High oxygen reduction reaction activity of Pt5Pr electrodes in acidic media

Advancing understanding of oxygen reduction reaction (ORR) electrocatalysis at platinum and platinum alloy surfaces is of great importance for the energy provision schemes that involve fuel cells. While the activity trends of model single crystal electrocatalysts are well-understood, there are still numerous open questions in the case of polycrystalline and nanostructured catalytic materials. The resulting ORR activity in these systems is frequently governed by so-called strain effects and surface imperfections, which are difficult to predict and interpret. Nevertheless, in some cases ORR activity can be correlated with relatively simple semi-empirical parameters such as the radii of the solute element in platinum alloys. In this work, using a simple radii-related consideration we discover high ORR activity of polycrystalline Pt5Pr alloy, which demonstrates similar to 4-fold improvement over pure Pt, overcoming or being similar to that of polycrystalline Pt3Ni and many other polycrystalline Pt-alloys, respectively. We explain the resulting ORR activity in terms of excessive compressive strains in a thin Pt-rich layer at the surface of Pt5Pr.