# US 7,608,557 B2 · Highly active photocatalyst and process for producing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 7,608,557 B2 - Document ID: US7608557B2 - Status: Granted - Kind: B2 - Application number: 10/518,934 - Filed: 2003-06-05 - Published: 2005-09-29 - Granted: 2009-10-27 - Earliest claimed: 2002-06-25 - Assignees: Nittetsu Mining Co., Ltd. - Inventors: Kazuyuki Tohji; Akira Kishimoto; Takafumi Atarashi - Web page: https://patentgrep.com/patent/US7608557B2 ## CPC - B01J 27/04: Sulfides - B01J 35/39: Photocatalytic properties - B01J 35/45: Nanoparticles - C01B 3/042: Decomposition of water (by electrolysis of water C25B1/04) - B01J 23/06: of zinc, cadmium or mercury - B01J 23/60: with zinc, cadmium or mercury - B01J 37/20: Sulfiding - B01J 2235/30: Scanning electron microscopy; Transmission electron microscopy - Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis - Y02P 20/133: Renewable energy sources, e.g. sunlight - B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS - C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C} - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract Provided are a photocatalyst which is high in catalytic activity, is nontoxic, has a long life, allows visible light to be used directly for its photocatalytic reaction and is especially useful for hydrogen generation, and a process for producing it. It contains a cadmium compound, has a capsular structure, has an average particle diameter of 100 nm or less and can be manufactured by dropping a solution of a cadmium salt into a solution of a sodium compound or admixing a solution of a sodium compound in a suspension of particles of a cadmium compound. ## Claims ### Claim 1 A photocatalyst comprising a capsule structure which comprises a cadmium compound shell and a void and having an average particle diameter of 50 nm or less. ### Claim 2 (depends on 1) The photocatalyst according to claim 1, wherein the cadmium compound is cadmium sulfide. ### Claim 3 (depends on 1) The photocatalyst according to claim 1, characterized by supporting a Group 8 to 11 metal. ### Claim 4 (depends on 3) The photocatalyst according to claim 3, characterized in that the metal is platinum. ### Claim 5 (depends on 1) The photocatalyst according to claim 1, which has a pore extending from its surface to its interior. ### Claim 6 (depends on 5) The photocatalyst according to claim 5, which has a multiplicity of such pores. ### Claim 7 A process for producing a photocatalyst comprising a capsule structure which comprises a cadmium compound shell and a void, said process comprising: dropping a solution of a cadmium salt into a solution of a sodium compound to first form a microscopic solid phase of cadmium hydroxide, which then turns into a cadmium compound instantaneously to form the shell of the capsule of the photocatalyst; and obtaining a photocatalyst comprising a capsular structure, which comprises a cadmium compound shell and void. ### Claim 8 (depends on 7) The process for producing a photocatalyst according to claim 7, wherein the solution of a sodium compound contains sodium sulfite. ### Claim 9 (depends on 7) The process for producing a photocatalyst according to claim 7, wherein the solution of a sodium compound contains sodium sulfide. ### Claim 10 (depends on 7) The process for producing a photocatalyst according to claim 7, wherein the cadmium salt is cadmium nitrate. ### Claim 11 A process for producing a photocatalyst comprising a capsule structure, which comprises a cadmium compound shell and a void and having an average particle diameter of 100 nm or less, said process comprising: admixing a solution of a sodium compound in a suspension of particles of a cadmium compound; and obtaining a photocatalyst comprising a capsular structure, which comprises a cadmium compound shell and void. ### Claim 12 (depends on 11) The process for producing a photocatalyst according to claim 11, wherein the cadmium compound is cadmium hydroxide. ### Claim 13 (depends on 11) The process for producing a photocatalyst according to claim 11, wherein the cadmium compound is cadmium oxide. ### Claim 14 (depends on 11) The process for producing a photocatalyst according to claim 11, wherein the suspension of particles of a cadmium compound is prepared by mixing a solution of cadmium nitrate with a solution containing sodium hydroxide. ### Claim 15 (depends on 14) The process for producing a photocatalyst according to claim 14, wherein the solution containing sodium hydroxide contains a chloride. ### Claim 16 (depends on 15) The process for producing a photocatalyst according to claim 15, wherein the chloride is sodium chloride. ### Claim 17 (depends on 11) The process for producing a photocatalyst according to claim 11, wherein the sodium compound is sodium sulfide. ### Claim 18 (depends on 7, 11) The process for producing a photocatalyst according to claim 7 or 11, wherein photocatalyst particles as obtained are caused to support a Group 8 to 11 metal. ### Claim 19 (depends on 18) The process for producing a photocatalyst according to claim 18, wherein the metal is platinum. ### Claim 20 (depends on 7, 11) The process for producing a photocatalyst according to claim 7 or 11, which further comprises suspending photocatalyst particles as obtained in a solution containing sodium sulfite and applying light thereto. ### Claim 21 (depends on 20) The process for producing a photocatalyst according to claim 20, wherein the light is visible light. ### Claim 22 (depends on 20) The process for producing a photocatalyst according to claim 20, wherein the light is solar or pseudo-solar light.