Interlaminar Anionic Transport in Layered Double Hydroxides: Estimation of Diffusion Coefficients

Abstract

Layered double hydroxides (LDHs) are materials with capacity of conducting anions. To get insight into the mechanisms controlling LDH intrinsic anionic transport properties, it is investigated the effect of composition on the anion diffusion coefficients in LDHs containing Mg or Zn as divalent cation, Al or Ga as trivalent cation, and OH– or Cl– as interlaminar anion. Diffusion coefficients are estimated simulating diffusion with a kinetic Monte Carlo algorithm on a potential energy surface (PES) associated with the dry interlayer anion. The PES is calculated using density functional theory. We find that at room temperature, diffusion coefficients increase as the difference in electronegativity between metal atoms composing the layers grows. However, at higher temperatures, systems with narrower PES basins become the ones with larger diffusion coefficients, owing to shorter residence times prior to hopping to a neighbor basin. We also find that Cl– has smaller diffusion coefficient than OH– owing to the l...