KR20120092055A - A proton exchange membrane for an electrochemical cell - Google Patents

Abstract

PURPOSE: A polymer electrolyte membrane is provided to have excellent electrochemical performance like ion conductivity, ion exchange capacity, etc, and to improve physical properties like durability, tensile strength, etc. CONSTITUTION: A polymer electrolyte membrane comprises a polymer having a unit structure in chemical formula 1, and an inorganic acid in which macro-molecule is substituted. The macro-molecule is a mixture of one or two selected from cesium, ammonium, rubidium, sodium and potassium. In chemical formula 1, R is hydrocarbon, m, n, p and q are integer from 1 or more, m=p, and n=q. the inorganic acid is a mixture of one or more selected from phosphotungstate, zirconium phosphate, silicotungstate, phosphomolybdate, and silicomolybdate.

Description

A polymer electrolyte membrane, an electrolytic device, a fuel cell and a fuel cell system including the same

The present invention relates to an ion exchange polymer electrolyte membrane, an electrolytic device, a fuel cell, and a fuel cell system including the same. More specifically, the present invention includes a polymer having a unit block crosslinked in a molecule and an inorganic acid substituted with macromolecules. Thus, the thermal stability is high, the electrochemical properties such as ionic conductivity, ion exchange capacity, etc. are excellent even at high temperatures, and the mechanical properties such as durability and tensile strength are improved, a method for producing a polymer electrolyte membrane, a polymer electrolyte membrane, and an electrolytic device using the electrolyte membrane The present invention relates to a fuel cell and a fuel cell system including the same.

In general, ion-exchangeable polymer electrolytes are widely used as ion exchange membranes (electrolyte membranes) such as electrolysis (water electrolysis) of water and fuel cells. The electrolysis (water electrolysis) apparatus of water is an apparatus that generates hydrogen and oxygen by electrochemically decomposing water, which is attracting attention for hydrogen production technology due to its high energy efficiency. In contrast, a fuel cell is an environmentally friendly power generation system that generates electricity by electrochemically reacting hydrogen and oxygen, which is one of the cores of new energy technology due to its simple and efficient energy conversion step. In particular, a fuel cell using a solid polymer electrolyte is notable because it is advantageous in terms of size, weight, and the like.

A solid polymer fuel cell (PEFC) generally has a membrane-electrode assembly (MEA) including a solid polymer electrolyte membrane, a catalyst layer bonded to both sides of the electrolyte membrane, and a gas diffusion layer bonded to the outside of the catalyst layer. In addition, a separator is disposed in the membrane-electrode assembly MEA. In addition, a gas flow path for supplying a fuel gas or an oxidant gas is formed in the contact portion or separator of the membrane-electrode assembly MEA and the separator. At this time, one electrode (fuel pole) is supplied with fuel gas such as hydrogen or methanol, and the other electrode (oxygen pole) is supplied with oxidant gas containing oxygen such as air to generate electricity.

In the above-described fuel cells, electrolytic devices, and the like, a polymer electrolyte membrane for exchanging ions is generally used by commercially available Nafion (manufactured by Dupont), a perfluorine-based membrane. However, Nafion membranes are complicated in manufacturing process and very expensive. In addition, it has been pointed out that the Nafion membrane is poor in electrochemical performance such as ionic conductivity at a high temperature of 80 ° C or higher.

Accordingly, Japanese Patent Laid-Open No. 06-93114 proposes a method for producing an electrolyte membrane based on sulfonated aromatic polyether ketone. However, when the degree of sulfonation is increased to increase ion exchangeability, the membrane is deteriorated by swelling, which is very difficult to handle, and mechanical properties such as durability and tensile strength are inferior, and thermal stability is not satisfactory. have. In addition, Japanese Patent Application Laid-Open No. 11-329062 discloses a polymer for producing an electrolyte membrane, in which two or more different fluorine-containing unit blocks are used, one of which has a sulfonic acid group, thereby improving mechanical properties. However, it is pointed out that the vinyl ether monomer is used as the unit block having a sulfonic acid group, so that the thermal stability is poor.

As described above, the polymer electrolyte membrane according to the prior art has low thermal stability, and thus, at high temperatures, the electrochemical characteristics such as ionic conductivity are decreased, and when the sulfonation degree is increased for ion exchangeability, the membrane is deteriorated by swelling. have. In addition, there is a problem that the mechanical properties such as durability and tensile strength is not good.

The present invention has been made to solve the above-mentioned problems, firstly, by including a polymer having a unit block cross-linked in the molecule, a macromolecule substituted inorganic acid, a polymer electrolyte membrane having electrochemical properties and durability and its preparation One purpose is to provide a method.

In addition, another object of the present invention is to provide a fuel cell system including a fuel cell, a fuel cell, and a fuel cell including a polymer electrolyte membrane prepared according to an embodiment of the present invention.

On the other hand, the objects of the present invention are not limited to the above-mentioned objects, other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above objects, the polymer electrolyte membrane according to an embodiment of the present invention is characterized in that it comprises a polymer having a repeating unit of the formula and an inorganic acid substituted with macromolecules, wherein the macromolecules are cesium, ammonium, Rubidium, sodium and potassium, characterized in that any one or a mixture of two or more selected from the group consisting of.

[Chemical Formula]

Preferably, in the above formula, R is a hydrocarbon and m, n, p and q are integers of at least 1, m = p and n = q.

Preferably, the inorganic acid is one or two or more mixtures selected from the group consisting of phosphotungstic acid, zirconium phosphoric acid, silicotungstic acid, phosphomolybdic acid and silicomolybdic acid.

Preferably, the polymer electrolyte membrane is characterized in that 20 to 40% by weight of the inorganic acid substituted with the macromolecule.

Preferably, the inorganic acid substituted with the macromolecule is substituted with 5 to 35% of the macromolecule relative to the cation of the inorganic acid.

On the other hand, the method for producing a polymer electrolyte membrane according to an embodiment of the present invention comprises the steps of introducing a sulfone group (-SO ₃ H) to the polymer; Introducing a sulfin group (-SO ₂ ) into the sulfonated polymer; A third step of partially reducing the sulfinated polymer such that sulfin groups (-SO ₂ ) and sulfonate groups (-SO ₂ M; M is a metal) are present in the polymer; Mixing the partially reduced polymer with a solvent and then adding and stirring a crosslinking agent to prepare a casting solution;

A fifth step of preparing a film by coating the casting solution; And a sixth step of replacing the sulfin group (-SO ₂ ) of the prepared membrane with a sulfone group (-SO ₃ H), wherein the fourth step further comprises adding an inorganic acid substituted with a macromolecule. do.

Preferably the macromolecule is characterized in that any one or two or more selected from the group consisting of cesium, ammonium, rubidium, sodium and potassium.

Preferably, the inorganic acid is one or two or more mixtures selected from the group consisting of phosphotungstic acid, zirconium phosphoric acid, silicotungstic acid, phosphomolybdic acid and silicomolybdic acid.

Preferably, the inorganic acid substituted with the macromolecule is characterized in that the macromolecule is substituted with 5 to 35% of the cation of the inorganic acid.

Preferably, the third step is: a) partially reducing the sulfonated sodium sulfonate group (—SO ₂ Na) in the sulfinated polymer; And b) replacing the sodium sulfonate group (-SO ₂ Na) with a lithium sulfonate group (-SO ₂ Li).

Preferably step a) is characterized in that using a sodium sulfite (Na ₂ SO ₃ ) solution of 0.5 to 2.0 molar concentration (M) as a partial reducing agent.

Preferably, the polymer is polyether ether ketone, polyarylene ether ketone, polysulfone, polyarylene ether sulfone, polyimide, polybenzimidazole, polybenzoxazole, polybenzithazole, polypyrrolone, polyphosphazene And one or two or more selected from the group consisting of copolymers thereof.

Preferably, the crosslinking agent of the fourth step is characterized in that the iodide alkene.

On the other hand, the electrolytic device according to an embodiment of the present invention is characterized in that it comprises a polymer electrolyte membrane produced by the above-described manufacturing method.

On the other hand, the fuel cell according to an embodiment of the present invention is characterized in that it comprises a polymer electrolyte membrane prepared by the above-described manufacturing method, the fuel cell system according to an embodiment of the present invention is characterized in that it comprises the above fuel cell It is done.

According to the present invention, the unit block having an ion exchange group has ion exchange properties, and further includes a unit block cross-linked in the molecule, and thus has high thermal stability and thus electrochemical characteristics such as ion conductivity and ion exchange capacity at high temperatures. It is excellent and has the effect that mechanical properties, such as tensile strength, improve.

In addition, when the macromolecule further includes a substituted inorganic acid, thermal stability, electrochemical properties, leaching of the inorganic acid, and durability of the polymer electrolyte membrane may be improved.

Figure 1 shows a CV curve of the MEA prepared in accordance with an embodiment of the present invention.
2 is a current-voltage graph of a MEA manufactured according to an embodiment of the present invention applied to a cell receiving a cell.

The terms used in the present invention are selected as general terms that are widely used at present, but in certain cases, the term is arbitrarily selected by the applicant. In this case, the meanings described or used in the detailed contents for carrying out the invention are not merely names of the terms. Considering this, the meaning should be grasped.

EMBODIMENT OF THE INVENTION Hereinafter, the technical structure of this invention is demonstrated in detail.

The polymer electrolyte membrane according to the present invention is prepared from a material comprising at least a polymer, wherein the polymer comprises a unit block A having an ion exchange group and a unit block B having a reactive group, wherein the unit block B is formed by a reactive group. Have a cross-linked structure. Specifically, the polymer has a repeating unit represented by the following formula (1).

[Formula 1]

In Formula 1, A is a unit block having an ion exchange group, B is a unit block having a reactive group and m, n, p and q are integers of 1 or more.

The polymer is preferably a polyether ether ketone, a polyarylene ether ketone, a polysulfone, a polyarylene ether sulfone, a polyimide, a polybenzimidazole, a polybenzoxazole, a polybenzisazole, a polypyrrolone, a polyphosphor It can be obtained based on one or more polymers selected from the group consisting of pazene, and copolymers thereof (e.g., polybenzoxazole-polypyrrolone, polybenzisazole-polypyrrolone, etc.).

Specifically, the polymer may be prepared so that the ion exchanger is introduced using the listed polymers as starting materials, and then, through the crosslinking reaction, the unit block A having the ion exchanger introduced therein and the crosslinked unit block B are simultaneously included in the molecule. have.

At this time, the ion exchange group of the unit block A includes any functional group having proton conductivity in the present invention, for example, sulfonic acid group, sulfonimide group, phosphonic acid group, carboxylic acid group and metal salts thereof Ammonium salts and the like.

In addition, the unit block B has a reactive group for crosslinking, which may be a double bond, a triple bond or an ion present in the unit block B.

In addition, the reactive group may be introduced separately substituted in the unit block B, for example, a sulfin group (-SO ₂ ) by sulfination.

[Formula 2]

In formula (2), A is a unit block having an ion exchange group, B is a unit block having a reactive group, R is a hydrocarbon and m, n, p and q are integers of 1 or more.

In Formula 2, R is a hydrocarbon, wherein the hydrocarbon includes aliphatic and aromatic hydrocarbons.

For example, R in Formula 2 may be an alkane-based, alkene-based, alkyne-based, cycloalkane-based, and aryl-based hydrocarbon.

Although not particularly limited, R in the formula (2) is preferably an aliphatic hydrocarbon having 1 to 12 carbon atoms, preferably 4 to 8 carbon atoms.

In addition, the polymer may be prepared to have a repeating unit of Formula 2 by the addition of a crosslinking agent.

In this case, R of the formula (2) is introduced by a crosslinking agent, the crosslinking agent is not particularly limited, but is preferably an alkene hydrocarbon having 1 to 12 carbon atoms, preferably 4 to 8 carbon atoms. As the crosslinking agent, iodide alkenes such as 1,4-diiodobutene can be usefully used.

According to the present invention, the thermal stability is increased by the unit block B having ion exchangeability but crosslinked (preferably covalently bonded by a crosslinking agent).

Accordingly, the polymer electrolyte membrane according to the present invention has high thermal stability as described above, and is excellent in electrochemical properties such as ionic conductivity even at high temperatures.

In addition, the polymer electrolyte membrane according to the present invention has a high water content and prevents swelling, and has excellent mechanical properties such as durability and tensile strength.

According to a more preferred embodiment of the present invention, the ion exchange group of the unit block A is a sulfone group (-SO ₃ H), the reactive group of the unit block B is a sulfin group (-SO ₂ ), the polymer of the formula It is preferable to have a repeating unit.

(3)

In formula (3), R is a hydrocarbon and m, n, p and q are integers of 1 or more.

The polymer of Formula 3 may be obtained based on aromatic polyether ether ketone.

In this case, the aromatic polyether ether ketone is excellent in heat resistance, fatigue resistance, hygroscopicity and chemical resistance, etc., compared to other polymers, it is possible to achieve a high sulfonation degree is preferably applied to the present invention.

In addition, in Chemical Formulas 1 to 3, m and p of the unit block A may be the same or different, and n and q of the unit block B may also be the same or different.

Preferably, at least in Formula 3, m = p, and n = q.

In addition, in the above Chemical Formulas 1 to 3, the larger m and p are advantageous in ion exchangeability, and the larger n and q may improve the mechanical properties, where m (p): It is preferable that n (q) is 1: 0.2-5.0.

The polymer electrolyte membrane according to the present invention may be prepared by a coating method such as a material containing at least the polymer, specifically, a casting solution containing at least the polymer and a solvent.

The polymer electrolyte membrane according to the present invention includes at least the above polymer, and further includes an inorganic acid substituted with macromolecules as an additive.

According to the present invention, the inorganic acid substituted with the macromolecule increases the surface area of the inorganic acid, thereby improving thermal stability and electrochemical properties, improving durability of the polymer electrolyte membrane, and improving stability such as preventing leaching of the inorganic acid. Have it.

At this time, the substitution amount of the macromolecule to the inorganic acid is not particularly limited, so that the tensile strength of the polymer electrolyte membrane may be lowered, so that the substitution of the macromolecule to the cation of the inorganic acid is preferably within 35%, preferably 5 to 25%. It is good to substitute within.

In addition, the inorganic acid substituted with the macromolecule is preferably contained in 20 to 40% by weight, wherein the inorganic acid in the crowd consisting of phosphotungstic acid, zirconium phosphoric acid, silico tungstic acid, phosphomolybdic acid and silicomolybdic acid One or more mixtures selected may be used.

In addition, the macromolecule may be used one or two or more selected from the group consisting of cesium, ammonium, rubidium, sodium and potassium, and the like.

The polymer electrolyte membrane according to the present invention as described above, according to a preferred embodiment of the present invention, can be prepared by the following method.

The method presented below is a method in which a sulfone group (-SO ₃ H) is introduced as an ion exchange group and a sulfin group (-SO ₂ ) is introduced through partial reduction as a reactive group for crosslinking.

This is only presented as an embodiment in the present invention, the polymer electrolyte membrane according to the present invention is not limited to that produced by the method shown below.

Polymer electrolyte membrane according to the present invention, (1) sulfone group (-SO ₃ H) introduction step (2) sulfin group (-SO ₂ ) introduction step (3) partial reduction step (4) casting solution manufacturing step ( 5) can be prepared from a method comprising at least a casting step and (6) sulfonic group (-SO ₃ H) substitution step and will be described in detail for each step as follows.

(1) Introduction of sulfone group (-SO ₃ H)

First, a sulfonating agent is reacted with a polymer of a starting material to substitute and introduce a sulfone group (-SO ₃ H).

In this case, as the starting material, the polymer may be a polyether ether ketone, a polyarylene ether ketone, a polysulfone, a polyarylene ether sulfone, a polyimide, a polybenzimidazole, a polybenzoxazole, a polybenzithiazole, Preference is given to one or two or more selected from the group consisting of polypyrrolone, polyphosphazene and copolymers thereof, more preferably aromatic polyetheretherketone.

In addition, the sulfonating agent may be used sulfuric acid (sulfuric acid, H ₂ SO ₄ ), sulfur trioxide (SO ₃ ) and chlorosulfonic acid (ClSO ₃ H).

At this time, 20 to 30 g of the polymer is added to the reactor in 400 ml of sulfonating agent and stirred at room temperature, but in order to prevent oxidation, it is preferable to prepare the sulfonated polymer by stirring in an inert atmosphere (nitrogen atmosphere, etc.) for 100 to 150 hours. . After washing with distilled water, it is better to dry.

(2) Introduction of sulfin group (-SO ₂ )

In order to introduce a sulfin group (-SO ₂ ) as a reactive group for crosslinking to the sulfonated polymer, the sulfonated polymer is dissolved in thionyl chloride (SOCl ₂ ) or the like.

At this time, the sulfonated polymer is substituted with -SO ₂ Cl instead of the sulfone group (-SO ₃ H).

Specifically, 10-15 g of sulfonated polymer is placed in 200 ml to 250 ml of thionyl chloride (SOCl ₂ ), and N, N-dimethylformamide (DMF; N, N-Dimethylformamide) is added, and then 60 After stirring at ~ 80 ℃ and distillation of 45 ~ 50 minutes at 85 ~ 90 ℃ to remove the remaining SOCl ₂ .

Next, the distilled polymer is diluted with tetrahydrofuran (THF; tetrahydrofuran) and the like, and then the precipitated solution is precipitated, washed with alcohol (methanol, iso-propanol, etc.), and dried.

(3) partial reduction step

The polymer in which the -SO ₂ Cl group is introduced is partially reduced such that a sulfin group (-SO ₂ ) and a sulfonate group (-SO ₂ M, where M is a metal) are simultaneously present in the polymer.

In this case, the sulfonate group (-SO ₂ M) is preferably a crosslinking reactive lithium sulfonate group (-SO ₂ Li), for this purpose, a sodium sulfonate group (-SO ₂ Na) with good reduction reactivity is introduced first, and then sulfonic acid It is preferable to replace the sodium group (-SO ₂ Na) with a lithium sulfonate group (-SO ₂ Li).

Specifically, so that the sulfonate group (-SO ₂ Na) is present in the polymer into which the -SO ₂ Cl group is introduced, sodium sulfite (Na ₂ SO ₃ ) and sodium sulfide hydrate (sodium sulfide) for partial reduction. In the partial reducing agent solution such as hydrate, Na ₂ S.nH ₂ O), the -SO ₂ Cl group introduction polymer prepared in step (2) is added and reacted. Next, in order to replace the sodium group (-SO ₂ Na) as the sulfonic acid group the sulfonic acid lithium (-SO ₂ Li), lithium chloride (lithium chloride, LiCl), lithium acetate dihydrate (lithium acetate dihydrate, and CH3COOLi 2H ₂ O It adds and stirs to lithiating solution solutions, such as). And after washing with distilled water or the like, it is good to dry.

(4) Casting solution manufacturing step

In the step (3), the partially reduced polymer, specifically, a polymer in which -SO ₂ Cl and -SO ₂ Li are introduced into the polymer is mixed with an organic solvent, and then a crosslinking agent is added and stirred to prepare a casting solution. do.

At this time, the crosslinking agent may be added, such as alkyne iodide, but is not particularly limited to 0.01 to 30 parts by weight based on 100 parts by weight of the partially reduced polymer in step (3).

(5) casting stage

The casting solution described above is coated in the same manner as usual and then dried to prepare a membrane.

(6) sulfone group (-SO ₃ H) substitution step

In the membrane prepared as described above, a -SO ₂ Cl group exists, which is substituted with a sulfone group (-SO ₃ H).

Specifically, the above (3) by partial reduction of the step, a portion of the -SO ₂ Cl group is substituted with -SO ₂ Li, some of which there remains a group -SO ₂ Cl, the sulfate membrane prepared in the above step (5) It is immersed in a (H ₂ SO ₄ ) solution or the like to replace the -SO ₂ Cl group with -SO ₃ H.

On the other hand, the method for producing a polymer electrolyte membrane according to the invention is characterized in that it further comprises the step of adding the inorganic acid substituted macromolecule.

The inorganic acid is preferably added before the stirring of the crosslinking agent. Specifically, in step (4), the inorganic acid is added in the process of mixing the partially reduced polymer and the organic solvent to immerse in the macromolecular solution before step (6) to replace the cation of the inorganic acid with the macromolecule or the inorganic acid the macromolecule. After titration with the solution, the inorganic acid substituted with the macromolecule is added in step (4), and then, the crosslinking agent is added and stirred.

At this time, the inorganic acid may use one or two or more selected from the group consisting of phosphotungstic acid, zirconium phosphoric acid, silicotungstic acid, phosphomolybdic acid and silicomolybdic acid as described above.

In addition, the macromolecule may use one or more mixtures selected from the group consisting of cesium, ammonium, rubidium, sodium, potassium, and the like as described above.

The polymer electrolyte membrane according to the present invention can be prepared through the above process, wherein the crosslinking of the unit block B in the formula (1) is not only the addition amount of the crosslinking agent, but also the sulfonate group (-SO ₂ M) in the step (3) ) Can be controlled according to the degree of introduction. As described above, in Chemical Formulas 1 to 3, larger m and p are advantageous for ion exchangeability, and larger n and q may improve mechanical properties, wherein the ratio of m (p) and n (q) is equal to ( In step 3) it can be controlled according to the degree of introduction of sulfonate group (-SO ₂ M).

More specifically, the molarity or amount of partial reducing agents such as sodium sulfite (Na ₂ SO ₃ ) and sodium sulfide hydrate (Na ₂ ㆍ nH ₂ O) solution, and lithium chloride (lithium chloride, The ratio of m (p) and n (q) can be controlled by controlling the concentration or amount of lithium agent such as LiCl) and lithium acetate dihydrate (CH ₃ COOLi.2H ₂ O) solution.

For example, if the molar concentration (M) of the sodium sulfite (Na ₂ SO ₃ ) solution used as the partial reducing agent is small, the electrochemical properties such as ionic conductivity may be increased, but the mechanical properties may be decreased. If the molar concentration (M) of the Pite (Na ₂ SO ₃ ) solution is large, electrochemical properties such as ionic conductivity may be lowered, but mechanical properties may be improved.

Although not particularly limited, the sodium sulfite (Na ₂ SO ₃ ) solution used as the partial reducing agent is 0.5 to 2.0 molar concentration (M), and the lithium chloride (LiCl) solution used as the lithium agent is 5 to 10 weight. % Can be used.

The polymer electrolyte membrane according to the present invention described above is included in the present invention as long as it is used for ion exchange in its use.

Preferably, it can be usefully applied to the electrolysis (water electrolysis) of water or an ion exchange membrane (electrolyte membrane) such as a fuel cell.

On the other hand, the electrolytic device and the fuel cell according to the present invention may have a structure as usual, and the polymer electrolyte membrane according to the present invention as an electrolyte is included in the present invention.

The electrolytic device according to the present invention comprises at least a membrane-electrode assembly (MEA) having, for example, an electrolyte membrane, an anode and a cathode catalyst layer formed on both surfaces of the electrolyte membrane, and supplying electrons, reactants and products, A frame arranged in a dischargeable form; Separator (separator plate); It may comprise a MEA support and a gasket (packing) and the like.

At this time, the electrolyte membrane constituting the membrane-electrode assembly (MEA) is composed of a polymer electrolyte membrane according to the present invention.

In addition, the fuel cell according to the present invention is, for example, a solid polymer fuel cell (PEFC) having a conventional structure, including an electrolyte membrane, a catalyst layer bonded to both sides of the electrolyte membrane, and a gas diffusion layer bonded to the outside of the catalyst layer. It may have a membrane-electrode assembly (MEA). In addition, a separator is disposed in the membrane electrode assembly MEA, and a gas flow path for supplying a fuel gas or an oxidant gas may be formed in a contact portion or separator of the membrane electrode assembly MEA and the separator.

Moreover, it has a fuel electrode to which fuel gas, such as hydrogen and methanol, is supplied, and an oxygen electrode to which oxidant gas, such as air and oxygen, is supplied.

At this time, the electrolyte membrane constituting the membrane-electrode assembly (MEA) is composed of a polymer electrolyte membrane according to the present invention.

In addition, the fuel cell system according to the present invention may have a structure as usual, and if the fuel cell according to the present invention is used as the fuel cell constituting the same, it is included in the present invention.

For example, a fuel cell system according to the present invention includes a fuel cell; A hydrogen generator for generating hydrogen from the source gas and supplying hydrogen to the fuel electrode of the fuel cell; An oxidant gas supply device for supplying oxidant gas (air, oxygen, etc.) to the oxygen electrode of the fuel cell; Fuel gas opening and closing means for opening and closing the entrance and exit of the anode; Oxidant gas opening and closing means for opening and closing an entrance and exit of an oxygen pole; Hydrogen opening and closing means for opening and closing the entrance and exit of the hydrogen generating device; And a control device for controlling the opening and closing operations of the fuel gas opening and closing means, the oxidant gas opening and closing means, and the hydrogen opening and closing means. In this case, the fuel cell is composed of a fuel cell including the polymer electrolyte membrane according to the present invention.

In addition, as the hydrogen generating device constituting the fuel cell system according to the present invention, the electrolytic device according to the present invention may be applied.

Hereinafter, an embodiment of the present invention is illustrated.

At this time, the following examples are merely provided to explain the present invention in more detail, whereby the technical scope of the present invention will not be limited.

Example 1

Covalently cross-linked SPEEK membrane (SPEEK; means sulfonated PEEK) was prepared by using an aromatic polyether ether ketone (hereinafter referred to as 'PEEK').

1. Manufacture of SPEEK

First, 20 g of PEEK (Vitrex, 450G) was dried at 100 ° C. for 12 hours to completely remove moisture, and then placed in a three neck flask with 400 ml of sulfuric acid (H ₂ SO ₄ ) and stirred at room temperature.

At this time, a nitrogen atmosphere was maintained to prevent oxidation, and was completely dissolved by stirring for 120 hours at a stirring speed of 350 rpm.

The prepared polymer was precipitated in ice water, and then again precipitated in distilled water for 12 hours. The precipitated polymer was repeatedly washed with distilled water several times until pH 7-8, and then completely dried in a vacuum dryer at 100 ° C. for 24 hours to prepare SPEEK (sulfonated polyether ether ketone) having a sulfonation degree of 90% or more. It was.

2. Preparation of PEEK-SO2Cl

In order to introduce sulfin groups into the prepared SPEEK, 12 g of the prepared SPEEK was dissolved in 200 ml of thionyl chloride (SOCl ₂ ), and then 3 ml of N, N-dimethylformamide (DMF) was added thereto. At the same time, the mixture was stirred at 60 ° C. for 3 hours and distilled at 85 ° C. for 50 minutes to remove the remaining amount of SOCl ₂ . The distilled polymer was diluted in 20 mL of tetrahydrofuran (THF), the diluted solution was precipitated in methanol, and the resulting polymer was washed several times. The resulting polymer was again dissolved in 120 mL of THF, precipitated in methanol, washed several times, and completely dried in a vacuum dryer at 25 ° C. for 24 hours to prepare PEEK-SO ₂ Cl.

3. Preparation of PEEK-SO ₂ Cl-SO ₂ Li

The prepared solution of PEEK-SO ₂ Cl 8g and sodium sulfate (sodium sulfate, Na ₂ SO ₃ ) was put into a three-necked flask and stirred at 70 ° C. for 24 hours to partially reduce the sulfin group to introduce -SO ₂ Na group into the polymer. (Manufactured by PEEK-SO ₂ Cl-SO ₂ Na)

At this time, the molar concentration (M, mole / L) of the sodium sulfate (Na ₂ SO ₃ ) solution was carried out to 0.5M, 1.0M, 1.5M and 2.0M to determine the characteristics of the membrane according to the degree of partial reduction.

Next, remove the resulting white suspension, which was substituted with this lithium chloride (lithium chloride, LiCl) and the solution was stirred for 1 hour, a group -SO ₂ Li, instead of group -SO ₂ Na.

In this case, in order to examine the characteristics of the film according to the degree of lithiation, the lithium chloride (LiCl) solution was different from 5 wt%, 7 wt%, and 10 wt% with respect to the polymer partially reduced with 2.0 M sodium sulfate (Na ₂ SO ₃ ) solution. Was used. After repeated washing with distilled water several times, completely dried in a vacuum dryer at 40 ℃ for 24 hours to prepare a partially reduced PEEK-SO ₂ Cl-SO ₂ Li.

4. Preparation of Membrane

3 g of the prepared polymer (PEEK-SO2Cl-SO2Li) was added to a solvent of n-methyl-2-pyrrolidinone (NMP) and dissolved therein, and then 1,4-diodobutene (1) as a crosslinking agent ( 1,4-diiodobutene) was added thereto, followed by vigorous stirring for 40 minutes to prepare a casting solution. After casting the prepared casting solution (coating machine, SinilEng. Korea), first dried at room temperature for 12 hours, then dried at 60 ℃ for 4 hours, then dried at 120 ℃ for 12 hours The membrane was prepared.

Next, the prepared membrane was immersed in a 10 wt% H ₂ SO ₄ aqueous solution for 24 hours to replace the sulfin group with a sulfone group, thereby preparing a solid polymer electrolyte membrane (covalently crosslinked SPEEK membrane) according to the present embodiment.

[Example 2]

In the same manner as in Example 1 above, a membrane was prepared by further adding phosphotungstic acid (H ₃ O ₄₀ PW ₁₂ ) as an inorganic acid before adding a crosslinking agent.

At this time, the content of the phosphotungstic acid (H ₃ O ₄₀ PW ₁₂ ) in the casting solution 10wt%, 20wt%, 30wt%, 40wt%, 50wt% and 60wt% to determine the characteristics of the membrane according to the amount of the inorganic acid added Otherwise added.

At this time, the concentration of sodium sulfate (Na ₂ SO ₃ ) solution was 2.0M, lithium chloride (LiCl) solution was used as the specimen of this embodiment that the 7wt%.

[Example 3]

In the same manner as in Example 2, to prepare the membrane by adding phosphotungstic acid (H ₃ O ₄₀ PW ₁₂ ) to the inorganic acid before adding the crosslinking agent in order to determine the properties of the membrane according to the macromolecular substitution method and the amount of substitution. It was immersed in 0.1M cesium (Cs) solution to make a polymer electrolyte membrane to which phosphotungstic acid substituted with cesium was added.

In addition, the cesium solution was titrated with phosphotungstic acid before addition to the polymer electrolyte membrane, and the volume ratio of the cesium solution to the phosphotungstic acid was added at 10 vol%, 25 vol%, 33 vol%, and 50 vol%.

At this time, the concentration of sodium sulfate (Na ₂ SO ₃ ) solution was 2.0M, lithium chloride (LiCl) solution 7% by weight and the addition amount of phospho tungstic acid substituted with a macromolecule was fixed to 30wt% to prepare a specimen of this embodiment .

[Comparative Example 1]

In contrast to Example 1 above, the cross-linking was not carried out through the partial reduction was applied as a specimen of this comparative example.

Specifically, SPEEK (sulfonated polyether ether ketone) prepared in step 1 of Example 1 was applied as a specimen of this comparative example.

For membrane specimens according to the above examples and comparative examples, hydrogen ion conductivity (S / cm), ion exchange capacity (meq / g-dry-membr.), Water content (%), and tensile strength (%) Characteristics such as MPa) and elongation (%) were evaluated.

<Evaluation of Electrolyte Membrane>

1. Physical property evaluation

end. Hydrogen ion conductivity evaluation

The prepared membranes were evaluated for hydrogen ion conductivity with temperature using an impedance measuring instrument (solartron 1260 analyzer).

At this time, the hydrogen ion conductivity (S / cm) was calculated by substituting the resistance (Ω) at 1KHz and then substituted in the following equation (1).

[Equation 1]

σ = 1 / ((r ₂ -r ₁ ) × S)

In Equation 1, σ is hydrogen ion conductivity (S / cm), r ₁ is the electrical resistance (Ω) of pure 1M H ₂ SO ₄ aqueous solution in the absence of a membrane, and r ₂ is the electrical resistance measured by inserting the membrane ( Ω), S is the film area (cm 2), and l is the film thickness (cm).

The results are shown in the following [Table 1].

<Hydrogen Conductivity Evaluation Results According to Temperature> division
Temperature (℃) 25 ℃ 60 ° C 80 ℃ Example 1 7.0 × 10 ^-2 to 7.5 × 10 ^-2
8.5 × 10 ^-1 to 9.0 × 10 ^-1 1.0 × 10 ^-1 to 1.1 × 10 ^-1 Example 2 9.0 × 10 ^-2 to 9.5 × 10 ^-2
1.0 × 10 ^-1 to 1.1 × 10 ^-1 1.2 × 10 ^-1 to 1.3 × 10 ^-1 Example 3 4.0 × 10 ^-2 to 6.3 × 10 ^-2
1.0 × 10 ^-1 to 1.2 × 10 ^-1 1.6 × 10 ^-1 to 2.3 × 10 ^-1 Comparative Example 1 2.5 × 10 ^-2 to 2.7 × 10 ^-2
3.7 × 10 ^-2 to 3.8 × 10 ^-2 swelling

As shown in Table 1 above, compared to the sulfonated SPEEK membrane, covalently cross-linked SPEEK membranes (Examples 1 and 2) were connected to improve conductivity of hydrogen ions, even at a high temperature of 80 ° C. Due to the crosslinking, the backbone of the polymer was not hydrolyzed, and it was found to have excellent ionic conductivity.

And it can be seen that the sulfonated SPEEK membrane (Comparative Example 1) is swelled at 80 ° C.

In addition, it can be seen that the case of Example 2 to which the phospho tungstic acid (H ₃ O ₄₀ PW ₁₂ ) is added as the inorganic acid than Example 1 is improved thermal stability and ionic conductivity because it gives phospho tungstic acid It seems to be.

On the other hand, it can be seen that the case of Example 3, such as the present invention than Example 1 and Example 2 is more thermal stability and ionic conductivity, which is fine pores are generated when the cesium is substituted by phosphotungstic acid It is believed that the proton conductivity is high because the surface area of the stick acid is increased.

I. Mechanical property evaluation

The mechanical properties (tensile strength and elongation) of the membranes according to Examples 1, 2, 3 and Comparative Example 1 were measured and the results are shown in the following [Table 2].

On the other hand, the measuring instrument was used LR-5K product of Llyod, UK, and measured the tensile strength and elongation of the film by the provisions of ASTM D 882 at room temperature of 25 ℃.

In the following [Table 2], the result of Example 1 is a result of measuring the concentration of the sodium sulfate (Na ₂ SO ₃ ) solution is 2.0M, the lithium chloride (LiCl) solution using 7wt% of the sample, results of example 2 shows the result of measurement was used the addition of the phosphine poteong stick acid (H ₃ PW ₄₀ O ₁₂₎ 30wt% in the specimen.

<Mechanical characteristic evaluation result> division Tensile Strength (MPa) Elongation (%) Example 1 64.25 52.93 Example 2 75.01 83.76 Example 3 47.3 40.4 Comparative Example 1 10.42 316.2

As shown in Table 2 above, it was found that the covalently crosslinked SPEEK membranes (Examples 1 and 2) were improved by 6 times or more compared to the sulfonated SPEEK membranes (Comparative Example 1). Could.

In particular, Example 3, such as the present invention can be seen that the tensile strength of about 5 times than the Comparative Example 1.

All. Evaluation of Durability Characteristics for Oxidation Stability

Oxidation Stability by Measuring Final Decomposition Time by Fenton Reagent Prepared by Mixing Ferric Sulfate (FeSO ₄ ) and Hydrogen Peroxide (H ₂ O ₂ ) Solution for Membranes according to Examples 1, 2, 3 and Comparative Example 1 The durability characteristics for were evaluated.

<Result of Evaluation of Durability Characteristics on Oxidation Stability> division Membrane Degradation Time by Fenton's Reagent (hour: minute) Example 1 29:41 Example 2 48:32 Example 3 1200: 00 Comparative Example 1 6:32

As shown in Table 3 above, the sulfonated SPEEK membrane (Comparative Example 1), the covalently bonded SPEEK membrane (Example 1), and the inorganic acid-added cocrosslinked SPEEK membrane (Example 2) In comparison, the co-crosslinked SPEEK membrane (Example 3) to which the cesium-substituted inorganic acid was added decreased the solubility and leaching amount of the inorganic acid, thereby reducing the hydrolysis caused by the swelling of the polymer electrolyte membrane, thereby improving oxidation stability.

From the above results, the sulfonated polymer membrane is easily hydrolyzed at high temperature and has low mechanical properties such as tensile strength. However, when covalently crosslinked according to the present invention, it is not hydrolyzed even at high temperature. And it was found that the water content is kept high, and the ionic conductivity is excellent, and mechanical properties such as tensile strength are improved.

In addition, as in Example 2, it was found that when the inorganic acid was further added, thermal stability and mechanical properties were further improved. In this case, it was found that the addition amount of the inorganic acid showed excellent results at 40 wt% or less, more preferably at 20 to 30 wt%. In addition, it can be seen from the above results that the electrochemical properties, thermal stability, inorganic acid stability and oxidation stability were further improved when the inorganic acid in which the cation was substituted with the macromolecule was added.

In this case, the amount of cesium substitution was 25 vol% or less, more preferably, in the substitution method, the method of immersing in a cesium solution after casting the membrane showed a good result.

Meanwhile, the membrane-electrode assembly (MEA) was prepared using the prepared membrane as described below, and the prepared MEA was applied to an electrolytic cell to evaluate electrical performance.

2. Fabrication of membrane-electrode assembly (MEA) and evaluation of electrolytic cell performance

As a manufacturing method of the membrane-electrode assembly (MEA), the platinum catalyst was impregnated using an impregnation-reduction method suitable for electrolysis, and the commercial membrane was used as the PEEK membrane prepared in Examples 1 and 1 above. Pt / PEM MEA was prepared according to a conventional method using Nafion 117 (manufactured by Dupont).

In addition, the prepared MEA was applied to a cell to receive a cell, and the voltage and current density of the electrolysis of water were measured.

At this time, a platinum reagent was used as tetraammineplathnium (II) chloride hydrate (Pt (NH ₃ ) ₄ Cl ₂ ), which is a platinum cationic compound, and sodium borohydride (NaBH ₄ ) as a reducing agent. Was used. After pre-treatment, the membrane with impurities removed was immersed in 5 mmol / L Pt (NH ₃ ) ₄ Cl ₂ ) solution for 1 hour, and then the platinum reagent was removed and 0.8 mol / L was used with a reducing agent NaBH ₄ adjusted to pH 13. Reduction was carried out at a concentration of 90 minutes.

FIG. 1 illustrates a CV curve of a MEA manufactured as described above, and FIG. 2 is a current-voltage graph of the manufactured MEA applied to a cell.

As shown in FIG. 1, the MEA made from the covalently crosslinked SPEEK membrane (Example 1) according to the present invention showed a high amount of current at 64.54 mC / cm 2.

Such a high amount of current means that a large amount of current flows when reacted for the same time, which means an excellent electrode having a fast reaction rate.

In addition, as shown in FIG. 2, the electrolysis voltage of water at 1 A / cm 2 was 1.85 V for cells with Nafion 117 membrane and 1.81 V for cells with covalently cross-linked SPEEK membrane (Example 1). In this case, it was found that the covalently crosslinked membrane had better performance.

From the above results, in the case of applying the covalently crosslinked membrane according to the present invention in the amount of current of the electrode MEA, the active surface area, the amount of platinum supported, and the electrical performance of the electrolytic cell, the sulfonated polymer membrane or the conventional commercialized It was found to have better properties than the Nafion product.

As described above, the present invention has been illustrated and described with reference to preferred embodiments, but is not limited to the above-described embodiments, and is provided to those skilled in the art without departing from the spirit of the present invention. Various changes and modifications are possible by this.

Claims (15)

To include a polymer having a repeating unit of the formula and a macromolecular acid substituted inorganic acid,
The macromolecule is a polymer electrolyte membrane, characterized in that any one or two or more selected from the group consisting of cesium, ammonium, rubidium, sodium and potassium.
[Chemical Formula]

(Wherein R is a hydrocarbon and m, n, p and q are integers of at least 1, m = p and n = q.)
The method of claim 1,
The inorganic acid is a polymer electrolyte membrane, characterized in that one or two or more selected from the group consisting of phosphotungstic acid, zirconium phosphoric acid, silico tungstic acid, phosphomolybdic acid and silicomolybdic acid.
The method of claim 2,
The polymer electrolyte membrane is a polymer electrolyte membrane, characterized in that 20 to 40% by weight of the inorganic acid substituted with the macromolecule.
The method of claim 3, wherein
The inorganic acid substituted with the macromolecule is a polymer electrolyte membrane, characterized in that the macromolecule is substituted by 5 to 35% relative to the cation of the inorganic acid.
Introducing a sulfone group (-SO ₃ H) into the polymer;
Introducing a sulfin group (-SO ₂ ) into the sulfonated polymer;
A third step of partially reducing the sulfinated polymer such that sulfin groups (-SO ₂ ) and sulfonate groups (-SO ₂ M; M is a metal) are present in the polymer;
Mixing the partially reduced polymer with a solvent and then adding and stirring a crosslinking agent to prepare a casting solution;
A fifth step of preparing a film by coating the casting solution; And
And a sixth step of replacing the sulfin group (-SO ₂ ) of the prepared membrane with a sulfone group (-SO ₃ H).
The fourth step is a method for producing a polymer electrolyte membrane, characterized in that the addition of the inorganic acid substituted macromolecule.
The method of claim 5, wherein
The macromolecule is a method for producing a polymer electrolyte membrane, characterized in that any one or two or more selected from the group consisting of cesium, ammonium, rubidium, sodium and potassium.
The method according to claim 6,
The inorganic acid is a method for producing a polymer electrolyte membrane, characterized in that one or two or more selected from the group consisting of phosphotungstic acid, zirconium phosphoric acid, silico tungstic acid, phosphomolybdic acid and silicomolybdic acid.
The method of claim 7, wherein
The inorganic acid substituted with the macromolecule is a method for producing a polymer electrolyte membrane, characterized in that the macromolecule is substituted by 5 to 35% relative to the cation of the inorganic acid.
The method of claim 5, wherein
The third step:
Partially reducing the sulfinated polymer so that a sodium sulfonate group (—SO ₂ Na) is present; And b) replacing the sodium sulfonate group (-SO ₂ Na) with a lithium sulfonate group (-SO ₂ Li).
The method of claim 9,
Step a) is a method of producing a polymer electrolyte membrane, characterized in that using a sodium sulfite (Na ₂ SO ₃ ) solution of 0.5 to 2.0 molar concentration (M) as a partial reducing agent.
The method of claim 5, wherein
The polymers include polyether ether ketones, polyarylene ether ketones, polysulfones, polyarylene ether sulfones, polyimides, polybenzimidazoles, polybenzoxazoles, polybenzisazoles, polypyrrolones, polyphosphazenes and their Method for producing a polymer electrolyte membrane, characterized in that one or two or more selected from the group consisting of copolymers.
The method of claim 5, wherein
The crosslinking agent of the fourth step is a method for producing a polymer electrolyte membrane, characterized in that the iodide alkene.
An electrolytic device comprising the polymer electrolyte membrane according to any one of claims 1 to 4.
A fuel cell comprising the polymer electrolyte membrane according to any one of claims 1 to 4.
15. The method of claim 14,
A fuel cell system comprising the fuel cell.

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