Dependence of vapor and liquid water removal on cross-flow in polymer electrolyte fuel cell investigated by operando synchrotron X-ray radiography

Abstract

Excessive liquid water in the gas diffusion layer (GDL) of a polymer electrolyte fuel cell is known to degrade the performance. Cross-flow through the GDL is applied to reduce the liquid water in the GDL. However, cross-flow has a disadvantage with a high pressure drop and is difficult in practical use. Controlled cross-flow has the possibility to reduce the liquid water, while the pressure drop remains acceptable for application. This study experimentally quantifies the amount of liquid water in the GDL by operando synchrotron X-ray radiography and the cross-flow rate with different GDL thicknesses. The relationship between the cross-flow rate and the amount of liquid water indicates that liquid water could be reduced by a smaller pressure drop with a thicker GDL. In addition, vapor removal by cross-flow is evaluated, and the relative humidity of cross-flow does not increase to 100% after flowing through the GDL containing liquid water.