Reaction-Dependent Structure-Activity Relationships in Penta-Twinned Palladium Nanocrystals.

Structural and electronic descriptors are widely used to rationalize electrocatalytic activity, but their predictive relevance can depend on the reaction pathway and adsorbed intermediates involved. Systematic comparisons of this reaction dependence using the same well-defined Pd nanostructures remain relatively limited. Here, two structurally related penta-twinned Pd nanocrystals, penta-twinned Pd nanosheets and decahedral nanocrystals, were comparatively evaluated for the oxygen reduction reaction, ethanol oxidation reaction, and formic acid oxidation reaction. For ORR, the more downshifted d-band center of penta-twinned Pd nanosheets accompanied higher intrinsic activity. In contrast, penta-twinned Pd nanosheets and decahedral nanocrystals exhibited nearly identical EOR-specific activities, together with closely comparable CO-stripping peak potentials. For FAOR, the activity order was reversed, with decahedral nanocrystals showing higher specific activity than penta-twinned Pd nanosheets. These contrasting trends demonstrate that the catalytic consequences of surface geometry and electronic structure depend on the adsorbates and elementary reaction pathways involved, highlighting the need to interpret catalyst descriptors in a reaction-specific context.