかる。 As a result of the measurement, the fluorine discharge rate of MEA containing CeF 3 was 0.4 μg / (cm 2 · hr). On the other hand, in the conventional MEA similarly configured except that it did not contain CeF 3 , the fluorine discharge rate was doubled to 0.8 μg / (cm 2 · hr). From this, it can be seen that in the MEA containing CeF 3 , the deterioration of the electrolyte membrane and the electrode was suppressed.
以上より、電解質膜および一対の電極の少なくとも一つに難溶性フッ化物を含む本発明のＭＥＡでは、電解質膜および電極の劣化が進行し難いことが確認できた。よって、本発明のＭＥＡを用いれば、長期間運転した場合でも電池性能の低下の少ない固体高分子型燃料電池を経済的に実現できる。 From the above, it was confirmed that in the MEA of the present invention in which at least one of the electrolyte membrane and the pair of electrodes contains a sparingly soluble fluoride, it is difficult for the electrolyte membrane and the electrode to deteriorate. Therefore, by using the MEA of the present invention, it is possible to economically realize a polymer electrolyte fuel cell with little deterioration in battery performance even when operated for a long time.
Claims (4)
該電解質膜および該一対の電極の少なくとも一つに過酸化物を分解する高温かつ酸性の条件で難溶性のフッ化物であって、希土類金属のフッ化物または遷移金属のフッ化物を含む固体高分子型燃料電池用電解質膜電極接合体。 An electrolyte membrane having ionic conductivity, and a pair of electrodes provided on both sides of the electrolyte membrane,
At least one of the electrolyte membrane and the pair of electrodes to a fluoride hardly soluble peroxide decomposing temperature and acidic conditions, a solid polymer containing a fluoride fluoride or transition metal rare earth metal -Type fuel cell electrolyte membrane electrode assembly.
該酸素極および前記電解質膜の少なくとも一つに前記難溶性フッ化物を含む請求項１に記載の固体高分子型燃料電池用電解質膜電極接合体。 The pair of electrodes includes a fuel electrode supplied with a fuel gas containing hydrogen and an oxygen electrode supplied with an oxidant gas containing oxygen,
The electrolyte membrane electrode assembly for a polymer electrolyte fuel cell according to claim 1, wherein the hardly soluble fluoride is contained in at least one of the oxygen electrode and the electrolyte membrane.
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| DE602005024002D1 (en) | 2004-06-22 | 2010-11-18 | Asahi Glass Co Ltd | ELECTROLYTE MEMBRANE FOR A FESTPOLYMER FUEL CELL, MANUFACTURING METHOD AND MEMBRANE ELECTRODE ASSEMBLY FOR A FESTPOLYMER FUEL CELL |
| JP3897059B2 (en) | 2004-06-22 | 2007-03-22 | 旭硝子株式会社 | Liquid composition, process for producing the same, and process for producing membrane electrode assembly for polymer electrolyte fuel cell |
| WO2007007767A1 (en) * | 2005-07-12 | 2007-01-18 | Asahi Glass Company, Limited | Electrolyte membrane for use in solid polymer-type fuel cell, process for production of the membrane and membrane electrode assembly for use in solid polymer-type fuel cell |
| JP5217129B2 (en) * | 2005-09-02 | 2013-06-19 | トヨタ自動車株式会社 | Fuel cell |
| US8628871B2 (en) * | 2005-10-28 | 2014-01-14 | 3M Innovative Properties Company | High durability fuel cell components with cerium salt additives |
| JP4514718B2 (en) * | 2006-01-20 | 2010-07-28 | 株式会社豊田中央研究所 | Membrane electrode assembly and polymer electrolyte fuel cell |
| JP2007257965A (en) * | 2006-03-22 | 2007-10-04 | Toyota Central Res & Dev Lab Inc | Solid polymer fuel cell and fuel cell system |
| JP4793317B2 (en) * | 2007-04-23 | 2011-10-12 | トヨタ自動車株式会社 | Membrane electrode assembly manufacturing method, membrane electrode assembly, membrane electrode assembly manufacturing apparatus, and fuel cell |
| JP5040437B2 (en) * | 2007-05-21 | 2012-10-03 | トヨタ自動車株式会社 | Fuel cell |
| GB0714361D0 (en) * | 2007-07-24 | 2007-09-05 | 3M Innovative Properties Co | Cation conductive membranes comprising polysulfonic acid polymers and metal salts having an F-containing anion |
| JP2008098179A (en) * | 2007-11-01 | 2008-04-24 | Asahi Glass Co Ltd | Electrolyte membrane for solid polymer electrolyte fuel cell, its manufacturing method, and membrane electrode assembly for polymer electrolyte fuel cell |
| JP5244148B2 (en) * | 2010-04-14 | 2013-07-24 | 株式会社豊田中央研究所 | Membrane electrode assembly and polymer electrolyte fuel cell |
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