JP6803001B2 - How to make catalyst ink for fuel cells - Google Patents

Description

The present invention relates to a method for producing a catalyst ink for a fuel cell.

A fuel cell usually includes a membrane electrode assembly, which is a power generator in which electrodes are arranged on both sides of an electrolyte membrane. The electrode of the membrane electrode assembly is formed as a catalyst electrode on which a catalyst for promoting a fuel cell reaction is supported. The catalyst electrode is generally formed by applying and drying a catalyst ink, which is a slurry in which catalyst-supported particles in which a catalyst is supported on conductive particles and ionomers are dispersed in an organic solvent or an inorganic solvent. ..

As a method for producing such a catalyst ink for a fuel cell, for example, as described in Patent Document 1, a step of preparing a catalyst dispersion liquid, a step of preparing an ionomer gel body, and a prepared catalyst dispersion liquid are used. And a method including a step of stirring and mixing the gel body is known.

International Publication No. 2013/031060

In the conventional method described in Patent Document 1, it is conceivable to reduce the solid content of the catalyst dispersion liquid and increase the solid content ratio of the gel body in order to shorten the preparation step time of the catalyst dispersion liquid. However, if such measures are taken, there is a risk that the non-uniformity of the gel body will increase during heating in the gel body preparation step.

Therefore, the present invention provides a method for producing a catalyst ink, which can suitably suppress an increase in non-uniformity of the gel body even if the solid content ratio of the gel body is increased, and can shorten the production time of the catalyst ink. The purpose is.

The method for producing a catalyst ink for a fuel cell according to one aspect of the present invention includes a step of preparing a catalyst dispersion liquid, a step of atomizing an ionomer and then redissolving it to prepare a gel body, and the catalyst dispersion liquid and the gel. Includes a step of mixing with the body.

According to this aspect, by performing the treatment of atomizing the ionomer, the deterioration of the gel non-uniformity due to the increase in the solid content ratio of the gel body can be suppressed, so that a gel body having a higher solid content ratio than the conventional one can be prepared. Is possible. As a result, the production process time of the catalyst dispersion liquid can be sufficiently shortened, and the production time of the catalyst ink finally produced can also be sufficiently shortened. As a result, even if the solid content ratio of the gel body is increased, the increase in the non-uniformity of the gel body can be suitably suppressed, and the preparation time of the catalyst ink can be shortened.

According to the present invention, there is provided a method for producing a catalyst ink, which can suitably suppress an increase in non-uniformity of a gel body even if the solid content ratio of the gel body is increased, and can shorten the production time of the catalyst ink. can do.

FIG. 1 is a flowchart showing each step of the catalyst ink producing method according to the present embodiment. FIG. 2 is a diagram showing the characteristics between the gel solid content ratio and the gel non-uniformity in the comparative example and the present embodiment. FIG. 3 is a flowchart showing each process of the conventional catalyst ink producing method.

Preferred embodiments of the present invention will be described with reference to the accompanying drawings. In each figure, those having the same reference numerals have the same or similar configurations.

First, with reference to FIG. 3, a conventional catalyst ink producing method described in Patent Document 1 will be described as a comparative example of the catalyst ink producing method according to the present embodiment. FIG. 3 is a flowchart showing each process of the conventional catalyst ink producing method.

In the catalyst ink dispersion step of step S11, catalyst-supported particles (for example, platinum-supported carbon) are dispersed in a solvent to prepare a catalyst dispersion liquid. Specifically, alcohol is added to a dispersed aqueous solution in which catalyst-supporting particles and water are mixed, and an ionomer solution containing the same type of ionomer as used in step S12 is further added to prepare a mixed solution. Then, this mixed solution is stirred using an ultrasonic disperser or the like to prepare a catalyst dispersion. When the process of step S11 is completed, the process proceeds to step S12.

In the ionomer gel preparation step of step S12, an ionomer gel body is prepared by mixing the ionomer and a volatile solvent. Specifically, a gel containing a predetermined viscoelasticity is prepared by heating a container containing an ionomer solution to evaporate water and then diluting with a volatile solvent (for example, an alcohol solution). When the process of step S12 is completed, the process proceeds to step S13.

In the ionomer gel charging step of step S13, the ionomer gel body prepared in step S12 is charged into the catalyst dispersion prepared in step S11, and the catalyst dispersion and the gel body are mixed. When the process of step S13 is completed, the process proceeds to step S14.

In the catalyst ink mixing step of step S14, the catalyst ink having a desired viscosity is obtained by stirring the catalyst dispersion liquid and the gel body mixed in step S13.

Next, the catalyst ink producing method according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a flowchart showing each step of the catalyst ink producing method according to the present embodiment.

In the conventional catalyst ink preparation method described with reference to FIG. 3, in the catalyst ink dispersion step of step 11, measures are taken to reduce the solid content ratio of the catalyst dispersion in order to shorten the preparation step time of the catalyst dispersion. It can be taken. The reason is that the higher the solid content ratio at the time of dispersion, the smaller the allowable dispersion force, and as a result, the longer the dispersion time (when the dispersion force is increased while the solid content ratio is high, carbon aggregates. Dispersion is poor). If the solid content ratio of the catalyst dispersion is lowered, the solid content ratio of the catalyst ink finally produced is lowered, and there is a possibility that the viscosity becomes insufficient and intermittent coating cannot be performed.

In order to reduce the solid content ratio of the catalyst dispersion while maintaining the solid content ratio of the catalyst ink, the gel body to be charged into the catalyst dispersion liquid, that is, the solid gel body produced in the ionoma gel preparation step of step S12. It is necessary to increase the fractionation ratio. However, if the solid content ratio of the gel body is increased, the temperature of the ionomer solution in the solution becomes non-uniform when the ionomer solution is heated, and the gel body may become non-uniform even after being diluted with alcohol. That is, in the conventional method shown in FIG. 3, since there is an upper limit of the gel solid content ratio and there is also a lower limit of the solid content ratio of the catalyst dispersion liquid, there is a restriction on shortening the preparation time of the catalyst ink. It will be.

In the catalyst ink producing method of the present embodiment, in order to solve the problem of the conventional method, instead of the ionomer gel producing step of step S12 of FIG. 3, as shown in FIG. 1, the ionomer atomization / redispersion of step S2 is performed. Carry out a heating and mixing step. Since the other steps S1, S3, and S4 shown in FIG. 1 are the same as the steps S11, S13, and S14 described with reference to FIG. 3, the description thereof will be omitted.

In the ionomer atomization / redispersion / heating mixing step of step S2, the ionomer is atomized and then redissolved to prepare a gel body. Specifically, first, the ionomer solution is atomized, the atomized ionomer solution is redistributed (redissolved) in a volatile solvent (for example, an alcohol solution), and then heated and mixed to prepare an ionomer gel. ..

The amount of the atomized ionomer solvent is preferably about 1/90 to 1/50 of the amount of the solvent contained before the atomization. This is because if the amount of solvent is large, it adheres to the inside of the facility and there is a concern that the yield may decrease, and if the amount of solvent is small, there is a concern that gel non-uniformity may occur.

In step S2, the ionomer atomization involves spraying a small amount of the ionomer solution with a spray-drying facility or the like, so that the temperature of the ionomer solution becomes uniform, and the solution can be maintained in a uniform state even after redispersion and heating and mixing. Therefore, it is possible to suppress the non-uniformity accompanying the increase in the gel solid content ratio, and it is possible to prepare a gel body having a higher solid content ratio as compared with the conventional method.

FIG. 2 is a diagram showing the characteristics between the gel solid content ratio and the gel non-uniformity in the comparative example and the present embodiment. The vertical axis of FIG. 2 represents gel non-uniformity, and the horizontal axis of FIG. 2 represents the gel solid content ratio. The characteristics between the gel solid content ratio and the gel non-uniformity of the ionoma gel produced in the catalyst ink producing method of the present embodiment are shown in Graph A, and in Comparative Example (ionoma gel produced by the conventional method shown in FIG. 3). The characteristics are shown in Graph B. As shown in FIG. 2, the ionoma gel prepared in this embodiment has a higher solid content ratio in which gel heterogeneity increases than in the comparative example. For example, the gel of the comparative example is produced with a solid content ratio of about 20 wt%, whereas the gel of the present embodiment can be produced with a solid content ratio of about 30 wt%. That is, in this embodiment, the range of use of the solid content ratio of the gel body can be made higher than that of the comparative example, and a gel body having a high solid content ratio can be prepared.

As described above, the catalyst ink producing method according to the present embodiment includes a step of preparing a catalyst dispersion liquid (step S1), a step of atomizing the ionomer and then redissolving it to prepare a gel body (step S2). The step (steps S3, S4) of mixing the catalyst dispersion prepared in step S1 and the gel body prepared in step S2 is included.

With this configuration, in particular, by performing the treatment of atomizing the ionomer in the ionomer atomization / redispersion / heating mixing step of step S2, the deterioration of the gel non-uniformity due to the increase in the solid content ratio of the gel body is suppressed as described above. Therefore, it is possible to prepare a gel body having a higher solid content ratio than before. That is, the requirement for the upper limit of the gel solid content ratio for maintaining the solid content ratio of the catalyst ink can be relaxed. As a result, the requirement for the lower limit of the solid content ratio of the catalyst dispersion liquid for maintaining the solid content ratio of the catalyst ink can be relaxed, so that the preparation process time of the catalyst dispersion liquid can be sufficiently shortened, and finally. The production time of the catalyst ink to be produced can be sufficiently shortened. As a result, in the catalyst ink producing method according to the present embodiment, even if the solid content ratio of the gel body is increased, the increase in the non-uniformity of the gel body can be suitably suppressed, and the production time of the catalyst ink can be shortened. it can.

The embodiments described above are for facilitating the understanding of the present invention, and are not for limiting and interpreting the present invention. Each element included in the embodiment and its arrangement, material, condition, shape, size, etc. are not limited to those exemplified, and can be changed as appropriate. In addition, the configurations shown in different embodiments can be partially replaced or combined.

The ionomer atomization / redispersion / heating and mixing step of step S2 described as a part of the procedure of the catalyst ink preparation method in the above embodiment may be another procedure as long as the gel body of the ionomer can be finally prepared. For example, only the step of atomizing the ionomer solution may be performed, and the atomized ionomer may be put into the catalyst dispersion in step S3, or the step of redispersing the atomized ionomer in the solvent may be performed. , This may be added to the catalyst dispersion in step S3.

S1 ... Catalyst ink dispersion step, S2 ... Ionomer atomization / redispersion / heating mixing step, S3 ... Ionomer gel injection step, S4 ... Catalyst ink mixing step

Claims (1)

The process of preparing the catalyst dispersion and
A step of spraying an ionomer solution by spray drying to atomize the ionomer , then redissolving the atomized ionomer solution in an alcohol solution and then heating and mixing to prepare a gel having a solid content ratio of 30 wt% or more. When,
The step of mixing the catalyst dispersion and the gel body,
How to make catalyst ink for fuel cells, including.