Fuel Cell Catalyst Core-Shell Composition to Limit Sintering
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing fuel cell catalysts, particularly for the oxygen reduction reaction at the cathode, face challenges in achieving both high activity and stability, with high-temperature annealing leading to sintering and reduced metal surface area.
Innovation Solution
A process involving the preparation of PtaXb alloy particles with a core-shell structure, where X is Co, Ni, Y, Gd, or Cu, applied on a support material, followed by a controlled surface reaction and lower temperature heating, then leaching a portion of metal X to create a platinum-rich surface, resulting in a catalyst with improved stability and performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high-temperature annealing is applied to form alloy catalysts, then catalyst activity is improved, but metal surface area is reduced due to sintering
Solution Approach 1:
The patent applies preliminary action by forming the core-shell structure with platinum-rich shell before the annealing process. The shell acts as a protective layer that prevents sintering during high-temperature treatment, allowing the catalyst to achieve high activity without losing metal surface area. This is evident in the process where Pt-M alloy particles with platinum-rich shells are formed first, then subjected to annealing that would normally cause sintering, but the shell structure prevents this harmful effect.
2Reliability
If de-alloying process is applied to create platinum-rich shells, then oxygen reduction reaction activity is enhanced, but structural control over the core and shell becomes difficult
Solution Approach 1:
The patent performs preliminary action by pre-forming the core-shell structure with controlled composition before de-alloying. The core is prepared with specific Pt-M alloy composition (where M is a base metal), and a platinum-rich shell is formed on the surface before the de-alloying process. This preliminary structuring enables better control over the final catalyst structure after de-alloying, as the core provides a template that maintains structural integrity.
Solution Approach 2:
The patent applies parameter changes by controlling the composition ratio of Pt to M in the core, the thickness and composition of the platinum-rich shell, and the de-alloying conditions. By adjusting these parameters, the patent achieves optimal structural control and oxygen reduction reaction activity. Specifically, the core is formulated with Pt:M ratios in specific ranges, and the shell thickness is controlled to maintain structural stability during de-alloying while ensuring sufficient platinum-rich surface area for high catalytic activity.
3Reliability
If platinum loading is increased to improve MEA performance, then catalyst activity increases, but cost increases
Solution Approach 1:
The patent applies local quality by creating a non-uniform distribution of platinum within the catalyst particles. The platinum-rich shell concentrates platinum at the particle surface where catalytic reactions occur, while the core contains less platinum. This local concentration of platinum in the shell region maximizes catalytic activity per unit mass of platinum, as the platinum is positioned exactly where it is needed for oxygen reduction reaction, rather than being uniformly distributed throughout the entire particle.
Solution Approach 2:
The patent uses composite materials by combining platinum with base metals (M) in a core-shell structure. The core consists of Pt-M alloy providing structural support and electrical conductivity, while the shell is platinum-rich providing catalytic activity. This composite structure reduces overall platinum loading compared to pure platinum catalysts, while maintaining or enhancing catalytic performance through the synergistic combination of materials with different properties.
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
The catalyst exhibits enhanced stability and performance, especially at high current densities, reducing the need for high-temperature annealing and minimizing sintering, thus optimizing the catalyst's activity and efficiency.
Implementation Method 1
high-temperature annealing leading to sintering and reduced metal surface area
Implementation Method 2
subjecting the material produced in step (iii) to conditions sufficient to leach a portion of metal X from the material
Data Source
AI summary
The present invention provides a process for preparing a catalyst precursor, said process comprising the steps of (i) providing PtaXb alloy particles on a support material and (ii) applying a shell of X to the PtaXb alloy particles to provide a catalyst precursor comprising particles having a PtaXb core and an X shell. The ratio of a to b is in the range of and including 10:1 to 1:2.5 and X is Co, Ni, Y, Gd, Sc or Cu. Also provided is a process for preparing a catalyst material.