Two-Stage Drying for Fuel Cell Catalyst Layers
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Solution Overview
Problem
High-temperature processing of catalyst layers in fuel cells can damage the electrolyte membrane and support film, leading to poor drainage performance and difficulty in peeling off the support film, which affects the power generation efficiency.
Innovation Solution
A two-stage drying process is employed, where the catalyst ink is first heated to evaporate the solvent to 30% or less at a lower temperature, and then further dried at a higher temperature above the glass transition temperature but below the melting point of the catalyst layer, preventing excessive heating and maintaining the electrolyte membrane's integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the catalyst ink is heated to a high temperature equal to or higher than the glass transition temperature to evaporate the solvent completely, then the drainage performance is improved, but the electrolyte membrane and support film are damaged and become difficult to peel off
Solution Approach 1:
The drying process is divided into two distinct stages: a first drying stage at a lower temperature (room temperature to 100°C) to remove most of the solvent, and a second drying stage at a higher temperature (glass transition temperature or higher) to remove the remaining solvent and improve drainage performance. This segmentation allows the process to achieve high drainage performance while avoiding excessive heating that would damage the electrolyte membrane and support film.
Solution Approach 2:
The first drying stage is performed as a preliminary action before the second drying stage. By removing the majority of the solvent at a lower temperature in advance, the subsequent high-temperature treatment can be applied more safely and effectively, achieving the desired drainage performance without causing damage to the membrane structure.
2Quantity of substance
If the catalyst ink is heated to a high temperature to decrease the free volume of constituent molecules, then the moisture content is reduced and drainage performance is improved, but the catalyst layer and electrolyte membrane are softened and become difficult to handle
Solution Approach 1:
The drying process is divided into two distinct stages: a first drying stage at a lower temperature (room temperature to 100°C) to remove most of the solvent, and a second drying stage at a higher temperature (glass transition temperature or higher) to remove the remaining solvent and improve drainage performance. This segmentation allows the process to achieve high drainage performance while avoiding excessive heating that would damage the electrolyte membrane and support film.
Solution Approach 2:
The temperature parameter is changed between two distinct stages: the first drying stage uses a lower temperature (room temperature to 100°C) to preserve structural stability, while the second drying stage uses a higher temperature (glass transition temperature or higher) to reduce moisture content and improve drainage performance. This parameter change allows optimization of both structural stability and drainage performance at different stages of the process.
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 method forms a catalyst layer with low moisture content, improving drainage performance and power generation efficiency while preventing damage to the electrolyte membrane and support film.
Implementation Method 1
heating the electrolyte membrane applied with the catalyst ink at a first temperature to evaporate a solvent contained in the catalyst ink
Implementation Method 2
drying the catalyst ink by heating the electrolyte membrane at a second temperature higher than the first temperature to form a catalyst layer
Data Source
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AI summary
An electrolyte membrane for a polymer electrolyte fuel cell is sent out from an unwinding roller and wound around a winding roller to be transported continuously at a constant speed in a roll-to-roll mode. Two stages of drying processes are performed on a catalyst ink layer applied to a surface of an electrolyte membrane with a backsheet in a first drying furnace and a second drying furnace. The first drying furnace blows a hot air of a first temperature lower than a glass transition temperature of the electrolyte membrane to evaporate a solvent from the catalyst ink layer. The second drying furnace blows a hot air of a second temperature higher than the first temperature and also higher than a glass transition temperature of a to-be-formed catalyst layer to turn the catalyst ink layer into a catalyst layer.