In situ diagnostic of two-phase flow phenomena in polymer electrolyte fuel cells by neutron imaging. Part B. Material variations

The formation of liquid water in operating polymer electrolyte fuel cells (PEFC) of industrial and laboratory size has been investigated by in situ neutron imaging. The influence of the materials chosen for the structural components of the cell on droplet formation and transport in flow fields and on liquid formation in gas diffusion layers has been studied. The changing of the cathodic gas diffusion layer material allowed the relationship between materials, liquid accumulation, and electrochemical performance to be examined. It has been shown that material choice has considerable bearing on the presence of liquid inside the porous structures and the electrochemical characteristics. A simplified quasi one-dimensional cell with an active area of 25 cm2 was used for materials comparison, and the results were related to technically relevant operating conditions - where inhomogeneities have to be considered - by subsequent examination of cells with an active area of 100 cm2.