# US 2021/0340683 A1 · Development of ruthenium-copper nano-sponge electrodes for ambient electrochemical reduction of nitrogen to ammonia

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- Number: US 2021/0340683 A1
- Document ID: US20210340683A1
- Status: Published application
- Kind: A1
- Application number: 17/085,720
- Filed: 2020-10-30
- Published: 2021-11-04
- Earliest claimed: 2020-05-01
- Assignees: University of Tennessee Research Foundation
- Applicants: University of Tennessee Research Foundation
- Inventors: Feng Yuan Zhang; Kui Li
- Web page: https://patentgrep.com/patent/US20210340683A1

## CPC

- C25B 11/031: Porous electrodes
- C01C 1/00: Ammonia; Compounds thereof {(C01C3/08, C01C3/14, C01C3/16, C01C3/20 take precedence)}
- C01C 1/02: Preparation, {purification} or separation of ammonia
- C25B 1/00: Electrolytic production of inorganic compounds or non-metals
- C25B 1/27: Ammonia
- C25B 11/052: Electrodes comprising one or more electrocatalytic coatings on a substrate
- C25B 11/061: Metal or alloy
- C25B 11/089: Alloys
- B82Y 30/00: Nanotechnology for materials or surface science, e.g. nanocomposites
- B82Y 40/00: Manufacture or treatment of nanostructures
- 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)
- C01C: AMMONIA; CYANOGEN; COMPOUNDS THEREOF ({metal hydrides, monoborane, diborane or addition complexes thereof C01B6/00}; salts of oxyacids of halogens C01B11/00; peroxides, salts of peroxyacids C01B15/00; thiosulfates, dithionites, polythionates C01B17/64; compounds containing selenium or tellurium C01B19/00; azides C01B21/08; {compounds other than ammonia or cyanogen, containing nitrogen, non-metals and optionally metals C01B21/082}; metal imides or amides C01B21/092; nitrites C01B21/50; {compounds of noble gases C01B23/0005}; phosphides C01B25/08; salts of oxyacids of phosphorus C01B25/16; compounds containing silicon C01B33/00; compounds containing boron C01B35/00)
- B82Y: SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES

## Abstract

A ruthenium-copper (RuCu) nano-sponge (NSP) electrocatalyst for use in the electrolytic reduction of nitrogen to provide ammonia is described. The RuCu NSP can be prepared as a porous nanoparticle comprising a RuCu alloy via facile reduction of Ru and Cu precursors under ambient conditions. Electrodes prepared with surface disposed RuCu NSPs can be used to prepare ammonia from nitrogen with good yields and Faradaic efficiency at room temperature and atmospheric pressure.

## Claims

### Claim 1

A method of producing ammonia, the method comprising contacting nitrogen with a source of protons and a source of electrons in the presence of a catalyst comprising a ruthenium-copper (RuCu) nano-sponge (NSP), thereby reducing the nitrogen to produce ammonia.

### Claim 2 (depends on 1)

The method of claim 1, wherein the RuCu NSP comprises porous nanoparticles comprising a bimetallic alloy of the formula RuxCu1-x, wherein 0.01≤x≤0.5.

### Claim 3 (depends on 2)

The method of claim 2, wherein 0.1≤x≤0.4.

### Claim 4 (depends on 3)

The method of claim 3, wherein x is 0.15.

### Claim 5 (depends on 1)

The method of claim 1, wherein the contacting is performed in an electrolytic cell, wherein the catalyst is disposed on the surface of a cathode electrode, wherein the electrolytic cell comprises an aqueous electrolyte, and wherein the contacting is performed by:
(i) feeding gaseous nitrogen to the electrolytic cell; and
(ii) running a current through the electrolytic cell.

### Claim 6 (depends on 5)

The method of claim 5, wherein the ammonia is produced at an electrode potential between about −1.0 volts (V) and about 0.2 V versus reversible hydrogen electrode (RHE).

### Claim 7 (depends on 6)

The method of claim 6, wherein the ammonia is produced at an electrode potential between about −0.5 V and about 0.05 V versus RHE.

### Claim 8 (depends on 7)

The method of claim 7, wherein the ammonia is produced at an electrode potential of about −0.2 V versus RHE.

### Claim 9 (depends on 6)

The method of claim 6, wherein the Faradaic efficiency of the catalyst is greater than about 0.5%.

### Claim 10 (depends on 9)

The method of claim 9, wherein the Faradaic efficiency of the catalyst is about 4.39%.

### Claim 11 (depends on 5)

The method of claim 5, wherein the aqueous electrolyte comprises between about 0.05 molar (M) and about 2 M potassium hydroxide.

### Claim 12 (depends on 1)

The method of claim 1, wherein the ammonia is produced at a rate of 20 micrograms per milligram of catalyst per hour (μg mgcat−1 h−1) or greater.

### Claim 13 (depends on 12)

The method of claim 12, where ammonia is produced at a rate of about 26.25 μg mgcat−1 h−1.

### Claim 14 (depends on 1)

The method of claim 1, wherein the contacting is performed at room temperature and/or atmospheric pressure.

### Claim 15

A method of preparing a ruthenium-copper (RuCu) nano-sponge (NSP), the method comprising:
(a) providing an aqueous solution comprising a ruthenium (Ru) precursor and a copper (Cu) precursor at a predetermined ratio, and
(b) contacting the aqueous solution from (a) with an aqueous solution of a borohydride reducing agent, thereby preparing the RuCu NSP.

### Claim 16 (depends on 15)

The method of claim 15, wherein the borohydride reducing agent is an alkali metal borohydride selected from lithium borohydride, potassium borohydride, and sodium borohydride.

### Claim 17 (depends on 15)

The method of claim 15, wherein the Ru precursor is a Ru halide.

### Claim 18 (depends on 15)

The method of claim 15, wherein the Cu precursor is a Cu halide.

### Claim 19 (depends on 15)

The method of claim 15, wherein the predetermined ratio results in a molar ratio of Ru to Cu of between 99:1 and 1:99.

### Claim 20

A composition comprising a ruthenium-copper (RuCu) nano-sponge (NSP), wherein the RuCu NSP comprises a porous nanoparticle comprising a RuCu alloy.

### Claim 21 (depends on 20)

The composition of claim 20, wherein the RuCu NSP comprises a porous nanoparticle comprising RuxCu1-x, where 0.01≤x≤0.50.

### Claim 22 (depends on 21)

The composition of claim 21, where 0.1≤x≤0.40.

### Claim 23 (depends on 22)

The composition of claim 22, where x is 0.15.

### Claim 24 (depends on 20)

The composition of claim 20, wherein the porous nanoparticle has an average diameter between about 10 nanometers (nm) and about 15 nm.

### Claim 25 (depends on 20)

An electrode comprising the composition of claim 20.