AVS 52nd International Symposium
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA6
Role of Dichlorocarbene in the Surface Chemsitry of Halomethanes on Fe@sub 3@O@sub 4@(111)-(2X2) ; a Comparative Thermal Desorption Study

Monday, October 31, 2005, 3:40 pm, Room 203

Session: Oxide Surfaces Structure and Reactivity
Presenter: Y. Le, Columbia University
Authors: Y. Le, Columbia University
G.G. Totir, Columbia University
G.W. Flynn, Columbia University
R.M. Osgood, Columbia University
Correspondent: Click to Email
Iron-oxide surface chemistry plays an important role in understanding chemical routes for the environmental degradation of chlorinated halocarbons. An earlier study had shown the importance of dichlorocarbene in controlling the thermal reaction products for CCl@sub 4@ chemisorbed on magnetite-terminated hematite surfaces. In this talk, we report on an investigation of the surface chemistry of CCl@sub 4@, CBr@sub 2@Cl@sub 2@, and CH@sub 2@Cl@sub 2@ on a UHV-prepared Fe@sub 3@O@sub 4@(111)-(2X2) selvedge of single-crystal @alpha@-Fe@sub 2@O@sub 3@ (0001). Our experiments use UHV, temperature programmed reaction and desorption (TPR/D) measurements of dosed surfaces, along with LEED and Auger probes. The TPR/D spectra show that dissociative formation of dichlorocarbene, followed by its reaction with lattice oxygen and other adsorbed surface species, is central to the surface chemistry of halocarbons in general, and of halomethanes in particular on the (2X2) reconstructed surface of hematite. The specific branching ratios of the various desorbed products including metal-halides are compared for adsorbed CCl@sub 4@, CBr@sub 2@Cl@sub 2@, and CH@sub 2@Cl@sub 2@ on the (2X2) surface. Our experiments show clearly the importance of CCl@sub 2@ intermediates in these surface reactions.