THE SURFACE-CHEMISTRY OF ACETONE ON A PT FOIL

The adsorption, desorption and decomposition of acetone on a Pt foil h ave been studied by high resolution electron energy loss spectroscopy (HREELS), temperature programmed desorption (TPD) and Auger electron s pectroscopy (AES). Two surface adsorption geometries occur for acetone on the foil: eta(1)(O)-(CH3)(2)CO (bonding end-on via the lone pair e lectrons on the oxygen) and eta(2)(O,C)-(CH3)(2)CO (bonding side-on vi a either pi-bonding or di-sigma bonding after rehybridization). For th e eta(1) species, reversible adsorption and desorption are dominant an d are similar in behavior on a Pt(111) surface, while conversion of et a(1) species to eta(2) species may also occur. For the eta(2) species, the decomposition channel is competitive with desorption, and the des orbed decomposition products are hydrogen and carbon monoxide. This pr ocess is associated with surface defects such as step sites, and pread sorbed hydrogen inhibits the decomposition channel thus providing addi tional support for this conclusion.