Gas Diffusion Layer Structure to Prevent Electrolyser Flooding
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Solution Overview
Problem
Conventional gas diffusion electrodes experience flooding issues due to low solubility of gaseous reactants in liquid electrolytes, leading to mass transfer limitations and decreased electrochemical conversion efficiency.
Innovation Solution
A non-porous, gas-permeable gas diffusion layer is used, comprising a selective skin layer and a microporous support, which operates on a sorption-diffusion mechanism to minimize mass transfer resistance and prevent liquid crossover, allowing for higher gas permeance and reduced flooding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a porous gas diffusion layer is used to supply gas reactants, then gas permeability is improved, but liquid electrolyte flooding occurs leading to mass transfer limitations
Solution Approach 1:
The gas diffusion layer is designed with spatially varying properties: a first region with higher porosity (30-70%) for optimal gas transport, and a second region with lower porosity (10-40%) to prevent liquid flooding. This local differentiation allows simultaneous achievement of high gas permeability and flood resistance without compromising overall electrode performance.
Solution Approach 2:
The gas diffusion layer employs a composite structure combining carbon-based materials (for conductivity and structural stability) with PTFE coating (for hydrophobicity and liquid repellency). This composite approach enables the layer to simultaneously provide electronic conductivity, gas permeability, and liquid blocking functionality, resolving the contradiction between gas supply and flood prevention.
2Object-affected harmful factors
If hydrophobic components are added to prevent flooding, then liquid crossover is reduced, but gas diffusion resistance increases
Solution Approach 1:
The PTFE coating is applied with controlled spatial distribution and concentration gradients. The first region contains lower PTFE content (5-20 wt%) to maintain gas diffusion pathways, while the second region has higher PTFE content (20-40 wt%) to provide enhanced liquid blocking. This local quality variation resolves the contradiction between flood prevention and gas transport.
Solution Approach 2:
The patent optimizes PTFE coating parameters including thickness (1-10 μm), porosity (10-40%), and hydrophobicity contact angle (120-150°). By precisely controlling these parameters, the coating provides sufficient liquid repellency while maintaining adequate gas permeability, thus resolving the contradiction between preventing liquid crossover and maintaining gas diffusion rate.
3Quantity of substance
If porosity is increased to enhance gas transport, then gas availability improves, but liquid electrolyte intrusion increases causing flooding
Solution Approach 1:
The gas diffusion layer features a gradient porosity structure where the first region (closer to gas inlet) has higher porosity (30-70%) to maximize gas availability and transport, while the second region (closer to catalyst layer) has lower porosity (10-40%) to act as a liquid barrier. This spatial differentiation allows high gas availability without compromising flood resistance.
Solution Approach 2:
The PTFE coating acts as an intermediary layer between the porous carbon substrate and the liquid electrolyte. It modifies the surface properties to be hydrophobic, preventing liquid electrolyte intrusion into the porous structure while allowing gas molecules to pass through. This intermediary function resolves the contradiction between high porosity for gas transport and low porosity for liquid blocking.
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 approach enhances electrochemical performance by increasing current densities, Faradaic efficiencies, and extending electrode lifetime while maintaining low flooding levels, even at higher operating pressures.
Implementation Method 1
operates on a sorption-diffusion mechanism to minimize mass transfer resistance
Implementation Method 2
operates on a sorption-diffusion mechanism to minimize mass transfer resistance
Implementation Method 3
The hydrophobic component, typically polytetrafluoroethylene, aids in avoiding crossover of liquid electrolyte to the gas phase
Data Source
AI summary
The invention is directed to a process for electrochemically converting a reactant gas, to an electrolyser, to a gas diffusion electrode, to a method for producing a gas diffusion electrode, to a gas diffusion layer, and to the use of said gas diffusion layer and/or gas diffusion electrode.The process comprises reacting a reactant gas at a gas diffusion electrode to form a product gas and/or a liquid product,wherein the gas diffusion electrode comprises a gas diffusion layer comprising a non-porous layer that is permeable to carbon monoxide and/or carbon dioxide gas, and a porous layer, andthe reactant gas comprises carbon monoxide and/or carbon dioxide.