Weakening Pd─O Bonds by an Amorphous Pd Layer to Promote Electrocatalysis

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Core-shell nanostructures offer enhanced catalytic properties due to geometric and electronic effects.
• Noble metal electrocatalysts are crucial for reactions like formic acid oxidation and oxygen reduction.
• Reducing noble metal usage while maintaining or improving performance is a key challenge.

Purpose of the Study:

• To synthesize and characterize a novel core-shell structured nanocatalyst with a thin amorphous palladium (Pd) shell and a crystalline PdCu core.
• To evaluate the electrocatalytic performance of this novel nanocatalyst for formic acid oxidation (FAO) and oxygen reduction reaction (ORR).
• To investigate the underlying mechanisms responsible for the enhanced electrocatalytic activity.

Main Methods:

• Synthesis of core-shell structured nanocatalysts (amorphous Pd shell/crystalline PdCu core).
• Electrochemical characterization including cyclic voltammetry and rotating disk electrode techniques.
• Computational calculations (e.g., Density Functional Theory) to understand electronic structure and bonding.

Main Results:

• The core-shell nanocatalyst demonstrated a 4.1 times higher catalytic peak current density for FAO compared to PdCu nanoalloy and commercial Pd-C catalysts.
• The novel catalyst exhibited superior stability in formic acid oxidation.
• Excellent electrocatalytic performance was also observed for the oxygen reduction reaction.
• Computational results indicated that the electronic state tuning by the amorphous Pd shell and Cu weakened surface Pd-O bonds, facilitating bond breaking.

Conclusions:

• The developed core-shell nanocatalyst significantly enhances electrocatalytic activity for both formic acid oxidation and oxygen reduction reactions.
• The synergistic effects between the amorphous Pd shell and the PdCu core, along with electronic structure modification, are responsible for the improved performance.
• This strategy effectively lowers noble metal loading while boosting catalytic efficiency and stability.