Core/Shell Catalyst Particles for Fuel Cell Durability
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Solution Overview
Problem
Current electrocatalysts for fuel cells, particularly in PEM fuel cells, face challenges in achieving high specific mass activity and low precious metal content while maintaining durability, which is essential for meeting automotive industry cost and performance requirements.
Innovation Solution
The development of core/shell type catalyst particles with a medium diameter of 20 to 100 nm, featuring a ceramic material in the core and a precious metal or alloy in the shell, specifically designed to mimic the characteristics of polycrystalline bulk precious metal surfaces, thereby increasing specific activity and reducing platinum content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If standard Pt/C electrocatalysts with high metal surface area are used, then catalytic activity is maintained, but precious metal content remains high and specific mass activity is low
Solution Approach 1:
The catalyst particle is segmented into a ceramic core and a precious metal shell, where only the shell material contributes to catalytic activity. This segmentation allows the precious metal to be concentrated at the surface where it is needed, reducing overall metal content while maintaining high specific mass activity.
Solution Approach 2:
A composite core/shell structure is created combining ceramic material (core) with precious metal (shell). The ceramic core provides structural support and volume without contributing to mass, while the thin precious metal shell provides the necessary catalytic surface area, achieving low precious metal content with high specific mass activity.
2Adaptability or versatility
If catalyst particles undergo load cycling between 0.6-1.1V, then dynamic operation requirements are met, but significant platinum loss and sintering occur
Solution Approach 1:
The ceramic core acts as a stable, non-consumable support that replaces the traditional carbon support. This durable ceramic foundation prevents the sintering and degradation that would otherwise occur during dynamic voltage cycling, maintaining catalyst reliability under automotive operating conditions.
Solution Approach 2:
The composite ceramic/precious metal structure provides both the adaptability needed for dynamic operation and the reliability required for durability. The ceramic core resists sintering while the shell maintains catalytic activity, together enabling the catalyst to withstand load cycling without significant platinum loss.
3Productivity
If solid uniform Pt particles with 30 nm medium size are used, then particle size effects are optimized, but most platinum is buried inside and cannot be utilized
Solution Approach 1:
The precious metal is extracted from the bulk interior and placed exclusively in the shell layer. This extraction ensures that 100% of the precious metal is positioned at the surface where it can participate in catalytic reactions, eliminating the waste of buried metal that occurs in solid uniform particles.
Solution Approach 2:
The precious metal is concentrated locally in the shell region rather than being distributed throughout the entire particle volume. This local concentration ensures maximum utilization of the precious metal at the catalytically active surface, achieving high specific mass activity with minimal metal content.
Data Source
AI summary
The invention is directed to core/shell type catalyst particles comprising a Mcore / Mshell structure with Mcore = inner particle core and Mshell = outer particle shell, wherein the medium diameter of the catalyst particle (dcore+shell) is in the range of 20 to 100 nm, 5 preferably in the range of 20 to 50 nm. The thickness of the outer shell (tshell) is about 5 to 20 % of the diameter of the inner particle core of said catalyst particle, preferably comprising at least 3 atomic layers. The inner particle core (Mcore ) of the particles com- prises metal or ceramic materials, whereas the material of the outer shell (Mshell) comprises precious metals and/or alloys thereof. The core/shell type catalyst particles are preferably supported on suitable support materials such as carbon black and can be used as electrocatalysts for fuel cells and for other catalytic applications.