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The Chemistry of Trimethylamine on Ru(001) and O/Ru(001) B. F. Hallac and M. Asscher*

Summary: The Chemistry of Trimethylamine on Ru(001) and O/Ru(001)
B. F. Hallac and M. Asscher*
Department of Physical Chemistry and the Farkas Center for Light Induced Processes, The Hebrew
UniVersity of Jerusalem, Jerusalem 91904, Israel
ReceiVed March 27, 2007. In Final Form: May 20, 2007
The interaction and reactivity of trimethylamine (TMA) has been studied over clean and oxygen-covered Ru(001)
under UHV conditions, as a model for the chemistry of high-density hydrocarbons on a catalytic surface. The molecule
adsorbs intact at surface temperature below 100 K with the nitrogen end directed toward the surface, as indicated from
work function change measurements. At coverage less than 0.05 ML (relative to the Ru substrate atoms), TMA fully
dissociates upon surface heating, with hydrogen as the only evolving molecule following temperature-programmed
reaction/desorption (TPR/TPD). At higher coverage, the parent molecule desorbs, and its desorption peak shifts down
from 270 K to 115 K upon completion of the first monolayer, indicating a strong repulsion among neighbor molecules.
The dipole moment of an adsorbed TMA molecule has been estimated from work function study to be 1.4 D. Oxygen
precoverage on the ruthenium surface has shown efficient reactivity with TMA. It shifts the surface chemistry toward
the production of various oxygen-containing stable molecules such as H2CO, CO2, and CO that desorb between 200
and 600 K, respectively. TMA at a coverage of 0.5 ML practically cleans off the surface from its oxygen atoms as
a result of TPR up to 1650 K, in contrast to CO oxidation on the O/Ru(001) surface. The overall reactivity of TMA
on the oxidized ruthenium surface has been described as a multistep reaction mechanism.
1. Introduction
The initial stages of hydrocarbon chemistry on catalytic metal


Source: Asscher, Micha - Institute of Chemistry, Hebrew University of Jerusalem


Collections: Chemistry