Plasma-Enabled Ligand Removal for Improved Catalysis: Furfural Conversion on Pd/SiO₂

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Palladium (Pd) nanoparticles are crucial in catalysis.
• Polyvinylpyrrolidone (PVP) is commonly used as a capping agent during nanoparticle synthesis.
• Efficient removal of PVP is essential for optimal nanoparticle performance.

Purpose of the Study:

• To investigate the efficacy of nonthermal, atmospheric He/O2 plasma (NTAP) for removing PVP from Pd nanoparticles.
• To compare NTAP with traditional calcination methods.
• To analyze the impact of PVP removal on Pd nanoparticle integrity and catalytic activity.

Main Methods:

• Synthesis of Pd cubic nanoparticles supported on SiO2 with PVP capping.
• Treatment with NTAP (He/O2 mixture) at atmospheric pressure.
• Characterization using Transmission Electron Microscopy (TEM), Fourier Transform Infrared (FTIR) spectroscopy, and X-ray Photoelectron Spectroscopy (XPS).
• Computational analysis using first-principles calculations.
• Catalytic reactivity testing for furfural conversion.

Main Results:

• NTAP effectively and controllably removed PVP from Pd nanoparticles.
• Pd nanoparticle size and shape remained intact after NTAP treatment, unlike calcination which caused sintering.
• XPS and FTIR spectroscopy provided quantitative PVP removal rates and insights into ligand-metal interactions.
• First-principles calculations elucidated electron transfer and estimated ligand coverage.
• PVP surface crowding was found to inhibit furfural conversion without affecting selectivity.

Conclusions:

• NTAP is a superior method for removing organic ligands like PVP from nanoparticles compared to calcination.
• NTAP preserves nanoparticle morphology and crystallinity.
• This technique offers enhanced control over nanoparticle synthesis and surface properties.