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Electronic Tuning of Gold Nanoparticle Active Sites for Reduction Catalysis
Sayed Abu Sufyan1, Brian van Devener2, Paulo Perez2
1Department of Chemical Engineering, University of Utah, Salt Lake City, Utah 84112, United States.
ACS Applied Materials & Interfaces
|December 29, 2022
Summary
This study demonstrates that electronic tuning of gold nanoparticle catalysts using organic ligands can control catalytic activity. Electron-donating ligands enhance activity in reduction reactions, while electron-withdrawing ligands do not.
Area of Science:
- Heterogeneous Catalysis
- Nanoparticle Synthesis
- Surface Chemistry
Background:
- Electronic tuning of heterogeneous catalysts with organic ligands is difficult due to ligand binding at active sites.
- Gold nanoparticles (Au NPs) offer a platform for studying ligand effects due to their tunable surface properties.
Purpose of the Study:
- To investigate the impact of electron-donating (phosphine) and electron-withdrawing (thiol) ligands on the catalytic activity of gold nanoparticles.
- To explore the selective tuning of catalytic performance in different reactions by modifying ligand electronic properties.
Main Methods:
- Synthesis of gold nanoparticles (<2 nm) functionalized with triphenylphosphine (TPP, electron-donating) and triphenylmethyl mercaptan (TPMT, electron-withdrawing) ligands.
- Characterization using X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) to confirm ligand binding and electronic effects.
- Quantification of surface active sites via 2-naphthalenethiol titration.
- Evaluation of catalytic activity in resazurin reduction, CO oxidation, and benzyl alcohol oxidation reactions.
Main Results:
- XPS and FTIR confirmed distinct electronic properties of TPP-bound (electron-rich) and TPMT-bound (electron-poor) Au NPs.
- Titration experiments showed similar numbers of accessible binding sites for both ligand-modified Au NPs.
- TPP-bound Au NPs were catalytically active in all tested reactions, including resazurin reduction.
- TPMT-bound Au NPs showed activity in CO and benzyl alcohol oxidation but were inactive in resazurin reduction.
Conclusions:
- The electronic nature of organic ligands significantly influences the catalytic activity of gold nanoparticle catalysts.
- Electron-donating ligands (TPP) promote activity in reduction reactions (resazurin reduction), while electron-withdrawing ligands (TPMT) do not.
- This work highlights a strategy for selectively tuning catalyst performance by controlling ligand electronic properties.
