Terminal-block Ionomer Cathode Catalyst Layer for Fuel Cells
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Fuel cells face challenges in simultaneously improving power generation performance during low and high load operations due to the trade-off between water retention and gas diffusion resistance, where reducing gas diffusion resistance to enhance high load performance leads to deteriorated water retention and catalyst drying at low loads.
Innovation Solution
A solid polymer fuel cell design incorporating a cathode catalyst layer with a terminal-block type ionomer having a hydrophilic block at the terminal of a copolymer with a hydrophobic portion, which maintains low gas diffusion resistance and high water retention, along with a cathode gas diffusion layer with a gas diffusion resistance coefficient of 3.2×10−4 m or lower, optimizing oxygen permeability and catalyst utilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the gas diffusion resistance is reduced by increasing the pore size in the gas diffusion layer to improve power generation performance during high load operation, then the gas diffusion resistance decreases, but water retention deteriorates which promotes drying of the catalyst layer
Solution Approach 1:
The gas diffusion layer is designed with a gradient structure where the pore size varies through the thickness. The surface layer has larger pores to reduce gas diffusion resistance for high load performance, while the inner layer maintains smaller pores to retain water and prevent catalyst drying. This local differentiation of pore sizes allows simultaneous optimization of both gas diffusion and water retention properties.
2Reliability
If water retention is improved to suppress catalyst drying during low load operation, then the catalyst utilization rate is maintained, but the gas diffusion resistance increases which reduces power generation performance during high load operation
Solution Approach 1:
The gas diffusion layer employs a gradient pore structure where the inner layer has smaller pores that provide excellent water retention to maintain catalyst utilization during low load operation, while the outer layer has larger pores that ensure low gas diffusion resistance for high load performance. This spatial differentiation resolves the contradiction between water retention and power generation capability.
3Power
If the pore size in the gas diffusion layer is increased to reduce gas diffusion resistance, then concentration overvoltage is suppressed during high load operation, but water retention deteriorates leading to catalyst layer drying
Solution Approach 1:
The gas diffusion layer is constructed with a gradient pore size distribution where the surface region has enlarged pores to minimize concentration overvoltage and enhance gas diffusion during high load operation, while the deeper regions maintain reduced pore sizes to retain water and prevent catalyst layer drying. This localized structural optimization simultaneously addresses both harmful effects.
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 design simultaneously enhances power generation performance during both low and high load operations by suppressing catalyst drying and reducing concentration overvoltage, while maintaining high oxygen permeability and water retention, thereby improving overall fuel cell efficiency.
Implementation Method 1
The cathode catalyst layer includes a terminal-block type ionomer having a hydrophilic block which is made of an aggregated structure of hydrophilic portions
Implementation Method 2
a cathode gas diffusion layer that is provided outside the cathode catalyst layer, wherein a gas diffusion resistance coefficient of the cathode gas diffusion layer is 3.2×10−4 m or lower
Data Source
AI summary
A fuel cell includes: an electrolyte membrane; an anode catalyst layer; a cathode catalyst layer; and a cathode gas diffusion layer. The cathode catalyst layer includes an ionomer, the ionomer includes copolymers each of which has a hydrophilic block. The hydrophilic block is positioned at a terminal of a copolymer which includes a hydrophobic portion and a hydrophilic portion having a sulfonic acid group. The hydrophilic block has an aggregated structure of the hydrophilic portion. A gas diffusion resistance coefficient of the cathode gas diffusion layer is 3.2×10−4 m or lower. The gas diffusion resistance coefficient is expressed by “Gas Diffusion Resistance Coefficient=Thickness of Cathode Gas Diffusion Layer/(Porosity of Cathode Gas Diffusion Layer)4”.