Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 42: Solid-Liquid Interfaces: Reactions and Electrochemistry - Theory II

O 42.1: Talk

Tuesday, March 21, 2017, 14:00–14:15, WIL B321

First-principles free-energy barriers for photo-electrochemical surface reactions: Proton abstraction at TiO₂(110) — •Thomas Stecher, Karsten Reuter, and Harald Oberhofer — Technische Universität 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. [1] We showcase the method by explicitly calculating the free-energy barrier for the initial proton abstraction in the water splitting reaction at rutile TiO₂(110), which was previously studied within the computational hydrogen electrode approach. [2] Combining electrostatic QM/MM embedding, an energy based reaction coordinate and state-of-the-art free-energy reconstruction techniques renders the calculation tractable at the hybrid density-functional theory level, which is required for a realistic description particularly of the transition state. The obtained free-energy barrier of approximately 0.2 eV, depending slightly on the orientation of the first acceptor water-molecule, suggests a hindered reaction on the pristine rutile surface.

[1] T. Stecher, K. Reuter and H. Oberhofer, Phys. Rev. Lett., accepted for publication (2016).

[2] H. Oberhofer and K. Reuter, J. Chem. Phys. 139, 044710 (2013).