(Invited) Ionic Liquid Interlayer for Enhanced Oxygen Reduction Reaction Electrocatalyst Activity and Durability

Abstract

After a period of dynamic advancement in oxygen reduction reaction (ORR) electrocatalyst activity, through the development of unique material nano-architectures and compositional gradients, we have seen a stagnation in the general performance metrics, especially at the membrane electrode assembly (MEA) level. We argue that in order to push past our current plateau, we must look beyond the catalyst material and develop strategies to manipulate and optimize the interface between the catalyst and the aqueous electrolyte. Here we will present our work in the development of ionic liquid interlayers, on the order of 1 nm in thickness, on nanostructured and single crystal electrocatalysts, which are found to yield significant enhancements in both ORR activity and durability. It is through the manipulation of interfacial water, due to the presence of the hydrophobic/protic ionic liquid interlayer, that a more optimal solvation of adsorbed intermediates is achieved, resulting in enhanced ORR activity, and a relative decrease in the oxophilicity of the surface, enhancing the potential dependent stability of the catalyst. Additionally, the low metal ion solubility within the ionic liquid interlayer increases the barrier for metal dissolution. We will present our analysis of the mechanism of activity and durability enhancement as well as demonstrate the unique advantages of ionic liquid interlayers in proton exchange membrane fuel cell (PEMFC) catalyst layers.