A simple equation for in situ measurement of the catalyst layer oxygen diffusivity in PEM fuel cell

We report a method for in situ determination of the oxygen diffusion coefficient D in the cathode catalyst layer (CCL) of a PEM fuel cell. The method is based on our recent model equation for the CCL polarization potential. Two low-current impedance spectra of the CCL should be measured for the same cell current and different oxygen concentrations. We show that D is given by D = ( k - 1 ) bl t / ( k 12 F δ R ccl c ) , where b is the Tafel slope, l t is the CCL thickness, δ R ccl is the difference of the low-frequency CCL resistivities, c is the smallest oxygen concentration used in experiments, and k > 1 is the ratio of two concentrations.