Method for preparing colloidal solution and carrier having colloidal particles fixed on surface thereof, fuel cell cathode, fuel cell anode and method for preparing the same and fuel cell using the same, and low temperature oxidation catalyst, method for preparing the same and fuel cell fuel modifying device using the same

Abstract

A method for forming colloidal particles by boiling a solution containing a metal salt and a reducing agent; and a method for preparing a colloidal solution wherein the concentration of the metal salt in the solution is 1×10⁻⁴ mol/L or more and less than 4×10⁻⁴ mol/L; the equivalent concentration of the reducing agent is four times or more and 20 times or less the equivalent concentration of the metal salt; and the reaction time is 60 minutes or more and 300 minutes or less. A carrier wherein colloidal particles are fixed on the surface of a substrate by applying the colloidal solution prepared by the above-described method. Methods for manufacturing a fuel cell cathode, a fuel cell anode, and a low temperature oxidation catalyst wherein a colloidal solution prepared in the state wherein a solution containing a metal salt and a reducing agent is boiled to remove dissolved oxygen is applied to a substrate and colloidal particles are fixed on the substrate.

Description

TECHNICAL FIELD [0001] The present invention relates to a method for paring a colloidal solution containing colloidal particles that can exert catalytic functions and the like; and to a carrier wherein the colloidal particles are fixed on various substrates. The present invention also relates to a fuel cell cathode that promotes oxygen reduction reaction; a method for the manufacture thereof, and a fuel cell using the same. The present invention also relates to a fuel cell anode that promotes hydrogen oxidation reaction; a method for the manufacture thereof; and a fuel cell using the same. Furthermore, the present invention relates to a low temperature oxidation catalyst the exhibits excellent catalytic activity under a service temperature of 300° C. or below, a method for the manufacture thereof and a fuel modifying device for a fuel cell using the low-temperature oxidation catalyst. BACKGROUND ART [0002] It is broadly known that fine particles of a metal, such as platinum, fiction...

AI Technical Summary

Benefits of technology

[0022] Since the colloidal particles prepared using the method of the present invention have particle diameters of the 10-nm order, and have extremely high uniformity, they can be easily and strongly fixed only be applying the colloidal solution onto porous glass fibers or the like using means well known to the art. Therefore, according to the present invention, a carrier having extremely high catalytic activity and durability can be easily manufactured.

[0023] The methods for manufacturing a fuel cell cathode, fuel cell anode, and a low-temperature oxidation catalyst according to the present invention are characterized in that colloidal particles are fixed on a substrate, using a colloidal solution pared in a state wherein a solution containing a metal salt and a reducing agent is boiled to remove dissolved oxygen. According to this method, since the colloidal solution having extremely high stability even without containing a stabilizer or the like is applied onto a substrate, no heating or firing of the substrate for forming the colloidal particles are required, the colloidal particles can be easily fixed on the substrate, and there is no lowering of the catalytic activity due to the formation of residue. Also since the above described colloidal solution can be prepared from an inexpensive metal salt as a starting material using a simple process, the paring costs are extremely low. Also since the above described colloidal solution has a uniform particle diameter, and Is difficult to aggregate even in high concentration, no stabilizers for preventing precipitation are required, and the colloidal particles can be evenly fixed on the substrate.

[0024] Also according to a fuel cell cathode according to the present invention, the oxygen reducing reaction can be efficiently started even if the quantity of adhered colloidal particles is small. Furthermore, according to a fuel cell according to the present invention, the efficiency of power generation can be improved.

[0025] Also according to a fuel cell anode according to the present invention, he hydrogen oxidizing reaction can be efficiently started even if the quantity of adhered colloidal particles is small. Furthermore, according to a fuel cell according to the present invention, the efficiency of power generation can be improved.

[0026] Also according to a low-temperature oxidation catalyst according to the present invention, a high catalytic activity can be exhibited even if the fixing rate of the catalyst is low. Furthermore, according to a fuel modifying device for a fuel cell according to the present invention, the CO shifting reaction can be started at a high efficiency even at a low temperature of 300° C. or below, in particular, 150 to 200° C. Therefore, since this device can contribute to the improvement of the power generating efficiency of fuel cells, and enables the use of members having not so high heat resistance, the option of member selection is widened.

Problems solved by technology

However, fine metal particles obtained using a dispersion method have large average particle diameters, and are relatively difficult to fix on the surface of a substrate.

For example, when glass fiber or the like is treated with acid and alkali to make the surface thereof porous, the average pore diameter of the formed pores in the order of 1 to 10 nm; therefore, fine metal particles cannot enter into the pores, and cannot be well fixed on the surface of the glass river.

Also in the dispersion method, since the width of the particle size distribution of fine metal particles is large, it is difficult to evenly fix fine metal particles on the surface of the substrate.

The reason of vigorous boiling during reaction is because oxygen in the air interferes with the reaction.

The platinum colloid must be eared in the state wherein dissolved oxygen is removed, and if the colloid is prepared in the state wherein the solution is not vigorously boiled, reproducible results cannot be obtained because a long time is consumed for the synthesis, or aggregation occurs.

Also the method described in Japanese Patent Application Laid-Open No. 07-256112 had a problem in that since ultra-fine platinum particles that exhibited catalytic activity were formed in the pores of zeolite, impurities contained in the materials of ultra-fine platinum particles or residue formed during the forming process could not be removed even if heating or firing were performed, and coated the surfaces of the ultra-fine platinum particles, or remained in the pores, lowering the catalytic activity in spite of the quantity of the fixed ultra-fine platinum particle&

Also the method described in Japanese Patent Application Laid-Open No. 2002-222655 had a problem in that impurities in the solution were adhered, or residue formed during the forming process remained on the surfaces of the carbon powder and the platinum-ruthenium alloy.

Furthermore, the method described in Japanese Patent Application Laid-Open No. 2001-357857 had a problem in that impurities in the solution were adhered, or residue formed during deposition remained on the surfaces of deposited ultra-fine platinum particles.

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