Solvation at Aqueous Metal Electrodes

TL;DR

This study investigates how ordered water layers at aqueous metal electrodes influence solvation, hydrophobicity, and dynamic heterogeneity, with implications for electrolysis and catalysis.

Contribution

It reveals the role of ordered water adlayers in creating long-range collective responses and dynamic heterogeneity at metal-water interfaces, a novel insight into interfacial solvation.

Findings

Ordered water layers facilitate collective responses over large scales.

Dynamic heterogeneity persists over nanoseconds due to adlayer defects.

Surface geometry influences the structure and dynamics of the water adlayer.

Abstract

We present a study of the solvation properties of model aqueous electrode interfaces. The exposed electrodes we study strongly bind water and have closed packed crystalline surfaces, which template an ordered water adlayer adjacent to the interface. We find that these ordered water structures facilitate collective responses in the presence of solutes that are correlated over large lengthscales and across long timescales. Specifically, we show that the liquid water adjacent to the ordered adlayers forms a soft, liquid-vapor-like interface with concomitant manifestations of hydrophobicity. Temporal defects in the adlayer configurations create a dynamic heterogeneity in the degree to which different regions of the interface attract hydrophobic species. The structure and heterogeneous dynamics of the adlayer defects depend upon the geometry of the underlying ordered metal surface. For both 100 and 111 surfaces, the dynamical heterogeneity relaxes on times longer than nanoseconds. Along with analyzing time scales associated with these effects, we highlight implications for electrolysis and the particular catalytic efficiency of platinum.