3D Visualization of Liquid Water in Catalyst Layer Using X-Ray CT

Abstract

Polymer electrolyte fuel cells (PEFCs) play an important role in solving environmental and energy problems, and are required to perform at higher current density to achieve the cost reduction. Under a certain operating condition, however, water condenses and accumulates in the cathode catalyst layers (CLs) and the gas diffusion layers (GDLs). In such cases, the oxygen transport is prevented by liquid water accumulation, and therefore more precise water management methods are required to perform at higher current density. In this study, we perform 3D visualization of liquid water not only in GDLs but also in CLs in order to study the mechanism of generation-discharge mechanism of liquid water in the membrane electrode assembly (MEA) in more detail.In this study, X-ray measurements were performed using laboratory-based X-ray imaging equipment Rigaku nano3DX. The fuel cell with an active area 1.0 × 1.0 mm2 was used. The GDLs used were Toray TGP-H-060 coated with micro porous layer (MPL). Considering X-ray transparency, CLs with relatively lower Pt loading (10wt%) was applied to the membrane. The images modification, which corrects displacements of membrane due to swelling, were performed to compare the wet case and the dry case. The present operation was performed under room temperature.The figure shows liquid water of cathode CL integrated in the thickness direction at current density of 1.0 A/cm2. It is observed that liquid water in CL accumulates above the Rib. In addition, it was found that liquid water in CL accumulates in the regions close to the liquid water accumulating in the cracks of MPL. Figure 1