# US 11,028,491 B2 · Electrolysis electrode featuring metal-doped nanotube array and methods of manufacture and using same

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- Number: US 11,028,491 B2
- Document ID: US11028491B2
- Status: Granted
- Kind: B2
- Application number: 16/102,576
- Filed: 2018-08-13
- Published: 2019-02-14
- Granted: 2021-06-08
- Earliest claimed: 2017-08-14
- Assignees: California Institute of Technology
- Applicants: California Institute of Technology
- Inventors: Michael R. Hoffmann; Yang Yang
- Web page: https://patentgrep.com/patent/US11028491B2

## CPC

- C25B 11/043: Carbon, e.g. diamond or graphene
- C01B 32/174: Derivatisation; Solubilisation; Dispersion in solvents
- C01G 23/047: Titanium dioxide
- C25B 11/069: consisting of at least one single element and at least one compound; consisting of two or more compounds
- C01B 2202/08: Aligned nanotubes
- C01B 2202/22: Electronic properties
- C01P 2002/52: containing elements as dopants
- C01P 2002/54: one element only
- C01P 2004/03: obtained by SEM
- C01P 2004/13: Nanotubes
- C01P 2006/10: Solid density
- Y02W 10/37: using solar energy
- C25B: ELECTROLYTIC OR ELECTROPHORETIC PROCESSES FOR THE PRODUCTION OF COMPOUNDS OR NON-METALS; APPARATUS THEREFOR (anodic or cathodic protection C23F13/00; single-crystal growth C30B)
- C01B: NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; {METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C}
- C01G: COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F (metal hydrides {monoborane, diborane or addition complexes thereof} C01B6/00; salts of oxyacids of halogens C01B11/00; peroxides, salts or peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium, or tellurium C01B19/00; binary compounds of nitrogen with metals C01B21/06; azides C01B21/08; {compounds containing nitrogen, other non-metals and metal C01B21/082}; metal amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; carbides C01B32/90; compounds containing silicon C01B33/00; compounds containing boron C01B35/00; compounds having molecular sieve properties but not having base-exchange properties C01B37/00; compounds having molecular sieve and base-exchange properties, e.g. crystalline zeolites, C01B39/00; cyanides C01C3/08; salts of cyanamide C01C3/16; thiocyanates C01C3/20)
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- Y02W: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO WASTEWATER TREATMENT OR WASTE MANAGEMENT

## Abstract

An electrolysis electrode includes a metal-doped array of nanotubes formed on a substrate. The nanotube array (NTA) may be a stabilized metal-doped black TiO2 NTA formed on a titanium substrate, and the metal dopant may include any suitable metal, for example, cobalt. The metal dopant improves the reactivity of the electrode and enhances its service life. The metal-doped NTA electrode may provide improved chlorine evolution and/or oxygen evolution activity for electrochemical wastewater treatment. The electrode may also be useful for water splitting applications. Increasing the loading of the metal dopant may lead to the formation of a metal oxide layer on top of the NTA, which improves oxygen evolution reaction (OER) overpotential.

## Claims

### Claim 1

An electrolysis electrode, comprising:
a substrate; and
cobalt-doped black TiO2 nanotube array contacting the substrate.

### Claim 2 (depends on 1)

The electrode of claim 1, further comprising a metal oxide film on top of the nanotube array.

### Claim 3 (depends on 1)

The electrode of claim 1, wherein the cobalt included in the cobalt-doped black TiO2 nanotube array has a loading of less than 5 μmol/cm2.

### Claim 4 (depends on 3)

The electrode of claim 3, wherein the cobalt included in the cobalt-doped black TiO2 nanotube array has a loading between about 0.17 μmol/cm2 and 0.54 μmol/cm2.

### Claim 5 (depends on 1)

The electrode of claim 1, wherein the amount of cobalt included in the cobalt-doped black TiO2 nanotube array is tuned to a predetermined amount based on the application of the electrode.

### Claim 6 (depends on 1)

The electrode of claim 1, wherein the substrate includes titanium.

### Claim 7 (depends on 1)

A water processing system, comprising:
the electrode of claim 1, configured to be, at least in part, in direct contact with water.

### Claim 8 (depends on 7)

The system of claim 7, further comprising a second electrode.

### Claim 9 (depends on 8)

The system of claim 8, wherein the second electrode includes a second substrate, and a metal-doped nanotube array contacting the second substrate.

### Claim 10 (depends on 7)

The system of claim 7, further comprising:
a voltage source connected to the electrode and a second electrode configured to contact the water;
wherein the voltage source is configured to switch polarity at a predetermined frequency so that the electrode operates as either an anode or a cathode based on the polarity of the voltage source.

### Claim 11 (depends on 7)

The system of claim 7, wherein the substrate includes titanium.