Theoretical Study on the Swelling Mechanism and Structural Stability of Ni₃Al-LDH Based on Molecular Dynamics

Abstract

layered double hydroxide (LDH) as a kind of 2D layer material has a swelling phenomenon. Because swelling significantly affects the adsorption, catalysis, energy storage, and other application properties of LDHs, it is essential to study the interlayer spacing, structural stability, and ion diffusion after swelling. In this paper, a periodic computational model of Ni 3 Al-LDH is constructed, and the supramolecular structure, swelling law, stability, and anion diffusion properties of Ni 3 Al-LDH are investigated by molecular dynamics theory calculations. The results show that the interlayer water molecules of Ni 3 Al-LDH present a regular layered arrangement, combining with the interlayer anions by hydrogen bonds. As the number of water molecules increases, the hydrogen bond between the anion and the basal layer gradually weakens and disappears when the number of water molecules exceeds 32. The hydrogen bond between the anion and the water molecule gradually increases, reaching an extreme value when the number of water molecules is 16. The interlayer spacing of Ni 3 Al-LDH is not linear with the number of water molecules. The interlayer spacing increases slowly when the number of water molecules is more than 24. The maximum layer spacing is stable at around 19 Å. The interlayer spacing, binding energy, and hydration energy show an upper limit for swelling: the number of water molecules is 32. When the number of interlayer water molecules is 16, the water molecules' layer structure and LDH interlayer spacing are suitable for anions to obtain the maximum diffusion rate, 10.97 × 10 −8 cm 2 •s −1 .

Layered Double Hydroxides for Regulating Phosphate in Water to Achieve Long-Term Nutritional Management

“…LDH materials belong to a class of inorganic functional layered materials that exhibit a diverse range of anionic layered structures, which is achieved by controlling the structure of the basal layers and the interlayer ions and molecules, as depicted in Figure 1b. 109 Though the adsorption−desorption of P by LDHs has been extensively studied, the practical applications for wastewater treatment suffer from low stability and decreased adsorption capability due to pH variation. 110 Lu et al prepared MnFe-LDH/magnetic composite as a P adsorbent, with a focus on tuning the stability of LDHs under different pH and P concentration conditions, as shown in Figure 4a.…”

Recent Advances in Co3O4-Based Composites: Synthesis and Application in Combustion of Methane

“…The utilization of carriers can scatter and stabilize cobalt ions and hasten the Co 2+ ↔ Co 3+ reaction [ 58 ]. While assembling the catalyst, distinct preparation techniques can potentially impact the specific surface area, micro morphology, the degree of dispersion of the active phase of the catalyst, and other structural regulations, which can ultimately influence the activity of the catalyst [ 59 , 60 , 61 ]. There are three common methods to improve the catalytic performance of Co 3 O 4 catalysts (as shown in Figure 4 ): (1) noble metal doping; (2) compounding with metal oxides (Al 2 O 3 [ 62 , 63 , 64 ], ZrO 2 [ 65 ], SnO 2 , ZnO [ 66 ], and CuO [ 67 , 68 , 69 ] are common); and (3) loading onto non-metal oxides (SiO 2 , porous ceramics [ 70 ]).…”