In situ diagnostic of liquid water distribution in cathode catalyst layer in an operating PEMFC by high-resolution soft X-ray radiography

To investigate the water transport behavior in the cathode catalyst layer (CCL) of an operating proton exchange membrane fuel cell (PEMFC), we examined transversal liquid water distributions in the CCL by using high-resolution soft X-ray radiography. The liquid water concentration gradient across the CCL was observed at a spatial resolution of 1.5 μm. More liquid water accumulated in the CCL at the gas diffusion layer side than at the polymer electrolyte membrane side. The effect of accumulated liquid water in the CCL on the charge-transfer resistance was confirmed by electrochemical impedance spectroscopy. Liquid water accumulation in the CCL corresponds to deterioration of charge-transfer in the electrode.

► We investigated the liquid water distribution in a PEMFC cathode catalyst layer.
► We used high-resolution soft X-ray radiography to observe the liquid water.
► More liquid water accumulated in the catalyst layer at the gas diffusion layer side.
► The accumulated liquid water increased the charge-transfer resistance.