JP5248792B2 - Dehumidifying element and manufacturing method thereof - Google Patents

Description

The present invention relates to a dehumidifying element and a manufacturing method thereof.

  Conventionally, after producing a porous solid polymer electrolyte-catalyst composite electrode matrix comprising a solid polymer electrolyte and catalyst particles, the electrode matrix is subjected to electroless plating treatment to thereby convert the electron conductive material into the electroconductive material. An electrode matrix is formed on the surface of the electrode matrix, an electron conductive material layer is formed on the surface of the electrode matrix, or an electron conductive material is supported on the surface of the pores in the electrode body, or the ion conductive region in the solid polymer electrolyte layer. A method for producing a solid polymer electrolyte electrode in which an electron conductive substance is supported on is known from Patent Document 1 described later. In addition, as a method of the above electroless plating treatment, for example, a platinum group metal compound ion is adsorbed on a solid polymer electrolyte in an electrode matrix, and the platinum group metal compound ion is reduced with an aqueous borohydride salt solution or hydrogen gas. Processing is also known from US Pat.

JP-A-11-217687

In a dehumidifying element in which a platinum group metal compound is supported on both sides of a solid polymer electrolyte manufactured by the above-described prior art, when a direct current is passed from both sides in the presence of water, the solid polymer electrolyte is catalyzed. The protons stored inside the solid polymer electrolyte move inside the solid polymer electrolyte . As a result, oxygen is generated on the anode side of the electrode surface and hydrogen is generated on the cathode side. At the same time, platinum ions existing on or inside the solid polymer electrolyte become platinum. Since this platinum part serves as a catalyst for oxidation and reduction reactions, gas such as oxygen, water, and hydrogen is generated in this part, and the solid polymer electrolyte expands and breaks due to the gas, and the performance as an electrode is lost. There was a problem that it was. An object of the present invention is to suppress problems caused by the catalyst remaining in the solid polymer electrolyte and to extend the life of the dehumidifying element .

A dehumidifying element according to the present invention has a catalyst layer containing at least one of a platinum group metal or a compound thereof, gold or a compound thereof, and nickel or a compound thereof on both surfaces of a membrane-like solid polymer electrolyte. In the dehumidifying element , the catalyst layer is a catalyst layer in which the catalyst is supported in a scaly shape only on the outside with the surface of the solid polymer electrolyte as a boundary, and exists in the interior with the surface of the solid polymer electrolyte as a boundary. The mass of the catalyst is 0.1% by mass or less.

Another dehumidifying element according to the present invention includes a catalyst layer containing at least one catalyst of a platinum group metal or a compound thereof, gold or a compound thereof, and nickel or a compound thereof on both surfaces of a film-shaped solid polymer electrolyte. a dehumidifier having a catalyst layer, which said catalyst is supported on scaly only its outer surfaces of the solid polymer electrolyte to the boundary, the surface of the solid polymer electrolyte therein the border A value obtained by dividing the mass of the catalyst present by the dry mass of the solid polymer electrolyte is 0.001 or less.

The method for producing a dehumidifying element according to the present invention includes a first step in which a membrane-like solid polymer electrolyte is immersed in a reducing agent aqueous solution, and the solid polymer electrolyte absorbs the reducing agent aqueous solution. A reducing agent aqueous solution in which a molecular electrolyte is immersed in an aqueous solution containing at least one catalyst ion of platinum group metal or a compound thereof, gold or a compound thereof, and nickel or a compound thereof, and the catalyst ion is absorbed by the solid polymer electrolyte. The second step of reducing by the reducing agent component contained in the catalyst and selectively supporting the catalyst only on the surface of the solid polymer electrolyte; the third step of immersing the solid polymer electrolyte obtained from the second step in the reducing agent aqueous solution It is characterized by including .

According to the dehumidifying element of the present invention, the residual amount of catalyst present in the interior of the solid polymer electrolyte as a boundary is as small as 0.1% by mass or less, or the interior of the solid polymer electrolyte as a boundary. Since the value obtained by dividing the catalyst mass present in the solid polymer electrolyte by the dry mass of the solid polymer electrolyte is 0.001 or less, the dehumidifying element using the solid polymer electrolyte electrode has a lifetime of the conventional solid polymer There is an extremely excellent effect of being longer than when an electrolyte electrode is used. According to the method for manufacturing a dehumidifying element of the present invention, the residual amount of catalyst present in the solid polymer electrolyte can be 0.1% by mass or less.

  Examples of the solid polymer electrolyte constituting the membrane-shaped solid polymer electrolyte having proton conductivity used in the present invention include DuPont's trade name Nafion, Asahi Glass's trade name Flemion, Asahi Kasei Corporation Aciplex, and W.C. L. The product name Gore Select of Gore & Associates may be known or well known in the art. The thickness is 50 μm to 500 μm, preferably 50 μm to 300 μm.

Platinum group metals used as catalysts and compounds thereof, gold or compounds thereof, or nickel or compounds thereof include metals such as Pt, Co, Rh, Pd, Ir, Au, Ni, [Pt (NH ₃ ) ₄ ]. Cl ₂ , H ₂ PtCl ₆ , Co [(NH ₃ ) ₆ ] Cl ₃ , Co [(NO ₂ ) (NH ₃ ) ₅ ] Cl ₂ , Rh [(NH ₃ ) ₆ ] Cl ₃ , [Pd (NH ₃ ) ₄ ] Cl ₂ , [Ir (NH ₃ ) ₆ ] Cl ₆ , NH ₄ [AuCl ₄ ], AuCl ₃ , NiCl ₂ , Ni (NO ₃ ) ₂ .6H ₂ O, etc. And its compounds are preferred.

Examples of the aqueous solution of the metal and the compound thereof used in the production method of the present invention include metals such as Pt, Co, Rh, Pd, Ir, Au, Ni, [Pt (NH ₃ ) ₄ ] Cl ₂ , H ₂ PtCl. ₆ , Co [(NH ₃ ) ₆ ] Cl ₃ , Co [(NO ₂ ) (NH ₃ ) ₅ ] Cl ₂ , Rh [(NH ₃ ) ₆ ] Cl ₃ , [Pd (NH ₃ ) ₄ ] Cl ₂ , Examples include aqueous solutions of [Ir (NH ₃ ) ₆ ] Cl ₆ , NH ₄ [AuCl ₄ ], AuCl ₃ , NiCl ₂ , Ni (NO ₃ ) ₂ .6H ₂ O, and the like.

  As the reducing agent used in the production method of the present invention, a substance capable of reducing the metal ions in the aqueous solution to precipitate the metal is used. For example, formaldehyde, hypophosphorous acid, sodium borohydride Hydrazine, dimethylamine borane and the like. Of these, sodium borohydride, hydrazine, and dimethylamine borane are preferable, and they are particularly effective in reducing and depositing platinum ions on a metal.

Embodiment 1 FIG.
FIG. 1 is a schematic sectional view showing a dehumidifying element according to Embodiment 1 of the present invention, and FIG. 2 is a schematic sectional view showing a conventional dehumidifying element . 1 and 2, the catalyst layer 1 is present on both surfaces of the membrane-shaped solid polymer electrolyte 2, but catalyst ions 3 are contained in the conventional membrane-shaped solid polymer electrolyte 2 shown in FIG. Exists in large quantities. On the other hand, in the embodiment of FIG. 1, the catalyst ions 3 do not exist, or even if they exist, only a small amount of 0.1% by mass or less is not shown.

  Hereinafter, the difference between the first embodiment of the present invention and the prior art will be described in detail. In the prior art, the membrane-like solid polymer electrolyte supporting the catalyst is manufactured through four steps of cleaning treatment on both sides, catalytic compound aqueous solution absorption treatment, reduction treatment (catalyst carrying treatment), and cleaning treatment in this order. In this case, after the cleaning treatment, the membranous solid polymer electrolyte is immersed in the catalyst compound aqueous solution to adsorb the catalyst compound in the membrane, and then the catalyst ions are reduced by dipping in the reducing agent to form the membrane surface. The catalyst is supported. Since the reducing agent is supplied from the liquid to the surface of the membrane solid polymer electrolyte, when the surface of the membrane is covered with a catalyst as the reduction reaction proceeds, the supply of the reducing agent to the catalyst ions is also stopped. As a result, the supporting reaction stops and unreacted catalyst ions remain in the membrane.

On the other hand, in the embodiment of the present invention, after the cleaning process similar to the conventional technique, the reducing agent absorption process, the immersion process (catalyst support process) in the catalyst compound aqueous solution, and the cleaning process are sequentially performed. Manufactured. In addition, between each process, washing | cleaning with ion-exchange water or a pure water is performed. The present invention is particularly characterized in that the substance adsorbed in advance in the membrane-shaped solid polymer electrolyte is a reducing agent (not a catalyst ion).

  Next, in the embodiment of the present invention, the reason why the catalyst is selectively supported only on the surface will be described. The reducing agent is previously absorbed in the membrane-like solid polymer electrolyte. When the membrane solid polymer electrolyte containing the reducing agent is immersed in an aqueous solution of catalyst ions, the reducing agent moves from the inside of the solid polymer electrolyte to the surface, and the catalyst ions move from the aqueous solution to the surface of the solid polymer electrolyte. The reducing agent that oozes from the surface of the solid polymer electrolyte and the catalyst ions in the aqueous solution give and receive electrons on the surface of the solid polymer electrolyte, and the catalyst is supported on the surface. When the reaction proceeds and the surface of the solid polymer electrolyte is covered with the catalyst, the diffusion of the catalyst ions into the membrane and the supply of the reducing agent to the catalyst ions present in the aqueous solution are inhibited, and the reaction is stopped. That is, when the reaction is stopped, the surface of the solid polymer electrolyte is covered with the catalyst, and the internal diffusion of the catalyst ions is inhibited. As a result, the catalyst residue in the solid polymer electrolyte can be prevented.

Embodiment 2. FIG.
In Embodiment 2, a specific method for manufacturing the dehumidifying element of the present invention will be described. Here, platinum was used as the catalyst, and Nafion 117 (manufactured by DuPont: thickness: 170 μm) was used as the membrane solid polymer electrolyte. The solid polymer electrolyte used in the present invention such as Nafion generally behaves as an electrolyte in the same manner as dilute sulfuric acid aqueous solution because it has a fine path for retaining and transmitting protons from the surface to the inside.

  First, the cleaning process will be described. Nafion has the aforementioned fine pathway for proton transfer. Therefore, organic substances and inorganic substances in the air are easily adsorbed on the fine path. In order to support the catalyst only on the surface of Nafion, it is preferable to clean the surface and the inside of the fine path. As the method, for example, Nafion is used in 30% by weight dilute hydrochloric acid heated to 70 ° C. Boiled for about 20 minutes. In order to further enhance the cleaning, hydrochloric acid and an equal amount of hydrogen peroxide water may be mixed. Subsequently, in order to sufficiently remove chlorine ions used for cleaning from the inside of Nafion, Nafion was immersed in 25 ° C. pure water or ion-exchanged water for 15 minutes or more and washed with water.

  In the next reducing agent absorption treatment, an aqueous solution having a concentration of 2.0 g / liter of sodium borohydride was used as the reducing agent with sodium hydroxide adjusted to a pH of 12. Nafion which completed the process mentioned above was immersed in this reducing agent aqueous solution, and the reducing agent component was absorbed into Nafion. In the case of Embodiment 2, the temperature of the reducing agent was 50 ° C., and the immersion time was 2 hours. In order to prevent the absorbed reducing agent from flowing out, washing with water after completion of absorption was performed for 1 minute, and only excess components near the surface were washed. If washing is performed excessively, the pH of the reducing agent absorbed by Nafion is lowered and the reducing power is lowered. As a result, care must be taken because platinum ions cannot be reduced and the catalyst cannot be supported. The amount of reducing agent absorbed by Nafion can be arbitrarily controlled by adjusting the immersion time and the reducing agent temperature. For example, when the temperature is raised, Nafion expands and the amount of reducing agent absorbed can be increased.

Next, the carrying process will be described. As a platinum aqueous solution, a tetraammine platinum dichloride 0.25 g / liter aqueous solution kept at 40 ° C. was used, and Nafion treated with a reducing agent was immersed in it for 10 minutes. By this immersion, a platinum layer of 1.1 mg / cm ² was formed and supported on each of both surfaces of Nafion. In addition, when the amount of catalyst adhesion is insufficient and electrical resistance increases by immersion alone, after supporting the catalyst as necessary, a metal is grown on the catalyst by electroless plating, electrolytic plating, etc. The resistance may be lowered.

  Finally, a cleaning process is performed. This is performed to remove excess platinum ions adhering to Nafion after the completion of the supporting process and to stabilize the catalyst. Specifically, as in the first normalization process, the temperature is set to 70 ° C. Nafion is boiled for about 10 minutes in heated 30% by weight dilute hydrochloric acid. Then, it is immersed in pure water or ion exchange water at 25 ° C. for 15 minutes or longer to sufficiently remove chlorine.

FIG. 3 shows a photograph of the surface state of Nafion prototyped by the above method. As shown in FIG. 3, it can be seen that the platinum catalyst is supported in a scaly shape on the surface of Nafion. When Nafion was analyzed by EPMA in the cross-sectional direction, the platinum concentration inside Nafion was 0.1% by mass or less. Furthermore, the solid polymer electrolyte electrodes (electrode area: 16.5cm ²⁾ obtained in the second embodiment assembled dehumidifier using a characterization was carried out through a direct current between both surfaces. As a result, when the current was 0.5 A and the current density was 3 A / dm ² , the dehumidified moisture content per hour was 170 mg. When a continuous energization test for 3000 hours was performed under these conditions, it was confirmed that the dehumidifying performance did not deteriorate.

  In order to prevent the diffusion of platinum into Nafion, it is important to adsorb as much reducing agent as possible to Nafion and to increase the concentration of the reducing agent as much as possible. Further, the platinum concentration of the catalyst soaking treatment liquid is as high as possible, the carrying treatment time is as short as possible, and the catalyst is preferably carried in a short time.

Further, hydrazine or dimethylamine borane can be used as the reducing agent. The reducing agent reduces catalyst ions and generates hydrogen gas and decomposes it. For this reason, the pH of the reducing agent adsorbed in Nafion increases and the reducing power fluctuates, but protons are stored inside Nafion, and protons are supplied from this part to the reducing agent, so the pH is kept constant. There is also an effect of sagging. As a catalyst supporting treatment solution, materials other than those described in the second embodiment, for example, it is possible to obtain the same effect with an aqueous solution four chloroplatinic was dissolved in aqueous ammonia.

Embodiment 3 FIG.
Embodiment 3 differs from Embodiment 2 only in that a 0.5 g / liter aqueous solution of tetraammine platinum dichloride is used as the aqueous platinum solution in the supporting treatment, and the other conditions are the same. In this way, 1.7 mg / cm ² of platinum was formed and supported on both surfaces of the Nafion membrane.

Embodiment 4 FIG.
Embodiment 4 differs from Embodiment 2 only in that a 1.0 g / liter aqueous solution of tetraammine platinum dichloride is used as the aqueous platinum solution in the supporting treatment, and the other conditions are the same. In this way, 1.8 mg / cm ² of platinum was formed and supported on both surfaces of the Nafion membrane.

Embodiment 5 FIG.
In the fifth embodiment,. In the second embodiment, the temperature of the reducing agent is 40 ° C. and the immersion time is 4 hours in the reducing agent absorption treatment, and only the immersion in the tetraammineplatinum dichloride aqueous solution kept at 25 ° C. in the supporting treatment is performed for 2 hours. However, the other conditions were the same, and by immersion in this aqueous solution, 0.9 mg / cm ² of platinum was formed and supported on both surfaces of the Nafion membrane.

Embodiment 6 FIG.
In order to improve the catalytic activity of the solid polymer electrolyte used in the dehumidifying element of the present invention, for example, the Nafion membrane, the contact area between the catalyst supported on the solid electrolyte and the liquid or gas that contributes to the reaction may be increased. It is known. Therefore, generally, the following measures are taken in order to improve the catalytic activity of the solid polymer electrolyte. First, the surface of the solid polymer electrolyte is subjected to a roughening treatment with an average surface roughness of about 0.5 to 1.0 μm. Thereafter, the catalyst is supported on the surface irregularities to increase the contact area between the catalyst and the reactant, and the catalyst nuclei are precipitated in a granular form while ensuring the continuity of the precipitated catalyst particles. However, in this granular precipitate, since there are minute voids between the particles and the surface of the solid polymer electrolyte, according to the reduction method shown in the first embodiment, as shown in FIG. Some particles on the outermost surface may remain in an ionic state (indicated by white circles). If such residual ions are present, the current that is energized is consumed for the reduction reaction of the residual ions in the initial stage of energization, so that the electrode performance becomes unstable, and in the worst case, the dehumidifying element of the present invention does not operate normally. Sometimes. In order to prevent this phenomenon, the surface of the solid polymer electrolyte 2 carrying the catalyst 1 may be reduced again by the method of the first embodiment. The method will be described below.

In the first embodiment, as shown in FIG. 4, when the catalyst ions are present in the voids of the catalyst 1 supported on the surface, the solid polymer electrolyte is again immersed in the reducing agent aqueous solution, and the catalyst in the voids is obtained. A reduction treatment of ions 3 is performed. That is, the catalyst compound aqueous solution immersion treatment and the cleaning treatment among the four steps of the cleaning treatment, the reducing agent absorption treatment, the catalyst compound aqueous solution immersion treatment (catalyst supporting treatment), and the cleaning treatment described in the first embodiment are described. A re-reduction treatment of the void catalyst ions 3 is inserted between the two.

As the re-reducing agent in the re-reducing treatment, a 0.5 g / liter aqueous solution of sodium borohydride adjusted to pH 12 with sodium hydroxide is used. This is the same aqueous solution as in the case of the reducing agent absorption treatment, but since the absolute amount of the catalyst ions 3 to be reduced is smaller than in the case of the catalyst supporting treatment, the concentration may be lower than that of the absorption treatment. . As an example, the specific conditions are as follows. From the case of Example 3, the concentration of tetraammine platinum chloride in the catalyst compound aqueous solution used for the supporting treatment is 0.25 g / liter, the immersion temperature is 40 ° C., and the immersion time is 10 minutes. The subsequent re-reduction treatment temperature was 50 ° C. and the immersion time was 2 hours. By this immersion, a platinum layer of 2.2 mg / cm ² was formed and supported on each of both surfaces of Nafion. FIG. 5 shows a schematic cross-sectional view of the dehumidifying element manufactured by the above method after the surface catalyst re-reduction treatment. As shown in FIG. 5, it can be seen that the catalyst on the surface is reduced to the catalyst 4 by the catalyst ions 3 existing in the voids by the re-reduction treatment.

  Further, as described in the first embodiment, also in the sixth embodiment, when the amount of catalyst is insufficient and the electrical resistance increases, the catalyst is obtained by electroless plating or electrolytic plating after re-reduction treatment as necessary. A metal may be grown on the catalyst to lower the electric resistance on the catalyst surface.

Comparative Example 1
The same Nafion as in Embodiment 2 was cleaned by boiling in 30% by weight diluted hydrochloric acid heated to 70 ° C. for 20 minutes and then maintained at 25 ° C. 1.0 g / liter of tetraammine platinum dichloride Soaked in an aqueous solution for 2 hours to treat the catalyst, then immersed in a 0.5 g / liter aqueous solution of sodium borohydride adjusted to pH 12 with sodium hydroxide at 40 ° C. for 2 hours for reduction treatment, A solid polymer electrolyte electrode of Comparative Example 1 was obtained by boiling for 10 minutes in a 30% by weight concentrated dilute hydrochloric acid heated to 70 ° C. and cleaning treatment.

Comparative Example 2
Comparative Example 1 is a comparative example in which a 0.5 g / liter aqueous solution of sodium borohydride was treated at the same conditions except that it was immersed in sodium hydroxide adjusted to pH 12 at 60 ° C. for 2 hours. 2 solid polymer electrolyte electrodes were obtained.

Comparative Example 3
In Comparative Example 2, a 0.25 g / liter aqueous solution of tetraammineplatinum dichloride maintained at 25 ° C. was used as the catalyst-supporting treatment solution, and a 1.0 g / liter aqueous solution of sodium borohydride was used for the reduction treatment. The solid polymer electrolyte electrode of Comparative Example 3 was obtained by performing the same treatment except that the pH was adjusted to 12.

By each solid polymer electrolyte electrodes which were obtained in the form 2-6 and Comparative Examples 1 to 3 of the embodiment, the electrode area of 16.5cm ^2, current density creates a dehumidifier of 3A / dm ^2, the following measuring initial dehumidification amount in the methods and conditions (mg / hour), life of the dehumidifier, and the amount of platinum present in the interior of the solid polymer electrolyte (wt%) was measured. The dehumidifying amount was measured from the humidity change by placing the dehumidifying element in a sealed space in an atmosphere of 30 ° C. and 60%, then operating the element, recording the change in humidity per unit time. The life of the dehumidifying element is defined as the time when the initial dehumidifying value of the dehumidifying element is 50% or less, or the point when the current stops flowing. Amount of platinum present in the interior of the solid polymer electrolyte is X-ray microanalyzer were measured in (detection limit of 0.1 wt%).

As a result of the above measurement, the initial dehumidification amount is 170 mg / hour in the second embodiment, 165 mg / hour in the third embodiment, 168 mg / hour in the fourth embodiment, 159 mg / hour in the fifth embodiment, In Embodiment 6, the dehumidifying element has a lifetime of 185 mg / hour, the lifetime of each of Embodiments 2 to 6 is 3000 hours or longer, and the amount of platinum present in the interior of each of Embodiments 2 to 6 is platinum. The value obtained by dividing the mass of the catalyst present in the solid polymer electrolyte below the detection limit amount by the dry mass of the solid polymer electrolyte is 0.001 or less, and the value of the dehumidifying element using the solid polymer electrolyte electrode is 0.001 or less . In this case, all of Embodiments 2 to 6 maintained characteristics and functions as dehumidifying elements even after 3000 hours, and the cross section of the solid polymer electrolyte membrane device of each dehumidifying element was observed. Time, aggregation of platinum was not observed.

  On the other hand, in Comparative Example 1, the initial dehumidification amount is 98 mg / hour, the lifetime of the dehumidifying element is 47 hours, the amount of platinum present inside is 2.5 mass%, and in Comparative Example 2, the initial dehumidification amount is 102 mg / hour. Time, the lifetime of the dehumidifying element is 78 hours, the amount of platinum present in the interior is 1.2% by mass, and in Comparative Example 3, the initial dehumidifying amount is 121 mg / hour, the lifetime of the dehumidifying element is 240 hours, and the platinum present in the interior The amount was 0.5% by mass.

  The present invention is not limited to the embodiment described above, and even if platinum group metals other than platinum or a compound thereof, gold or a compound thereof, or nickel or a compound thereof is used as a catalyst, the same effects as in the case of platinum are used. Is obtained.

The present invention is used as a dehumidifying element using a solid polymer electrolyte electrode .

It is a schematic sectional drawing which shows the dehumidification element in Embodiment 1 of this invention. It is a schematic sectional drawing which shows the conventional dehumidification element . It is an electron micrograph of a solid polymer electrolyte table surface of the dehumidifier according to the first embodiment. It is a schematic sectional drawing of the dehumidification element before the surface catalyst re-reduction process in Embodiment 6 of this invention. It is a schematic sectional drawing of the dehumidification element after the surface catalyst re-reduction process in Embodiment 6 of this invention.

  1: catalyst, 2: membrane-like solid polymer electrolyte, 3: catalyst ion, 4: catalyst reduced by re-reduction treatment.

Claims (5)

A dehumidifying element having a catalyst layer containing a catalyst of at least one of a platinum group metal or a compound thereof, gold or a compound thereof, and nickel or a compound thereof on both surfaces of a membrane-shaped solid polymer electrolyte, the catalyst The layer is such that the catalyst is supported in a scaly shape only on the outside with the surface of the solid polymer electrolyte as a boundary, and the mass of the catalyst existing inside the surface with the surface of the solid polymer electrolyte as a boundary. A dehumidifying element that is 0.1% by mass or less. A dehumidifying element having a catalyst layer containing a catalyst of at least one of a platinum group metal or a compound thereof, gold or a compound thereof, and nickel or a compound thereof on both surfaces of a membrane-shaped solid polymer electrolyte, the catalyst In the layer, the catalyst is supported in a scaly manner only on the outside with the surface of the solid polymer electrolyte as a boundary, and the mass of the catalyst existing inside the surface with the surface of the solid polymer electrolyte as a boundary. A dehumidifying element having a value obtained by dividing the solid polymer electrolyte by the dry mass is 0.001 or less. The dehumidifying element according to claim 1 or 2, wherein the catalyst layer is made of platinum or a compound thereof. A first step of immersing the membrane-shaped solid polymer electrolyte in a reducing agent aqueous solution and allowing the solid polymer electrolyte to absorb the reducing agent aqueous solution,
The solid polymer electrolyte obtained from the first step is immersed in an aqueous solution containing at least one of a platinum group metal or a compound thereof, gold or a compound thereof, and nickel or a compound thereof. A second step of reducing by the reducing agent component contained in the reducing agent aqueous solution absorbed by the solid polymer electrolyte and selectively supporting the catalyst only on the surface of the solid polymer electrolyte;
A method for producing a dehumidifying element, comprising a third step of immersing the solid polymer electrolyte obtained from the second step in an aqueous reducing agent solution. 5. The method of manufacturing a dehumidifying element according to claim 4, wherein in the second step, the element is immersed in an aqueous solution containing at least one kind of catalyst ion of platinum or a compound thereof.