Does the platinum-loading in proton-exchange membrane fuel cell cathodes influence the durability of the membrane-electrode assembly?†

MEAs with various cathode Pt loadings were elaborated and aged using a multiple-stressor accelerated stress test (AST) in a segmented PEMFC. The thinnest (lowest Pt loading) cathodes have lower initial activity, owing to larger oxygen reduction reaction hindrance and oxygen transport resistance. Although the lowest cathode Pt loadings initially degrade faster, the overall loss of ECSA at end-of-test is nearly similar whatever the cathode Pt loading, with no local heterogeneities of aging detected along the gas channels. The cathode Pt/C catalyst degrades mostly by Ostwald ripening (which seems more pronounced for lower cathode Pt loading) and nanoparticles agglomeration, owing to superficial carbon functionalization and related Pt crystallite migration: no consequent carbon corrosion is witnessed in this AST. Also, the oxidized Pt²⁺ ions formed by Pt corrosion diffuse/migrate roughly in a similar manner through the membrane for all cathode Pt loadings, and are re-deposited by crossover H₂ close to the cathode|membrane interface. Overall, the mechanisms of Pt/C degradation are not depending on the cathode Pt loading for the chosen AST.

Keywords: Proton exchange membrane fuel cells (PEMFC); Cathode catalyst layer (CL); Platinum loading; Durability.