Shape-Controlled Synthesis of Dumbbell-like Pt–Fe3O4–MnOx Nanoparticles by Governing the Reaction Kinetics

The production of shape-controlled heterometallic nanoparticles (NPs) consisting of Pt and nonprecious metal oxides is crucial to demonstrate the composition–property relationship of NPs. Herein, we report a facile one-pot approach for the controlled synthesis of dumbbell-like Pt–Fe3O4–MnOx and dendritic Pt–MnOx NPs. The key to the success of this synthesis is in changing the quantity of Fe(CO)5 additive to control the reaction kinetics. In the absence of Fe(CO)5, dendritic Pt–MnOx NPs were synthesized through the assembly of small seed NPs. On the other hand, dumbbell-like Pt–Fe3O4–MnOx NPs were obtained in the presence of Fe(CO)5 through controlling the nucleation and growth of Fe and Mn on the Pt NPs, followed by air oxidation. Compared to a Pt/graphene oxide (GO) catalyst, dumbbell-like Pt–Fe3O4–MnOx NPs on GO showed an enhancement of specific activity toward the oxygen reduction reaction owing to the compressive-strain effect exerted on the Pt lattice.