Lattice contracted Pd-hollow nanocrystals: Synthesis, structure and electrocatalysis for formic acid oxidation

• Pd-hollow/C was prepared via galvanic replacement reaction with Kirkendall effect.
• The electron transfer originally results in the lattice contraction in the hollow Pd.
• The formation of hollow structure promotes the activity for formic acid oxidation.
• The down-shift of d-band center is also origin to the enhanced activity of hollow Pd.

Hollow metal nanocrystals with tuned electronic and geometric structure are highly desirable for the efficient catalytic and/or electrocatalytic reactions. Herein, we report the synthesis of carbon-supported Pd hollow nanocrystal (Pd-hollow/C) catalyst through a galvanic replacement reaction combined with Kirkendall effect without the use of polymeric stabilizer. The Pd-hollow structure is verified by scanning transmission electron microscopy. Noticeable lattice contraction in the Pd-hollow nanocrystal has been observed by high resolution transmission electron microscopy and X-ray diffraction with a decrease in the Pd (111) lattice distance. X-ray photoelectron spectroscopy indicates that the surface Pd atoms donate more electrons to the overlap with the sub-layer atoms, suggesting a strengthened d-hybridization and a down-shift of d-band center relative to the Fermi level on the surface. Electrochemical measurements show that the Pd-hollow/C catalyst exhibits a significantly enhanced electrocatalytic activity toward formic acid oxidation. The collective effects of the hollow structure and down-shift of Pd d-band center could explain well such an enhanced catalytic activity. The present study provides new insights into the relevancy of lattice parameter, electronic structure with catalytic property, and suggests design features for excellent nanostructured catalysts.

Both structural effect and variation of electronic structure in the hollow-structured Pd supported on carbon play important roles in enhancing electrocatalytic activity for formic acid oxidation.Figure optionsDownload as PowerPoint slide