Femtosecond electron transfer dynamics across the D$_2$O/Cs$^+$/Cu(111) interface: The impact of hydrogen bonding

TL;DR

This study investigates how hydrogen bonding influences ultrafast electron transfer at a water-electrode interface, revealing that water aggregation and H-bonding modulate electron lifetime and energy transfer dynamics.

Contribution

It provides new insights into the role of hydrogen bonding and nanoscale water network formation on electron transfer processes at water-metal interfaces.

Findings

Electron lifetime increases from 40 to 60 fs across water aggregation regimes.

Energy transfer to structural rearrangements decreases from 0.3 to 0.2 eV.

H-bonding influences formation of nanoscale water networks.

Abstract

Hydrogen bonding is essential in electron transfer processes at water-electrode interfaces. We study the impact of the H-bonding of water as a solvent molecule on real-time electron transfer dynamics across a Cs+-Cu(111) ion-metal interface using femtosecond time-resolved two-photon photoelectron spectroscopy. We distinguish in the formed water-alkali aggregates two regimes below and above two water molecules per ion. Upon crossing the boundary of these regimes, the lifetime of the excess electron localized transiently at the Cs+ ion increases from 40 to 60 femtoseconds, which indicates a reduced alkali-metal interaction. Furthermore, the energy transferred to a dynamic structural rearrangement due to hydration is reduced from 0.3 to 0.2 eV concomitantly. These effects are a consequence of H-bonding and the beginning formation of a nanoscale water network. This finding is supported by real-space imaging of the solvatomers and vibrational frequency shifts of the OH stretch and bending modes calculated for these specific interfaces.