JP2006236935A - Electrolyte for solid polymer fuel cell, solid polymer fuel cell, solid polymer fuel cell system and fuel cell vehicle - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte for a solid polymer fuel cell capable of maintaining performance of an electrolyte membrane for a long period of time. <P>SOLUTION: The electrolyte for a solid polymer fuel cell includes a compound having a standard oxidation reduction potential in a range from 0.68[V] to 1.00[V]. The compound is shown in general formula (I). In the formula, X represents an oxygen atom or a hydroxyl group. Y1 and Y2 are the same or different, and are a kind of substituent selected from a group consisting of an alkyl group, an aryl group, an alkoxy group and substituents including a hydrogen atom, respectively. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electrolyte for a polymer electrolyte fuel cell, a polymer electrolyte fuel cell, a polymer electrolyte fuel cell system, and a fuel cell vehicle.

Fuel cell technology is attracting attention as a means of solving the recent energy resource problems and global warming problems associated with CO ₂ emissions. A fuel cell is one in which fuel such as hydrogen, methanol, or other hydrocarbons is electrochemically oxidized in the cell, thereby converting the chemical energy of the fuel directly into electric energy and taking it out. For this reason, the fuel cell has been attracting attention as a clean electric energy source without generating NO _X or SO _X due to fuel combustion in an internal combustion engine such as thermal power generation and automobile.

  There are several types of fuel cells. Among them, the polymer electrolyte fuel cell (PEFC) has attracted the most attention and is being developed. PEFC is (1) easy to start and stop due to low temperature operation, (2) high theoretical voltage and high conversion efficiency, and (3) flexible cell structure such as vertical because there is no liquid phase in the electrolyte. There are various advantages such as that design is possible, and that (4) a large amount of current can be taken out by controlling the three-phase interface and a high output density can be obtained at the ion exchange membrane / electrode interface.

  However, even though PEFC has received the most attention, there are still many problems. Among them, polymer electrolyte membrane technology is one of the most important issues. At present, perfluorosulfonic acid polymers, which are the most widely used electrolyte membranes and are fluorine-based electrolyte membranes represented by Nafion (registered trademark) membranes commercially available from DuPont, USA, are used as positive electrodes ( It has been developed as a film resistant to active oxygen generated at the air electrode). However, in a long-term durability test, it cannot be said that there is still sufficient resistance (see Non-Patent Document 1).

The operating principle of a fuel cell consists of two electrochemical processes: H ₂ oxidation at the negative electrode (fuel electrode) and water generation by 4-electron reduction of molecular oxygen (O ₂ ) at the positive electrode (oxygen electrode). ing.

Negative electrode side: H ₂ → 2H ⁺ + 2e ⁻ (1)
Positive electrode side: (1/2) O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O (2)
However, in an actual fuel cell, side reactions occur simultaneously in addition to these reactions. A typical example is the production of hydrogen peroxide (H ₂ O ₂ ) by two-electron reduction of O _{2 at} the positive electrode.

Positive electrode side: O ₂ + 2H ⁺ + 2e ⁻ → H ₂ O ₂ Formula (3)
Hydrogen peroxide has a weak oxidizing power but is stable and has a long life. Hydrogen peroxide is decomposed according to the following reaction formulas (4) and (5). The radicals generated at the time of decomposition have a very strong oxidizing power, and the perfluorosulfonated polymer used as the electrolyte membrane may be decomposed by long-term use.

H ₂ O ₂ → 2.OH Formula (4)
H ₂ O ₂ → · H + · OOH (5)
The reactions of the formulas (4) and (5) shown here are Haber-Weiss reactions in the presence of metal ions such as Fe ²⁺ and Cu ²⁺ . In the Harbor Weiss reaction, hydrogen peroxide is converted into hydroxy radicals (.OH) by a catalytic action such as metal ions. Hydroxyl radicals are known to be most reactive among active oxygens and have very strong oxidizing power. When the metal ion is an iron ion, the Harbor Weiss reaction is known as a Fenton reaction represented by the following formula (6).

Fe ²⁺ + H ₂ O ₂ → Fe ³⁺ + OH ⁻ + · OH (6)
As described above, when metal ions are mixed in the electrolyte membrane, hydrogen peroxide is changed into hydroxy radicals by the Harbor Weiss reaction in the electrolyte membrane, and the electrolyte membrane may be deteriorated by the hydroxy radicals (non-patent). Reference 1).

Therefore, as a method for preventing radicalization of hydrogen peroxide, for example, a method of blending an electrolyte membrane with a compound that traps and inactivates peroxide radicals such as a compound having a phenolic hydroxyl group has been proposed ( (See Patent Document 1 and Patent Document 2.) In addition, a method of eliminating generated radicals by blending a phenol compound, an amine compound, a sulfur compound, a phosphorus compound or the like into the electrolyte membrane as an antioxidant has been proposed (see Patent Document 3). Furthermore, a molecule having a binding energy smaller than that of the carbon-fluorine bond is contained in a catalyst layer disposed adjacent to the electrolyte membrane, and this molecule preferentially reacts with a hydroxyl radical to protect the electrolyte membrane. A method has been proposed (see Patent Document 4).
JP 2001-118591 A JP 2000-223135 A JP 2004-134269 A JP 2003-109623 A New Energy and Industrial Technology Development Organization Subcontractor, Graduate School of Engineering, Kyoto University, “2001 Results Report, Research and Development of Solid Polymer Fuel Cells, Research on Degradation Factors of Polymer Electrolyte Fuel Cells, Basics on Degradation Factors Research (1) Electrode catalyst / electrolyte interface degradation factors ", March 2002, p. 13, 24

  However, a compound that inactivates a peroxide radical loses the function of inactivating the peroxide radical by reducing the hydroxy radical, and the compound itself is consumed by being oxidized. For this reason, it is difficult to deactivate the peroxide for a long period of time. In addition, oxygen and platinum as the electrode catalyst exist in the vicinity of the three-phase interface of the positive electrode where there is the highest possibility of generating hydroxy radicals. In the method in which only the compound to be prevented is contained, the compound may be oxidized and lost regardless of the presence or absence of the hydroxy radical, and the efficiency is poor. Furthermore, the compound may become unstable radicals or peroxides by reaction with hydroxy radicals and become a new oxidation reaction initiator, which may cause electrolyte membrane deterioration. Also, hydrocarbon electrolyte membranes developed for fuel cells are more susceptible to degradation by oxidation than fluorine electrolyte membranes.

  The present invention has been made to solve the above-mentioned problems. The electrolyte for a polymer electrolyte fuel cell according to the first invention has a standard oxidation-reduction potential of 0.68 [V] to 1.00 [1.00]. The main point is to have a compound in the range of V].

  The solid polymer fuel cell according to the second invention is characterized in that at least one of the electrolytes for solid polymer fuel cells according to the first invention is used.

  Furthermore, the solid polymer fuel cell system according to the third invention is characterized by comprising the solid polymer fuel cell according to the second invention.

  According to a fourth aspect of the present invention, there is provided a fuel cell vehicle on which the polymer electrolyte fuel cell system according to the third aspect is mounted.

  According to the first invention, the compound contained in the polymer electrolyte fuel cell electrolyte functions as a reducing agent at a potential lower than the oxidation-reduction potential of the hydroxy radical, and hydrogen peroxide functions as the reducing agent. Since it has a redox cycle that acts as an oxidant at a potential higher than the redox potential, it acts as a catalyst for decomposing active oxygen. Moreover, since this compound returns to the original type by the redox cycle of the compound after decomposing active oxygen, it can be used many times. For this reason, it is possible to realize an electrolyte for a polymer electrolyte fuel cell in which durability performance is maintained.

  According to the second invention, it is possible to realize a solid polymer fuel cell in which durability performance is maintained.

  According to the third invention, it is possible to realize a polymer electrolyte fuel cell system whose performance is maintained for a long time.

  According to the fourth aspect of the invention, a fuel cell vehicle that can withstand long-time continuous operation can be realized.

  Hereinafter, details of an electrolyte for a polymer electrolyte fuel cell, a polymer electrolyte fuel cell, a polymer electrolyte fuel cell system, and a fuel cell vehicle according to embodiments of the present invention will be described based on the embodiments.

  First, an embodiment of an electrolyte for a polymer electrolyte fuel cell according to an embodiment of the present invention will be described. The electrolyte for a polymer electrolyte fuel cell according to the present embodiment is characterized by having a compound having a standard oxidation-reduction potential in the range of 0.68 [V] to 1.00 [V].

Active oxygen is generated by the side reaction of the 4-electron reduction of oxygen represented by the above formula (2). Examples of the active oxygen include superoxide (O ₂ ⁻ ) which is an oxygen one-electron reductant, hydroperoxy radical (· OOH) which is a conjugate acid of superoxide, and hydrogen peroxide (H ₂ O ₂ ) which is a two-electron reductant. ), A hydroxy radical (.OH) that is a three-electron reduced form of oxygen, and the generation mechanism is considered to pass through elementary reaction processes represented by the following formulas (7) to (11), respectively.

O ₂ + e ⁻ → O ₂ ⁻ (7)
O ₂ ⁻ + H ⁺ → · OOH Formula (8)
O ₂ + 2H ⁺ + 2e ⁻ → 2H ₂ O ₂ Formula (9)
H ₂ O ₂ + H ⁺ + e ⁻ → H ₂ O + · OH Formula (10)
H ₂ O ₂ → 2.OH Formula (11)
The generated active oxygen is considered to be finally reduced to water by the elementary reactions shown in the following formulas (12) to (14). Note that E ₀ is represented by a normal redox potential (Normal Hydrogen Electrode; NHE).

OOH + H ⁺ + e ⁻ → H ₂ O ₂ E ₀ = 1.50 [V] (12)
H ₂ O ₂ + 2H ⁺ + 2e ⁻ → 2H ₂ O E ₀ = 1.77 [V] (13)
OH + H ⁺ + e ⁻ → H ₂ O E ₀ = 2.85 [V] (14)
The problem here is a hydroxy radical having a high redox potential, that is, a strong oxidizing power. Both hydroperoxy radicals and hydrogen peroxide may go through hydroxy radicals in the process of being reduced to water. Hydroxyl radicals have a high redox potential of 2.85 [V], have a short lifetime due to their strong oxidizing power and high reactivity as radicals, and react with other molecules unless they are rapidly reduced. It is considered that most of the deteriorations caused by various oxidations that are a problem in fuel cells are via hydroxy radicals, and as described above, the electrolyte membrane is also considered to be decomposed by hydroxy radicals.

  Here, FIG. 1 shows redox potentials of hydroxy radicals, oxygen, hydrogen peroxide, hydrogen, and the like. The right column of this figure shows the oxidation half reaction formula of the reducing agent, and the left column shows the reduction half reaction formula of the oxidizing agent. The vertical axis represents the oxidation-reduction potential, and the oxidation-reduction potential increases as it goes upward. In other words, the higher the position is, the stronger the oxidizing power is, and it is difficult to oxidize. The lower the position, the weaker the oxidizing power and the easier it is to oxidize. In addition, the numerical value shown in the parenthesis after the half reaction formula is the oxidation-reduction potential of the compound acting as an oxidizing agent or a reducing agent. Since the oxidation-reduction potential is affected by pH and temperature, FIG. 1 shows the standard oxidation-reduction potential corrected for the standard hydrogen electrode (NHE). In the electrolyte, there is a compound that has a redox cycle that acts as a reducing agent at a potential lower than the redox potential of the hydroxy radical and that acts as an oxidizing agent at a potential higher than the redox potential at which hydrogen peroxide acts as a reducing agent. In other words, when the oxidation-reduction potential of the compound is in the range of 0.68 [V] to 2.85 [V] (vs. NHE), this compound acts as a catalyst to produce a hydroxyl radical or peroxidation. Decomposes active oxygen such as hydrogen.

  As shown in the above formula (13) and the following formula (15), hydrogen peroxide acts as a reducing agent for substances having a higher redox potential than hydrogen peroxide, while it has a redox potential higher than that of hydrogen peroxide. It is known to act as an oxidant for low substances.

^{_{H 2 O 2 → O 2 +}} 2H + + 2e - E 0 = 0.68 [V] ··· formula (15)
When a compound having an oxidation-reduction potential of 0.68 [V] or more is contained in the electrolyte membrane, hydrogen peroxide acts as a reducing agent for the compound, and hydrogen peroxide is oxidized by this compound. It is decomposed into oxygen. On the other hand, when the oxidation-reduction potential of the compound contained in the electrolyte membrane is 2.85 [V] or less, this compound acts as a reducing agent for the hydroxy radical, and the hydroxy radical is reduced and decomposed into water. When a fluorine-based membrane is used as the electrolyte membrane, this fluorine-based electrolyte membrane has the property of being oxidized by a compound having an oxidation-reduction potential of 2.8 [V] or higher, so that it depends on the compound contained in the electrolyte membrane. There is almost no problem that the electrolyte membrane is oxidized. On the other hand, when a hydrocarbon-based electrolyte membrane is used as the electrolyte membrane, 2.00 [V] for benzene, 1.93 [V] for toluene, Then, since it is oxidized at a potential of 1.58 [V], if the redox potential of the compound contained in the electrolyte membrane is high, the hydrocarbon-based electrolyte membrane may be oxidized. Therefore, by setting the upper limit of the oxidation-reduction potential of the compound contained in the electrolyte membrane to 1.00 [V] or less, the electrolyte membrane is not oxidized even when the electrolyte membrane is a hydrocarbon-based membrane. , Hydrogen peroxide and hydroxy radicals can be effectively decomposed.

  Therefore, the polymer electrolyte fuel cell electrolyte according to the present embodiment includes a compound having a standard oxidation-reduction potential in the range of 0.68 [V] to 1.00 [V] (vs. NHE). Hydroxy radicals and hydrogen peroxide are decomposed by the catalytic action of the compound contained in the electrolyte membrane without oxidizing the electrolyte membrane. Further, the compound having a catalytic action for decomposing active oxygen can be used any number of times since it takes an oxidant and a reductant by a redox cycle of the compound after decomposing active oxygen. For this reason, it is possible to realize an electrolyte for a polymer electrolyte fuel cell in which durability performance is maintained. In addition, since the actual oxidation-reduction potential (Real Hydrogen Electrode; RHE) of each compound varies depending on various conditions such as pH and temperature, it is preferable to use a range in accordance with each condition. In order to maintain durability over a long period of time, it is more preferable that the oxidized form and reduced form of this compound are relatively stable compounds. However, considering the poisoning of platinum used in the electrode, the compound used for the electrolyte for the polymer electrolyte fuel cell according to the present embodiment is an organic compound composed only of carbon, hydrogen, oxygen and nitrogen. It is preferable that

Further, this compound is represented by the following general formula (I)

(In the formula, X represents an oxygen atom or a hydroxyl group. Y1 and Y2 are the same or different and are each a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group and a substituent containing a hydrogen atom. When Y1 and Y2 are an alkyl group or an alkoxy group, they may be an alkyl group, an alkoxyl group, an unsaturated alkyl group or an alkoxy group partially substituted with an arbitrary group, and these groups are chain-like And Y1 and Y2 may contain oxygen and nitrogen atoms, and when Y1 and Y2 are aryl groups, they are aryl groups partially substituted with an arbitrary group. Y1 and Y2 may form a ring and may contain oxygen and nitrogen atoms).

  This compound is known to be oxidized and reduced by elementary reactions represented by the following formulas (16) and (17).

> NOH →> NO · + H ⁺ + e ⁻ (16)
> N ⁺ = O + e ⁻ → NO.
FIG. 2 shows the compound represented by the general formula (I) and its radical form, and shows a mechanism for decomposing hydroxy radicals and hydrogen peroxide over a long period of time by cycling between the oxidant and the reductant. . FIG. 2 (a) shows the redox cycle of the N-hydroxyimide derivative (reduced form) and its radical form (oxidized form), and FIG. 2 (b) shows the N-oxyl derivative (oxidized form) and radical form thereof. The redox cycle of (reduced form) is shown.

  In FIG. 2 (a), the reduced form of the N-hydroxyimide derivative acts as a reducing agent for the hydroxy radical, and supplies hydrogen radical (H.) to the hydroxy radical generated in the electrolyte membrane to reduce it to water. To do.

> NOH + .OH →> NO. + H ₂ O (18)
On the other hand, the oxidant of the N-hydroxyimide derivative acts as an oxidant for hydrogen peroxide, extracts hydrogen, oxidizes hydrogen peroxide to oxygen, and recovers to a reduced form.

2> NO · + H ₂ O ₂ → 2> NOH + O ₂ Formula (19)
The compound recovered in the reduced form reduces the hydroxy radical again. In this way, the oxidation-reduction cycle of the N-hydroxyimide derivative is reduced between the reductant and the oxidant, and at the same time, the hydroxy radicals and oxygen peroxide are decomposed to prevent the oxidation of the electrolyte.

In FIG. 2B, the reduced form of the N-oxyl derivative acts as a reducing agent for the hydroxy radical, and supplies electrons (e ⁻ ) to the hydroxy radical generated in the electrolyte membrane to OH ⁻ . Reduce.

> NO · + · OH →> N ⁺ = O + OH ⁻ (20)
On the other hand, the oxidant of the N-oxyl derivative acts as an oxidant for hydrogen peroxide, extracts hydrogen, oxidizes hydrogen peroxide to oxygen, and recovers to a reduced form.

2> N ⁺ = O + H ₂ O ₂ → 2> NO · + 2H ⁺ + O ₂ Formula (21)
The compound recovered in the reduced form reduces the hydroxy radical again. In this way, the N-oxyl derivative can undergo a redox cycle between the reductant and the oxidant, and at the same time, it can decompose hydroxy radicals and oxygen peroxide and prevent oxidation of the electrolyte.

  In the compound represented by the general formula (I), when the substituents Y1 and Y2 are alkyl groups, for example, methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl , Hexyl, heptyl, octyl, decyl group and the like, such as a linear or branched alkyl group having about 1 to 10 carbon atoms. Preferred is a lower alkyl group having about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms.

  In addition, examples of the aryl group include a phenyl group and a naphthyl group, and examples of the cycloalkyl group include a cyclopentyl, cyclohexyl, and cyclooctyl groups. Examples of the alkoxy group include about 1 to 10 carbon atoms, preferably about 1 to 6 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, t-butoxy, pentyloxy, and hexyloxy groups, and more preferably about 1 to 6 carbon atoms. Is a lower alkoxy group having about 1 to 4 carbon atoms.

  Examples of the alkoxy group include about 1 to 10 carbon atoms, preferably about 1 to 6 carbon atoms, such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutoxy, t-butoxy, pentyloxy, and hexyloxy groups, and more preferably about 1 to 6 carbon atoms. Is a lower alkoxy group having about 1 to 4 carbon atoms. Moreover, examples of the optional group include a hydroxyl group, an alkoxy group, a carbonyl group, an alkoxycarbonyl group, an acyl group, a nitro group, a cyano group, and an amino group.

Further, the compound represented by the general formula (I) is represented by the following general formula (II)

(Wherein R1 and R2 are an alkyl group or an alkyl group partially substituted with an arbitrary group, and R1 and R2 may be linear, cyclic, or branched. R1 and R2 are bonded to each other. It may form a ring and may contain oxygen and nitrogen atoms). In the compound represented by the general formula (II), examples of the substituents R1 and R2 include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, Examples thereof include a linear or branched alkyl group having about 1 to 10 carbon atoms such as a decyl group. Preferred is a lower alkyl group having about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms.

Further, the compound represented by the general formula (II) is represented by the following general formula (III)

(In the formula, R1 to R4 are alkyl groups or alkyl groups partially substituted with an arbitrary group, and R1 to R4 may be chain, cyclic, or branched. Also, R1 and R2 Or R3 and R4 may be bonded to each other to form a ring, which may contain oxygen and nitrogen atoms). In the compound represented by the general formula (III), examples of the substituents R1 to R4 include methyl, ethyl, propyl, isopropyl, butyl, isobutyl, sec-butyl, t-butyl, pentyl, hexyl, heptyl, octyl, Examples thereof include a linear or branched alkyl group having about 1 to 10 carbon atoms such as a decyl group. Preferred is a lower alkyl group having about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms.

Further, the compound represented by the general formula (III) is represented by the following general formula (IV)

In the formula, ring Y is preferably a compound represented by Y1 and Y2 to form either a 5-membered ring or a 6-membered ring. Examples of such a ring include, for example, a non-aromatic hydrocarbon ring such as a cycloalkane ring typified by a cyclohexane ring, a cycloalkene ring typified by a cyclohexene ring, and a bridged type typified by a 5-norbornene ring. Non-aromatic bridged rings such as hydrocarbon rings, aromatic rings such as benzene rings and naphthalene rings are included. In addition, these rings may have a substituent.

Further, the compound represented by the general formula (IV) is represented by the following general formula (V)

(Wherein, Z is a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some of the groups may be chain, cyclic, or branched, and oxygen In the case where Z is an aryl group, it may be an aryl group partially substituted with an arbitrary group, and may contain oxygen and nitrogen atoms). Preferably there is.

  In the substituent Z, the alkyl group includes an alkyl group having about 1 to 6 carbon atoms among the same alkyl groups as those described above, and examples of the aryl group include a phenyl group and a naltyl group. As the alkoxy group, an alkoxy group having about 1 to 6 carbon atoms is particularly included among the same alkoxy groups as the above alkyl group, and examples of the carboxyl group include a carboxyl group having about 1 to 4 carbon atoms. As the alkoxycarbonyl group, for example, the carbon number of the alkoxy moiety such as methoxycarbonyl, ethoxycarbonyl, propoxycarbonyl, isopropoxycarbonyl, butoxycarbonyl, isobutoxycarbonyl, t-butoxycarbonyl, pentyloxycarbonyl, hexyloxycarbonyl group and the like is 1 About 10 to 10 alkoxycarbonyl groups. A lower alkoxycarbonyl group having preferably about 1 to 6 carbon atoms, more preferably about 1 to 4 carbon atoms, is preferable.

  An example of the compound represented by the general formula (V) is TEMPO (2,2,6,6-tetramethylpiperidine-1-oxyl). Examples of compounds represented by TEMPO and general formula (V) are shown in FIG. TEMPO shown in FIG. 3 (i) is an N-hydroxyimide derivative having a reversible redox cycle, and is redoxed by the elementary reactions shown in the following formulas (22) and (23), and the redox potential is 0. .81 [V].

TEMPO ⁺ + e ⁻ → TEMPO E ₀ = 0.81 [V] (formula 22)
TEMPO → TEMPO ⁺ + e ⁻ E ₀ = 0.81 [V] (23)
The redox potential of TEMPO is higher than the redox potential of hydrogen peroxide and lower than the redox potential of hydroxy radicals. For this reason, TEMPO acts as an oxidizing agent for hydrogen peroxide to oxidize hydrogen peroxide to oxygen, and acts as a reducing agent for hydroxy radicals to reduce hydroxy radicals to water.

Further, the compound represented by the general formula (IV) is represented by the following general formula (VI)

(Wherein, Z is a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some of the groups may be chain, cyclic, or branched, and oxygen In the case where Z is an aryl group, it may be an aryl group partially substituted with an arbitrary group, and may contain oxygen and nitrogen atoms). The compound represented by the general formula (IV) may be represented by the following general formula (VII):

(Wherein, Z is a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some of the groups may be chain, cyclic, or branched, and oxygen In the case where Z is an aryl group, it may be an aryl group partially substituted with an arbitrary group, and may contain oxygen and nitrogen atoms). There may be. When the compound is represented by general formula (VI) or general formula (VII), the same substituents as those of the compound represented by general formula (V) can be used.

  Examples of the compounds represented by general formula (IV) and general formula (VII) are shown in FIGS. Examples of compounds represented by general formula (IV) and general formula (VII) include PROXYL (2,2,5,5-tetramethylpyrrolidine-1-oxyl) and DOXYL (4,4-dimethyloxazolidine-3- Oxyl). These compounds also have a reversible redox cycle similar to TEMPO, and the redox potential is in the range of 0.68 [V] to 1.00 [V]. For this reason, these compounds also act as an oxidizing agent for hydrogen peroxide to oxidize hydrogen peroxide to oxygen, and act as a reducing agent for hydroxy radicals to reduce hydroxy radicals to water.

  What is important in selecting a compound having such a catalytic action is the stability, durability, heat resistance, and solubility in the electrolyte membrane of the compound. In particular, the stability and durability of the compound is most important in the case where the fuel cell is used for a long period of time and in the sense that it continues to decompose active oxygen. Further, considering that the steady-state operating temperature of the fuel cell is 80 to 90 [° C.] and the heat resistance of the electrolyte membrane is improved in the future, the electrolyte membrane can sufficiently withstand even at a temperature of about 120 [° C.]. Must have heat resistance. Moreover, in order to dissolve this compound uniformly in the electrolyte membrane, it may be difficult to dissolve, but it is necessary to dissolve in water. If the compound is insoluble in water, it will precipitate in the electrolyte membrane, making it difficult for hydrogen radicals to enter and exit or to exchange electrons, and the effect of decomposing active oxygen such as hydroxy radicals and hydrogen peroxide will not be sufficiently exhibited. In addition, an organic solvent can be used alone or as a mixed solvent with water as required, but in this case, care is taken to confirm beforehand that it does not affect the power generation performance.

  Thus, in the polymer electrolyte fuel cell electrolyte according to the embodiment of the present invention, a compound having a standard oxidation-reduction potential in the range of 0.68 [V] to 1.00 [V] contains active oxygen. Acts as a catalyst to decompose. Moreover, since this compound returns to the original type by the redox cycle of the compound after decomposing active oxygen, it can be used many times. For this reason, it is possible to realize an electrolyte for a polymer electrolyte fuel cell in which durability performance is maintained.

  The electrolyte for a polymer electrolyte fuel cell according to the embodiment of the present invention can be used as an electrolyte membrane for a polymer electrolyte fuel cell. In this case, the fuel type is not limited as long as it is a fuel cell using a proton conductive polymer electrolyte membrane, and is not limited to a hydrogen type solid polymer fuel cell, a direct methanol type solid polymer fuel cell, a direct hydrocarbon type. It can be used for any fuel cell such as a solid polymer fuel cell.

  The solid polymer fuel cell according to the embodiment of the present invention can be used in a fuel cell system using a proton conductive polymer electrolyte membrane, and its use is limited to a fuel cell vehicle. The present invention can be applied to a fuel cell cogeneration power generation system, a fuel cell home appliance, a fuel cell portable device, and a fuel cell transport device.

  Hereinafter, the electrolyte for a polymer electrolyte fuel cell according to the embodiment of the present invention will be described more specifically with reference to Examples 1 to 14 and Comparative Examples 1 to 8, but the scope of the present invention is limited thereto. It is not limited. These examples are investigations of the effectiveness of the polymer electrolyte fuel cell electrolyte according to the present invention, and show examples of polymer electrolyte fuel cell electrolytes prepared with different raw materials. .

<Preparation of sample>
In Examples 1 to 7 and Comparative Examples 1 to 4, a sulfonated polyethersulfone (S-PES) membrane was used as the hydrocarbon electrolyte membrane. S-PES membrane is the New Energy and Industrial Technology Development Organization FY 2002 Results Report “Solid Polymer Fuel Cell System Technology Development Business Solid Polymer Fuel Cell Element Technology Development Business, etc. An equivalent product described in “Research and Development of Durable Hydrocarbon Electrolyte Membrane” P31 was obtained and used.

Example 1
An S-PES film (thickness 150 [μm]) was cut into 1 [cm] squares and used. The pretreatment of the S-PES membrane was performed by boiling for 1 [hour] in distilled water, followed by boiling for 1 [hour] in 1 [M] sulfuric acid aqueous solution, and finally boiling for 1 [hour] in distilled water. . Next, after adding 0.5 [mM] 4-hydroxy-TEMPO (Aldrich) shown in FIG. 3 (ii) as a compound that decomposes active oxygen to the pre-treated S-PES film, 30 [ %] Hydrogen peroxide water (Wako Pure Chemicals special grade) diluted with ultrapure water and adjusted in 0.5 [%] hydrogen peroxide 10 [cm ³ ] at 80 [° C.] for 24 [hours], Used for evaluation of durability against hydrogen peroxide.

(Example 2)
In Example 2, as a compound that decomposes active oxygen, 4-carboxy-TEMPO (Aldrich) 0.5 [mM] shown in FIG. 3 (ii) was added instead of 4-hydroxy-TEMPO. 2. Other processing was the same as in Example 1.

(Example 3)
In Example 3, Example 3 was prepared by adding TEMPO (Aldrich) 0.5 [mM] shown in FIG. Other processing was the same as in Example 1.

Example 4
In Example 4, a compound to which 3-carbamoyl-PROXYL (Aldrich) 0.5 [mM] shown in FIG. 4 (xiii) was added as a compound that decomposes active oxygen was used as Example 4. Other processing was the same as in Example 1.

(Example 5)
In Example 5, Example 5 was obtained by adding 3-carboxy-PROXYL (Aldrich) 0.5 [mM] shown in FIG. Other processing was the same as in Example 1.

(Example 6)
In Example 6, as a compound that decomposes active oxygen, 3-carbamoyl-2,2,5,5-tetramethylpyrrolin-1-yloxy (Aldrich) 0.5 [mM] shown in FIG. Example 6 was added. Other processing was the same as in Example 1.

(Example 7)
In Example 7, Example 7 was prepared by adding 0.5 [mM] of di-t-butyl nitroxide (Aldrich) shown in FIG. 4 (xx) as a compound that decomposes active oxygen. Other processing was the same as in Example 1.

(Comparative Example 1)
In Comparative Example 1, Comparative Example 1 was obtained by adding no compound that decomposes active oxygen to the S-PES film that had been pretreated in the same manner as in Example 1. Other processing was the same as in Example 1.

(Comparative Example 2)
In Comparative Example 2, Comparative Example 2 was obtained by adding 0.5 [mM] of N-hydroxy-phthalimide (NHPI: Aldrich) as a compound that decomposes active oxygen. Other processing was the same as in Example 1.

(Comparative Example 3)
In Comparative Example 3, Comparative Example 3 was obtained by adding 0.5 [mM] of N-hydroxy-maleic acid imide (NHMI: Aldrich) as a compound that decomposes active oxygen. Other processing was the same as in Example 1.

(Comparative Example 4)
In Comparative Example 4, Comparative Example 4 was obtained by adding 0.5 [mM] of N-hydroxy-succinimide (NHSI: Aldrich) as a compound that decomposes active oxygen. Other processing was the same as in Example 1.

In Examples 8 to 14 and Comparative Examples 5 to 8, a DuPont Nafion (registered trademark) 117 film (thickness 175 [μm]) was cut into 1 [cm] squares as a fluorine-based electrolyte membrane. Using. The Nafion (registered trademark) membrane is pretreated according to NEDO PEFC R & D project standard treatment, boiled in 3% hydrogen peroxide water for 1 hour, then boiled in distilled water for 1 hour. M] The solution was boiled in an aqueous solution of sulfuric acid for 1 hour, and finally boiled in distilled water for 1 hour. Since the fluorine-based electrolyte membrane is more resistant than the hydrocarbon-based membrane, a Nafion (registered trademark) membrane that has been pre-treated with 100 [mM] FeSO is used for the purpose of promoting deterioration in the hydrogen peroxide durability test. ₄ After immersion in aqueous solution for more than one night, the counterion of Nafion (registered trademark) was exchanged from H ⁺ to Fe ²⁺ by removing the ions adhering to the membrane using ultrasonic cleaning in distilled water for 15 minutes. . As a reagent, Wako Pure Chemicals special grade FeSO ₄ · 7H ₂ O was used.

(Example 8)
After adding 0.5 [mM] of 4-hydroxy-TEMPO (Aldrich) as a compound that decomposes active oxygen to the ion-exchanged Nafion (registered trademark) membrane, 30 [%] hydrogen peroxide (Wako Pure) It was immersed in 10 [%] hydrogen peroxide 10 [cm ³ ] prepared by diluting the drug special grade) with ultrapure water at 80 [° C.] for 12 [hour] and used for evaluation.

Example 9
In Example 9, Example 9 was prepared by adding 4-carboxy-TEMPO (Aldrich) 0.5 [mM] instead of 4-hydroxy-TEMPO. Other processes were the same as in Example 8.

(Example 10)
In Example 10, Example 10 was prepared by adding TEMPO (Aldrich) 0.5 [mM] as a compound that decomposes active oxygen. Other processes were the same as in Example 8.

(Example 11)
In Example 4, Example 11 was prepared by adding 3-carbamoyl-PROXYL (Aldrich) 0.5 [mM] as a compound that decomposes active oxygen. Other processes were the same as in Example 8.

(Example 12)
In Example 12, Example 12 was obtained by adding 3-carboxy-PROXYL (Aldrich) 0.5 [mM] as a compound that decomposes active oxygen. Other processes were the same as in Example 8.

(Example 13)
In Example 13, a compound in which 3-carbamoyl-2,2,5,5-tetramethylpyrrolin-1-yloxy (Aldrich) 0.5 [mM] was added as a compound that decomposes active oxygen and Example 13 was used. did. Other processes were the same as in Example 8.

(Example 14)
In Example 14, Example 14 was prepared by adding 0.5 [mM] of di-t-butyl nitroxide (Aldrich) as a compound that decomposes active oxygen. Other processes were the same as in Example 8.

(Comparative Example 5)
In Comparative Example 5, Comparative Example 5 was used in which no compound that decomposes active oxygen was added. Other processes were the same as in Example 8.

(Comparative Example 6)
In Comparative Example 6, Comparative Compound 6 was obtained by adding 0.5 [mM] NHPI (Aldrich) as a compound that decomposes active oxygen. Other processes were the same as in Example 8.

(Comparative Example 7)
In Comparative Example 7, Comparative Compound 7 was obtained by adding 0.5 [mM] NHMI (Aldrich) as a compound that decomposes active oxygen. Other processes were the same as in Example 8.

(Comparative Example 8)
In Comparative Example 8, Comparative Example 8 was obtained by adding 0.5 [mM] NHSI (Aldrich) as a compound that decomposes active oxygen. Other processes were the same as in Example 8.

  Here, the S-PES film and the Nafion (registered trademark) film treated by the above method were evaluated by the following methods.

<Membrane degradation analysis>
In the case of the S-PES film, the deterioration analysis of the film was performed by measuring the sulfate ion concentration generated along with the decomposition, and in the case of the Nafion (registered trademark) film, measuring the fluorine ion generated along with the decomposition of the film. . The eluting ions were detected by diluting the sample solution prepared by the above method 10 times with ultrapure water and measuring the diluted solution with an ion chromatograph. An ion chromatograph manufactured by Dioneck (model name: DX-AQ type) was used.

<Measurement of redox potential>
The oxidation-reduction potentials of the compounds used in the examples were measured using glassy carbon as the working electrode, platinum as the counter electrode, a saturated calomel electrode (SCE) as the reference electrode, and 1 [M] sulfuric acid as the electrolyte. A measurement example of TEMPO is shown in FIG. In FIG. 7, in order to match the oxidation-reduction potential of each substance, the standard potential E ⁰ (NHE) is corrected and displayed by the following equation (36).

E ⁰ (NHE) = E (SCE) +0.24 [V] (24)
Table 1 below shows compounds that decompose active oxygen used in Examples 1 to 7 and Comparative Examples 1 to 4 using S-PES membranes as electrolyte membranes, oxidation-reduction potentials of the compounds, and hydrogen peroxide durability. The concentration of sulfate ion detected later is shown.

  In Examples 1 to 7 containing a compound that decomposes active oxygen, the concentration of sulfate ions detected after 24 hours was 0.5 to 0.7 [ppm]. In contrast, 2.5 [ppm] sulfate ion was detected in Comparative Example 1 in which a compound that decomposes active oxygen was not added. From comparison between Example 1 to Example 7 and Comparative Example 1, it was found that all of the compounds shown in Examples 1 to 7 decomposed active oxygen and prevented oxidation of the electrolyte membrane. Comparative Examples 2 to 4 are examples in which a compound having a redox potential of 1.0 [V] or more was added. The compounds used in Comparative Examples 2 to 4 have redox potentials of 1.34 [V], 1.35 [V], and 1.35 [V], respectively. The NHPI used in Comparative Example 2 is taken as an example. NHPI has a reversible redox cycle, and when oxidized, it becomes PINO (phthalimide-N-oxyl), and when PINO is reduced, it returns to NHPI. NHPI and PINO have a redox potential of 1.34 [V].

NHPI → PINO + H ⁺ + e ⁻ E ₀ = 1.34 [V] (25)
PINO + H ⁺ + e ⁻ → NHPI E ₀ = 1.34 [V] (26)
Since this oxidation-reduction potential is a potential for oxidizing the S-PES film, the S-PES film, which is an electrolyte film, is decomposed. For this reason, in Comparative Example 2, more sulfate ions were detected than in Comparative Example 1 which did not contain a compound that decomposes active oxygen. Similarly, in Comparative Example 3 and Comparative Example 4, more sulfate ions were detected than in Comparative Example 1.

Next, Table 2 below shows compounds that decompose active oxygen used in Examples 8 to 14 and Comparative Examples 5 to 8 using Nafion (registered trademark) membranes as electrolyte membranes, and oxidation-reduction potentials of the compounds. And the concentration of fluorine ions detected after hydrogen peroxide durability.

  In Examples 8 to 14 containing a compound that decomposes active oxygen, the concentration of fluorine ions detected after 24 hours was 0.2 to 0.4 [ppm]. On the other hand, 1.5 [ppm] of fluorine ions was detected in Comparative Example 5 in which no compound that decomposes active oxygen was added. From comparison between Example 8 to Example 14 and Comparative Example 5, it was found that any of the compounds shown in Examples 8 to 14 decomposed active oxygen and prevented oxidation of the electrolyte membrane. Comparative Examples 6 to 8 are examples in which a compound having a redox potential of 1.0 [V] or more was added. The concentration of fluorine ions detected in Comparative Examples 6 to 8 is 0.3 to 0.4 [ppm] which is almost equivalent to that in Examples 8 to 14, and the same level as in Examples 8 to 14. The antioxidant effect of was shown. This is because the fluorine-based electrolyte membrane has higher oxidation resistance than the hydrocarbon-based electrolyte membrane, so that even when the oxidation potential of the compound that decomposes the added active oxygen is somewhat high, the electrolyte membrane is oxidized by the compound. It was suggested that there was nothing.

Next, a fuel cell single cell using the membranes obtained in Examples and Comparative Examples as electrolyte membranes and platinum-supported carbon as electrodes was prepared, and repeated start-stop durability tests were performed. Platinum-supported carbon (20 wt% Pt / Vulcan XC-72 manufactured by Cabot) was applied to the surfaces of the electrolyte membrane to be the anode and cathode so as to be 1 [mg / cm ² ], and the membrane-electrode assembly ( MEA) was prepared. The produced MEA was incorporated into a single cell and used as a single cell for PEFC for evaluation. The single cell was a 5 [cm ² ] single cell.

  Here, the start / stop repeated experiment was performed by the following method.

<Start / stop repeated endurance test>
70 [° C.] humidified hydrogen gas (atmospheric pressure) as the anode gas and 70 [° C.] humidified oxygen gas (atmospheric pressure) as the cathode gas are supplied to a single cell maintained at 70 [° C., and 30 [ Minutes] and then the test was started. In the test, gas was flowed through the single cell at a flow rate of 300 [dm ³ / min], the current density was increased from the discharge open circuit state, and discharge was performed until the terminal voltage became 0.3 [V] or less. Then, after the terminal voltage became 0.3 [V] or less, the circuit was held again for 5 [min] as an open circuit state. This operation was repeated, and the durability performance was compared with the number of times that the voltage when the power was generated at a current density of 1 [mA / cm ³ ] became 0.4 [V] or less. Although the S-PES film was used as it was, Nafion (registered trademark) films were all replaced with Fe ²⁺ type in order to promote the durability test.

FIG. 8 shows a graph of an initial value of a current-voltage curve of a start-stop repeated endurance test of the manufactured fuel cell single cell and a current-voltage curve after endurance. In this graph, the degree of deterioration of the electrolyte membrane after the endurance test was determined using the number of times that the voltage when power was generated at a current density of 1 [mA / cm ³ ] became 0.4 [V] or less. Table 3 below shows compounds that decompose active oxygen and the number of repetitions of starting and stopping in Examples 1 to 7 and Comparative Examples 1 to 4 using the S-PES film.

As shown in Comparative Example 1, when a compound that decomposes active oxygen was not added, the number of repetitions of starting and stopping was 50, and the voltage when power was generated at a current density of 1 [mA / cm ³ ] was 0.4. [V] Decreased below. On the other hand, in Examples 1 to 7 to which a compound capable of decomposing active oxygen was added, the voltage became 0.4 [V] or less after the number of repetitions of start and stop was 400 times or more, which is also effective in the power generation test. It has been shown. On the other hand, in Comparative Examples 2 to 4 to which a compound having a redox potential higher than 1.0 [V] was added, the number of start / stops was 30 times, and the voltage was 0.4 [V] or less. The result was not obtained.

Next, Table 4 below shows compounds that decompose active oxygen and the number of repetitions of starting and stopping in Examples 8 to 14 and Comparative Examples 5 to 8 using Nafion (registered trademark) membranes.

As shown in Comparative Example 5, when a compound that decomposes active oxygen is not added, the number of repetitions of starting and stopping is 70, and the voltage when power is generated at a current density of 1 [mA / cm ³ ] is 0.4. [V] Decreased below. On the other hand, in Examples 8 to 14 to which a compound capable of decomposing active oxygen was added, the voltage became 0.4 [V] or less at 500 or more start / stop repetitions, which is also effective in the power generation test. It has been shown. On the other hand, in Comparative Examples 6 to 8 to which a compound having a redox potential higher than 1.0 [V] was added, the number of start / stops was 500 times or more and the voltage was 0.4 [V] or less. In the case of using a Nafion (registered trademark) membrane as a compound, it was found that the compound is effective even when the oxidation-reduction potential of the compound that decomposes active oxygen is higher than 1.0 [V].

  As shown above, hydrocarbon-based electrolyte membranes such as S-PES membranes developed for fuel cells contain a compound having a redox potential in the range of 0.68 [V] to 1.00 [V]. By using it, it becomes possible to suppress the oxidative deterioration of the electrolyte membrane, and the durability performance of the fuel cell can be improved. It was also found that this compound can maintain its effect over a long period of time by reversibly oxidizing and reducing. Further, this compound can suppress oxidative deterioration of the electrolyte membrane even when a fluorine-based electrolyte membrane is used, but the oxidation-reduction potential is in the range of 0.68 [V] to 1.00 [V]. It was found that by using the compound in the above, it is possible to prevent oxidation of not only the fluorine-based electrolyte membrane but also the hydrocarbon-based electrolyte membrane.

 The embodiment of the present invention has been described above. However, it should not be understood that the description and drawings constituting a part of the disclosure of the above embodiment limit the present invention. From this disclosure, various alternative embodiments, examples, and operational techniques will be apparent to those skilled in the art.

It is explanatory drawing which shows oxidation-reduction potentials, such as a hydroxyl radical, oxygen, hydrogen peroxide, and hydrogen. (A) It is explanatory drawing which shows the oxidation-reduction cycle of an N-hydroxyimide derivative and its radical body. (B) It is explanatory drawing which shows the oxidation-reduction cycle of an N-oxyl derivative and its radical body. It is an example of the compound contained in an electrolyte membrane. It is another example of the compound contained in an electrolyte membrane. It is another example of the compound contained in an electrolyte membrane. It is another example of the compound contained in an electrolyte membrane. It is a cyclic voltammogram in the electrode reaction of TEMPO. It is a graph which shows the initial value of the current-voltage curve of the start-stop repetition endurance test of the produced fuel cell single cell, and the current-voltage curve after durability.

Claims (12)

  A solid polymer fuel cell electrolyte characterized by having a compound having a standard oxidation-reduction potential in the range of 0.68 [V] to 1.00 [V]. The compound is represented by the following general formula (I)

(In the formula, X represents an oxygen atom or a hydroxyl group. Y1 and Y2 are the same or different and are each a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group and a substituent containing a hydrogen atom. When Y1 and Y2 are an alkyl group or an alkoxy group, they may be an alkyl group, an alkoxyl group, an unsaturated alkyl group or an alkoxy group partially substituted with an arbitrary group, and these groups are chain-like And Y1 and Y2 may contain oxygen and nitrogen atoms, and when Y1 and Y2 are aryl groups, they are aryl groups partially substituted with an arbitrary group. And Y1 and Y2 may form a ring and may contain oxygen and nitrogen atoms.) The solid content according to claim 1, Type fuel cell electrolyte. The compound represented by the general formula (I) is represented by the following general formula (II)

(Wherein R1 and R2 are an alkyl group or an alkyl group partially substituted with an arbitrary group, and R1 and R2 may be linear, cyclic, or branched. R1 and R2 are bonded to each other. The electrolyte for a polymer electrolyte fuel cell according to claim 2, which may form a ring and may contain oxygen and nitrogen atoms. The compound represented by the general formula (II) is represented by the following general formula (III):

(In the formula, R1 to R4 are alkyl groups or alkyl groups partially substituted with an arbitrary group, and R1 to R4 may be chain, cyclic, or branched. Also, R1 and R2 Or R3 and R4 may be bonded to each other to form a ring, and may contain oxygen and nitrogen atoms.), A solid polymer according to claim 3, Type fuel cell electrolyte. The compound represented by the general formula (III) is represented by the following general formula (IV):

The ring Y is a compound represented by the formula (6), wherein Y1 and Y2 are bonded to form either a 5-membered ring or a 6-membered ring. Electrolyte for polymer electrolyte fuel cell. The compound represented by the general formula (IV) is represented by the following general formula (V)

(Wherein, Z is a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some of the groups may be chain, cyclic, or branched, and oxygen In the case where Z is an aryl group, it may be an aryl group partially substituted with an arbitrary group, and may contain oxygen and nitrogen atoms). The electrolyte for a polymer electrolyte fuel cell according to claim 5, wherein the electrolyte is provided. The compound represented by the general formula (IV) is represented by the following general formula (VI)

(Wherein, Z is a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some of the groups may be chain, cyclic, or branched, and oxygen In the case where Z is an aryl group, it may be an aryl group partially substituted with an arbitrary group, and may contain oxygen and nitrogen atoms). The electrolyte for a polymer electrolyte fuel cell according to claim 5, wherein the electrolyte is provided. The compound represented by the general formula (IV) is represented by the following general formula (VII)

(Wherein, Z is a kind of substituent selected from the group consisting of an alkyl group, an aryl group, an alkoxy group, a carboxyl group, an alkoxycarbonyl group, a cyano group, a hydroxyl group, a nitro group, an amino group, and a substituent containing a hydrogen atom. In the case where Z is an alkyl group, the alkyl group may be partially substituted with an arbitrary group, and some of the groups may be chain, cyclic, or branched, and oxygen In the case where Z is an aryl group, it may be an aryl group partially substituted with an arbitrary group, and may contain oxygen and nitrogen atoms). The electrolyte for a polymer electrolyte fuel cell according to claim 5, wherein the electrolyte is provided.   A polymer electrolyte fuel cell comprising the electrolyte for a polymer electrolyte fuel cell according to any one of claims 1 to 8.   10. The polymer electrolyte fuel cell according to claim 9, wherein the polymer electrolyte fuel cell is one selected from a hydrogen type, a direct methanol type, and a direct hydrocarbon type.   A polymer electrolyte fuel cell system comprising the polymer electrolyte fuel cell according to claim 9. 12. A fuel cell vehicle comprising the polymer electrolyte fuel cell system according to claim 11 mounted thereon.

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