Theoretical Study of the Adsorption/Dissociation Reactions of Formic Acid on the α-Al₂O₃(0001) Surface

Abstract

Formic acid was used as the model of lauric acid to investigate the microscopic mechanism of the anti-icing behavior and was checked to find out if it can be catalyzed to produce H2 for fuel cells by the α-Al2O3(0001) 2 × 2 supercell slab model. The density functional theory with the all-electron double numerical polarized basis sets was employed. The results show that when it involves the carboxyl O and hydroxyl H atom the 1,2-dissociated adsorbate is the most stable intermediate on the dry Al2O3(0001) surface and is energetic barrier free to form the fairly stable ROCO- and HO-covered surface with the binding energy of 59.5 kcal/mol, and this dissociation mode has the lowest energy barrier of 14.9 kcal/mol to form the HOCO- and H2O-covered surface after the surface is fully hydroxylated. The energetic barrier of the HCOOH dehydrogenation and dehydration reactions on the alumina surface decreased considerably from 65.3 to 30.6 kcal/mol and from 62.1 to 26.8 kcal/mol, respectively, in comparison with the gaseous decomposition. The dissociated configuration of lauric acid was tested, and it was found that it dissociated with free energy barrier through 1,2-hydrogen migration into the C11H23OCO- and HO-covered surface with a binding energy of 60.7 kcal/mol. The present theoretical work is useful to gain some new insights on the microscopic interaction mechanism of the superhydrophobic alumina surface fabrication procedure and on the heterogeneous catalysis reactions of the H2 production.

Convenient and large-scale fabrication of cost-effective superhydrophobic aluminum alloy surface with excellent reparability

“…The unreacted lauric acid has a large binding force with water due to the existence of the carboxyl group, resulting in a small contact angle of water on the surface, only 124.9°, which is consistent with the research in ref . Their molecular dynamics theorical research shows that excessive modifier will accumulate on top of the monomolecular adsorption layer and will not react with the surface.…”

“…However, this method has a relatively large limitation on the size and placement state of the surface and will cause serious waste of the modifier. By means of molecular dynamics, the influence of the amount of modifier on the final wettability was studied with ref . It is found that the modifier can form only a monomolecular adsorption layer on the surface, not a multimolecular adsorption layer, so the use of excessive modifier will cause great waste.…”

Molecular level insight on the adsorption of carboxylic acids to oxide nanoparticles in aqueous solution by X-ray photoelectron spectroscopy

“…4 where a proton of formic acid is transferred to the NPs surface. The identical mechanism was recently proposed based of DFT calculations for the adsorption of HCOOH on the fully hydroxylated a-Al 2 O 3 (0001) surface by Ruan et al 30 The addition of 0.2 M formic acid to the NP suspension causes the zeta potential to decrease (closed squares of Fig. 1d) despite the overwhelming increase in the fraction of protonated surface sites (Fig.…”

Assessing thermochemical properties of materials through ab initio quantum-mechanical methods: the case of α-Al2O3

“…1 Corundum (α-Al 2 O 3 , the most stable form of aluminum oxide, whose atomic structure is sketched in Figure 1) and its polymorphs (the so-called transitions aluminas) also exhibit unique surface properties, which make them suitable both as catalysts for several reactions [2][3][4][5][6][7][8][9] and as support for other catalysts. [10][11][12][13][14] Furthermore, the thermodynamic properties of corundum are of particular interest in calorimetric studies in that it constitutes a standard reference material (SRM-720) for the calibration of some calorimeters.…”