Ionic Liquid Modulation in Electrocatalytic Oxygen Reduction

Ionic liquids (ILs) have emerged as versatile modifiers of electrocatalyst interfaces to accelerate the oxygen reduction reaction (ORR) in fuel cells and related devices. By forming a thin liquid film or filling porous support structures, ILs tailor the local chemical environment at the catalyst surface, enhancing oxygen solubility and controlling water management. Their intrinsic properties—high ionic conductivity, low volatility and tunable hydrophilicity—enable suppression of undesired side reactions, mitigation of catalyst oxidation and improved mass transport of reactants and products.

Integration of ILs into platinum-based and non-precious metal catalysts has delivered notable advances. In platinum systems, carefully chosen IL structures inhibit Pt oxide formation and unlock buried active sites, yielding higher specific and mass activities. In carbon-based non-precious catalysts, ILs preferentially occupy micropores to improve wetting, increasing the density of accessible reactive sites. Across all platforms, IL modulation has demonstrated enhanced durability under accelerated stress testing and elevated temperature, promising more robust electrocatalytic layers in practical membrane electrode assemblies.

Research from Nature Portfolio

Recent studies have shown that imidazolium-derived ILs incorporated into high-surface-area carbon supports can dramatically improve both activity and durability of platinum catalysts under realistic membrane electrode assembly conditions. By correlating physical characteristics of the ILs—such as proton conductivity, oxygen solubility and wettability—with electrochemical performance, researchers have revealed how hydrophilic/hydrophobic balance at the triple-phase interface governs oxygen access and water expulsion. Optimised IL–catalyst composites achieved mass activities exceeding 340 A g₋₁Pt at 0.9 V and maintained over 90 % of their potential after thousands of stress cycles, illustrating a pathway to highly efficient, long-lived fuel cell cathodes.

Ionic Liquid Modulation in Electrocatalytic Oxygen Reduction publication trend

The graph below shows the total number of articles in ionic liquid modulation in electrocatalytic oxygen reduction across all publications each year (not limited to Nature Index journals).

Technical terms

Ionic liquid: A salt with a melting point below 100 °C composed of bulky organic cations and anions, notable for high ionic conductivity, negligible vapour pressure and adjustable solvent properties.

Oxygen reduction reaction (ORR): The cathodic process in fuel cells and metal–air batteries in which molecular oxygen is reduced to water or hydroxide in multi-electron steps.

Membrane electrode assembly (MEA): The core component of a polymer electrolyte fuel cell, consisting of catalyst-coated membranes and gas diffusion layers that enable reactant delivery and product removal.

Mass activity: A measure of electrocatalytic performance defined as the current output per unit mass of precious metal (e.g., Pt) at a specified potential.

References

1. Increasing Accessible Active Site Density of Non-Precious Metal Oxygen Reduction Reaction Catalysts through Ionic Liquid Modification. ACS Applied Materials & Interfaces (2023).
2. Revealing the role of ionic liquids in promoting fuel cell catalysts reactivity and durability. Nature Communications (2022).
3. The effect of temperature on ionic liquid modified Fe-N-C catalysts for alkaline oxygen reduction reaction. Journal of Energy Chemistry (2022).
4. Improve the Activity and Stability of PtCo/C Catalyst by Ionic Liquid in Proton Exchange Membrane Fuel Cell. Journal of The Electrochemical Society (2022).
5. Engineering the Electrochemical Interface of Oxygen Reduction Electrocatalysts with Ionic Liquids: A Review. Advanced Energy and Sustainability Research (2020).