1. Field of the Invention
The present invention relates to a method of manufacturing a catalyst carrier, the catalyst carrier, and an electrode of a fuel battery cell.
2. Background Art
Conventionally, a catalyst carrier such as containing a noble metal, being a catalyst, dispersed and supported in a carrier, is a mainstream as a catalyst carrier. In order to provide a catalyst carrier having a high performance, a catalyst active material such as platinum (Pt) must be carried in a highly dispersed state. Therefore, it is important that a carrier material is a crystalline rough surface forming material, namely, it is important that the carrier is formed in a porous state. In addition, in recent years, the catalyst carrier is used in an electrode of a fuel battery cell, particularly used in an automobile. Therefore, in order to smoothly deliver energy required for activating the catalyst, a further thinner film of the carrier for catalyst is highly desired.
Zeolite, which is a typical example of a material for forming a crystalline rough surface, is an attractive material because of its fine hole structure, having solid acid property, ion exchange capacity, adsorption separation capacity, and fine holes of a molecular level. However, zeolite crystal does not have a self-sintering property. Thus, the zeolite can be obtained only in a form of powders under a normal hydrothermal synthesis condition, and it is difficult to form a film of the zeolite crystal. In addition, a blocking process by sintering is required for catalyst carrying ceramics focusing on alumina other than zeolite, and it is not easy to realize a thinner film. Therefore, a process of high cost and high temperature such as a CVD method must be used to realize the thinner film. Thus, in the conventional catalyst carrier, a base material is ceramics in many cases, and when a reaction occurs on the catalyst carried on the ceramics, it is difficult to perform a smooth heat conduction. Also, it is difficult to realize the thinner film of the catalyst carrier, because the base material must be prepared by sintering. For example, a honeycomb-like pellet is commercially-available as the catalyst carrier. This pellet has a size of a few centimeters because this pellet is prepared by being sintered at a high temperature. The catalyst active material such as Pt is precipitated on this carrier for catalyst by complex solution, etc, and is sintered and utilized for the catalyst carrier in many cases. In industrial fields, this type of catalyst-carrying pellet is used as a catalyst reactor stored in a container made of stainless for example. However, in a castalyst process using this catalyst container, exchange of heat required for the catalyst reaction is frequently performed via a ceramic base material with inferior heat conduction, and as a result, catalyst reaction efficiency is determined by this heat conduction. Therefore, excellent performance can not be exhibited.
Note that conventionally, a technique of forming a film on a substrate surface is proposed as a related art, as follows. According to the conventional technique, deposition processing is performed by splaying ultra fine particles on a workpiece, thereby improving a processing speed and processing accuracy (for example, see patent document 1). Film deposition is performed in such a manner that the second aerosol is sprayed, directed to the first aerosol, thereby activating a surface, and this activated second aerosol is sprayed on a base material. By this film deposition, a dense film with high film adhesion is realized (for example, see patent document 2). Particles are made to collide with each other at high speed and are deformed or crushed by impact of collision. Then, fine particles are mutually bonded via a newly formed active surface generated by deformation and destruction of the particles, to form a film coating. A fragile property of a structure, which is readily destructed, is thus prevented (for example, see patent document 3).    [Patent Publication 1] Japanese Laid-Open Publication No. H3-231096    [Patent Publication 2] Japanese Laid-Open Publication No. 2006-144054    [Patent Publication 3] Japanese Patent No. 3716913
When a base material for a catalyst carrier is ceramics, this base material is hardly formed into a film. For example, in a case of the zeolite, when its thickness is thinner, this thickness is close to a size of a crystal grain constituting the zeolite, and therefore an influence of this crystal grain can not be ignored. Accordingly, when the base material is zeorite, the base material of 100μm or less is hardly formed into a film. Therefore, it can be so considered that a substrate having an excellent heat conductivity is utilized as the base material, and by using the technique disclosed in the patent documents 1 to 3, ceramics powders are sprayed on the substrate having excellent heat conductivity, to form a thin film, so that this film carries the catalyst. However, a ceramic film formed on the substrate has a dense structure (paragraph [0011] of Patent Publication 2 and paragraph [0033] of Patent Publication 3), and therefore the ceramic film can not carry a large number of catalysts, like porous zeolite.
As a result, in a conventional catalyst carrier formed by using the aerosol deposition method, it is impossible to smoothly remove a thermal energy required for an exothermic reaction, at an active site of the catalyst carried on the ceramic film. In addition, it is impossible to smoothly transmit the thermal energy which is also required for an endothermic reaction. Further, it is impossible to respond to a request of development of an electrode of a fuel battery cell having excellent characteristics.
Therefore, the present invention is provided, and it is desired to provide a method of manufacturing a catalyst carrier capable of smoothly performing incoming and outgoing of the thermal energy required at the active site of the catalyst, the catalyst carrier, and an electrode of a fuel battery cell.