Gas Diffusion Layer Structure for Bonding and Mass Transport
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Solution Overview
Problem
Existing gas diffusion layers in fuel cells and electrolyzers face challenges with unreliable metallurgical bonding between layers, leading to increased electrical resistance and mechanical instability, which affects the efficiency and overvoltage of the electrochemical reaction.
Innovation Solution
A gas diffusion layer comprising a first nonwoven layer of fine metal fibers, a second nonwoven layer with larger metal fibers, and a third porous metal layer, where the second nonwoven layer is metallurgically bonded to both, reducing the size difference and enhancing bonding reliability, and a third porous layer with larger pores for improved mass flow, while the second nonwoven layer acts as an intermediary for stable bonding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a first nonwoven layer of fine metal fibers is used to contact the proton exchange membrane, then the contact area with the PEM is increased and capillarity for mass transport is improved, but the metallurgical bonding to the third porous metal layer becomes unreliable and electrical resistance increases
Solution Approach 1:
The patent introduces a second nonwoven layer of metal fibers as an intermediary layer between the first nonwoven layer (contacting PEM) and the third porous metal layer. This intermediate layer acts as a mediator that facilitates reliable metallurgical bonding between the fine fibers of the first layer and the larger structure of the third layer, thereby reducing electrical resistance and improving bonding reliability.
Solution Approach 2:
The patent applies different fiber diameters to different layers: fine metal fibers (first equivalent diameter) in the first nonwoven layer for optimal PEM contact and capillarity, and larger metal fibers (second equivalent diameter greater than first) in the second nonwoven layer for improved metallurgical bonding. This local differentiation of fiber qualities optimizes each layer's specific function while resolving the bonding resistance contradiction.
2Productivity
If the third porous metal layer has larger pores for efficient planar mass flow, then mass transport is improved, but direct metallurgical bonding with the first nonwoven layer becomes troublesome and unreliable
Solution Approach 1:
The second nonwoven layer of metal fibers serves as an intermediary between the first nonwoven layer and the third porous metal layer with larger pores. This intermediate layer with intermediate pore size and fiber diameter enables reliable metallurgical bonding while maintaining the large pore structure of the third layer for efficient mass transport, thus resolving the contradiction between productivity and manufacturing ease.
3Productivity
If the thickness of the third porous metal layer is increased to provide larger cross section for planar mass flow, then mass transport efficiency is improved, but the overall device complexity increases
Solution Approach 1:
The gas diffusion layer is segmented into three distinct porous metal layers with different functions: the first nonwoven layer for PEM contact and capillarity, the second nonwoven layer for metallurgical bonding, and the third porous metal layer with larger pores and increased thickness for planar mass flow. This segmentation allows each layer to be optimized for its specific function, achieving high productivity while managing device complexity through functional specialization.
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 configuration reduces ohmic resistance, improves mechanical stability, and decreases overvoltage by ensuring reliable metallurgical bonding and efficient mass transport, enhancing the performance of fuel cells and electrolyzers.
Implementation Method 1
the fine pores - present because of the use of the fine fibers in the first nonwoven layer - allow capillarity for efficient mass transport to and from the reaction sites at the PEM
Implementation Method 2
The second nonwoven layer is metallurgically bonded to the first nonwoven layer and to the third porous metal layer
Implementation Method 3
The metallurgical bonds between the layers are important, as such bonds provide for a low electrical resistance between the layers
Data Source
Figure 1~2
Figure 3
AI summary
A gas diffusion layer for an electrolyser or for a fuel cell comprises a first nonwoven layer of metal fibers provided for contacting a proton exchange membrane, a second nonwoven layer of metal fibers, and a third porous metal layer. The first nonwoven layer of metal fibers comprises metal fibers of a first equivalent diameter. The second nonwoven layer of metal fibers comprises metal fibers of a second equivalent diameter. The second equivalent diameter is larger than the first equivalent diameter. The third porous metal layer comprises open pores. The open pores of the third porous metal layer are larger than the open pores of the second nonwoven layer of metal fibers. The second nonwoven layer is provided in between and contacting the first nonwoven layer and the third porous metal layer. The second nonwoven layer is metallurgically bonded to the first nonwoven layer and to the third porous metal layer. The thickness of the third porous metal layer is at least two times – and preferably at least three times – the thickness of the first nonwoven layer.