Enhanced Activity of Oxygen Reduction Reaction on Pr 6 O 11 -Assisted PtPr Alloy Electrocatalysts.

Pt-based alloy catalysts for oxygen reduction reaction (ORR) with outstanding performance have been well-studied in recent years. Among these, Pt-lanthanide alloy catalysts have been developed with quite a competitive ORR activity. However, to promote practical applications of a proton-exchange membrane fuel cell (PEMFC), catalysts with superior activity are still being explored. Herein, we present the Pr 6 O 11 -assisted Pt-Pr catalyst exhibiting further improved ORR activity than the state-of-the-art Pt/C. A simple annealing treatment is applied after the synthesis of the Pt-Pr alloy, obtaining Pr 6 O 11 nanoparticles attached to the surface of the Pt-Pr alloy to form a Pt-Pr/Pr 6 O 11 composite catalyst. Experimental and theoretical studies reveal that the electronic state of Pt in the Pt-Pr/Pr 6 O 11 system is modified. It was found that the strong oxophilicity of Pr adjusts the active site of Pt and promotes the adsorption and dissociation of O 2 . The preeminent intrinsic ORR activity on the Pt-Pr/Pr 6 O 11 catalyst reaches the promoted specific activity (2.01 mA cm -2 ) and mass activity (1.3 A mg Pt -1 ), which were 5.91- and 5.90-fold higher than those obtained by the state-of-the-art Pt/C catalyst (0.34 mA cm -2 and 0.22 A mg Pt -1 ). This study provides us with an idea that the ORR performance of Pt-based alloy could be enhanced with the assistance of the metal oxide phase.