Platinum-Based PEMFC Electrodes – Can Electrodes with Low Pt Loading be Durable?
Authors: Chattot Raphaël , Asset Tristan , Micoud Fabrice , Nayoze-Coynel Christine , Dubau Laetitia , Maillard Frederic , Chatenet Marian 
Published: February 2020

Proton exchange membrane fuel cells now present performances that enable their commercialization, as demonstrated by the recent release of fuel-cell powered vehicles (forklifts by Plug Power, FCEV Miraï by Toyota, etc.). The goal of PEMFC manufacturers is now to reduce the materials cost of their system and to enhance their durability/reliability, so that they can meet the market requirements. To that goal, highly-efficient oxygen reduction reaction (ORR) electrocatalysts have been developed recently [1-6], these materials mostly originating from the dealloying of PtM/C electrocatalysts (M = Ni, Cu, etc.) initially rich in M. Unfortunately, to date, the scientific community has failed to properly use these materials in an operating PEFMC: neither are their apparent performances approaching those expected from tailored data obtained in rotating disk electrode setup (Figure 1), nor are the materials presenting a sufficient durability in the operating conditions of a PEMFC (see for example [7]).
In this tutorial, some reasons for our present incapacity to operate properly membrane electrode assemblies based on low-Pt-loading of highly-efficient Pt-based electrocatalysts will be discussed. In particular, it will be shown that the degradation mechanisms at stake for present (conventional) PtM/C electrocatalysts (coarsening of the nanoparticles, loss of their shape/texture, selective dissolution of the M element, corrosion of the carbon support, etc.) still operate (at least for some of them) for the advanced electrocatalysts. Besides, the inevitable leaching of the M element raises issues of pollution of the ionomer [8], which is particularly detrimental, not only to the proton conduction, but also to the mass-transport of oxygen to the active sites. In addition, as these electrocatalysts are more active, their optimized operation relies on an emphasized mass-transport of reactants (both H+ and O2) to the catalytic sites, which is not granted for present ionomers and MEA structure [9, 10].

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Figure 1