Kinetic modeling reveals catalyst layer drying and elevated currents increase the apparent Tafel slope in PEM fuel cells, indicating water management dictates active platinum site availability.
The recent analytical model for Damjanović kinetics of the oxygen reduction reaction (ORR) is analyzed. The analysis shows that the number of free sites on the Pt surface depends on the water content of the catalyst layer and the ORR overpotential. Drying the catalyst layer shifts the platinum surface towards a blocking state, whereas a high water content facilitates the electrochemical ORR steps. The effect of Pt surface blocking is also observed at higher overpotentials (currents). Catalyst layer drying or an increase in cell current lead to an increase in the apparent Tafel slope.
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Andrei Kulikovsky (2026) studied this question.
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