Core-Shell Platinum Catalyst for Direct Methanol Fuel Cells
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Solution Overview
Problem
Direct methanol fuel cells (DMFCs) face challenges in achieving high output density due to insufficient catalytic activity and durability of existing platinum/ruthenium alloy catalysts, particularly with regards to carbon monoxide poisoning and ruthenium elution during power generation.
Innovation Solution
A core-shell type platinum-containing catalyst is developed, featuring a platinum shell layer on a non-platinum core particle, with a specific thickness and distribution to enhance catalytic activity and durability, reducing platinum usage while maintaining high performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If platinum/ruthenium alloy catalysts are used to enhance catalytic activity, then output density is improved, but carbon monoxide poisoning and ruthenium elution occur during power generation
Solution Approach 1:
The catalyst is segmented into a core-shell structure where the ruthenium core provides catalytic activity and the platinum shell protects against carbon monoxide poisoning. This segmentation allows each material to perform its optimal function while mitigating the weaknesses of the individual components.
Solution Approach 2:
A composite catalyst structure is created by combining ruthenium and platinum in a core-shell configuration. The composite material leverages the high catalytic activity of ruthenium while using the platinum shell to prevent carbon monoxide adsorption and reduce ruthenium dissolution, thereby improving both output density and durability.
2Productivity
If more platinum is used to improve catalytic activity and resistance to carbon monoxide poisoning, then performance is enhanced, but cost and platinum usage increase
Solution Approach 1:
Platinum is applied locally only as a thin shell layer on the ruthenium core, rather than using bulk platinum. This local quality approach ensures that platinum is present only where needed to protect against carbon monoxide poisoning, minimizing overall platinum usage while maintaining high catalytic activity.
Solution Approach 2:
The composite catalyst structure allows for reduced platinum content by combining it with a ruthenium core. The ruthenium provides the majority of the catalytic activity, while the thin platinum shell provides targeted protection against carbon monoxide, thereby reducing total platinum usage compared to pure platinum catalysts.
3Productivity
If existing catalyst structures are used to achieve high output density, then power generation performance is improved, but ruthenium elution occurs during continuous operation
Solution Approach 1:
The harmful effect of ruthenium elution is addressed by extracting or removing the vulnerable ruthenium from direct contact with the electrolyte. The platinum shell acts as a protective barrier that prevents ruthenium dissolution while allowing the ruthenium core to maintain catalytic activity.
Solution Approach 2:
The composite core-shell structure protects the ruthenium core from elution by enclosing it within a platinum shell. This composite design maintains the high power generation performance of ruthenium while significantly improving its stability and resistance to dissolution during continuous operation.
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 achieves a high output density of 70 mW/cm2 and retains 90% of its initial performance after 800 hours of continuous operation, with improved resistance to carbon monoxide poisoning and reduced ruthenium elution.
Implementation Method 1
a shell layer (platinum layer) and a fuel cell using the same, a platinum-containing catalyst resistant to carbon monoxide poisoning
Implementation Method 2
reduced ruthenium elution
Data Source
AI summary
In one example embodiment, a core-shell type platinum-containing catalyst is allowed to reduce the amount of used platinum and has high catalytic activity and stability. In one example embodiment, the core-shell type platinum-containing catalyst includes a core particle (with an average particle diameter R1) made of a non-platinum element and a platinum shell layer (with an average thickness ts) satisfying 1.4 nm≦R1≦3.5 nm and 0.25 nm≦ts≦0.9 nm. The core particle includes an element satisfying Eout≧3.0 eV, where average binding energy relative to the Fermi level of 5d orbital electrons of platinum present on an outermost surface of the shell layer is Eout. In a fuel cell including a platinum-containing catalyst which contains a Ru particle as a core particle, the output density at a current density of 300 mA/cm2 is 70 mW/cm2 or over, and an output retention ratio is approximately 90% or over.