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 methods to reduce poisoning often compromise proton conductivity or oxygen permeability.

Purpose of the Study:

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

Main Methods:

• Utilized COF-366-OH as an additive to modify the Pt/ionomer interface in PEMFC cathodes.
• Investigated the role of hydroxyl groups in COF-366-OH in forming hydrogen bonds with PFSA ionomers to mitigate Pt poisoning and improve ionomer distribution.
• Assessed the impact of COF-366-OH's ordered mesopores on oxygen diffusion.

Main Results:

• COF-366-OH addition led to a 19% increase in dry-proton accessibility and a 33% reduction in oxygen-transfer resistance.
• At ultralow Pt loading (0.05 mgPt cm⁻²), the COF-366-OH modified cathode achieved peak power densities of 1.67 W cm⁻² (H₂-O₂) and 0.83 W cm⁻² (H₂-air).
• These represent significant performance improvements of 57.5% and 31.7% compared to conventional Pt/C cathodes.

Conclusions:

• COF-366-OH acts as an effective interface engineering strategy for low-Pt PEMFCs.
• The hydrogen-bond-driven approach successfully addresses both Pt poisoning and mass-transport limitations.
• This work offers a promising direction for developing highly efficient and cost-effective PEMFCs.