THE SURFACE-CHEMISTRY OF ACETONE ON A PT FOIL

The adsorption, desorption and decomposition of acetone on a Pt foil have been studied by high resolution electron energy loss spectroscopy (HREELS), temperature programmed desorption (TPD) and Auger electron spectroscopy (AES). Two surface adsorption geometries occur for acetone on the foil: eta(1)(O)-(CH3)(2)CO (bonding end-on via the lone pair electrons on the oxygen) and eta(2)(O,C)-(CH3)(2)CO (bonding side-on via either pi-bonding or di-sigma bonding after rehybridization). For the eta(1) species, reversible adsorption and desorption are dominant and are similar in behavior on a Pt(111) surface, while conversion of eta(1) species to eta(2) species may also occur. For the eta(2) species, the decomposition channel is competitive with desorption, and the desorbed decomposition products are hydrogen and carbon monoxide. This process is associated with surface defects such as step sites, and preadsorbed hydrogen inhibits the decomposition channel thus providing additional support for this conclusion.