Carbon Fiber Gas Diffusion Substrate with Fluorinated Polymer Coating
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Solution Overview
Problem
Gas diffusion substrates prepared using an intermediate-temperature process have lower corrosion resistance compared to those made with high-temperature processes, which can affect their durability and performance in fuel cells.
Innovation Solution
A porous gas diffusion substrate is developed with a non-woven carbon fibre web coated with a fluorinated polymer and inert particles, processed at lower temperatures to achieve improved corrosion resistance while maintaining flexibility, using a carbonisable resin impregnation and heat treatment steps.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by stationary object
If an intermediate-temperature process is used to manufacture gas diffusion substrates, then energy consumption and cost are reduced, but corrosion resistance deteriorates
Solution Approach 1:
The invention uses a composite material system consisting of carbon fibres as the base substrate and fluorinated polymer as a protective coating layer. This composite structure combines the electrical conductivity and porosity of carbon fibres with the corrosion resistance of fluorinated polymer, achieving both low-energy manufacturing and high corrosion resistance. The fluorinated polymer coating is applied to the carbon fibre surface through impregnation and heat treatment, forming a protective barrier that prevents corrosion while maintaining the substrate's functional properties.
2Reliability
If a high-temperature process is used to manufacture gas diffusion substrates, then corrosion resistance is improved, but energy consumption increases
Solution Approach 1:
The invention applies a fluorinated polymer coating to the carbon fibre substrate before the final heat treatment step. This preliminary protective action ensures that the carbon fibre surface is already protected against corrosion before undergoing the intermediate-temperature heat treatment (900-2000°C), eliminating the need for high-temperature processing while still achieving high corrosion resistance. The coating is cured at lower temperatures (100-300°C) before the carbonisation step, preventing degradation during subsequent processing.
3Adaptability or versatility
If an intermediate-temperature process is used, then flexibility is improved, but corrosion resistance worsens
Solution Approach 1:
The composite structure of carbon fibres with fluorinated polymer coating provides both flexibility and corrosion resistance. The carbon fibre non-woven web maintains the mechanical flexibility needed for fuel cell assembly, while the fluorinated polymer coating layer provides the corrosion protection. The coating is applied in a controlled manner to ensure it does not compromise the flexibility of the underlying carbon fibre structure.
4Reliability
If fluorinated polymer coating is applied to carbon fibres, then corrosion resistance is enhanced, but manufacturing complexity increases
Solution Approach 1:
The fluorinated polymer coating is applied to the carbon fibres during the substrate manufacturing process itself, specifically during the impregnation and heat treatment steps that are already required for substrate formation. The coating application is integrated into the existing manufacturing workflow, and the coating is cured at low temperatures (100-300°C) before the carbonisation step, avoiding the need for separate high-temperature processing steps and simplifying the overall manufacturing 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
The substrate exhibits enhanced corrosion resistance and flexibility, suitable for use in fuel cells, with reduced energy consumption and cost, as demonstrated by electrochemical tests and contact angle measurements.
Implementation Method 1
heating at a temperature of up to 400° C. to provide the gas diffusion substrate
Implementation Method 2
carrying out a heat treatment step to carbonise/graphitise the carbonisable resin at a temperature of from 900° C. to 3000° C.
Implementation Method 3
a porous non-woven web comprising carbon fibres
Implementation Method 4
Gas diffusion substrates must allow the reactants to reach the electrocatalyst layer
Implementation Method 5
the gas diffusion layer must be porous and electrically conducting
Data Source
AI summary
A porous gas diffusion substrate that includes: (a) a porous non-woven web comprising carbon fibers; and (b) a carbonaceous residue; wherein the carbonaceous residue is embedded within the porous non-woven web; (c) a fluorinated polymer; and (d) inert particles wherein at least some of the carbon fibers of the porous non-woven web have a coating comprising the fluorinated polymer and inert particles is disclosed.