Interactions between a catalytic particle and its support are two-fold: constraint of particle size and shape, and particle chemical modification by charge transfer, oxidation, etc. Here we attempt to separate size/shape effects from chemical effects by modeling interactions on an isolated particle initially constrained to bond on a SrTiO3 (001) surface. A theoretical and computational study of the reduction of acrolein (Ac) by hydrogenation on platinum nanoparticles (PtN) was performed. Equilibrium adsorption states were modeled with acrolein bound to the nanoparticle surfaces, edges, and corners to explore structure sensitivity. The bottom layer of PtN was held constrained consistent with the experimentally observed STO lattice constant, approximating substrate bonding effects. Platinum surface, edge, and corner morphologies were chosen to reproduce experimental observations of particle shape changes, driven by substrate modification[1]. First principles Density Functional Theory (DFT) was used as the primary modeling tool. Top-, bridge-, and hollow-sites for adsorption and hydrogenation were surveyed. Each site was simulated with several specific initial orientations of acrolein which model adsorption at the positive, neutral, and negatively charged molecular regions. Sites and orientations for acrolein and for its hydrogenated products were ranked by energies; reaction paths are proposed. Bader topological atom and spherical volume averaging (Wigner-Seitz) charge analysis was performed to understand bonding structures. Density of states analysis was performed for use as a catalytic descriptor. Calculated energy differences and spectral features between local equilibrium states of Ac and Ac + hydrogen on Pt were used to interpret observed activity differences in production of propanol, propanal and allyl alcohol. 1 F. Silly and M. R. Castell, Phys. Rev. Lett. 94, 046103 2005.

Modeling acrolein hydrogenation on constrained platinum nanoparticles

249th National Meeting (2015)

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