An Investigation of Direct Hydrocarbon (Propane) Fuel Cell Performance Using Mathematical Modeling

An improved mathematical model was used to extend polarization curves for direct propane fuel cells (DPFCs) to larger current densities than could be obtained with any of the previous models. DPFC performance was then evaluated using eleven different variables. The variables related to transport phenomena had little effect on DPFC polarization curves. The variables that had the greatest influence on DPFC polarization curves were all related to reaction rate phenomena. Reaction rate phenomena were dominant over the entire DPFC polarization curve up to 100 mA/cm2, which is a value that approaches the limiting current densities of DPFCs. Previously it was known that DPFCs are much different than hydrogen proton exchange membrane fuel cells (PEMFCs). This is the first work to show the reason for that difference. Reaction rate phenomena are dominant in DPFCs up to the limiting current density. In contrast the dominant phenomenon in hydrogen PEMFCs changes from reaction rate phenomena to proton migration through the electrolyte and to gas diffusion at the cathode as the current density increases up to the limiting current density.