Abstract:
A comprehensive agglomerate model for the cathode catalyst layer (CCL) performance in a
polymer electrolyte membrane fuel cell (PEMFC) has been developed. The overall transport
phenomena and the electrochemical kinetics of each species namely oxygen, electrons and
protons inside the CCL is considered in this model. The model is developed in such a way that it
can be reduced to a pseudo-homogenous model when the agglomerate radius approaches zero.
The validation of the model is done with the experimental results of Ticianelli et.al [39] .This is
done by first estimating the value of agglomerate radius, ionomer film thickness and ionomer
volume fraction for one set of operating conditions and then validating the model for another set
of operating conditions. The agglomerate model is compared with pseudo-homogenous model. It
is found that the pseudo-homogenous model over predicts the cell voltage, particularly at high
current densities. The effect of two operational parameters namely operating temperature and
oxygen pressure and five structural parameters namely agglomerate radius, ionomer film
thickness, platinum loading, ionomer volume fraction and catalyst layer (CL) thickness on
PEMFC performance is investigated. It is found that the increase in operating temperature and
pressure improves the performance of PEMFC while the increase in agglomerate radius and
ionomer film thickness has a negative influence on PEMFC performance. Optimum values of
platinum loading and ionomer fraction is calculated for three overpotentials: 0.3, 0.6 and 0.9 V.
The results show that the optimum platinum loading decreases while the optimum ionomer
fraction increases with increase in overpotential. The utilization of the CL is found to decrease
with increase in CL thickness.
