Anion Exchange Membrane Coating to Minimize Swelling
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Solution Overview
Problem
Existing methods for producing catalytically coated anion exchange membranes (CCM) for alkaline water electrolysis face challenges such as high temperature sensitivity of membrane materials, use of CMR solvents, and the need for transfer substrates that are environmentally harmful and costly, leading to membrane distortion and inefficiencies in industrial-scale production.
Innovation Solution
A direct coating process using a viscous composition containing electrocatalyst, anion-conducting polymer, solvent, and antiswelling agent, where the solvent and polymer are matched to minimize swelling and eliminate the need for transfer films, utilizing CMR-free solvents and ensuring planarity for efficient industrial production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional coating methods using transfer substrates are used, then catalyst coating can be achieved, but membrane distortion and wrinkles occur due to temperature sensitivity
Solution Approach 1:
The patent eliminates the transfer substrate (PTFE film) from the coating process entirely. The catalyst-containing composition is applied directly to the anion exchange membrane without requiring a intermediate transfer carrier, thus removing the source of thermal stress and mechanical distortion that causes wrinkles.
Solution Approach 2:
The patent modifies the coating composition by formulating it with specifically selected solvents and viscosity modifiers that enable direct application at lower temperatures. The composition parameters (viscosity, solvent type, solid content) are optimized to allow direct coating without thermal processing that would distort the temperature-sensitive membrane.
2Strength
If high temperature processing is used for catalyst coating, then adhesion is improved, but membrane material degrades due to temperature sensitivity
Solution Approach 1:
The patent changes the chemical composition parameters of the coating mixture to include adhesion promoters and specifically selected solvents that enable effective catalyst bonding to the membrane at reduced temperatures. The composition formulation allows achieving sufficient adhesion strength without subjecting the temperature-sensitive membrane to high thermal stress.
3Productivity
If CMR solvents are used in coating composition, then coating performance is improved, but environmental impact and safety issues increase
Solution Approach 1:
The patent substitutes CMR (carcinogenic, mutagenic, reprotoxic) solvents with alternative solvents that provide comparable or sufficient coating performance while eliminating harmful effects. The solvent selection focuses on achieving appropriate viscosity, drying characteristics, and catalyst dispersion without using substances classified as CMR, thus improving environmental and safety profiles.
4Ease of manufacture
If transfer films are used for coating, then catalyst application is facilitated, but material costs and environmental harm increase
Solution Approach 1:
The patent removes the transfer film component entirely from the manufacturing process. By enabling direct coating of the catalyst-containing composition onto the anion exchange membrane, the process eliminates material costs associated with PTFE transfer films and their disposal, while also reducing environmental impact from film waste.
5Manufacturing precision
If membrane swelling occurs during coating, then coating application becomes difficult, but planarity is compromised
Solution Approach 1:
The patent selects solvents and composition parameters that minimize osmotic pressure differential between the coating mixture and the membrane matrix. By carefully controlling solvent type, concentration, and addition rate, the process prevents excessive membrane swelling that would compromise planarity, while still allowing sufficient composition penetration for effective catalyst adhesion.
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 process achieves wrinkle-free, efficient, and cost-effective production of CCMs suitable for alkaline water electrolysis, reducing material costs and environmental impact while maintaining high reaction efficiency and safety.
Implementation Method 1
the anion exchange membrane transports the hydroxide ions onto the anode side
Implementation Method 2
the anion-conducting polymer, the membrane material and the solvent are selected to be matched to one another such that the anion-conducting polymer and the membrane material are each soluble in the solvent
Implementation Method 3
the solubility parameters δD, δP and δH of the organic substance determined according to Hansen are in the following ranges
Implementation Method 4
catalytically active or activatable materials (also known as electrocatalysts) are incorporated both on the cathode side and on the anode side
Implementation Method 5
They are generally used to separate reaction products from the anode and the cathode
Implementation Method 6
applying the viscous composition to the anion exchange membrane
Data Source
AI summary
The invention relates to the coating of anion exchange membranes (AEM) with catalytically active substances. The CCM thus obtained are used in electrochemical cells, especially for alkaline water electrolysis. It was an object of the invention to specify a process for producing a CCM by direct coating which maintains the necessary planarity of the AEM and ideally avoids the use of lost films and eschews CMR substances. Swelling shall also be minimized. The process shall also be performable with fluorine-free ionomers. The invention is based on the finding that the addition of certain organic substances has the result that the AEM swells only to a small extent, if at all (antiswelling agent). It has surprisingly been found that substances suitable as antiswelling agents are identifiable by their solubility behaviour, more particularly by their Hansen parameters.