Modeling of the electric double layer at metal oxide electrode/electrolyte interfaces with density functional theory based molecular dynamics

过渡金属氧化物在设计新型高效(光)电催化剂方面发挥着重要作用，这是德国和世界范围内日益增长的能源需求和相关环境问题所要求的。大多数富含稀土的金属氧化物只在碱性溶液(PH 14)中稳定。因此，对金属氧化物电极/电解液界面上吸附的水和氢氧化物离子去质子化形成的双电层(EDL)进行建模和模拟是优化能量转换成本效率的一个组成部分。然而，缺乏对操作条件下金属氧化物电化学界面的详细原子学理解，这在很大程度上阻碍了进展。在这里，作为项目的核心目标，我建议发展和研究基于密度泛函理论(DFT)的分子动力学(MD)和显式处理溶剂的质子EDL的模型。重点将放在EDL的介电特性上。作为光电化学能量转换高技术兴趣的一个例子，我们将研究平带条件下模型二氧化钛/电解液界面上的质子电致发光。通过首次将电化学中的(单)电极电势和周期体系中的Berry相极化的概念相结合，我们有望实现对电解液中EDL和离子屏蔽的更真实的模拟。特别是，这种方法使我们能够在固定的化学成分下对双层进行充电，并计算极化作为新的观测值，以及双层中的亥姆霍兹电容和介电响应的详细空间变化。与传统的连续介质理论和当前简化的原子超细胞模型相比，这种新的方法将是一个巨大的飞跃。这将进一步为进一步研究EDL与电催化过程的耦合机理奠定有价值的基础，这对于设计高效、经济的电催化剂和光催化剂具有重要意义。

Transition metal oxides play a prominent role in the design of new, efficient (photo) electrocatalysts demanded by the increased energy need and the related environmental issues in Germany and worldwide. Most earth-abundant metal oxides are only stable in alkaline solution (pH 14). Modeling and simulation of the electric double layer (EDL) formed by deprotonation of adsorbed water and hydroxide ions at the metal oxide electrode/electrolyte interfaces is therefore an integral part of optimizing the cost efficiency of energy conversion. However, the lack of a detailed atomistic understanding of metal oxide electrochemical interfaces under operating conditions considerably hampers progresses. Here, as the core objective of the project, I propose to develop and investigate the modeling of protonic EDL's using density functional theory (DFT) based molecular dynamics (MD) with explicit treatment of solvent. The focus will be on the dielectric properties of the EDL. As an example of high technological interest for photoelectrochemical energy conversion, we will study the protonic EDL at a model TiO2/electrolyte interface under the flatband conditions. By combining concepts of (single) electrode potentials in electrochemistry and Berry phase polarization in periodic systems for the first time, we expect to achieve a more realistic modeling of the EDL and ionic screening in the electrolytic solution. In particular, the proposed approach would enable us to charge the double layer at fixed chemical composition and compute the polarization as a new observable as well as the Helmholtz capacitance and the detailed spatial variation of the dielectric response in the double layer. This novel method will represent a considerable leap forward with respect to traditional continuum theories and current simplified atomistic supercell models. It would further lay down a valuable basis for future research towards a mechanistic understanding of the coupling of EDL with electrocatalytic processes, which is highly relevant for the design of efficient and economical electrocatalysts and photocatalysts.