Ozone (O3) has been utilized as an O-atom source for reactions occurring on metal surfaces and nanoparticles, including CO oxidation.  We employ DFT methods to investigate O3 as an O-atom source to facilitate CO oxidation over unsupported Au atoms.  Geometry optimizations and vibrational frequency calculations (B3LYP/SDD/6-311+G(3df)) of [Au+O3]qand [O3+Au+CO]q complexes, (q=-1,0,+1), are used to predict structures and IR spectra of possible reaction intermediates to guide experimental matrix isolation spectroscopy studies.  We also utilize intrinsic reaction coordinate (IRC) calculations and ADMP to investigate the lowest energy pathways between stable minima.  ADMP calculations are launched from transition state structures, with small initial energies, to investigate formation of products, specifically O2 and CO2.  Calculations have indicated reactions with barriers lower than the reactant asymptote(s) via two main pathways:  a single-step oxidation of CO by molecular O3 and a two-step process, where O3 oxidizes Au to form [O2+AuO]q and [AuO]q subsequently oxidizes CO with O2 remaining as a spectator species.  Results suggest a charge dependent trend related to �selection� of the single or two step reactions, where the importance of Au oxidation may increase with increasing electron density.  As the initial electron density increases, the energy of the transition state of the two-step (Au oxidation) process lowers near to and then below that of the single-step process.  A trend related to spin states shows that cationic and anionic triplet states have the two-step process as the lower energy pathways, while the cationic and anionic singlet and neutral doublet states have the one-step process as the lower energy pathways.  Preliminary analysis also suggests that CO and O3 cooperatively bind to Au, which lead to lower reaction barriers, compared to [Au+O3]q barriers.

Understanding the reaction profiles of CO oxidation with ozone and Au<sup>q</sup> atoms (q=-1,0,+1) utilizing DFT calculations and AIMD

246th National Meeting (2013)

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Understanding the reaction profiles of CO oxidation with ozone and Auq atoms (q=-1,0,+1) utilizing DFT calculations and AIMD

Understanding the reaction profiles of CO oxidation with ozone and Au^q atoms (q=-1,0,+1) utilizing DFT calculations and AIMD