Options
MODEL STUDIES OF HYDROGEN REACTIVITY AND PRODUCTION ON METAL SURFACES
VESSELLI, ERIK
2005-03-25
Loading...
Contributor(s)
SENATORE, GAETANO
•
BARALDI, ALESSANDRO
Abstract
Hydrogen is considered as a possible solution for limiting the environmental impact caused by the growing energy demand. It can be used as a clean energy vector for feeding fuel cells and can be obtained also from renewable energy sources, like for example biomasses. Experimental studies within the framework of surface science techniques are of core importance for a deep understanding and a proper description of the chemical and kinetic mechanisms involved in catalytic reactions. Hydrogen atoms adsorbed on a surface have weak scattering properties, high diffusion rates and generally show small cross sections to conventional surface science probes. This makes experiments on hydrogen-metal systems particularly hard to be carried out. For example, even the simple determination of the adsorption site for an H atom on a single crystal metal surface is nota straightforward task. As part of this thesis, the H/Rh(lOO) system was studied and it was shown that adsorption site identification can be obtained with the aid of high energy resolution Synchrotron Radiation (SR) X-Ray Photoelectron Spectroscopy (XPS) of the metal core levels. A well known limit of UHV surface science techniques is the pressure gap: the chemical behaviour of catalytic systems can change substantially under different pressure regimes. In the case of hydrogen, atomic sources allow to gain the H2 molecule dissociation energy: in this way more energy is available for surface reactions upon adsorption and absorption, thus simulating higher pressure conditions. For these reasons, a Bischler and Berte! atomic hydrogen source has been built and fully characterized within this PhD project. Using this source, model hydrogenation reactions by gas phase atomic hydrogen have been carried out on nickel (110) and ruthenium (10 l O) single crystal surfaces. The final part of the present thesis reports about an experimental study of ethanol decomposition on Rh(111). Ethanol can be easily obtained by waste bio-mass fermentation and is considered as a promising clean hydrogen source. High rhodium selectivity towards the intramolecular C-C bond cleavage under UHV conditions is reported and the overall metal reactivity is qualitatively compared to the real catalytic conditions.
Insegnamento
Publisher
Università degli studi di Trieste
Languages
en
File(s)