Proton exchange membrane fuel cells (PEMFCs) are a promising means to decarbonize the global vehicle fleet, but commercialization is currently limited by costly Pt catalysts. PEMFCs with lower Pt loading typically suffer anomalous performance losses. Previous studies have agreed that poor device performance is linked to complex physiochemical processes in the cathode catalyst layer (CL), more specifically to sluggish proton and/or oxygen transport through the nano-thin Nafion ionomer in the CL. Previous studies have also identified that the properties of nano-thin Nafion, which moves reactants and products (protons, H2O, and O2) to and from the catalyst, vary from those measured for thicker membranes. However, research has not yet definitively connected CL polymer properties with PEMFC limitations in low-loaded cells, nor found a means to address the limitations for low cost, high-performance PEMFCs.<br/><br/>In this presentation, we will describe efforts to quantify thin-film Nafion structure-property relationships and incorporate these relationships into PEMFC numerical simulations to identify advantageous catalyst layer designs. Structure-property relationships are based on in situ neutron reflectometry and conductivity measurements on thin film Nafion, and result in a model that calculates the conductivity and O2 diffusion coefficients as a function of temperature, water uptake, film thickness, and underlying substrate (Pt or carbon). Incorporating these into a PEMFC cathode half-cell model improves the model fit to PEMFC data with varying Pt loading and provides new insight into the complex coupling between kinetic, mass transport, and Ohmic losses in low-Pt-loaded PEMFC cathodes. Finally, we present a parametric study of PEMFC CL design parameters with low Pt loading. Results identify functionally graded catalyst layer designs that could significantly improve PEMFC power density with low Pt loading.

Structure-property relationships for thin-film Nafion to improve catalyst layer design in low Pt loaded PEMFCs

Fall 2022 abstracts, posters, and presentations will launch in mid-September.

ACS Fall 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.