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O: Fachverband Oberflächenphysik

O 60: Chemistry at Solid/Liquid Interfaces

O 60.6: Vortrag

Mittwoch, 9. März 2016, 16:30–16:45, S052

First-principles reaction barriers for the splitting of water on rutile TiO₂ (110) — •Thomas Stecher, Harald Oberhofer, and Karsten Reuter — TU München, Garching, Deutschland

First-principles modelling of electrocatalytic surface reactions is still largely defined by the computational hydrogen approach. This approach evaluates free energy differences between consecutive reaction steps and thereby accounts only for thermodynamic barriers. In order to access additional kinetic barriers in the photocatalytic oxidation of water we present an approach based on ab initio molecular dynamics (AIMD) simulations and umbrella sampling. As a first showcase system we consider the initial proton-transfer step during water-splitting on a rutile TiO₂ (110) surface, which was previously studied within the computational hydrogen electrode approach [1]. AIMD on a system of this size is enabled by an electrostatic embedding approach of both the solid and liquid parts of the reaction site. Furthermore it was found to be imperative that the rearrangement of water, which plays a key role, be considered in the definition of the reaction coordinate. This is achieved by an energy-based reaction coordinate inspired by Marcus theory. Finally, hybrid-level DFT functionals are required for a realistic description particularly of the transition state. Bringing these computational ingredients together allows us to disentangle thermodynamic and kinetic contributions to the reaction barrier. [1] H. Oberhofer and K. Reuter, J. Chem. Phys. 139, 044710 (2013).