Microstructural Analysis of Electrode Performance in Fuel Cells at Varying Water Contents

Abstract

A novel nucleation based water intrusion algorithm is used to simulate liquid water accumulation in a catalyst layer (CL) microstructure. The algorithm is based on a clustered full morphology model that tracks the liquid water propagation in the CL. A numerical electrode model capable of simulating proton conduction in the ionomer and oxygen transport in the ionomer, gas filled pores and liquid filled pores along with electrochemical reaction at the ionomer-solid interface is used to simulate the electrochemical reactions in the partially saturated CLs at different saturations obtained from the water intrusion algorithm. Simulations on a representative elementary volume of a CL show that the local saturation does not have a significant effect on the current density due to small diffusion length. Analysis of electrochemical performance on a full, 1.8 μm, through-plane cross-section of the CL shows that liquid water accumulation results in mass transport losses of nearly 12% at a saturation of 59.7% even at low volumetric current densities of 4599 A/cm3. The results from the current simulations indicate that a representative elementary volume analysis of the electrochemical performance of the CL at different saturations might not provide insight into the pore-scale electrochemical reactions and full CL simulations might be needed to describe the effects of local flooding in the CL.