JPH02227138A - Catalyst carrier - Google Patents

Abstract

PURPOSE:To use catalysts effectively by forming a catalyst carrier having predetermined area using activated acetylene black and carrying catalysts in such a condition that the catalysts are distributed all over the catalyst carrier. CONSTITUTION:Catalyst carriers having a specific area of 100-500m<2>/g are formed using acetylene black to which activation treatment has been applied. When said carriers are applied to a phosphoric acid type fuel cell, the fuel cell is comprised of an electrolytic matrix 1, a fuel electrode 2 having three- phase interfacial electrodes on both surfaces thereof, an air electrode 5, and interconnectors 4, 5 covering the outer surfaces of the fuel cell. The fuel electrode 2 and air electrode 3 are composed of a porous carbon paper substrate 1, which catalyst carriers 6 are bonded to by means of polytetrafluoroethylene. Further, a number of recesses 6a are formed over the surfaces of carbon particles using activation agents.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a catalyst carrier for supporting a catalyst used in a fuel cell or the like.

[Prior art and problems to be solved by the invention] In conventional phosphoric acid fuel cells, a chain with excellent gas flow and electrical conductivity is used to support a catalyst used in the decomposition reaction of fuel such as hydrogen gas. Acetylene black with a similar structure is used. However, since ordinary acetylene black has a small specific surface area of about 80 m2/g, it is difficult to disperse and support the catalyst over the entire carrier, and there is a risk that the entire catalyst cannot be used effectively.

This invention has been made to solve the above problems, and the purpose is to provide a catalyst that can maintain a catalyst in a dispersed state throughout the catalyst carrier and that can efficiently use the catalyst. The purpose is to provide a carrier.

[Means and effects for solving the problems] In order to achieve the above object, in the present invention, a catalyst carrier is formed using an activated acetylene resin. When the activation treatment is performed, the specific surface area is reliably increased without impairing the flowability and conductivity of fuel gas such as hydrogen. By increasing the specific surface area, the amount of catalyst per unit area of the electrode increases and power generation capacity can be amplified, which naturally reduces the structure volume and reduces the cost of carbon materials, which is one of the problems with fuel cells. can.

In addition, it is desirable that the specific surface area is 100 to 500 rrr/g. If it is less than 100 m2/g, the dispersion state of the catalyst will deteriorate, and if it is less than 50 rrrf/g, it will not form a chain structure and the conductivity will decrease. However, this results in a decrease in

Now, to explain the structure of a phosphoric acid fuel cell, as shown in FIG. It includes an air electrode 3 and an interconnector 4.5 that covers the outer surface of the picture electrode 2.3. Passages 4a and 5a are formed between each interconnector 4.5 and each electrode 2.3 for supplying fuel gas consisting of hydrogen and air as an oxidizing agent.

The electrolyte matrix l is obtained by firing a mixture of silicon carbide powder and polytetrafluoroethylene,
It is impregnated with phosphoric acid after firing.

The fuel electrode 2 and the air electrode 3 have porous carbon paper as a base material, and a catalyst carrier 6 shown in FIG. 1 is bound to the base material using polytetrafluoroethylene. This catalyst carrier 6 contains platinum.

Metal catalysts such as silver and nickel are supported.

Approximately 1 mg/+aa of platinum catalyst is supported on the catalyst carrier 6 of the fuel electrode 2, and approximately 0.005 W of platinum catalyst is supported on the catalyst carrier 6 of the air electrode 3.
+g/aJ of platinum-rubidium catalyst is supported.

By supplying hydrogen gas and air to the fuel electrode 2 and air electrode 3, the following reactions occur in each electrode 2.3, and a predetermined electromotive force is generated between the picture electrodes 2.3. It has become.

Reaction H2-1 at fuel electrode → 2H++ 20 Reaction 2H” at air electrode + 1/202 +2 e H20
The above catalyst carrier 6 is made of acetylene black. This acetylene black is produced by heating acetylene to about 800° C. in a decomposition furnace, and is composed of carbon particles connected in a chain. Therefore, it has excellent gas flowability and electrical conductivity.

When activating acetylene black, acetylene black is heated at a temperature of 500° C. or higher for a predetermined period of time (1 to 12 hours), and an activator is injected onto the sample during that time. This activator attacks the carbon particle surface,
By enlarging the defective part of the crystal structure, the first
As shown in the figure, a large number of recesses 6a are formed on the particle surface. As a result, acetylene black with a large specific surface area is obtained. The specific surface area is preferably 100 to 500 rd/g. If it is less than 100 rrr/g, the rate of increase in the specific surface area before and after activation will be small and the catalyst will not be sufficiently dispersed, and if it exceeds 500 rrr/g,
This is because the chain structure is destroyed and the conductivity decreases.

As the activator, it is desirable to use steam, which is available at low cost.

[Example 1] Acetylene black having the physical properties shown in Table 1 was activated by injecting water vapor and heating at 1000° C. for 4 hours while stirring. The physical properties of activated acetylene black are shown in Table 2.0 As is clear from Table 2, the specific surface area and iodine adsorption amount of activated acetylene black are each about 2
．． 7 times and about 1. This has increased up to 9 times, making it possible to uniformly disperse and support the catalyst. Moreover, no large change is observed in the bulk density, and furthermore, there is no crystal change in the size of the peak in powder X-ray diffraction, and the gas flowability and conductivity before activation are not impaired by activation.

[Example 2] For the same sample as in Example 1 above, only the heating time was changed to 1.
The activation treatment was performed for 5 hours. The results are also shown in Table 2. In this case, the specific surface area and iodine adsorption amount increased approximately 2 times and 1.7 times, and as in Example 1, the gas flowability and conductivity of acetylene black increased. It became possible to uniformly disperse and support the catalyst without damaging the properties.

[Comparative Examples 1 and 2] The same samples as in each Example were subjected to heat treatment except that only the activator was changed to carbon dioxide, and the other conditions were the same as in Examples 1 and 2. As a result, as is clear from Table 2,
Almost no increase in specific surface area was observed, and the amount of iodine adsorbed was 1.2.
It was at a low level, just under twice that.

Bulk density of acetylene black Moisture (a) (b) g/aJ
χ m2/g seaweed gelO, 0240, 1283
Bulk density of acetylene black of 100 2 volumes Moisture (a) (bl Unit electrode area g/cgi χ rd/g vag/l
Amount of platinum per mg/aJ Example 1 Example 2 Comparative example 1 Comparative example 2 0.028 0.031 0.033 0.030 0.32 225 185 0.1950.
20 0.112 0.02 0.03~0.05 0.03 0.03~0.07 In each of the above tables, (a) indicates the specific surface area measured using nitrogen gas, (b) shows the amount of iodine adsorbed.

[Effects of the Invention] As described in detail above, the present invention exhibits the excellent effect that the catalyst can be maintained in a dispersed state throughout the catalyst carrier and the catalyst can be used efficiently. Furthermore, the amount of carbon in the electrode material can be reduced, and further compactness and increased power generation capacity can be expected.

[Brief explanation of the drawing]

FIG. 1 is a partially enlarged sectional view showing acetylene black after activation, and FIG. 2 is an exploded perspective view schematically showing a fuel cell. 6... Catalyst carrier. Patent applicant IBIDEN Co., Ltd. Agent
Patent Attorney On 1) Bosenmi

Claims (1)

[Scope of Claims] 1. A catalyst carrier characterized by being formed of acetylene black subjected to activation treatment. 2. The catalyst carrier according to claim 1, having a specific surface area of 100 to 500 m^2/g.