Electronic Structure Simulations of the Platinum/Support/Ionomer Interface in Proton Exchange Membrane Fuel Cells

Abstract

In this work, we present electronic structure calculations to quantify and rationalize the interactions between catalyst, support, ionomer, and active molecular species in proton exchange membrane fuel cells. Quantifying interaction energies and their scaling with size allows us to rationalize and compare the fundamental driving forces behind structure formation and material properties. Our basic approach involves simplifying the most important interactions between different components using smaller model systems, such as limited-size platinum nanoparticles, polyaromatic hydrocarbons (graphene flakes), and fragments of various functional units of the Nafion ionomer while applying unbiased first-principles (density functional theory) simulation methods. To guide this quantification, we propose an analysis based on the linear dependence of interaction energy on the number of interacting atom pairs in the interface. This enables us to compare and categorize interactions between catalyst, ionomer, and support with interactions like catalyst–reactant and catalyst–catalyst poison.