Kronberg Rasmus, Laasonen Kari
Research Group of Computational Chemistry, Department of Chemistry and Materials Science, Aalto University, P.O. Box 16100, FI-00076 Aalto, Finland.
J Phys Chem Lett. 2021 Oct 21;12(41):10128-10134. doi: 10.1021/acs.jpclett.1c02493. Epub 2021 Oct 12.
Facile solvent reorganization promoting ion transfer across the solid-liquid interface is considered a prerequisite for efficient electrocatalysis. We provide first-principles insight into this notion by examining water self-ion dynamics at a highly rigid NaCl(100)-water interface. Through extensive density functional theory molecular dynamics simulations, we demonstrate for both acidic and alkaline solutions that Grotthuss dynamics is not impeded by a rigid water structure. Conversely, decreased proton transfer barriers and a striking propensity of HO and OH for stationary interfacial water are found. Differences in the ideal hydration structure of the ions, however, distinguish their behavior at the water contact layer. While hydronium can maintain its optimal solvation, the preferentially hypercoordinated hydroxide is repelled from the immediate vicinity of the surface due to interfacial coordination reduction. This has implications for alkaline hydrogen electrosorption in which the formation of undercoordinated OH at the surface is proposed to contribute to the observed sluggish kinetics.
促进离子跨固液界面转移的简便溶剂重组被认为是高效电催化的先决条件。我们通过研究高度刚性的NaCl(100)-水界面处的水自离子动力学，对这一概念提供了第一性原理的见解。通过广泛的密度泛函理论分子动力学模拟，我们证明了在酸性和碱性溶液中，Grotthuss动力学都不会受到刚性水结构的阻碍。相反，发现质子转移势垒降低，并且HO和OH对静止界面水具有显著的倾向。然而，离子理想水合结构的差异区分了它们在水接触层的行为。虽然水合氢离子可以保持其最佳溶剂化，但由于界面配位减少，优先超配位的氢氧根离子被排斥在表面附近。这对碱性氢电吸附有影响，其中表面低配位OH的形成被认为是观察到的缓慢动力学的原因。
