(214aa) Ab Initio Modeling of the Direct Interaction of Surface Plasmons With Adsorbates On Metal Nanostructures

We recently reported on a new family of photo-catalysts that can efficiently couple thermal energy and photonic stimuli to drive photo-chemical transformations with unprecedentedly high efficiencies.[1,2,3] These materials are plasmonic nanostructures of coinage metals which respond to low intensity visible light through a formation of a collective, oscillating electrons.

We will discuss our approach to study these reactions from first principles. We have employed Langevin dynamics simulations to investigate the activation of adsorbed diatomic molecules over plasmonic metal nanostructures.[4] Using these simulations we calculated molecular dissociation probabilities and reaction rates at different light intensities. These stochastic simulations combine Newton’s equations of motion with electronic drag from the surface. The electronic friction is caused by partial charge transfer between substrate and adsorbed molecule due to changes in the electronic structure induced by direct interactions of adsorbates with low energy electron in plasmons. We calculated electronic friction from the adiabatic electronic wavefunctions from Density Functional Theory, using a quantum model to obtain an electron distribution in the surface plasmon, a collection of low-energy excited electrons.[5][6] We compare this approach to desorption induced by (multiple) electronic transitions (DIET/DIMET) model, another mechanism proposed for this type of plasmonic photocatalytic enhancement.

[1] P. Christopher, H. Xin, M. Andiappan and S. Linic. Nat. Mat. 11, 1044 2012

[2] P. Christopher, H. Xin, S. Linic. Nat. Chem. 3, 467 2011

[3] S. Linic, P. Christopher, D. B. Ingram. Nat. Mat. 10, 911 2011

[4] T. Olsen and J. Schiøtz. J. Chem. Phys. 133, 034115 2010

[5] V. Krishna and J. C. Tully. J. Chem. Phys. 125, 054706 2006

[6] L. Genzel, T. P. Martin, U. Kreibig. Z. Physik B. 21, 339 1975