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Growth and Electrostatic/chemical Properties of Metal/LaAlO3/SrTiO3 Heterostructures
Published on: February 8, 2018
Characterization of electron donor sites on Al2O3 surface
Dmitrii A Medvedev1, Alexandra A Rybinskaya, Roman M Kenzhin
1Boreskov Institute of Catalysis, Prospekt Lavrentieva 5, Novosibirsk 630090, Russia.
Physical Chemistry Chemical Physics : PCCP
|January 24, 2012
Summary
Electron donor sites on alumina were studied using 1,3,5-trinitrobenzene (TNB). Radical anion formation indicates these sites are not true electron donors but involve hydroxyl group substitution.
Area of Science:
- Surface Chemistry
- Materials Science
- Spectroscopy
Background:
- Alumina (Al(2)O(3)) is a widely used material with various polymorphs.
- Understanding surface properties, particularly electron donor sites, is crucial for catalytic and adsorption applications.
- Electron paramagnetic resonance (EPR) spectroscopy is a powerful tool for studying radical species and surface interactions.
Purpose of the Study:
- To investigate the nature of electron donor sites on different alumina polymorphs.
- To characterize the formation mechanism of radical anions from 1,3,5-trinitrobenzene (TNB) adsorption.
- To determine the concentration and properties of surface donor sites on various alumina phases.
Main Methods:
- Electron Paramagnetic Resonance (EPR) spectroscopy was employed to study the adsorption of 1,3,5-trinitrobenzene (TNB).
- In situ EPR experiments were conducted under varying solvent and temperature conditions.
- Quantum chemical simulations were used to support experimental findings and propose a structural model.
Main Results:
- The concentration of TNB radical anions was found to be largely independent of solvent and temperature, suggesting a measure of total donor sites.
- Donor site concentrations were similar across alumina polymorphs, except for α-Al(2)O(3).
- The formation rate and activation energy of TNB radical anions depend on solvent donor properties, and a liquid phase adsorbate is necessary.
Conclusions:
- The studied sites are not genuine electron donor sites capable of direct electron transfer.
- A proposed model suggests TNB radical anions substitute hydroxyl groups, forming neutral ion pairs with surface aluminum cations.
- The mechanism involves simple radical migration and does not require long-distance charge separation, initiated by negatively charged surface hydroxyl groups.
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