Fuel Cell Separator Cr Oxide Surface Primer Adhesion
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Solution Overview
Problem
The existing fuel cell separators face issues with sealant peeling due to acid resistance limitations of silicone rubber and primer adhesion degradation, leading to potential leakage and reduced durability.
Innovation Solution
A fuel cell separator with a Cr oxide-rich surface, combined with Mo oxide, Fe oxide, and Ni, where the Cr oxide composition is 60% or more, forming strong hydrogen bonds with hydroxyl groups on the primer, enhancing adhesion and corrosion resistance, thereby preventing peeling of the sealant over a longer period.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If silicone rubber is used as the rubber in the sealant, then the sealant can maintain elasticity at sub-zero temperatures and prevent gas leakage, but the silicone rubber deteriorates due to acid exposure and loses elasticity near the electrolyte membrane
Solution Approach 1:
A primer layer is introduced as an intermediary between the silicone rubber sealant and the metal separator. This primer acts as a protective barrier that shields the silicone rubber from direct contact with acid, preventing deterioration while maintaining the sealant's elasticity and sealing function.
Solution Approach 2:
The sealant structure is designed as a composite system consisting of multiple layers: the silicone rubber layer for elasticity and sealing, and the primer layer for acid resistance. This composite structure combines the advantages of different materials to overcome their individual limitations.
2Reliability
If a Cr-rich layer is formed on the separator surface, then the primer is strongly bonded to the separator and peeling is prevented, but the manufacturing process becomes more complex
Solution Approach 1:
The surface composition of the separator is controlled by adjusting the ratios of metal elements (particularly Cr, Fe, and Ni) during manufacturing. By optimizing these compositional parameters, a Cr-rich surface layer is formed that provides strong primer adhesion without requiring additional complex processing steps.
3Reliability
If the sealant is disposed between the separator and electrolyte electrode assembly, then gas leakage is prevented, but the sealant peels off from the separator due to acid exposure and adhesion deterioration
Solution Approach 1:
The primer serves as a mediator between the sealant and separator, providing both acid resistance and strong adhesion. This intermediary layer protects the sealant from acid exposure while maintaining durable bonding to the separator, preventing peeling and ensuring long-term sealing performance.
Solution Approach 2:
The multi-layer sealant structure with primer and rubber layers creates a composite system where each layer performs its specific function: the primer provides acid resistance and adhesion, while the rubber layer provides elasticity and sealing, together achieving both sealing function and long-term durability.
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 solution effectively maintains strong bonding between the separator and the primer, and between the primer and the rubber, preventing peeling and ensuring long-term adhesion and corrosion resistance, even in acidic environments.
Implementation Method 1
The fuel cell separator and a primer in the sealant have hydroxyl groups (—OH groups) on the outermost surfaces. The hydroxyl groups are hydrogen-bonded to each other, whereby the fuel cell separator and the primer are strongly connected.
Implementation Method 2
the Cr oxide is more corrosion-resistant than the Fe oxide, whereby the fuel cell separator is hardly corroded
Data Source
AI summary
First, a passive film is removed from a surface of a separator sheet. For example, the separator sheet may be immersed in an acidic liquid to remove the passive film. Then, the separator sheet is washed with water, taken out from the water, and heated. After the heating, the separator sheet is subjected to an electrolytic treatment to obtain a separator for a fuel cell. The resultant separator has a seal forming portion, and the outermost surface of the seal forming portion contains, based on 100% by weight of the total of a Cr oxide, an Mo oxide, an Fe oxide, Fe, and Ni, 5% by weight or less of the sum of the Fe and Ni and 60% by weight or more of the Cr oxide.