Microporous Layer Coating on PEMFC Active Layers Without Sintering
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Solution Overview
Problem
Current methods for forming a microporous layer (MPL) in proton exchange membrane fuel cells (PEMFCs) face challenges such as the use of toxic fluorinated solvents, limited deposition techniques, and the need for high-temperature sintering, which can damage the active layer and hinder industrial scalability.
Innovation Solution
A non-aqueous dispersion ink comprising carbonaceous particulate material and poly(vinylidene fluoride-co-hexafluoropropene) copolymer (PVDF-HFP) is used to form a microporous layer directly on the active layer, allowing for deposition by spraying or coating without damaging the layer and eliminating the need for sintering, using inert organic solvents like ethyl acetate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a microporous layer is formed by depositing ink using spraying technique with fluorinated solvents, then the layer can be formed on the active layer surface, but the process becomes complex and requires high-temperature sintering that may damage the active layer
Solution Approach 1:
The patent changes the chemical composition parameters of the ink by replacing fluorinated solvents with inert organic solvents (ethyl acetate, isopropanol, ethanol) and adjusting the polymer content (PVDF, PVDF-HFP) to achieve the desired hydrophobicity and mechanical properties without requiring high-temperature sintering. This parameter modification simplifies the overall process while maintaining MPL formation quality.
Solution Approach 2:
The patent uses composite ink formulations combining carbonaceous particulate materials (carbon black, carbon nanotubes, graphite) with polymeric binders (PVDF, PVDF-HFP) dispersed in inert organic solvents. This composite approach enables the MPL to achieve both electrical conductivity from carbon particles and hydrophobicity/mechanical strength from the polymer matrix, eliminating the need for complex high-temperature processing.
2Reliability
If high-temperature sintering is used to make the MPL hydrophobic, then the MPL achieves required hydrophobicity, but the active layer may be damaged
Solution Approach 1:
The patent fundamentally changes the approach to achieving hydrophobicity by selecting polymers (PVDF, PVDF-HFP) with inherent hydrophobic properties and using inert organic solvents that evaporate at low temperatures. The ink formulation parameters are optimized to provide sufficient hydrophobicity through the polymer-carbon composite structure itself, eliminating the need for high-temperature sintering that could damage the active layer catalyst particles and binder.
3Ease of manufacture
If toxic fluorinated solvents are used to solubilize the polymer, then the ink can be properly formed, but the process becomes environmentally harmful and less suitable for industrial production
Solution Approach 1:
The patent changes the solvent parameter from toxic fluorinated solvents to inert organic solvents (ethyl acetate, isopropanol, ethanol) that are environmentally friendly and suitable for industrial production. The ink formulation is optimized with appropriate polymer concentrations and carbon content to ensure proper solubilization and dispersion without requiring hazardous chemicals, thereby maintaining ease of manufacture while eliminating toxicity concerns.
4Productivity
If the ink is deposited by coating instead of spraying, then the process is simpler and more suitable for industrial scale, but the solvent contact time with active layer increases causing potential damage
Solution Approach 1:
The patent changes the solvent parameter to inert organic solvents (ethyl acetate, isopropanol, ethanol) that have lower reactivity with the active layer materials compared to previously used solvents. This parameter change enables the use of coating deposition methods at industrial scale, as the extended contact time during coating does not result in significant damage to the active layer, thereby improving productivity while maintaining layer integrity.
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 results in a microporous layer with good hydrophobicity and mechanical strength, suitable for industrial-scale production, offering flexibility in deposition techniques and eliminating the use of toxic solvents, while achieving the required properties without high-temperature processing.
Implementation Method 1
The microporous character of the MPL can be attributed to the presence of HFP units in the polymer chain, which have a tendency to aggregate during the evaporation of the solvent and to form a continuous hydrophobic phase.
Implementation Method 2
step (c) proceed to the evaporation of said solvent(s) to form said MPL microporous layer
Data Source
Figure 1~2
Figure 3~3b
Figure 4~4b
AI summary
The invention relates to a method for forming an electroconductive and hydrophobic microporous layer (MPL) on the surface of an active layer for an electrochemical converter, comprising at least the following steps: (a) having a non-aqueous dispersion, called "ink", comprising at least one carbonaceous particulate material and at least one organic solvent; (b) forming a deposit of said ink on the surface of said active layer; and (c) evaporating said solvent(s) to form said microporous MPL, step (c) being carried out simultaneously and/or subsequent to step (b); wherein said ink comprises at least one poly(vinylidene fluoride-co-hexafluoropropene) copolymer, denoted PVDF-HFP, in solution in said organic solvent.It also relates to ink for the preparation of such a microporous layer; a multilayer structure comprising at least one active layer supported by a solid electrolyte membrane and being in contact, at its face opposite said solid membrane, with a microporous layer obtained by the process of the invention, a membrane/electrode assembly (MEA), comprising such a multilayer structure, as well as their use in a cell of an electrochemical converter, in particular in a PEMFC.