Water dynamics and sum-frequency generation spectra at electrode/aqueous electrolyte interfaces.

Area of Science:

• Electrochemistry
• Physical Chemistry
• Materials Science

Background:

• Understanding water dynamics at electrode-electrolyte interfaces is critical for redox reactions and charge transfer.
• While electric double-layer structure is well-studied, interfacial water dynamics remain poorly understood.
• Interfacial water dynamics result from complex water-water, water-electrode, and water-ion interactions.

Purpose of the Study:

• To investigate the impact of ion concentration and electrode potential on interfacial water reorientational dynamics.
• To elucidate the mechanisms governing water dynamics at graphene electrode interfaces.

Main Methods:

• Molecular dynamics simulations of aqueous NaCl solutions at graphene electrode interfaces.
• Analysis of interfacial water reorientational dynamics under varying ion concentrations and electrode potentials.

Main Results:

• Water dynamics exhibit asymmetric behavior: slowing at positive potentials and accelerating at negative potentials.
• At negative potentials, dynamics are primarily potential-dependent; at positive potentials, they are influenced by ion-water and electrode-water interactions.
• These behaviors are linked to the interfacial hydrogen-bond network structure and ion surface affinity.

Conclusions:

• Electrode potential and ion interactions significantly modulate interfacial water dynamics.
• The findings highlight distinct mechanisms governing water dynamics at positive versus negative electrode potentials.
• Vibrational sum-frequency generation spectroscopy can probe these dynamics and structural rearrangements.