Insights into Palladium Deactivation during Advanced Oxidation Processes

Area of Science:

• Materials Science
• Catalysis
• Surface Chemistry

Background:

• Catalyst deactivation mechanisms are critical for developing efficient and durable catalysts.
• Palladium (Pd) supported on corundum (Al2O3) is a widely studied catalytic material.

Purpose of the Study:

• To investigate the behavior of Pd/corundum catalysts during hydrogen adsorption/desorption cycles.
• To elucidate the role of different Pd species (nanoparticles, clusters, single atoms) in catalyst deactivation.

Main Methods:

• Temperature-programmed desorption coupled with mass spectrometry (TPD-MS).
• Aberration-corrected transmission electron microscopy (AC-TEM).
• Preparation of Pd/corundum by impregnation and sputtering.

Main Results:

• Uniformly dispersed Pd nanoparticles were observed in both preparation methods.
• Single atoms and small Pd clusters were exclusively found in materials prepared by impregnation.
• Larger Pd nanoparticles (>2 nm) transformed into a Pd/PdHₓ core-shell structure upon hydrogen exposure.
• Pd nanoparticles <2 nm and single atoms remained unchanged.

Conclusions:

• The long-term activity of Pd/corundum catalysts prepared by impregnation is attributed to the stability of small Pd clusters and single atoms.
• Understanding the deactivation of larger Pd nanoparticles is key to improving catalyst longevity.