Catalyst particles, carbon-supported catalyst particles and fuel cell catalysts, and methods of manufacturing such catalyst particles and carbon-supported catalyst particles

Abstract

A catalyst particle is composed of an inner particle and an outermost layer that includes platinum and covers the inner particle. The inner particle includes on at least a surface thereof a first oxide having an oxygen defect.

1 . A catalyst particle comprising:
 an inner particle containing on at least a surface thereof a first oxide having oxygen defects, the inner particle having a center particle and an intermediate layer covering the center particle, the center particle containing a second oxide that is free of oxygen defects and that includes an element common with an element other than oxygen included in the first oxide, and the intermediate layer containing the first oxide; and   an outermost layer formed from a single material that contains platinum and covers the inner particle, the outermost layer covering at least a portion of the intermediate layer.   
     
     
         2 . The catalyst particle according to  claim 1 , wherein the second oxide is an oxide that, by reducing a surface of the center particle, has generated oxygen defects in the first oxide. 
     
     
         3 . The catalyst particle according to  claim 1 , wherein the first oxide includes an element selected from the group consisting of titanium, tin, tantalum, niobium and silicon. 
     
     
         4 . The catalyst particle according to  claim 1 , wherein an average particle size of the catalyst particle is 2 to 20 nm. 
     
     
         5 . The catalyst particle according to  claim 1 , wherein the outermost layer has a degree of coverage of from 70 to 100% with respect to the inner particle. 
     
     
         6 . The catalyst particle according to  claim 1 , wherein the outermost layer is a layer of three or fewer atoms. 
     
     
         7 . A carbon-supported catalyst particle comprising:
 the catalyst particle according to  claim 1 ; and   a carbon support that supports the catalyst particle.   
     
     
         8 . The carbon-supported catalyst particle according to  claim 7 , wherein the carbon support is composed of at least one carbon material selected from the group consisting of acetylene black, furnace black, carbon black, activated carbon, mesophase carbon and graphite. 
     
     
         9 . A fuel cell catalyst, including the carbon-supported catalyst particle according to  claim 7 . 
     
     
         10 . A method of manufacturing the catalyst particles
 according to  claim 1 , comprising:   preparing a dispersion of particles composed of a second oxide that is free of oxygen defects;   preparing a dispersion of platinum ions;   mixing together the dispersion of particles composed of the second oxide and the dispersion of platinum ions, and reducing at least the surfaces of the particles composed of the second oxide to a first oxide having oxygen defects, and moreover forming on the first oxide an outermost layer containing platinum formed by reduction of the platinum ions; and   heating the mixture after forming the outermost layer on the first oxide.   
     
     
         11 . The manufacturing method according to  claim 10 , wherein, by reducing at least the surfaces of the particles composed of the second oxide to a first oxide having oxygen defects, an intermediate layer containing the first oxide is formed at the surfaces of the particles composed of the second oxide. 
     
     
         12 . The manufacturing method according to  claim 10 , further comprising:
 prior to reducing at least the surfaces of the particles composed of the second oxide to a first oxide having oxygen defects, pre-reducing at least the particles composed of the second oxide within the dispersion of particles composed of the second oxide.   
     
     
         13 . The manufacturing method according to  claim 10 , wherein:
 the dispersion of particles composed of the second oxide is a dispersion of reversed micelles containing particles composed of the second oxide;   the dispersion of platinum ions is a dispersion of reversed micelles containing platinum ions;   when at least the particles composed of the second oxide are pre-reduced, a reducing agent is additionally mixed into the mixture of the dispersion of reversed micelles containing particles composed of the second oxide with the dispersion of reversed micelles containing platinum ions; and   the mixture is heated after adding an alcohol to the mixture following formation of the outermost layer on the first oxide.   
     
     
         14 . The manufacturing method according to  claim 13 , wherein the dispersion of reversed micelles containing particles composed of the second oxide is obtained by mixing an aqueous solution or aqueous dispersion of particles composed of the second oxide with an organic solvent solution of a surfactant. 
     
     
         15 . The manufacturing method according to  claim 14 , wherein the dispersion of reversed micelles containing platinum ions is obtained by mixing an aqueous solution of the platinum ions with an organic solvent solution of a surfactant. 
     
     
         16 . The manufacturing method according to  claim 13 , wherein the second oxide is an oxide selected from the group consisting of titanium (IV) oxide (TiO 2 ), tin (IV) oxide (SnO 2 ), tantalum (V) oxide (Ta 2 O 5 ), niobium (V) oxide (Nb 2 O 5 ) and silicon dioxide (SiO 2 ). 
     
     
         17 . The manufacturing method according to  claim 10 , wherein:
 the second oxide has a photocatalytic activity, and   a sacrificial reagent is additionally mixed into the mixture of the dispersion of particles composed of the second oxide with the dispersion of platinum ions, following which the mixture is irradiated with light.   
     
     
         18 . The manufacturing method according to  claim 17 , wherein:
 the dispersion of particles composed of the second oxide is a dispersion of reversed micelles containing particles composed of the second oxide;   the dispersion of platinum ions is a dispersion of reversed micelles containing platinum ions; and   an alcohol is added to the light-irradiated mixture, following which the mixture is heated.   
     
     
         19 . The manufacturing method according to  claim 18 , wherein the dispersion of reversed micelles containing particles composed of the second oxide is obtained by mixing together an aqueous solution or aqueous dispersion of particles composed of the second oxide with an organic solvent solution of a surfactant. 
     
     
         20 . The manufacturing method according to  claim 18 , wherein the dispersion of reversed micelles containing platinum ions is obtained by mixing together the aqueous solution of platinum ions with an organic solvent solution of a surfactant. 
     
     
         21 . The manufacturing method according to  claim 17 , wherein the second oxide having a photocatalytic activity is a metal oxide selected from the group consisting of titanium (IV) oxide (TiO 2 ) and tin (IV) oxide (SnO 2 ). 
     
     
         22 . A method of manufacturing carbon-supported catalyst particles composed of catalyst particles that are obtained by the manufacturing method according to  claim 13  and that have been supported on a carbon support, the method comprising:
 when a reducing agent is to be used to pre-reduce particles composed of at least the second oxide, admixing the carbon support either before additionally mixing the reducing agent into the mixture of the dispersion of reversed micelles containing particles composed of the second oxide with the dispersion of reversed micelles containing platinum ion or after additionally mixing the reducing agent into the mixture. 
 
     
     
         23 . The method of manufacturing carbon-supported catalyst particles according to  claim 22 , wherein the carbon support is a support composed of at least one carbon material selected from the group consisting of acetylene black, furnace black, carbon black, activated carbon, mesophase carbon and graphite. 
     
     
         24 . A method of manufacturing carbon-supported catalyst particles composed of catalyst particles that are obtained by the manufacturing method according to  claim 17  and that have been supported on a carbon support, the method comprising:
 when the platinum ions are to be reduced by light irradiation, additionally mixing a sacrificial reagent into the mixture of the dispersion of particles composed of the second oxide with the dispersion of platinum ions, and irradiating the mixture with light, following which a carbon support is additionally mixed into the light-irradiated mixture. 
 
     
     
         25 . The method of manufacturing carbon-supported catalyst particles according to  claim 24 , wherein the carbon support is a support composed of at least one carbon material selected from the group consisting of acetylene black, furnace black, carbon black, activated carbon, mesophase carbon and graphite.