DE1496228A1 - Membranes and catalysts for fuel cells and their manufacture - Google Patents

Description

Patent attorneys

DIPL-ING. R. OKMSTEDE DIPL.-ING. B. SCHMID Stuttgart, Falbetihennenstr. 17th

Or. Ex].

Membranes and catalysts for fuel cells and their manufacture.

The invention relates to membranes and catalysts for fuel cells and their production.

It is known the liquid electrolytes of a fuel cell to replace it with an ion exchange membrane, this Membrane acts as an ion carrier between the two electrodes (anode and cathode) of the cell.

It is also known to use mineral ion exchange compounds such as phosphates, vanadium salts, tungstates, arsenic salts, molybdates, Phosphorus tungstates and phosphorus molybdates of the metals of the 4th and 5th groups of the periodic table, especially tin

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(IV) phosphate, titanium (IV) phosphate, niobium (V) phosphate and Ge: manium (£ V) phosphate, used as electrolysis in a fuel cell to use.

The invention relates to new membrane for fuel cells, the fine particles of at least one mineral Contain ion exchangers together with a binder. The particles of the ion exchanger must be as fine as ^ be possible. It was found that particles with a average diameter less than 0.075mm are satisfactory.

The ion exchange compound that is used for the inventive Membrane is used, is appropriate from the group of phosphates, vanadium salts, volframates, arsenic salts, Molybdates, phosphotungstates and phosphorus molybdates of the Metals of the 4th and 5th group of the periodic table, which have ion exchange properties.

ψ The preferred ion exchange compound is tin (TV) phosphate. The binder used according to the invention is preferably a natural or synthetic rubber or resin, for example carboxymethyl cellulose, a polyvinyl ether, nitrile rubber, natural rubber or a mixture thereof. Suitable binders are those under the trademark "Pliobond" (a thermoplastic adhesive consisting of a resin and nitrile rubber) from the Goodyear Company (USA), the

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under the trademark "Butakon" from Imperial Chemical Industries (U.E.) and those under the trademark "Oppanol" the Badische Anilin- und ßoda Factory A. G. (Germany) known products »

The membranes according to the invention are preferably in In the form of thin rolled sheets, for example 250 microns thick.

According to another feature of this invention are Provide the membrane with outer layers that contain a catalyst such as platinum black. This catalyst can possibly be applied to a carrier pressed onto the membrane.

This carrier is advantageously a graphite or carbon cloth or graphite or carbon pulp, such as the charcoal cloth TCM 216, distributed by the French SocietS Le Carbone Lorraine company.

The invention also relates to a fuel cell which contains a membrane as described above, this membrane is preferably impregnated with a liquid aqueous electrolyte such as sulfuric acid.

The invention also relates to a method of manufacture a membrane for a fuel cell described above. According to the invention, fine particles become mineral

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ion exchange compound to a solution of a minimum mixed in a solvent and the solvent is then removed from the resulting mixture. It becomes expedient an organic solvent, preferably a dialkyl ketone such as acetone or methyl ethyl ketone, or a mixture of these compounds.

According to one feature of the invention, the solvent is removed from the mixture by pouring the latter into a P stirred liquid which is mixed with the solvent cannot be mixed in order to obtain a sponge-like mass. This mass is washed with the said liquid, dried and rolled to the ground.

Another feature of the invention is a catalyst applied to at least one side of the membrane.

It is possible to press a layer on one or both sides of the membrane that contains a catalyst such as fiatin, ^ on a carrier, for example a graphite or carbon cloth or a graphite or carbon pulp contains.

Other features and advantages of the subject invention The embodiments can be seen from the following examples describe to which the invention is not limited.

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example 1

Stermi phosphate in powder form was finely ground to particles having a mean diameter of less than 0.073 to obtain mm. A gel of sodium arboxymethyl cellulose in water was added and mixed with the mineral exchangers in the following proportions:

Stenni phosphate 5 g

Sodium carboxymethyl cellulose 5 g water 220 g

Then ropes of 240 ml of the "homogeneous" mixture poured onto a clean glass surface (25cm 25cm). the Layers were then dried at room temperature in a room where a slight breeze was maintained became. The drying was continued until no more damp spots appeared on the membrane. These Membrane was treated for a period of 0 to 100 hours in the following mixture:

Methyl alcohol 100 ecm

deionized water 10 ecm

concentrated sulfuric acid 5 to 15 ecm.

The membranes were then washed in water until the pH des Wash water had reached 6.

Before the membranes were used in a fuel cell, they were dissolved in sulfuric acid (10 to 20%)

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Treated for hours (0-20 hours) at a temperature of 20 to 80 ° O.

The membranes produced in this way had the following average properties:

132 microns thick

Dry weight 8.7 mg / cm

Wet weight 16 mg / cm

Liquid content ο

(HSO ₄ ) 7.3 mg / cnn

Absorption of H ₂ SO ₄ 84%

electrolytic resistance _P

(H ₂ SO ₄ 1 n) 0.13 ohm / cnr

Voltage difference of

Membrane between solutions

(1 M and 0.5 M) H ₂ SO ₄ + 3 »16 millivolts

Tensile strength 8.3 kg / cm ²

Example 2

The same procedure was used as in Example 1, only that stannous phosphate is in gel form instead of powder form Stannic phosphate was used.

The membrane obtained had the following average properties:

Thickness ^r 238 microns

electrolytic P

Resistance (H ₂ SO ₄ In) 0.26 Ohm / cur

Voltage difference of

Membrane between solutions

(1M and 0.5M) HOl +0.93 millivolts

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Example 3

Powdery Stann i phosphate was finely ground. Particles less than 0.075 in diameter have now been chosen.

A solution of a binder such as Pliobond (trademark for a thermoplastic adhesive made from a resin and nitrile rubber, from Goodyear Company U.S.A.) in a solvent (1/2 mixture of methyl ethyl ketone

and acetone). Λ

This solution became stannous phosphate particles in the following Added to ratios and mixed with them:

Stannous phosphate 68.5 g

Binder 31 g

Solvent 54- nil

The resulting mixture was poured into water which was stirred by means of a magnetic stirrer, whereby a fibrous, sponge-like mass was obtained. This material was washed with water, then pressed between sheets of filter paper and dried for one hour at room temperature, the dry product was then rolled to form a white membrane 250 microns thick.

Before the membrane was used in a fuel cell, it was treated in for a few hours (5 hours) Sulfuric acid at 50 ° 0.

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The membrane obtained had the following average properties:

thickness

Dry weight Wet weight Liquid content ( ₂₄ absorption of sulfuric acid

electrolytic resistance (H ₂ SO ₄ 2M)

Difference in tension of the membrane between two sulfuric acid solutions (0.2M and 0.1M)

Tensile strength Elongation (%) Gas impermeability

250 microns 4-2.8 mg / cm ² 50.8 mg / cm ²

8 mg / cm 18.7 %

0.63 ohm / cm *

+ 4.8 millivolt 21.8 kg / cm ² 30 %

ο up to 250 g / cm

Example 4

Particles with a diameter of 0.075 rom of Stanniphosphate were mixed with a solution of Butakon X A 1100 (Trademark for a binder of Imperial Chemical Industries, U.K.) in methyl ethyl ketone in the following proportions mixed:

Stannipho sphat binder solvent

88 g

12 g

200 ml

The mixture obtained was as described in Example 3 treated, with the difference that the sponge-like material was dried for 15 minutes.

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Before the membrane was inserted into a fuel cell, it was treated with sulfuric acid (15 ^) for a few hours (5 hours) at 50 ⁰ O.

The membrane obtained had the following average properties:

thickness

Dry weight moisture liquid content absorption electrolytic resistance (2M H

Difference in tension of the membrane between two sulfuric acid solutions £ 0.2M and 0.1M)

Tensile strength elongation

Gas impermeability (O ₂ )

250 microns 36.9 mg / cm 45.2 mg / cm ² 7.3 mg / cm ² 19.2 mg / cm ²

0.56 ohm / em ²

+ 4.7 millivolts 3.92 kg / cm ²

105 % to 378 g / cm

Example 5

Powdered stannous phosphate (particle size less than 0.075 mm) were treated with a solution of binders in mixed in the following proportions:

Stannic phosphate 88 g

Binder (1/1 mixture of

Pliobond 30 / trademarks / and

Butakon XA 1100 / Trademark /) 6 g

Methyl ethyl ketone 20 cm ⁵

Acetone 10 cnr

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The mixture was treated as described in Example 3. The membrane obtained had the following average properties:

thickness 250 microns Dry weight 37.1 mg / cm light weight 45 mg / cm 3? Liquid content ρ
7 »9 mg / cm absorption 21.3% electrolytic
Resistance (2M H ₂ SO ₄ ) 0.33 ohm / cm ²

Difference in tension of the membrane between two sulfuric acid solutions (0.2M and 0.1M) + 4.5 millivolts

Tensile strength 3.92 kg / cm ²

Elongation (%) 120 %

Gas impermeability (O ₂ ) up to 23I g / cm

Example 6

A membrane made according to any mix of those described above Procedure that has been established has been incorporated into an electrolytic cell, for example a cell used for fuel cell tests is used. A mixture of 2.5 ml of a 50% aqueous solution of methanol and 1 ml Platinum hydrochloric acid was applied to the membrane.

The cell was then ^{warmed to 31 0} O and a drop (about 0.25 ml) of a 24% solution of hydrazine (reducing agent)

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medium) on the membrane · The system reacted for about For 30 minutes. The membrane was then washed with water.

This catalytic ^ deposition of platinum improves the The cell's performance is exceptional.

Example 7

A membrane produced by the method described above was coated with a layer of platinum black or platinum soot coated.

Example 8

This experiment as well as those according to example 9 and 10 concern the production of a catalytic arc or a catalytic electrode consisting of a support, on which the catalyst is deposited. This carrier is a graphite or carbon pulp or a graphite or Charcoal cloth.

The catalytic sheets or the electrode was prepared as described in the examples, M 8, 9 and 10 and the can be pressed according to Examples 1 to 6 manufactured on a membrane.

The graphite pulp or cloth used in Examples 8, 9 and 10 is a under the name "toile de carbone TOM 216"

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known from the French company SOOIEiEE LE OAHBOHE LOHHAIITE commercial fabric.

Samples were cut to the correct size in immersed in the following baths:

Platinum hydrochloric acid solution for the anode

H ₂ PtOl ₆ 3g

Lead acetate (n / 10 solution) 0.25 ml

Water enough to make 100 ml.

Platinum hydrochloric acid solution for the cathode

H ₂ PtOl ₆ ". 3g

Ammonium tungstate

(Solution 10-3 mol / liter) 0.1 ml.

Lead acetate (n / 10 solution) 0.25

Water enough to make 100 ml.

Both solutions contained about 12 g / l platinum and had one pH from 1.3 to 1.4.

After an immersion time of 30 seconds, the impregnated Sample of tissue subjected to electrolysis to electrochemically reduce the platinum hydrochloric acid to get platinum.

The following conditions were established for both electrodes which uses electrolysis:

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The samples were exposed to a voltage of -475 millivolts with respect to the saturated calomel electrode for 15 minutes electrolyzed. After rinsing the electrodes with water they returned to -475 milli for 15 minutes volt electrolyzed. Finally, the electrodes were rinsed with running water for 15 hours.

Example 9

Samples of the TGM 216 (trade mark) coal wrap were 30 Immersed in the following solutions for seconds:

Platinum hydrochloric acid solution for the anode

H ₂ PtOl ₆ 3 g

Lead acetate (n / 10 solution) 0.25 ml

Water enough to make 100 ml.

Platinum hydrochloride acidless ^ Tig for the cathode

. 3 g

Lead acetate (n / 10 solution) 0.25 ml

Ammonium tungstate 0.1 ml

Water enough to make 100 ml.

After draining, the samples were soaked in a 12% aqueous hydrazine solution for 10 seconds. Then they were taken out of the bath containing the reducing agent (hydrazine), rinsed with distilled water, and dried.

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Soaking, rinsing and drying are repeated (generally 7 to 9 sharks) until the platinizing solution is discolored and the electrodes do not react with the hydrasin solution. The FoPtCIg is then chemically reduced to Ft. Finally the platinum-plated electrodes were rinsed with running distilled water and dried. Ss were 8.57 Platinum / cm applied to the fabric support.

Example 10

The same platinum hydrochloric acid solutions as in Example 9 were used to produce an electrode by thermal reduction of H _{2 PtClg.}

0.0714 ml / cm of each of the platinum hydrochloric acid solutions were applied to samples of soleplate. TGR 216 (Trade Mark) which was then placed in a dryer at 175 ° C for 10 minutes.

0.0714 ml / cm of these solutions were again applied to the samples poured, which were dried again at 175 ° C.

These operations were repeated 10 times

The cloth had then absorbed 0.714 ml / cm of platinum hydrochloric acid (i.e. 8.57 mg of platinum / cm).

After the final drying at 175 ° C for 24 hours,

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the electrodes were placed in an oven which contained an atmosphere of pure (99.99%) hydrogen and left here at 210 ^° C. for two hours. After the furnace had cooled, the hydrogen was removed under vacuum and the furnace was filled with argon. Finally, the electrode was taken out of the oven and soaked in distilled water that was saturated with hydrogen and then dried.

Applying a catalyst to a carbon cloth increases the dispersion of the catalyst and allows for a close Contact of the catalyst with the membrane when the platinum-coated cloth is pressed onto the membrane.

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Claims (34)

U96228 Claims i7) membrane for a fuel cell, characterized in that they are small particles of at least one mineral ion exchange compound together with a binder. 2. Membrane according to claim 1, characterized in that the mineral ion exchange compound a phosphate, a vanadium salt, a tungstate, an arsenic salt, a molybdate » a phosphotungstate or phosphotungstate of metals of the 4th and 5th groups of the periodic table, the ion exchange properties have, is. 3. Membrane according to claim 2, characterized in that the ion exchange compound is tin (IV) phosphate. 4. Membrane according to one of the preceding claims, characterized in that the binder is either Hatur or Is synthetic rubber, a resin or a cellulose derivative. 5 «Membrane according to claim 4, characterized in that the binder is carboxamethyl cellulose. 6. Membrane according to claim 4, characterized in that the binder is polyvinyl ether. 7. Membrane according to claim 4, characterized in that the binder is a nitrile rubber, optionally mixed with natural rubber, is. 909839/0466 U96228 - 17 -. 8. Membrane according to one of the preceding claims, characterized in that it has the shape of a rolled arc having. 9. Membrane according to one of the preceding claims, characterized in that it has a pere layer, which contains a catalyst. 10. Membrane according to claim 9 »characterized in that the catalyst is applied to a support. 11. Membrane according to claim 9 or 10, characterized in that the catalyst is platinum. 12. Membrane according to claim 9 or 10, characterized in that the catalyst is platinum black. 13. Membrane according to claim 10, characterized in that the carrier is carbon black. 14. Membrane according to claim 10, characterized in that the carrier is a graphite or carbon pulp or a graphite I or charcoal cloth. 15. Fuel cell, characterized in that it has a Contains membrane according to one of the preceding claims. 16. Fuel cell according to claim 15, characterized in that the membrane is impregnated with a liquid electrolyte is. 90983 9/0466 17 · Fuel cell according to claim yf ^ characterized in that the liquid electrolyte is an aqueous sulfuric acid solution. 18. A method for producing a membrane for a fuel cell according to any one of claims 1 to 14, characterized in that the fine particles of the mineral ion exchange compound is mixed to a solution of the binder in a solvent and then the solvent * out the resulting mixture is removed. 19. The method according to claim 18, characterized in that as mineral ion exchange compound a phosphate, a vanadium salt, a tungstate, an arsenic salt, a molybdate Phosphorus tungstate or a phosphorus molybdate of metals of the 4th and 5th groups of the Periodic Table are the ion exchange properties have, is used. 20. The method according to claim 19, characterized in that as Ion exchange compound tin (IV) phosphate is used. 21. The method according to claim 18, characterized in that natural or synthetic rubber or a resin is used as the binder will. 22. The method according to claim 18, characterized in that as Solvent for the binder an organic solvent is used. 909839/0466 I <t y D Z Z Ö - 19 - 25. The method according to claim. 22, characterized in that as A dialkyl ketone solvent is used. 24. The method according to claim 18, characterized in that the Solvent is removed from the mixture by pouring the mixture into an "agitated liquid that is mixed with is immiscible with the solvent, resulting in a sponge-like hatch which then with the liquid washed, then dried and rolled into sheets. 25. The method according to claim 23 and 24, characterized in that that water is used as the liquid. 26. The method according to any one of claims 18 to 25, characterized in that that the catalyst is applied to at least one side of the membrane. 27 «Method according to claim 26, characterized in that a Platinum catalyst by chemical reduction of platinum hydrochloric acid, which is applied to the membrane this membrane is deposited. 28. The method according to any one of claims 18 to 25, characterized in that a layer containing a catalyst contains on a carrier, is pressed onto at least one side of the membrane. 29. The method according to claim 28, characterized in that a graphite or carbon pulp or a graphite or Charcoal cloth is used. 909839/0466 30. The method according to claims 28 and 29, characterized in that that the catalyst on the graphite or carbon pulp or on the graphite or carbon cloth Impregnation with a platinum hydrochloric acid is applied and then the platinum hydrochloric acid is reduced to platinum. 31. The method according to claim 30, characterized in that the impregnated pulp or the impregnated cloth is subjected to an electrochemical reduction. 32. The method according to claim 3O _9, characterized in that the impregnated cellulose or the impregnated cloth is subjected to a chemical reduction. 33 · The method according to claim 30, characterized in that the impregnated cellulose or the impregnated cloth is subjected to a thermal reduction. 34. Catalyst unit for a fuel cell, characterized in that that it consists of a graphite or carbon cloth or a graphite or carbon pulp that or the with Is impregnated with platinum. 909839/0466