Characterizing heterogeneous dynamics at hydrated electrode surfaces

TL;DR

This study analyzes the complex, heterogeneous dynamics of water molecules at hydrated platinum surfaces using tools from glassy systems, revealing surface-dependent behaviors influenced by voltage and molecular frustration.

Contribution

It introduces a quantitative framework to characterize dynamic heterogeneity of water at metal surfaces, highlighting the role of surface structure and voltage in modulating these dynamics.

Findings

Dynamics are facilitated by transient disorder in hydrogen bonding networks.

Heterogeneity varies qualitatively between Pt 111 and Pt 100 surfaces.

Voltage influences the asymmetry of water dynamics on the surfaces.

Abstract

In models of Pt 111 and Pt 100 surfaces in water, motions of molecules in the first hydration layer are spatially and temporally correlated. To interpret these collective motions, we apply quantitative measures of dynamic heterogeneity that are standard tools for considering glassy systems. Specifically, we carry out an analysis in terms of mobility fields and distributions of persistence times and exchange times. In so doing, we show that dynamics in these systems is facilitated by transient disorder in frustrated two-dimensional hydrogen bonding networks. The frustration is the result of unfavorable geometry imposed by strong metal-water bonding. The geometry depends upon the structure of the underlying metal surface. Dynamic heterogeneity of water on the Pt 111 surface is therefore qualitatively different than that for water on the Pt 100 surface. In both cases, statistics of this adlayer dynamic heterogeneity responds asymmetrically to applied voltage.