Surface Electrochemistry and Electrocatalysis

Tetrahedral Pd Nanocrystals

We have shown that slightly contracted Pt(111) facets are among the most active surfaces for the ORR. That was motivation to synthesize tetrahedral Pd (PdTH) nanocrystals with cleaned surfaces. Considering the specific requirements of the ORR, their facet-specific electrochemical properties make PdTH a new interesting support for Pt_ML catalysts.

The surfaces of the PdTH core are composed of (111) facets wherein the Pd atoms are highly coordinated and have low surface energy. Our results revealed that in comparison with spherical Pd/C-supported Pt_ML or pure Pt, the PdTH-supported Pt_ML features more surface contraction and a downshift of the d-band relative to the Fermi level. The Pt_ML/PdTH produced a specific- and mass-activity of 0.64 mA/cm² Pt, and 1.02 A/mg_Pt, which are higher than that of the Pt NPs consisting of (110)- and (111)-facets. These geometric- and electronic-effects determine the higher activity of Pt_ML/PdTH/C for the ORR compared to that of Pt_ML/Pd/C. This shape-property interdependence opens up a new approach in research on Pt-based ORR electrocatalysts that may be important for future catalyst development.

Z. Phys. Chem. 226 (2012) 1025–1038