Precise measurement of effective oxygen diffusivity for microporous media containing moisture by review of galvanic cell oxygen absorber configuration

The performance of polymer electrolyte fuel cells is influenced by moisture control in their gas diffusion layer (GDL). Therefore, to achieve suitable control, it is necessary to clarify the mass transfer characteristics within a GDL by high precision measurement of oxygen diffusivity. We have previously proposed that measurement of the effective oxygen diffusivity in a GDL containing moisture can be achieved using a galvanic cell oxygen absorber and demonstrated this to be an effective technique for the measurement of microporous media. However, the diffusion resistance of a single dry GDL is low, so that the margin of error in the oxygen diffusivity measurement is high. In this study, high precision measurement of the oxygen diffusivity in a GDL was developed further by analysis of the major error factors and modification of the measurement apparatus configuration. The results indicate a reduction in the maximum measurement error from 50% to 20% for a dry GDL with minimal diffusion resistance.