Solvation and Charge Transfer Processes at Semiconductor/Liquid Water Interfaces

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Interfaces between metal oxides and liquid water play a crucial role for numerous systems ranging from heterogeneous catalysis to biological processes. Especially important are charge transfer processes across the interface because the metal oxide is able to catalyze reactions which occur in the adjacent liquid phase. A promising application is photocatalytic water splitting into hydrogen and oxygen. During this process, photons are absorbed by the metal oxide and the gained energy is used to split water at its surface. The process can thus be utilized to generate carbon-neutral fuel. Despite its relevance there is only little information about the exact molecular processes at the interface. For example, it is especially interesting how water molecules interact with the oxide in detail as well as how and where charges are localized at the interface. Those questions can be addressed using methods of computational chemistry, in particular ab initio molecular dynamics~(AIMD). These methods are able to realistically model the structural dynamics of an oxide/water interface at the atomistic level. Still, the simulations are challenging, even for modern high-performance computers, since the electronic structure of oxide/water interfaces is highly complex. Therefore, “machine learning” approaches are to be used in this project to accelerate the AIMD simulations. The ultimate goal of the project is to gain a deep understanding of microscopic properties, such as structure, dynamics and reactivity of liquid water and charge carriers at a given metal oxide surface. Here, WO3 is chosen as the model system being a promising material to act as a photoactive electrode for the oxygen evolution reaction. The obtained insights on the WO3/water interface are then to be generalized to predict properties of other metal oxide/water interfaces. Moreover, the AIMD simulations complement existing experimental data and are also an integral contribution to understand experiments at the microscopic level.