X-Ray Tomographic Microscopy of Phosphoric Acid in High Temperature PEFC Components

In high-temperature polymer electrolyte fuel cells (HTPEFC) the quantity and concentration of phosphoric acid (PA) in the catalyst layer and, if wetted, in the gas diffusion layer (GDL) depends on operating conditions. The distribution, concentration and mobility of the PA relates to performance and durability of the HT-PEFC [1]. X-ray radiography (providing 2D information) has been developed for in-situ investigation of PA in HT-PEFC [2, 3]. However, while 2D imaging has advantages with time resolution, the determination of the PA concentration is tedious due to expansion of the acid with dilution [3]. Therefore, in order to better understand this correlation, X-ray tomographic microscopy workflows are developed to determine the PA properties in the GDL. As a basis the X-ray properties of PA are measured ex-situ in impregnated GDLs.