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Enhanced Activity of Oxygen Reduction Reaction on Pr6O11-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 Pr6O11-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 Pr6O11 nanoparticles attached to the surface of the Pt-Pr alloy to form a Pt-Pr/Pr6O11 composite catalyst. Experimental and theoretical studies reveal that the electronic state of Pt in the Pt-Pr/Pr6O11 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 O2. The preeminent intrinsic ORR activity on the Pt-Pr/Pr6O11 catalyst reaches the promoted specific activity (2.01 mA cm-2) and mass activity (1.3 A mgPt-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 mgPt-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.