Effect of humidity of reactants on the cell performance of PEM fuel cells with parallel and interdigitated flow field designs

This study investigates the effects of the relative humidity (RH) of the reactants on the cell performance and local transport phenomena in proton exchange membrane fuel cells with parallel and interdigitated flow fields. A three-dimensional model was developed taking into account the effect of the liquid water formation on the reactant transport. The results indicate that the reactant RH and the flow field design all significantly affect cell performance. For the same operating conditions and reactant RH, the interdigitated design has better cell performance than the parallel design. With a constant anode RH = 100%, for lower operating voltages, a lower cathode RH reduces cathode flooding and improves cell performance, while for higher operating voltages, a higher cathode RH maintains the membrane hydration to give better cell performance. With a constant cathode RH = 100%, for lower operating voltages, a lower anode RH not only provides more hydrogen to the catalyst layer to participate in the electrochemical reaction, but also increases the difference in the water concentrations between the anode and cathode, which enhances back-diffusion of water from the cathode to the anode, thus reducing cathode flooding to give better performance. However, for higher operating voltages, the cell performance is not dependent on the anode RH.