(745b) Engineering the Active Site for Oxygen Electroreduction in Fuel Cells
Polycrystalline Pt5Gd shows a 5-fold increase in ORR activity , relative to Pt. The active phase consists of a compressed Pt overlayer formed by acid leaching. Mass-selected PtxGd nanoparticles present a significant ORR activity enhancement as compared to pure Pt nanoparticles, PtxGd 8 nm showing 3.6 A (mg Pt)-1 mass activity [3,4]. The activity of PtxGd nanoparticles correlates strongly with compressive strain . In order to study the trends in ORR activity for different levels of compression, we studied eight novel polycrystalline Pt-lanthanide and Pt-alkaline earth electrocatalysts . Pt5Tb is the most active polycrystalline Pt-based catalyst ever reported. All the materials present a 3 to 6-fold activity enhancement over Pt. Notably, the experimental ORR activity (kinetic current density measured at 0.9 V vs. the reversible hydrogen electrode, jk (0.9 V vs. RHE)) versus the bulk lattice parameter determined by X-ray diffraction follows a â??volcanoâ? relation. We use the lanthanide contraction to control strain effects and tune the electrocatalytic activity, stability and reactivity.
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