We adopt an agglomerate catalyst layer (CL) model, and recast it into a condensed form, for optimization of polymer electrolyte fuel cell (PEFC) cathodes. This model captures the essential features in transport processes within the gas diffusion layer (GDL) and accounts for chemical species, proton, and electron transport processes along the CL width, as well as, transport and reaction processes within an individual agglomerate particle in CL. Our reformulated model possesses two limiting behaviors with simpler physics, the pseuodo-homogenous model and a model with negligible polymer-electrolyte membrane (PEM) film thickness agglomerates. The model equations are discretized using a finite difference method and the resulting nonlinear program is linked to a state-of-the-art interior point optimization algorithm, IPOPT [1].
Platinum (Pt) minimization for a specified cell current density is performed, and optimal Pt distribution along CL width is obtained that maximizes the current density by solving multi-zone partial differential equation-constrained optimization problem. For special limiting cases, we have verified, both the simulation and optimization results obtained by Secanell et al.[2,3]. Optimal distribution of parameters was obtained along the CL width using IPOPT by solving the 2N partial differential equations-constrained optimization problem. Our preliminary results show an exponential decay of Pt mass along the CL width from CL-PEM to the CL-GDL interfaces. The decay rate depends strongly on the current density of operation, and increases with current density. We further examined optimal conditions for minimum Pt usage and intend to generalize our analysis to multi-objective optimization for maximizing current density and minimizing Pt amount simultaneously.
Our procedure provides a fast, robust, and efficient solution methodology, which is suitable for system level optimization of PEFC devices.
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