Photothermal deflection measurement of effective gas diffusion coefficient of a porous medium

Abstract.

In this work, an effective gas diffusion coefficient of a porous medium was measured using photothermal deflection (PD) technique. An in-house made Loschmidt diffusion cell with a photothermal-deflection probe were employed to measure the effective gas diffusion coefficient of a gas diffusion layer (GDL) with a porosity ε ≈ 0.7. The concentration evolutions of CO₂ in O₂ with and without the GDL were measured, respectively, using a transverse normal PD technique. The concentration variations were used to deduce the gas diffusion coefficients in the presence and absence of the GDL by solving mass diffusion equations. The effective gas diffusion coefficient of the GDL was calculated from the diffusion coefficients using a model of an equivalent resistance to diffusion and found to be 4.39 × 10^-6 m²s^-1, demonstrating that PD technique can be employed to determine the effective gas diffusion coefficient of a porous medium.