AVS 50th International Symposium
    Surface Science Monday Sessions
       Session SS1-MoM

Paper SS1-MoM2
Photoinduced Electron Transfer Chemistry and Dissociation of Adsorbed CO@sub 2@: Harnessing Å-Scale Molecular Acceleration Towards a Surface

Monday, November 3, 2003, 8:40 am, Room 326

Session: Gas-Surface Dynamics
Presenter: R. Zehr, University of Virginia
Authors: R. Zehr, University of Virginia
T. Wagner, University of Essen, Germany
I. Samanta, University of Virginia
I. Harrison, University of Virginia
Correspondent: Click to Email
Activated dissociation of molecules on a metal surface is essential to many catalytic syntheses (e.g. N@sub 2@ dissociation in NH@sub 3@ synthesis) and a firm scientific understanding of this process is important to advancing the field of heterogeneous catalysis. In commercial catalysis, activation energy barriers are invariably surmounted by random thermal energy and not through a more directed use of the energy in light, despite the ubiquitous example of photosynthesis in nature. Potential advantages of using light to overcome a rate-limiting dissociative adsorption step in catalysis include better selectivity towards a chosen reaction pathway, the ability to work at much reduced reaction temperatures, and the opportunity to exploit solar energy. Here, we present evidence that photoinduced electron transfer from a low temperature Pt(111) surface to physically adsorbed CO@sub 2@ leads to rapid acceleration of the newly formed negative ion towards the surface, neutralization, and a high energy collision with the surface that efficiently dissociates (ca. 30%) and desorbs CO@sub 2@. Importantly, this photochemical activation mechanism constitutes an Å-scale molecular accelerator that may be applicable to other hard-to-activate adsorbates. The ability to photochemically induce an adsorbate/surface collision at chemically significant energies (up to ~2.5 eV), after an acceleration over a distance of no more than a few Å from an initial configuration prescribed by the physisorption binding potential, provides novel opportunities to drive energetic dissociation and desorption processes at low temperatures and to examine the reaction dynamics of catalysis.