Metal nanoparticles play a key role as electrocatalysts in electrochemical energy conversion, electosynthesis and other important fields. The electrocatalytic nanoparticles depend strongly both on their bulk and surface structures. The bulk structure could be tuned by changing the chemical nature and composition, while tuning the surface structure is more difficult, especially the high activity corresponding to high surface energy that leads to disappear the nanoparticles during their growth. We have focused, in recent years, on the structure design and controlled synthesis of nanoparticle electrocatalysts of high surface energy, prepared platinum group metal-based electrocatalysts through the development of electrochemical methods, and investigated systematically their catalytic property towards fuel cell applications.

(1)   Tuning the surface atomic arrangement of well-defined metal nanocatalysts. Well-defined Pt, Pd and Rh nanocrystals enclosed by high-index facets have been successfully obtained by developing electrochemically shape-controlled synthesis, such as tetrahexahedral nanocrystals (THH NCs) enclosed with {hk0} high-index facets, trapezohedral nanocrystals (TPH NCs) with {hkk} high-index facets, triambic icosahedral nanocrystals (TIH NCs) with {hhl} high-index facets and hexoctahedral Pt NCs (HOH NCs) with {hkl} facets. As high-index facets containing a high density of active centers, these NCs exhibit high electrocatalytic activity for small organic fuel oxidation reactions as anodic reactions of direct Fuel Cells.

(2)   Tuning the electronic structure of Pt- and Pd-based nanocatalysts. The electronic structure of NCs catalysts has been turned either by surface decoration using foreign adatoms, or through alloying Pt and Pd with other metals. Different adatoms such as Bi, Ru and Au were used to decorate the THH Pt NCs, and both THH and TPH Pt-based alloy nanocatalysts were prepared by electrochemically shape-controlled synthesis. The THH and TPH alloy NCs preserve the high-index facets while hold a synergy of electronic effect that enhances further the electrocatalytic activity.

Acknowledgements. The studies were supported by NSFC (21361140374, 21229301, and 21321062)

 

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