Porous Catalyst-Coated Anion Exchange Membranes for Water Electrolysis
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Solution Overview
Problem
Existing anion exchange membranes in electrochemical cells for water electrolysis face challenges in achieving efficient catalytic activity due to the encapsulation of electrocatalysts by polymeric adhesion promoters, leading to reduced accessibility of reactants and increased internal resistance, which affects energy efficiency and catalyst longevity.
Innovation Solution
A method involving the incorporation of particulate inorganic materials into the catalyst coating, followed by leaching to create porous structures, ensuring electrocatalytic centers are accessible while maintaining conductivity and gas permeability, using alkali metals to convert the inorganic material into water-soluble products that can be washed out, leaving behind voids.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If polymeric adhesion promoters are used to bond catalyst particles to the membrane, then catalyst immobilization is improved, but reactant accessibility to catalytically active centers deteriorates
Solution Approach 1:
The patent creates a porous coating layer by incorporating particulate inorganic material (such as silica or alumina) into the polymer adhesion promoter matrix, then leaching out the inorganic material to leave behind pores. This porous structure allows reactants to access the catalytically active centers while the polymer provides sufficient adhesion to immobilize the catalyst particles on the membrane surface.
Solution Approach 2:
The patent uses an intermediary approach by introducing particulate inorganic material as a temporary structure-modifying agent during coating application. This inorganic material serves as a space holder that creates porosity when removed, mediating between the need for strong adhesion (provided by the polymer) and the need for reactant accessibility (provided by the pores).
2Loss of energy
If catalyst coating is applied directly to the membrane, then internal resistance is reduced, but catalyst particle accessibility deteriorates due to encapsulation
Solution Approach 1:
The patent applies a porous coating layer containing pores formed by leached inorganic material. This porous structure reduces internal resistance by providing direct pathways for ion and reactant transport to the catalyst particles, while preventing encapsulation of the catalytically active centers through the created porosity.
3Stability of the object's composition
If inorganic material is incorporated into the coating, then porosity is improved, but manufacturing complexity increases
Solution Approach 1:
The patent incorporates the particulate inorganic material into the coating composition before application to the membrane. This preliminary incorporation allows the inorganic material to be uniformly distributed in the coating matrix, and subsequent leaching creates the desired porosity structure through a simple wash step, avoiding complex post-processing operations.
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 results in a catalytically active anion exchange membrane with improved reactant accessibility, reduced internal resistance, and enhanced energy efficiency, as demonstrated by lower power consumption during water electrolysis.
Implementation Method 1
at least a portion of the particulate inorganic material is reacted within the layer with the alkaline solution to form at least one product
Implementation Method 2
the solvent is depleted from the coating, so that the substrate receives a layer in which the particulate electrocatalyst and the particulate inorganic material different from the electrocatalyst are enriched and immobilized on the substrate via the polymer
Implementation Method 3
The anion exchange membrane transports the hydroxide ions to the anode side, where they are oxidized to oxygen
Data Source
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AI summary
The invention relates to catalytically coated anion exchange membranes and their production. The catalytically active coated anion exchange membranes are used in electrochemical cells, in particular for water electrolysis. The object of the invention was to provide a process for producing an electrocatalytically active coated anion exchange membrane whose coating is porous and thus the electrocatalytically active centers located in the coating are easily accessible to the reactants. A basic idea of the process according to the invention is to incorporate particulate inorganic material into the catalyst coating as a placeholder, to solidify the coating, and then to leach the inorganic material out of the coating. The leaching converts the inorganic material into a water-soluble product that can be easily washed out of the coating.What remains are voids (pores) where the particulate inorganic material was previously located within the coating. The inorganic material therefore assumes the function of a structure-imparting agent within the coating composition, which is lost during the catalytically active coating process.