Advanced In-situ Analysis of Reactant Gas Partial Pressure at Catalyst Layer/PEM Interfaces

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An advanced in-situ analysis technique for evaluating the reactant gas partial pressure at the catalyst layer/polymer electrolyte membrane (CL/PEM) interfaces has been developed using a Pt probe inserted into the PEM. The results showed that the H2 partial pressure drop through the anode diffusion electrodes was significant and was affected by the relative humidity of the reactant gases. The O2 partial pressure drop through the cathode diffusion electrodes was affected by both the relative humidity of the reactant gases and the O2 partial pressure in the gas flow channels. The effect of the O2 partial pressure at the cathode CL/PEM interfaces on performance was also investigated. The results suggest that IR loss due to proton transport in the cathode might dominate performance under high O2 concentration conditions. On the other hand, the O2 partial pressure might dominate performance under low O2 partial pressure.