Three-dimensional reconstruction of coarse-dense dual catalyst layer for proton exchange membrane fuel cells

An exploration on self-humidifying membrane electrode assembly in proton exchange membrane fuel cells (PEMFCs) has attracted great attention for their potential use in the practical system. Recently, several researchers succeeded in improving the self-humidifying performance with multiple-layered electrodes, by retaining the liquid water, despite the fact that mechanistic details in such electrode structures are yet in vague. In this work, we report a three-dimensional reconstruction of the dual-layered electrode for PEMFCs. The PEMFC catalyst layer fabricated by a serial decal-transfer method is characterized by the focused ion beam-scanning electron microscope; the segmented images on the electrode structures are integrated by the tomography analysis. This approach allows a complete consideration of the electrode morphology, providing several key pore-structural information, e.g., porosity, diffusivity and tortuosity. As compared with the inner catalyst layer, the outer catalyst layer may significantly reduce the diffusion rate and thus promote the structural-driven retention of liquid water during the PEMFC operation.