Engineering Pt/Ionomer Interface via Strengthening Hydrogen-Bond Network for High-Performance Low-Pt Fuel Cells

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• Proton-exchange membrane fuel cells (PEMFCs) face challenges with limited catalyst utilization due to platinum (Pt) poisoning and mass transport issues at the Pt/perfluorosulfonic acid (PFSA) ionomer interface.
• Existing strategies to reduce poisoning often compromise proton conductivity or oxygen permeability.

Purpose of the Study:

• To introduce hydroxyl-functionalized covalent organic framework (COF-366-OH) as a multifunctional additive to engineer the Pt/ionomer interface in PEMFCs.
• To enhance active-site availability, proton accessibility, and oxygen flux for improved fuel cell performance.

Main Methods:

• Incorporation of COF-366-OH as an additive in the cathode catalyst layer.
• Utilizing the hydroxyl groups in COF-366-OH to form hydrogen bonds with PFSA ionomers, mitigating Pt poisoning and improving ionomer distribution.
• Leveraging the ordered mesopores of COF-366-OH for efficient oxygen diffusion.

Main Results:

• COF-366-OH modified electrodes showed a 19% increase in dry-proton accessibility and a 33% reduction in oxygen-transfer resistance.
• Membrane electrode assemblies with COF-366-OH at ultralow Pt loading (0.05 mgPt cm⁻²) achieved significantly higher peak power densities: 1.67 W cm⁻² (H₂-O₂) and 0.83 W cm⁻² (H₂-air).
• Performance improvements over conventional Pt/C cathodes were 57.5% (H₂-O₂) and 31.7% (H₂-air).

Conclusions:

• COF-366-OH acts as a hydrogen-bond-driven interface engineering strategy for PEMFCs.
• This approach effectively addresses both Pt poisoning and mass-transport limitations.
• Demonstrates a promising pathway for developing highly efficient, low-platinum PEMFCs.