Simulative Investigation on Local Hydrogen Starvation in PEMFCs: Influence of Water Transport and Humidity Conditions

Abstract

Durability targets of automotive polymer electrolyte membrane fuel cells (PEMFCs) could be crucially threatened by local hydrogen starvation, typically induced by local blockage of gas channels. To gain a deep insight on the evolving of such starvation events and related carbon corrosion losses, we have developed a numerical model with transient nature that includes detailed transport phenomena and electrochemistry. Special focus is on water transport and sensitivity of relative humidity (RH) on both anode and cathode sides, whose influences were commonly neglected in starvation-related modeling studies. Utilizing the model, we show the dominating effect of in-plane hydrogen convection within the anode gas diffusion layer, which is again determined by the accumulation of other gas species including water vapor. We demonstrate how this is again linked with the water management throughout the fuel cell. Furthermore, water transport is shown to affect local current density and membrane oxygen permeability, both being critical influential factors regarding the severity of a local starvation event. The developed model is validated by conducting transient current density distribution measurements. As RH levels are crucial operational conditions within automotive PEMFCs, this work serves as useful input towards development of future operation strategies for better PEMFC durability.