Polarization Decomposing of Proton Exchange Membrane Fuel Cell Considering Liquid Water Accumulation

Abstract

To realize the high-power density of the proton exchange membrane fuel cell (PEMFC), it is important to explain the influence of liquid water on cell voltage quantitatively, which is still not fully understood yet. This paper proposes a study on polarization decomposing of PEMFC considering effect of liquid water accumulation. The voltage model starts from oxygen transport resistance, which is described as the summation of molecular diffusion resistance, Knudsen diffusion resistance, and transport resistance in the ionomer of the catalyst layer. Then the concentration polarization on the cathodic side of the MEA is described using oxygen transport resistance and liquid water saturation ratio based on Fick’s law. Equations for the influences of liquid water saturation ratio on activation and concentration polarization are deduced mathematically. Based on the model and experiments, a comprehensive polarization decomposition method is proposed. Using this method, cell polarization can be decomposed in detail, and the liquid water saturation ratio under various operation conditions can also be estimated. This work can also be applied to the improvement of fuel cell performance and the evaluation of water content within fuel cells.