Freestanding Penta-Twinned Palladium Nanosheets.

Control over the morphology of nanomaterials to have a 2D structure and manipulating the surface strain of nanostructures through defect control have proved to be promising for developing efficient catalysts for sustainable chemical and energy conversion. Here a one-pot aqueous synthesis route of freestanding Pd nanosheets with a penta-twinned structure (PdPT NSs) is presented. The generation of the penta-twinned nanosheet structure can be succeeded by directing the anisotropic growth of Pd under the controlled reduction kinetics of Pd precursors. Experimental and computational investigations showed that the surface atoms of the PdPT NSs are effectively under a compressive environment due to the strain imposed by their twin boundary defects. Due to the twin boundary-induced surface strain as well as the 2D structure of the PdPT NSs, they exhibited highly enhanced electrocatalytic activity for oxygen reduction reaction compared to Pd nanosheets without a twin boundary, 3D Pd nanocrystals, and commercial Pd/C and Pt/C catalysts.