Numerical investigation of the effects of catalyst layer composition and channel to rib width ratios for low platinum loaded PEMFCs

Abstract

Understanding the interaction between catalyst layer (CL) design parameters is a prerequisite for decreasing the platinum (Pt) loading in proton exchange membrane fuel cells without sacrificing the cell performance, and this requires exploring the origins of transport resistances for low Pt-loaded CLs under various CL design characteristics. In this study, a multiphase non-isothermal pseudo-three-dimensional model is coupled with a detailed electrochemical kinetic sub-model considering the ionic and oxygen transport processes in the cathode CL. The effect of four deterministic CL parameters is investigated to understand the interplay between CL characteristics providing the constant CL porosity. The oxygen transport resistance significantly increases at low Pt-loadings boosting the cathodic overpotential and reducing the cell performance consequently. The addition of bare carbon particles does not modify the cathodic overpotential per se, however, it decreases the limiting current density and, hence, reduces the maximum power density. Lower ionomer content intensifies the ionomer potential loss, whereas a higher content dramatically increases the cathodic overpotential due to the higher transport resistances. Under low Pt-loading criteria, the flow field design parameters are more influential in achieving an active electrochemical reaction. The wider channel improves the oxygen concentration in the CL pores and Pt surfaces; therefore, the cell performance and peak power density improve as well.