Structural and Dynamical Characterization of Aqueous Hexahydrate Aluminum Nitrate Electrolyte Solution

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Growing demand for safer, high-performance electric batteries necessitates exploring new aqueous electrolyte systems.
• Hexahydrate aluminum nitrate solvated in water is a promising candidate due to its nontoxic nature.
• Limited theoretical studies exist on the complex interactions within this aqueous system.

Purpose of the Study:

• To conduct a theoretical investigation of the structure and dynamics of hexahydrate aluminum nitrate in water.
• To develop an accurate force field for simulating this complex electrolyte system.
• To understand the impact of solute-water interactions on system dynamics and transport properties.

Main Methods:

• Quantum chemical calculations were used to develop a force field for the hexahydrate aluminum nitrate-water system.
• Molecular dynamics simulations were performed on a 1 M solution to analyze structural and transport properties.
• Nuclear magnetic resonance (NMR) spectroscopy was employed to experimentally validate computed diffusion coefficients.

Main Results:

• The developed force field accurately predicts diffusion coefficients, showing excellent agreement with NMR experimental data.
• Diffusion of free water molecules is reduced by over 50% compared to pure water, indicating strong intermolecular correlations.
• Calculated radial distribution functions reveal pronounced structural correlations, and trajectory analyses offer insights into species dynamics on different timescales.

Conclusions:

• The computational approach and developed force field are validated by experimental NMR data.
• Strong correlations between hexahydrate aluminum nitrate and water molecules significantly impact system dynamics, particularly water diffusion.
• This study provides a fundamental understanding of the structure-dynamics relationship in aqueous aluminum nitrate solutions, relevant for battery applications.