# US 11,298,689 B2 · Multi-spectral photocatalytic compounds

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- Number: US 11,298,689 B2
- Document ID: US11298689B2
- Status: Granted
- Kind: B2
- Application number: 16/105,117
- Filed: 2018-08-20
- Published: 2020-02-20
- Granted: 2022-04-12
- Earliest claimed: 2018-08-20
- Assignees: The United States of America as represented by the Secretary of the Army
- Applicants: United States of America as Represented by The Secretary of The Army
- Inventors: Emily Asenath-Smith; Emma K Ambrogi
- Web page: https://patentgrep.com/patent/US11298689B2

## CPC

- B01J 23/80: with zinc, cadmium or mercury
- B01D 53/86: Catalytic processes
- B01D 53/8668: {Removing organic compounds not provided for in B01D53/8603 - B01D53/8665}
- B01J 23/06: of zinc, cadmium or mercury
- B01J 23/72: Copper
- B01J 23/745: Iron
- B01J 35/39: Photocatalytic properties
- C02F 1/30: by irradiation
- C02F 1/32: with ultraviolet light
- C02F 1/725: {by catalytic oxidation}
- B01D 2255/20738: Iron
- B01D 2255/20761: Copper
- B01D 2255/20792: Zinc
- B01D 2255/802: Photocatalytic
- B01D 2257/708: Volatile organic compounds V.O.C.'s
- B01D 2259/4508: for cleaning air in buildings
- B01J 2235/00: Indexing scheme associated with group B01J35/00, related to the analysis techniques used to determine the catalysts form or properties
- B01J 2235/15: X-ray diffraction
- B01J 2235/30: Scanning electron microscopy; Transmission electron microscopy
- C02F 2305/10: Photocatalysts
- Y02W 10/37: using solar energy
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- B01D: SEPARATION (separating solids from solids by wet methods B03B, B03D; by pneumatic jigs or tables B03B; by other dry methods B07; magnetic or electrostatic separation of solid materials from solid materials or fluids, separation by high-voltage electric fields B03C; centrifuges, vortex apparatus B04; presses per se for squeezing-out liquid from liquid-containing material B30B9/02; treatment of water C02F, e.g. softening by ion-exchange C02F1/42; {arrangements of air intake cleaners in gas turbine plants F02C7/05} ; arrangements or mounting of filters in air-conditioning, air-humidification or ventilation F24F13/28)
- C02F: TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE (separation in general B01D; special arrangements on waterborne vessels of installations for treating water, waste water or sewage, e.g. for producing fresh water, B63J; adding materials to water to prevent corrosion C23F; treating radioactively-contaminated liquids G21F9/04; regeneration of reactants for recirculation into processes, see the relevant places for the processes)
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

Disclosed are various combinations of three different metal-oxide photocatalysts with three different bandgaps that can be used to harvest multiple wavelengths of incident solar radiation and to thus efficiently degrade recalcitrant contaminants. The photocatalysts are from the class of transition metal oxides and are non-toxic compounds based on earth-abundant materials. In some embodiments, particles of the photocatalysts are formed to be greater in diameter than about 0.1 μm in order to make them easier to filter out after treating the contaminant. In some embodiments, the metal-oxide photocatalysts are zinc oxide which is ultraviolet active, hematite which is active in the visible spectrum, and copper oxide which is active in the near infrared spectrum. Various combinations in various embodiments achieve measured contaminant degradation rates greater than the sum of the degradation rates of the individual photocatalysts that make up the combination.

## Claims

### Claim 1

A photocatalytic compound comprising:
a first metal-oxide semiconductor photocatalyst with a first bandgap; and
a second metal-oxide semiconductor photocatalyst distinct from the first metal-oxide semiconductor photocatalyst with a second bandgap distinct from the first bandgap;
wherein the first bandgap makes the first metal-oxide semiconductor photocatalyst reactive to visible incident light,
wherein the second bandgap makes the second metal-oxide semiconductor photocatalyst reactive to near-infrared incident light, and
wherein the first and second metal-oxide semiconductor photocatalysts are chosen so that a reactant reduction rate of the photocatalytic compound is at least 20% greater than a sum of individual reactant reduction rates of the first and second metal-oxide semiconductor photocatalysts.

### Claim 2 (depends on 1)

The photocatalytic compound of claim 1 wherein the first and second metal-oxide semiconductor photocatalysts comprise particles a majority of which have diameters greater than 0.1 μm.

### Claim 3 (depends on 1)

The photocatalytic compound of claim 1:
wherein the first metal-oxide semiconductor photocatalyst is Fe.sub.2O.sub.3;
wherein the second metal-oxide semiconductor photocatalyst is CuO; and
wherein a molar ratio of the first and second metal-oxide semiconductor photocatalysts in the photocatalytic compound is approximately 1:1 (approximately 2:1 by weight).

### Claim 4 (depends on 1)

The photocatalytic compound of claim 1 further comprising:
a third metal-oxide semiconductor photocatalyst distinct from the first and second metal-oxide semiconductor photocatalysts with a third bandgap distinct from the first and second bandgaps;
wherein the third bandgap makes the third metal-oxide semiconductor photocatalyst reactive to ultraviolet incident light, and
wherein the first, second, and third metal-oxide semiconductor photocatalysts are chosen so that a reactant reduction rate of the photocatalytic compound is at least 20% greater than a sum of individual reactant reduction rates of the first, second, and third metal-oxide semiconductor photocatalysts.

### Claim 5 (depends on 1)

A method of purifying a contaminated item comprising exposing the contaminated item to broad-spectrum light in the presence of the photocatalytic compound of claim 1.