Core-shell catalysts MEAs

The 10% Ft ML core-shell catalysts were tested in an MEA and gave satisfactory performance with 10 ppm CO in H2 with an electrode loading of 0.018 mg Ft cm-. i A similar surface modification of a Ft core with Ru has been investigated by Crabb et al. They reported that, on reduction, a surface FtRu alloy formed and showed similar CO tolerance to a conventional nanoparticle FtRu alloy. 

Figure 19.8 illustrates the effect of hold time at each current density point in MEA tests using different nanostructured thin film (NSTF) MEAs, showing increased MEA mass activity at 900 mV using 5 s holds (matching RDE values more closely) compared with lower MEA mass activity using 1,050 s holds at each point in the polarization curve [13] similar variations in activity between the MEA and RDE techniques may also be expected for core-shell catalyst materials. 

We have reviewed the family of dealloyed Pt-based nanoparticle electrocatalysts for the electroreduction of oxygen at PEMFC cathodes, which were synthesized by selective dissolution of less-noble atoms from Pt alloy nanoparticle precursors. The dealloyed PtCua catalyst showed a promising improvement factor of 4-6 times on the Pt-mass ORR activity compared to a state-of-the-art Pt catalyst. The highly active dealloyed Pt catalysts can be implemented inside a realistic MEA of PEMFCs, where an in situ voltammetric dealloying procedure was used to constructed catalytically active nanoparticles. The core-shell structural character of the dealloyed nanoparticles was cmifirmed by advanced STEM and elemental line profile analysis. The lattice-contracted transition-metal-rich core resulted in a compressive lattice strain in the Pt-rich shell, which, in turn, favorably modified the chemisorption energies and resulted in improved ORR kinetics. 

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