A multiscale model for proton exchange membrane fuel cells with order-structured catalyst layers

Abstract

• A multiscale model to investigate the mass transport characteristics of PEMFCs with ordered catalyst layers is developed. • Local oxygen transport resistances show an inverse proportional function of Pt loading. • A logarithmic normalized method is proposed to calculate local oxygen transport resistance in the limiting and non-limiting current conditions. • The ionomer-Pt interfacial resistance is dominant in the limting current conditions. Order-structured catalyst layers offer a promising solution to substantially reducing the Pt loading while maintaining the performance of proton exchange membrane fuel cells (PEMFCs). In this work, we develop a multiscale model to investigate the mass transport characteristics of a PEMFC with ordered catalyst layers. A Langmuir adsorption equation is proposed to describe the ionomer-Pt interfacial transport process in a local oxygen transport sub-model, which is integrated into a two-dimensional, two-phase cell-scale model. Simulations are validated against experimental data in the literature. Results show that the fuel cell with ordered catalyst layers can achieve much higher performance than that with conventional catalyst layers, due to the enhanced bulk and local oxygen transport. Moreover, both local oxygen transport resistances of ordered and conventional catalyst layers show an inverse proportional function of Pt loading, while the ordered catalyst layers exhibit a much smaller local oxygen transport resistance than their conventional counterparts. Under limiting current conditions, oxygen transport across the ionomer-Pt interface dominates the local transport resistance, thus hindering the cell performance. The effects of pore size of the ordered catalyst layers and relative humidity on the oxygen transport characteristics and cell performance are also investigated. This work provides new insights into the mass transport mechanisms in ordered catalyst layers, which will facilitate the development of high-performance PEMFCs with low Pt loading.