Sulfonated MOF‑Enhanced Nafion Membranes for High‑Temperature, Durable Proton Exchange Membrane Water Electrolysis

Area of Science:

• Materials Science
• Electrochemistry
• Chemical Engineering

Background:

• High-temperature proton exchange membrane water electrolysis (HT-PEMWE) offers efficient hydrogen production but requires advanced proton exchange membranes (PEMs).
• Existing PEMs often lack the necessary proton conductivity and long-term stability at high operating temperatures.
• Metal-organic frameworks (MOFs) show promise for proton conduction, but their integration into PEMs for HT-PEMWE is underexplored.

Purpose of the Study:

• To design and fabricate a novel sulfonated MOF-reinforced Nafion (S/N-Nafion) composite membrane for HT-PEMWE.
• To evaluate the proton conductivity, mechanical strength, and dimensional stability of the S/N-Nafion membrane at elevated temperatures.
• To assess the performance and durability of the S/N-Nafion membrane as a solid electrolyte in HT-PEMWE.

Main Methods:

• Fabrication of a sulfonated MOF-reinforced Nafion composite membrane (S/N-Nafion).
• Measurement of proton conductivity at 100 °C and comparison with recast Nafion.
• Electrochemical performance testing of an electrolyzer using S/N-Nafion at 120 °C and 3.0 A cm⁻².
• Durability testing of the S/N-Nafion membrane in an HT-PEMWE cell over 300 hours at 120 °C and 1.0 A cm⁻².

Main Results:

• The S/N-Nafion membrane exhibited a proton conductivity of 154.7 mS cm⁻¹ at 100 °C, double that of recast Nafion (75.6 mS cm⁻¹).
• The composite membrane demonstrated excellent mechanical strength and dimensional stability at high temperatures.
• Electrolyzer performance showed a lower cell voltage (1.59 V) with S/N-Nafion compared to recast Nafion (1.71 V) at 120 °C and 3.0 A cm⁻².
• A remarkably low voltage decay rate of 6.0 µV h⁻¹ was observed during a 300-hour durability test.

Conclusions:

• The S/N-Nafion composite membrane significantly enhances proton conductivity and stability for HT-PEMWE.
• This novel membrane material shows great potential for improving the efficiency and longevity of electrolytic hydrogen production.
• The findings highlight the successful integration of MOFs into Nafion for advanced electrochemical applications.