  Ever since modeling has become a mature part of proton exchange membrane fuel
cell (PEMFC) research and development, it has been plagued by significant
uncertainty lying in the detailed knowledge of material properties required.
Experimental data published on several transport coefficients are scattered
over orders of magnitude, even for the most extensively studied materials such
as Nafion membranes, for instance. For PEMFC performance models to become
predictive, high-quality input data is essential. In this bipartite paper
series, we determine the most critical transport parameters for which accurate
experimental characterization is required in order to enable performance
prediction with sufficient confidence from small to large current densities. In
the first part, a macro-homogeneous two-phase membrane-electrode assembly model
is furnished with a comprehensive set of material parameterizations from the
experimental and modeling literature. The computational model is applied to
demonstrate the large spread in performance prediction resulting from
experimentally measured or validated material parameterizations alone. The
result of this is a ranking list of material properties, sorted by induced
spread in the fuel cell performance curve. The three most influential
parameters in this list stem from membrane properties: The Fickean diffusivity
of dissolved water, the protonic conductivity and the electro-osmotic drag
coefficient.
