Bias-dependent local structure of water molecules at a metallic interface

Area of Science:

• Physical Chemistry
• Computational Electrochemistry
• Surface Science

Background:

• Understanding water's behavior at electrode interfaces is vital for aqueous electrochemistry.
• Realistic simulations are challenging, especially with differing electrode potentials.
• Accurate modeling requires accounting for out-of-equilibrium conditions.

Purpose of the Study:

• To develop and apply a computational framework for simulating water at biased metallic electrode interfaces.
• To investigate the electronic properties and atomic forces of a water molecule at a gold surface under applied bias.
• To correlate computational results with experimental chemical potentials.

Main Methods:

• Combined Density Functional Theory (DFT) and Non-Equilibrium Green's Function (NEGF) methods.
• Simulated semi-infinite surfaces under external bias potential.
• Calculated out-of-equilibrium forces and dynamics.

Main Results:

• The water molecule aligns its dipole moment with the applied electric field.
• Water molecules are repelled or attracted to the gold surface based on bias.
• The interaction exhibits an asymmetric response to the applied bias.

Conclusions:

• The DFT-NEGF framework accurately models water-metal interfaces under bias.
• Applied bias significantly influences water molecule orientation and interaction strength.
• The findings provide insights into the fundamental electrochemistry at interfaces.