Membrane Electrode Assembly Heat Treatment Solvent Removal
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Solution Overview
Problem
Existing methods for manufacturing membrane electrode assemblies in fuel cells lead to the thermal decomposition of ionomers due to oxidation heat, resulting in increased sulfate ions, which reduces proton conductivity and increases impedance, causing power generation output to decrease.
Innovation Solution
A method involving a drying step followed by a heat treatment step, where the solvent gas concentration is maintained below a predetermined threshold to prevent oxidation heat generation, ensuring the ionomer is not thermally decomposed, and the heat treatment is performed at a temperature equal to or higher than the glass transition temperature of the ionomer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If heat treatment is performed on the electrode catalyst layer in an environment where solvent gas remains, then the structure strength of the electrode catalyst layer is improved, but oxidation heat is generated causing thermal decomposition of the ionomer
Solution Approach 1:
The patent applies preliminary action by completely removing solvent gas from the heat treatment environment before performing heat treatment. The drying step is conducted first to evaporate and remove the solvent, creating a solvent-free environment. Only after complete removal does the heat treatment begin, preventing oxidation heat generation while still achieving the desired structure strength improvement through controlled heating at temperatures above the glass transition temperature of the ionomer.
Solution Approach 2:
The patent creates an inert environment by eliminating the oxidizable solvent gas from the heat treatment atmosphere. By ensuring complete solvent removal through the drying step before heat treatment, the environment becomes inert with respect to oxidation reactions. This prevents the catalyst from generating oxidation heat that would otherwise cause thermal decomposition of the ionomer, while still allowing the heat treatment to strengthen the electrode catalyst layer structure.
2Strength
If heat treatment is performed to improve electrode catalyst layer structure, then adhesion between carbon particles and ionomer is enhanced, but sulfate ions are produced reducing proton conductivity
Solution Approach 1:
The patent applies preliminary action by removing solvent gas before heat treatment. This prevents the formation of sulfate ions during the heat treatment process by eliminating the source of oxidation reactions. The heat treatment is then performed in a clean, solvent-free environment, allowing the ionomer structure to be strengthened and adhesion to be enhanced without the harmful side effect of sulfate ion generation that would compromise proton conductivity.
3Loss of substance
If drying is performed to remove solvent, then solvent is evaporated from catalyst ink, but solvent gas remains in the heating chamber
Solution Approach 1:
The patent applies the extraction principle by completely removing solvent gas from the heating chamber after the drying step. The system is designed to evacuate or vent the chamber to eliminate accumulated solvent vapor. This ensures that when heat treatment begins, the chamber environment is free of solvent gas, preventing oxidation reactions while maintaining the benefits of complete solvent removal from the catalyst ink.
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 approach suppresses the production of sulfate ions, maintains proton conductivity, reduces impedance, and enhances the power generation output of fuel cells by preventing thermal decomposition of the ionomer during the heat treatment process.
Implementation Method 1
a drying step of drying a substrate sheet to which a catalyst ink is applied
Implementation Method 2
a heat treatment step of performing a heat treatment on the substrate sheet, on which the catalyst ink is dried, after the drying step at a heat treatment temperature which is equal to or higher than a glass transition temperature of the ionomer
Data Source
AI summary
Provided is a method of manufacturing a membrane electrode assembly in which an electrode catalyst layer is formed on a surface of an electrolyte membrane. This method includes: a drying of drying a substrate sheet to which a catalyst ink is applied, the catalyst ink containing catalyst support particles on which a catalytic metal is supported, a solvent, and an ionomer; and a heat treatment of performing a heat treatment on the substrate sheet, on which the catalyst ink is dried, after the drying at a heat treatment temperature which is equal to or higher than a glass transition temperature of the ionomer to prepare the electrode catalyst layer. The heat treatment is performed after a concentration of a solvent gas obtained by gasification of the solvent, which remains in a chamber of a heating device for performing the heat treatment, is a predetermined concentration threshold or lower.