Adsorptions of Formic and Acetic Acids on Ice Surface: Surface Binding Configurations and a Possibility of Interfacial Proton Transfer

Abstract

Adsorptions of formic (FA) and acetic acids (AA) on I h ice surface were studied using quantum mechanical/ effective fragment potential (QM/EFP) scheme. Contrasting to the earlier studies in which trans-conformers were found as major surface configurations, our QM/EFP models found various cisand trans-conformers on ice surfaces with the cis-conformers being more stable. The surface binding energies and configurations were largely dependent on surface heterogeneity yielding the various surface conformers. In addition, the overall binding energies of acetic acid are slightly higher as compared to formic acid, implying the stabilization effect of methyl group. Our study also found a feasible deprotonation route of adsorbed transformic acid. In contrast, acetic acid prefers molecular form due to the unfavorable hydrophobic methyl group. Therefore it is interesting to note that the additional methyl group of acetic acid enhances surface binding energies. But at the same time it reduces the chance of its deprotonation. Our ice model clearly demonstrated the significant effects of intrinsic surface heterogeneity on the distributions of surface binding energies and configurations, which cannot be represented by small water clusters.

Na+, F–, Br–, and Cl– Adsorptions and Penetrations on an Ice Surface

“…Improved ice models, such as models using periodic boundary conditions, 37−39 nanoparticle models, 40 as well as a quantum mechanics/molecular mechanics (QM/ MM) 41 model, have been recently used. We have also demonstrated 42,43 that the long-range electrostatic interactions and hydrogen disorders can significantly affect the chemical adsorptions on an ice surface. In the case of an ice surface, surface heterogeneity additionally needs to be modeled in which oxygen dangling bonds (ODBs) (Figure 1a) as well as hydrogen dangling bonds (HDBs) (Figure 1b) are distributed statistically.…”

“…We adopted the effective fragment potential 1–Hartree–Fock (EFP1–HF) water model for the EFP part of our hybrid models. The validity and accuracy of our QM/EFP model was thoroughly tested in our earlier studies. , All of the computations were performed without imposing symmetry, unless otherwise specified. The general atomic and molecular electronic structure system (GAMESS) program was used for all of the computations.…”

Grand canonical Monte Carlo simulation on adsorption of aniline on the ice surface

“…((S)VOCs) on the ice surface. [9,[23][24][25][39][40][41][42][43][44][45][46] The setup of simulation box was the same as that in our recent study on the adsorption of nitrobenzene on the ice surface. [39] Specifically, the simulation box was rectangular, with the X, Y, and Z edges being 100, 35.926, and 38.891 Å.…”

Atomistic View of Mercury Cycling in Polar Snowpacks: Probing the Role of Hg2+ Adsorption Using Ab Initio Calculations

“…To understand chemical processes in polar environments or interstellar media, unusual chemical reactions on ice-Ih surfaces have been studied with sophisticated experimental techniques [50,[77][78][79][80][81][82]. Theoretical approaches using the ab initio calculations have also been applied to the adsorption of specific adsorbents on ice-Ih surfaces, such as acids (HOCl, HCOOH, and CH 3 COOH), halide ions (F − , Cl − , and Br − ), alkali metals (Na and Na + ), and heavy metals (Hg 0 ) [19,49,83,84]. In these studies, the dangling H and O atoms and the proton defects were revealed to be the reactive adsorption sites on the (0001) cleaved surfaces because of their electronic instability.…”