First-Principles Study on Interlayer Spacing and Structure Stability of NiAl-Layered Double Hydroxides

Area of Science:

• Materials Science
• Computational Chemistry
• Nanotechnology

Background:

• Layered double hydroxides (LDHs) are versatile materials with applications in adsorption, catalysis, and energy storage.
• Interlayer spacing and structural stability are critical for LDH performance, yet the influence of interlayer anions is not fully understood.
• Previous studies have less explored the impact of diverse interlayer anions on LDH structural properties.

Purpose of the Study:

• To investigate the effect of various interlayer anions on the interlayer spacing and structural stability of Ni-Al layered double hydroxides (LDHs).
• To analyze the correlation between anion properties (size, charge, shape) and LDH structural characteristics.
• To explore the influence of the Ni/Al ratio on interlayer spacing in Ni-Al-Cl-LDHs.

Main Methods:

• Density Functional Theory (DFT) calculations were employed to model Ni3Al-A-LDHs with 10 different anions.
• Four Ni-Al-Cl-LDH models with varying Ni2+/Al3+ ratios (R=2, 3, 5, 8) were constructed.
• Calculations focused on determining interlayer spacing, structural stability, and binding energies.

Main Results:

• Interlayer spacing increased with larger and more complex anions, with C12H25SO3- yielding the largest spacing (24.262 Å).
• Interlayer spacing in Ni-Al-Cl-LDHs increased with the Ni2+/Al3+ ratio, from 7.964 Å to 8.124 Å.
• Binding energy was highest for CO3^2-, indicating stronger stability, and decreased with larger/more complex anions; smaller spacing correlated with higher binding energy and stability.

Conclusions:

• Interlayer anion choice critically dictates LDH interlayer spacing and structural stability.
• Anion size, shape, and charge influence hydrogen bonding and electronic interactions, thereby affecting material properties.
• DFT provides a robust framework for predicting and optimizing LDH structures for specific applications.