Why is ePTFE preferred for CO2RR gas diffusion layers? Achieve Durable Performance in Carbon Reduction

Expanded polytetrafluoroethylene (ePTFE) is the preferred choice for gas diffusion layers in carbon dioxide reduction reactions (CO2RR) primarily because of its exceptional hydrophobicity and chemical stability. Unlike traditional carbon-based alternatives, its non-conductive structure maintains a robust barrier against liquid water, ensuring consistent performance during electrolysis.

The non-conductive skeleton of ePTFE provides a durable hydrophobic state that prevents the wetting issues common in carbon-based layers. This unique structural stability effectively mitigates flooding and salt deposition, securing long-term pathways for gas transport.

The Limitation of Traditional Materials

Instability of Carbon-Based Layers

Standard gas diffusion layers (GDLs) rely heavily on carbon. While conductive, these traditional carbon-based layers often struggle to maintain their hydrophobic state over time.

The Flooding Risk

When the hydrophobic character of a GDL degrades, liquid electrolyte infiltrates the pores. This phenomenon, known as flooding, blocks the pathways required for carbon dioxide gas to reach the catalyst, severely impeding the reaction.

The Mechanics of ePTFE Superiority

Durable Hydrophobicity

The core advantage of ePTFE lies in its non-conductive skeleton. This structure is inherently resistant to wetting and degradation under harsh electrochemical conditions.

Prevention of Salt Deposition

By maintaining a dry environment within the gas pores, ePTFE effectively prevents salt deposition. In other materials, electrolyte intrusion leads to salt crystallization, which physically clogs the diffusion pathways and degrades performance.

Sustained Gas Transport

The chemical stability of ePTFE ensures that gas transport pathways remain open over the long term. This reliability is critical for continuous operation, where consistent CO2 delivery is required for efficient reduction.

Understanding the Trade-offs

Electrical Conductivity

It is important to note that ePTFE is defined by its non-conductive nature. While the reference highlights this as a benefit for maintaining hydrophobicity (unlike conductive carbon skeletons which degrade), it implies a fundamental design difference.

System Integration

Because the ePTFE skeleton does not conduct electrons, the electrical current required for electrolysis must be managed differently than in fully conductive carbon papers. The focus shifts entirely to using the ePTFE as a physical barrier and gas conduit, rather than an electrical conductor.

Making the Right Choice for Your Goal

The selection of a gas diffusion layer depends on prioritizing stability against specific failure modes.

• If your primary focus is long-term stability: ePTFE is superior because its durable hydrophobic state prevents the flooding and salt buildup that degrade performance over time.
• If your primary focus is preventing pore clogging: ePTFE is the optimal choice as its chemical stability maintains open gas pathways better than carbon-based alternatives.

By leveraging the inert properties of ePTFE, you ensure reliable gas delivery essential for efficient and sustained carbon dioxide reduction.

Summary Table:

Feature	ePTFE Gas Diffusion Layer	Traditional Carbon GDL
Material Base	Non-conductive ePTFE skeleton	Conductive carbon fiber/paper
Hydrophobicity	Inherently durable & stable	Degrades over time
Flooding Resistance	Excellent (Prevents liquid entry)	Moderate to Low (Prone to wetting)
Salt Deposition	Effectively mitigated	High risk of pore clogging
Long-term Stability	High (Maintains gas pathways)	Lower (Due to degradation)

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References

1. Hugo‐Pieter Iglesias van Montfort, Thomas Burdyny. Non-invasive current collectors for improved current-density distribution during CO2 electrolysis on super-hydrophobic electrodes. DOI: 10.1038/s41467-023-42348-6

This article is also based on technical information from Kintek Solution Knowledge Base .