# US 11,441,232 B2 · Anodization method for the production of one-dimensional (1D) nanoarrays of tin oxide

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- Number: US 11,441,232 B2
- Document ID: US11441232B2
- Status: Granted
- Kind: B2
- Application number: 15/914,555
- Filed: 2018-03-07
- Published: 2019-09-12
- Granted: 2022-09-13
- Earliest claimed: 2018-03-07
- Assignees: King Fahd University of Petroleum and Minerals
- Applicants: King Fahd University of Petroleum and Minerals
- Inventors: Ahsanulhaq Qurashi; Muhammad Raashid; Ibrahim Khan
- Web page: https://patentgrep.com/patent/US11441232B2

## CPC

- C25D 11/34: of metals or alloys not provided for in groups C25D11/04 - C25D11/32
- C01G 19/02: Oxides
- C25B 1/04: by electrolysis of water
- C25B 1/55: Photoelectrolysis
- C01P 2002/72: by d-values or two theta-values, e.g. as X-ray diagram
- C01P 2002/84: by UV- or VIS- data
- C01P 2002/85: by XPS, EDX or EDAX data
- C01P 2004/16: Nanowires or nanorods, i.e. solid nanofibres with two nearly equal dimensions between 1-100 nanometer
- C01P 2004/61: Micrometer sized, i.e. from 1-100 micrometer
- C01P 2004/62: Submicrometer sized, i.e. from 0.1-1 micrometer
- Y02E 60/36: Hydrogen production from non-carbon containing sources, e.g. by water electrolysis
- Y02P 20/133: Renewable energy sources, e.g. sunlight
- C25D: PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- 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)
- 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)
- C01P: INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- 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

A one dimensional (1D) nanoarray of SnO nanostructures on a substrate is disclosed. The nanostructures of SnO have diameters of 200 nm-1 μm and lengths of 500 nm-3 μm, and are attached to and substantially perpendicular to the substrate. The one-dimensional nanoarray may have a nanostructure density of 220-300 nanostructures per 100 μm2 substrate and a band gap energy of 2.36-2.46 eV. The one-dimensional nanoarray may be formed by anodization of Sn foil in an electrochemical cell subjected to a voltage of 15-25 V for 1-3 hours at room temperature. The formed one-dimensional nanoarray may be used for the photo-electrochemical decomposition of water into O2 and H2.

## Claims

### Claim 1

A nanoarray structure, comprising:
a one-dimensional nanoarray of SnO nanorods; and
a substrate of Sn:
wherein,
the SnO nanorods have diameters of from 200 nm-1 μm and lengths of 500 nm-3 μm,
an aspect ratio of the longest dimension (length) of the nanorod to the next longest dimension (width) of the nanorod is from 1.5:1-12:1,
an end of each nanorod is attached to the Sn substrate,
the longitudinal axis of each nanorod is substantially perpendicular to the Sn substrate, and
the SnO is in a tetragonal crystal phase.

### Claim 2 (depends on 1)

The nanoarray structure of claim 1, wherein the nanorods have conical tips.

### Claim 3 (depends on 1)

The nanoarray structure of claim 1, wherein a nanorod nanostructure density is from 220-300 nanostructures per 100 μm2 of the Sn substrate.

### Claim 4 (depends on 1)

The nanoarray structure of claim 1, wherein a band gap energy of one-dimensional nanoarray of SnO nanorods is from 2.36 eV to 2.46 eV.

### Claim 5 (depends on 1)

The nanoarray structure of claim 1, wherein the nanorods are discrete and separated by inter-nanostructure gaps or an inter-nanostructure distance of 1-50 nm.

### Claim 6 (depends on 1)

The nanoarray structure of claim 1, wherein an average surface to surface inter-nanostructure distance of the nanorods is less than 200% of their average diameter.

### Claim 7 (depends on 1)

The nanoarray structure of claim 1, wherein an average surface to surface inter-nanostructure distance of the nanorods is less than 10% of their average diameter.

### Claim 8 (depends on 1)

The nanoarray structure of claim 1, wherein the SnO nanorods comprise from 0.001 wt % to 5 wt % of at least one material selected from the group consisting of SnO2, alpha Sn and beta Sn.

### Claim 9 (depends on 1)

The nanoarray structure of claim 1, further comprising inter-nanostructure gaps in the form of pores or depressions in the substrate which have a maximum depth of 3 μm below that of the original plane of the substrate surface.

### Claim 10 (depends on 9)

The nanoarray structure of claim 9, wherein the inter-nanostructure gaps are elongated and form grooves or channels having a width of from 50 nm to 1 μm between rows of nanorods.

### Claim 11 (depends on 1)

A photo-electrochemical cell, comprising the nanoarray structure of claim 1.

### Claim 12 (depends on 1)

A method for producing the nanoarray structure of claim 1, comprising:
subjecting an electrochemical cell to 15-25 V for 1-3 hours, the electrochemical cell comprising:
a working electrode comprising tin (Sn) foil in contact with an electrolyte solution and
a counter electrode in contact with the electrolyte solution,
wherein nanorods of SnO are grown on the tin foil, forming the one-dimensional nanoarray, and
wherein the tin foil is the substrate.

### Claim 13 (depends on 12)

The method of claim 12, wherein the counter electrode comprises gold, platinum, or carbon.

### Claim 14 (depends on 12)

The method of claim 12, wherein the counter electrode is in the form of a mesh.

### Claim 15 (depends on 12)

The method of claim 12, wherein a surface area of the working electrode in contact with the electrolyte solution is not greater than a surface area of the counter electrode in contact with the electrolyte solution.

### Claim 16 (depends on 12)

The method of claim 12, wherein the electrolyte solution has an electrolyte concentration of 0.2-2.0 M.

### Claim 17 (depends on 12)

The method of claim 12, wherein the electrolyte solution has a temperature of 20-30° C.

### Claim 18 (depends on 12)

The method of claim 12, wherein the electrolyte solution comprises at least one selected from the group consisting of chromic acid, oxalic acid, sulfuric acid, phosphoric acid, and ammonium fluoride.

### Claim 19 (depends on 18)

The method of claim 18, wherein the electrolyte solution comprises ammonium fluoride and phosphoric acid.

### Claim 20 (depends on 11)

A method of decomposing water into H2 and O2, comprising:
contacting the photo-electrochemical cell of claim 11 with water; and
irradiating the photo-electrochemical cell with an electromagnetic radiation having a wavelength of 200-700 nm.