Synthesis of self-assembled PtPdAg nanostructures with a high catalytic activity for oxygen reduction reactions.

Designing a self-assembling structure for a Pt-based catalyst offers a great opportunity to enhance the electrocatalytic performance and maximize the use of precious metals. Herein, we report an etching method based on thermal treatment for the removal of less active metals from Pt-based alloys for the enhancement of the oxygen reduction reaction. PtPdAg nanostructures' self-assembly can be easily controlled to the dimer stage or nanowires by stirring the nanoparticles in formamide with or without potassium iodide under heat for specific times. Thus oxygen reduction reaction-favoring PtPdAg hollow nanoparticle, nanodimer and nanowire catalysts are synthesized, all of which have been demonstrated to be promoting factors for the ORR. In a Pt-based catalyst, the arrangement and configuration of the surface or topmost few layer atoms influence the adsorption of oxygen and activation for ORR. The PtPdAg dimer catalyst shows excellent ORR activity compared to other PtPdAg nanostructures and commercial Pt/C i.e. 7.2 times higher specific activity and 4.1 times higher mass activity. We further carried out DFT calculations and from the results, we conclude that the most chemically inequivalent structure such as PtPdAg/C nanodimer alloys possesses the weakest oxygen binding energy.