PtNi Core-Shell Nanoparticles via Oxidation-Induced Segregation

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Solution Overview

Problem

Existing methods for synthesizing platinum-based nanomaterials, such as PtNi core/shell structures, require high-temperature annealing, which leads to sintering and shape changes of nanoparticles, posing challenges in achieving high activity and durability while being cost-effective.

Innovation Solution

An oxidation-induced segregation method is employed to form PtNi core/shell nanoparticles without annealing, where PtNi particles are exposed to air at moderate temperatures to form a nickel oxide coating, followed by acid leaching to remove it, resulting in a Pt-rich skin and maintaining the nanoparticle's morphology.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Quantity of substance

If high-temperature annealing is used to form Pt skin on nanoparticles, then Pt loading and mass activity are improved, but nanoparticle sintering and shape changes occur

Engineering Contradiction:

ImprovePt loadingVSAvoidnanoparticle shape

Core Design Contradiction:

Quantity of substanceVSShape

Solution Approach 1:

The patent changes the temperature parameter from high-temperature annealing to moderate-temperature oxidation, and changes the chemical environment from inert to oxidative conditions. This allows Pt skin formation through oxidation-induced segregation at temperatures that do not cause sintering, while achieving high Pt loading and maintaining nanoparticle shape.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs strong oxidizing conditions (oxidative atmosphere, oxygen plasma, or hydrogen peroxide treatment) to accelerate the oxidation of Ni atoms to the surface, inducing Pt skin formation without requiring high-temperature annealing. This resolves the contradiction by enabling Pt enrichment through chemical oxidation rather than thermal diffusion.

Inventive Principle:

Principle #38Strong oxidants (Accelerated oxidation)

2Reliability

If high-temperature annealing is applied to achieve Pt skin formation, then catalytic activity is improved, but process complexity and energy consumption increase

Engineering Contradiction:

Improvecatalytic activityVSAvoidenergy consumption

Core Design Contradiction:

ReliabilityVSUse of energy by stationary object

Solution Approach 1:

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent replaces the thermal mechanism (annealing) with a chemical mechanism (oxidation-induced segregation). Instead of using thermal energy to drive Pt diffusion, the patent uses chemical oxidation to drive Ni atoms to the surface, which passively induces Pt skin formation at much lower temperatures, reducing energy consumption.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Stability of the object's composition

If conventional multistep annealing process is used, then Pt skin is formed, but manufacturing precision and scalability are reduced

Engineering Contradiction:

ImprovePt skin formationVSAvoidprocess control

Core Design Contradiction:

Stability of the object's compositionVSManufacturing precision

Solution Approach 1:

The patent merges multiple steps (Pt skin formation and Ni oxidation) into a single oxidative treatment step. Instead of separate annealing and oxidation steps, the oxidative treatment simultaneously achieves Pt skin formation through oxidation-induced segregation, simplifying the process and improving manufacturing precision and scalability.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent introduces oxidation as an intermediary mechanism that mediates between Pt skin formation and Ni surface segregation. The oxidative environment acts as a mediator that drives Ni atoms to the surface, which passively induces Pt skin formation without requiring high-temperature annealing, thereby improving process control and scalability.

Inventive Principle:

Principle #24Intermediary (Mediator)

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method achieves higher Pt loading and mass activity with a thinner catalyst layer, reducing mass transport resistance and maintaining nanoparticle shape, suitable for industrial production.

Implementation Method 1

oxidation-induced segregation method for synthesis of PtNi core/shell nanoparticles

Methodology Applied

Scientific EffectOxidation-induced segregation: Oxidation

Implementation Method 2

oxidative driven segregation induced core/shell structures

Methodology Applied

Scientific EffectSegregation:

Implementation Method 3

acid leaching to remove it, resulting in a Pt-rich skin

Methodology Applied

Scientific EffectAcid leaching:

Data Source

PatentUS11628427B2Segregation induced core-shell structure

Publication Date: 2023.04.18 UCHICAGO ARGONNE LLC

AI summary

A process for synthesis of PtNi high surface area core/shell particles. The processing including formation of PtNi nanoparticles, exposure of the PtNi nanoparticles to oxygen to form a nickel oxide coating on the nanoparticles at the same time the segregation of Ni to surface induces a Pt-skin with PtNi core structure, removal of the nickel oxide coating to form PtNi core/Pt shell (or Pt-skin) structure.