# US 4,394,293 A · Catalyst for the photolytic production of hydrogen from water

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- Number: US 4,394,293 A
- Document ID: US4394293A
- Status: Granted
- Kind: A
- Application number: 06/184,673
- Filed: 1980-09-05
- Granted: 1983-07-19
- Earliest claimed: 1979-09-08
- Assignees: Engelhard Corporation
- Inventors: Michael Gratzel; John Kiwi
- Web page: https://patentgrep.com/patent/US4394293A

## CPC

- B01J 23/38: of noble metals
- C01B 3/042: Decomposition of water (by electrolysis of water C25B1/04)
- Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
- 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

## Abstract

A catalytic dispersion of fine metal particles mediates the photodissociation of water into hyrogen gas. A protective agent adsorptive to said particles and selected from among homopolymers, copolymers, hydrocarbyl radicals and polysaccharides stabilizes the said dispersion.

## Claims

### Claim 1

A stabilized catalyst for promoting electron transfer to water protons for mediating evolution of hydrogen gas by photolysis comprising an active catalytic reducing amount of Noble metal particles in finely divided form and a water permeable protective agent adsorptive to said metal particles and being polyvinyl alcohol.

### Claim 2 (depends on 1)

The catalyst of claim 1 wherein the Noble metal is selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, osmium, silver, gold and mixtures thereof.

### Claim 3 (depends on 1)

The catalyst of claim 1 wherein the Noble metal is platinum, palladium or a mixture thereof.

### Claim 4 (depends on 1)

The catalyst of claim 1 where the Noble metal is platinum.

### Claim 5 (depends on 1)

A method for preparing the catalyst of claim 1 having a particle size not greater than 500 A diameter said method comprising (1) adding one or more reducible Noble metal compounds to an aqueous medium, (2) reducing said Noble metal compounds in the presence of polyvinyl alcohol and (3) separating from the resultant mixtures particles larger than 500 A diameter to obtain said catalyst.

### Claim 6 (depends on 5)

The method of claim 5 wherein the separation of step 3 is achieved by centrifugation or ultra-filtration.

### Claim 7 (depends on 5)

The method of claim 5 wherein the separation of step 3 is achieved by centrifugation at at least about 20,000 r.p.m. conducted over a period of not less than about 2 hours.

### Claim 8 (depends on 5)

The method of claim 5 wherein the Noble metal compound is selected from the group consisting of platinum, palladium, rhodium, ruthenium, iridium, osmium, silver, gold or mixtures thereof.

### Claim 9 (depends on 5)

The method of claim 5 wherein the Noble metal compound is platinum, palladium or a mixture thereof.

### Claim 10 (depends on 5)

The method of claim 5 wherein the Noble metal compound is platinum.

### Claim 11 (depends on 10)

The method of claim 10 wherein the reducible metal compound is chloroplatinic acid.

### Claim 12 (depends on 5)

The method of claim 5 wherein the particle size is not greater than 250 A.