Solvation and Charge Transfer Processes at Semiconductor/Liquid Water Interfaces

金属氧化物和液态水之间的界面在从多相催化到生物过程的众多系统中起着至关重要的作用。尤其重要的是界面上的电荷转移过程，因为金属氧化物能够催化发生在相邻液体中的反应。光催化将水分解为氢和氧是一个很有前途的应用。在这个过程中，光子被金属氧化物吸收，获得的能量被用来在其表面分裂水。因此，该工艺可用于生产碳中性燃料。尽管它是相关的，但关于界面上的确切分子过程的信息很少。例如，特别有趣的是水分子如何详细地与氧化物相互作用，以及电荷在界面上如何定位以及在哪里定位。这些问题可以用计算化学的方法，特别是从头算分子动力学(AIMD)来解决。这些方法能够在原子水平上真实地模拟氧化物/水界面的结构动力学。尽管如此，即使对现代高性能计算机来说，模拟也是具有挑战性的，因为氧化物/水界面的电子结构非常复杂。因此，在本项目中将使用“机器学习”方法来加速AIMD模拟。该项目的最终目标是深入了解微观性质，如给定金属氧化物表面的液态水和电荷载流子的结构、动力学和反应性。选择WO_3作为模型体系，是一种很有前途的光催化析氧电极材料。所获得的关于WO_3/水界面的见解将被推广到预测其他金属氧化物/水界面的性质。此外，AIMD模拟补充了现有的实验数据，也是对在微观层面上理解实验的不可或缺的贡献。

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.