A review on the Proton-Exchange Membrane Fuel Cell break-in physical principles, activation procedures, and characterization methods

The proton exchange membrane fuel cell (PEMFC) is an emission-free alternative to the internal combustion engine. Post-assembly, a PEMFC must be “activated’, to elevate and stabilize its performance to a reproducible threshold value. This procedure is costly, time-consuming, and not suited for mass-production. This paper provides a detailed review of the break-in physical principles, activation procedures and characterization methods. First, all sparse knowledge from the literature is translated into a set of activation mechanisms. Activating a cell mainly alters the membrane electrode assembly morphology (e.g. catalyst layer porosity, catalyst size, shape and activity, polymer chain orientation). Second, an in-depth analysis off all break-in methods is provided. Cell components can be pre-activated using steam, acid, plasma or through compression. Dynamic, high temperature/pressure and supersaturated operation promote break-in kinetics. Generating oxidizing and reducing conditions is essential, and is achievable by short circuit, Cyclic Voltammetry, cathode starvation or reactant switch. Uniform activation over the cell surface is obtained with gas flow direction reversal or hydrogen pumping. Compression cycles minimize PEMFC contact resistances. Finally, deficiencies of conventional break-in characterization methods (to measure cell performance and impact on durability) are highlighted. Better reproducibility is achievable using advanced electrochemical characterization, post-mortem and cell output species analysis.