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Synthesis of Ionic Liquid Based Electrolytes, Assembly of Li-ion Batteries, and Measurements of Performance at High Temperature
Published on: December 20, 2016
Protic phosphonium-based ionic liquids for intermediate temperature polymer electrolyte membrane fuel cells
T Bertolin1, V Theußl1, R Leiritz2
1Institute of Energy Technologies - Electrochemical Processes Engineering (IET-4), Forschungszentrum Jülich GmbH 52428 Jülich Germany c.korte@fz-juelich.de.
RSC Advances
|July 24, 2026
Summary
Protic sulfoalkylphosphonium-based ionic liquids (PPILs) show promise for intermediate-temperature polymer electrolyte membrane fuel cells (IT-PEMFCs). These PPILs offer improved oxygen solubility and higher current densities, simplifying water and heat management in fuel cell technology.
Area of Science:
- Electrochemistry
- Materials Science
- Chemical Engineering
Background:
- Intermediate-temperature polymer electrolyte membrane fuel cells (IT-PEMFCs) operating around 100 °C offer simplified water and heat management compared to traditional PEMFCs.
- Anhydrous proton conduction is crucial at elevated temperatures, driving research into novel electrolyte materials.
- Ionic liquids, particularly protic sulfoalkylphosphonium-based ionic liquids (PPILs), are emerging as promising electrolytes due to their anhydrous proton conductivity.
Purpose of the Study:
- To investigate the potential of six protic sulfoalkylphosphonium-based ionic liquids (PPILs) as electrolytes for IT-PEMFCs.
- To evaluate the impact of different anions ([TfO], [TFSI]) and cations ([tBP], [tBB], [tOP]) on PPIL properties.
- To assess oxygen solubility, diffusivity, and limiting current densities for the Oxygen Reduction Reaction (ORR).
Main Methods:
- Synthesis and characterization of six novel PPILs.
- Measurement of oxygen solubility and diffusivity in PPILs at elevated temperatures.
- Electrochemical evaluation of PPILs for ORR performance, including limiting current density determination.
Main Results:
- PPILs exhibited significantly higher oxygen solubility (10⁻⁵ mol cm⁻³) compared to N-analogues (10⁻⁶ mol cm⁻³) at 120 °C.
- Oxygen diffusivities varied, with [TfO]-based PPILs showing lower values than their N-analogues, while [TFSI]-based PPILs had similar values.
- Higher limiting current densities for ORR (10⁻¹ mA cm⁻²) were observed with PPILs compared to N-analogues (10⁻² mA cm⁻²) at 80 °C.
- The thermal stability of [TfO]-based PPILs was found to be sufficient for IT-PEMFC applications.
Conclusions:
- Protic sulfoalkylphosphonium-based ionic liquids demonstrate excellent potential as electrolytes for anhydrous operation in IT-PEMFCs.
- The investigated PPILs offer advantages in oxygen transport and ORR kinetics, crucial for efficient fuel cell performance.
- These findings support the advancement of PPILs as a viable technology for next-generation fuel cells.
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