AVS 61st International Symposium & Exhibition
    Surface Science Monday Sessions
       Session SS+EN-MoM

Paper SS+EN-MoM6
STM Spectroscopic Studies of TMAA Photocatalysis on TiO2

Monday, November 10, 2014, 10:00 am, Room 315

Session: Photocatalysis and Photochemistry at Surfaces
Presenter: Denis Potapenko, Columbia University
Authors: D.V. Potapenko, Columbia University
Z. Li, Columbia University
R.M. Osgood, Columbia University
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Titanium oxide is a versatile photocatalytic material and it has been the subject of much research throughout the last two decades. Scanning Tunneling Microscopy (STM) allows explorations on the single molecule basis thus providing important insight into the physical phenomena involved in photocatalysis. Our experiments examine the tip-induced chemistry of tri-methyl acetic acid (TMAA) molecules adsorbed on TiO2 rutile(110) surface;this systems was chosen as a model for light-driven catalysis since it is easily imaged with STM and since this system has been the subject of many earlier studies of photo and thermal chemistry. In the present work we combine three methods of initiation of surface chemistry: a) excitation of charge carriers in bulk TiO2 with monochromated light from a UV-vis lamp, b) injection of the charge carriers from the STM tip directly into an adsorbed molecule, and c) injection of hot carriers into the substrate from the STM tip. In the latter case the surface reactions are initiated in the vicinity of the injection point by the electrical charges diffusing in the bulk of TiO2, thus giving a unique insight into the charge dynamics. We show that there is a threshold energy for a hot hole below the edge of the TiO2 valence band that is required for TMAA photo-decomposition.