Cross-linked Polymer Electrolyte Membrane for Fuel Cells
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Solution Overview
Problem
Conventional proton conductive membranes in fuel cells, such as those using Nafion, suffer from methanol cross-over issues, leading to unstable output voltage and high production costs, and existing solutions like cross-linking compromise proton conductivity, while sulfonation techniques face challenges with non-uniform reactions and material deterioration.
Innovation Solution
A proton conductive membrane with a cross-linked polymer electrolyte containing a nitrogen-containing hetero ring structure is introduced, which reduces methanol cross-over and improves sulfonic acid permeability, achieved by impregnating a porous substrate with specific monomers and sulfonating agents, allowing for a more uniform and cost-effective membrane production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a cross-linked structure is introduced into the electrolytic membrane to suppress methanol cross-over, then methanol permeability is reduced, but proton conductivity decreases seriously
Solution Approach 1:
The membrane is divided into two functional components: a porous substrate providing mechanical strength and a polymer electrolyte layer providing ion conductivity. This segmentation allows the substrate to be cross-linked for methanol rejection while the electrolyte layer maintains proton conductivity through its ionic channels, resolving the contradiction between methanol suppression and proton transport
Solution Approach 2:
The invention uses a composite structure combining a porous substrate (such as polyolefin) with a polymer electrolyte (such as sulfonated polysulfone or Nafion). The substrate provides structural integrity and can be cross-linked to block methanol, while the electrolyte component ensures high proton conductivity, thus achieving both methanol rejection and maintained proton conductivity
2Reliability
If Nafion is used as the proton conductive membrane, then excellent proton conductivity is achieved, but production cost increases
Solution Approach 1:
Instead of using expensive Nafion throughout the entire membrane structure, the invention places the polymer electrolyte only in the porous substrate layer, while the support layer can be made from cheaper materials like polyolefin. This local application of high-performance material reduces overall cost while maintaining necessary proton conductivity in the electrolyte region
Solution Approach 2:
The invention employs cost-effective polymer electrolytes such as sulfonated polysulfone or other sulfonated polymers as alternatives to expensive Nafion. These materials provide sufficient proton conductivity for fuel cell operation at a fraction of the cost, making the overall system more economically viable
3Quantity of substance
If sulfonation is performed using conventional methods, then sulfonic acid groups are introduced, but the reaction is non-uniform and causes material deterioration
Solution Approach 1:
The polymer is sulfonated before being incorporated into the membrane structure. This preliminary sulfonation allows for controlled introduction of sulfonic acid groups under optimized conditions, ensuring uniform distribution and appropriate sulfonation degree before the polymer is processed into the final membrane, thereby avoiding non-uniform reactions and material deterioration during subsequent manufacturing steps
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 membrane exhibits reduced methanol cross-over and enhanced proton conductivity, enabling stable and efficient fuel cell performance while being produced at a lower cost, facilitating the commercialization of direct methanol fuel cells.
Implementation Method 1
a proton conductive film comprising a porous substrate whose pores are filled with a polymer having a sulfonic acid group
Implementation Method 2
a proton conductive film comprising a porous substrate whose pores are filled with a polymer having a sulfonic acid group
Implementation Method 3
it has been known to depress swelling by introducing a cross-linked structure into the electrolytic membrane to thereby suppress methanol cross-over
Data Source
AI summary
An electrolytic membrane comprising a porous membrane substrate containing a cross-linked polymer electrolyte having at least a structural component shown by following chemical formula 1:wherein A represents a repeating unit having an aromatic hydrocarbon group substituted by at least a sulfonic acid group, B represents a repeating unit having one of a nitrogen-containing hetero ring compound residue, and the sulfate, hydrochloride or organic sulfonate thereof, C represents a repeating unit having a cross-linked group, and X, Y and Z represent mol fractions of respective repeating units in the chemical formula 1, with 0.34≦X≦0.985, 0.005≦Y≦0.49, 0.01≦Z≦0.495 and Y≦X and Z≦X, provided that, in the repeating unit A, a ratio of the aromatic hydrocarbon group substituted by at least a sulfonic acid group is 0.3 to 1.0, and the number of the sulfonic acid group in the aromatic hydrocarbon group is 1 to 3.