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O: Fachverband Oberflächenphysik

O 60: Chemistry at Solid/Liquid Interfaces

O 60.5: Vortrag

Mittwoch, 9. März 2016, 16:15–16:30, S052

What quantum dynamics tells us about photocatalytic water splitting — •Jan Mitschker and Thorsten Klüner — Carl-von-Ossietzky-Universität, Oldenburg, Germany

Combining quantum chemistry with quantum dynamics is a valuable tool to simulate processes on a femtosecond time scale. In this contribution, the focus is on the photochemistry of water on a rutile (110) surface. Highly accurate potential energy surfaces for the adsorption of water on rutile were calculated on a CASSCF level of theory. The rutile surface is modelled by a cluster embedded in a large point charge field. The electronically excited state resulting from a hole attack on the water molecule was simulated by a positively charged adsorbate. From about 170000 data points for each state the potential energy surfaces were constructed using artificial neural networks for the interpolation.

Two photoreactions were studied: photodesorption and photodissociation. Numerical wave-packet propagation solves the time-dependent Schrödinger equation and accounts for all quantum effects. Our results indicate an MGR mechanism for the desorption due to the repulsive interaction between adsorbate and substrate in the excited state. Describing the photodissociation, however, is much more complicated due to the underlying Hamiltonian. Using a simpler two-dimensional model, the process is dominated by an energy barrier near the Franck-Condon region leading to a splitting of the wave-packet and introducing strong isotope effects.