# US 2015/0147682 A1 · Nitride Stabilized Core/Shell Nanoparticles

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- Number: US 2015/0147682 A1
- Document ID: US20150147682A1
- Status: Published application
- Kind: A1
- Application number: 14/554,583
- Filed: 2014-11-26
- Published: 2015-05-28
- Earliest claimed: 2013-11-27
- Assignees: Brookhaven Science Associates, LLC
- Applicants: Brookhaven Science Associates, LLC
- Inventors: Kurian Abraham Kuttiyiel; Kotaro Sasaki; Radoslav R. Adzic
- Web page: https://patentgrep.com/patent/US20150147682A1

## CPC

- H01M 4/92: Metals of platinum group (H01M4/94 {, H01M4/9058} take precedence)
- H01M 4/8657: {layered}
- H01M 4/921: {Alloys or mixtures with metallic elements}
- H01M 4/923: {Compounds thereof with non-metallic elements}
- H01M 4/926: {on carbon or graphite}
- B01J 23/40: of the platinum group metals
- H01M 2008/1095: {Fuel cells with polymeric electrolytes}
- Y02E 60/50: Fuel cells
- H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- B01J: CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
- Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION

## Abstract

Nitride stabilized metal nanoparticles and methods for their manufacture are disclosed. In one embodiment the metal nanoparticles have a continuous and nonporous noble metal shell with a nitride-stabilized non-noble metal core. The nitride-stabilized core provides a stabilizing effect under high oxidizing conditions suppressing the noble metal dissolution during potential cycling. The nitride stabilized nanoparticles may be fabricated by a process in which a core is coated with a shell layer that encapsulates the entire core. Introduction of nitrogen into the core by annealing produces metal nitride(s) that are less susceptible to dissolution during potential cycling under high oxidizing conditions.

## Claims

### Claim 1

A catalyst nanoparticle comprising:
a non-noble metal solid solution core, and
a continuous and nonporous noble metal shell surrounding the non-noble metal solid solution core;
wherein the non-noble metal solid solution core comprises a nitride of a non-noble metal selected from the group consisting of nickel (Ni), cobalt (Co), iron (Fe), Copper (Cu) and mixtures thereof.

### Claim 2 (depends on 1)

The catalyst nanoparticle of claim 1, wherein the catalyst nanoparticle is substantially spherical having an external diameter of less than 20 nm.

### Claim 3 (depends on 1)

The catalyst nanoparticle of claim 1, wherein, the nonporous noble metal shell has a thickness, of between 0.5 nm and 3 nm.

### Claim 4 (depends on 1)

The catalyst nanoparticle of claim 1, wherein the nonporous noble metal shell comprises at least one noble metal selected from the group consisting platinum (Pt), palladium (Pd), gold (Au), rhodium (Rh), iridium (Ir), ruthenium (Ru), silver (Ag), rhenium (Re), alloys and combinations thereof.

### Claim 5 (depends on 4)

The catalyst nanoparticle of claim 4, wherein the at least one noble metal comprises platinum (Pt).

### Claim 6 (depends on 1)

The catalyst nanoparticle of claim 1, wherein the nonporous noble metal shell comprises 1 to 12 monolayers of platinum (Pt).

### Claim 7 (depends on 6)

The catalyst nanoparticle of claim 6, wherein the nonporous noble metal shell comprises 2 to 4 monolayers of platinum (Pt).

### Claim 8 (depends on 1)

The catalyst nanoparticle of claim 1, wherein the non-noble metal solid solution core comprises a nickel nitride (Ni4N).

### Claim 9 (depends on 8)

The catalyst nanoparticle of claim 8, wherein an amount of nickel nitride (Ni4N) within the non-noble metal solid core is between 20 and 50% wt. %.

### Claim 10

A method of forming nitride stabilized nanoparticles comprising:
producing a plurality of nanoparticles of a first metal,
(i) by pulse potential deposition in a solution comprising a salt of the first metal; or
(ii) by adding a chemical reducing agent to a solution comprising a salt of the first metal; or
(iii) by heating a dry mixture of carbon and adsorbed first metal ions in hydrogen; forming a shell layer of a noble second metal on an external surface of the nanoparticles to form core-shell nanoparticles; and
annealing the core-shell nanoparticles under a nitrogen source to produce a nitride of the first metal.

### Claim 11 (depends on 10)

The method of claim 10, wherein producing a plurality of nanoparticles of a first metal by pulse potential deposition comprises:
forming a thin film of a carbon powder on an electrode;
immersing the electrode in a pH-buffered solution containing a salt of the first metal;
applying a first potential pulse sufficient to reduce the first metal and nucleate metal nanoparticles on surfaces of the carbon powder; and
applying a second potential pulse sufficient to increase the size of the nucleated metal nanoparticles.

### Claim 12 (depends on 11)

The method of claim 11, wherein the shell layer of the second metal is formed by galvanic displacement.

### Claim 13 (depends on 10)

The method of claim 10 wherein the nitrogen source comprises a nitrogen gas (N2), an ammonium gas (NH3) or a combination thereof.

### Claim 14 (depends on 10)

The method of claim 10, wherein the annealing comprises exposing the core-shell nanoparticles to a temperature between 200 to 300° C. under N2 gas or between 400 to 700° C. under NH3 for 1 to 10 hours independently or in sequence.

### Claim 15 (depends on 10)

The method of claim 10, wherein producing a plurality of nanoparticles of a first metal by adding a chemical reducing agent to a solution comprises:
combining the solution of the salt of the first metal and carbon powder to form a slurry solution;
sonicating and deaerating the slurry solution to disperse the carbon powder in the solution; and adding the chemical reducing agent to the solution.

### Claim 16 (depends on 15)

The method of claim 15, wherein an excess of Ni ions is present in the solution to ensure that the chemical reducing agent is fully consumed.

### Claim 17 (depends on 16)

The method of claim 16, wherein a noble metal shell is formed by adding the solution comprising a salt of the noble metal into the slurry solution.

### Claim 18 (depends on 1)

An energy conversion device comprising:
a first electrode;
a conducting electrolyte; and
a second electrode,
wherein at least one of the first or second electrodes comprises a plurality of catalyst nanoparticles of claim 1.

### Claim 19 (depends on 18)

The energy conversion device of claim 18, wherein the catalyst nanoparticle comprises platinum (Pt) shell having a shell wall thickness of 2 to 4 atomic layers and nickel (Ni) core comprises 5-50 wt. % nickel (Ni) nitride.

### Claim 20 (depends on 19)

The energy conversion device of claim 19, wherein the energy conversion device is a fuel cell.