High-temperature hydroxylation of alumina crystalline surfaces

Chandrasekharan, Ramesh; Zhang, Luning; Ostroverkhov, Victor; Prakash, Shaurya; Wu, Yan; Shen, Y. R.; Shannon, Mark A.

doi:10.1016/j.susc.2008.02.009

Cited by 27 publications

(25 citation statements)

References 20 publications

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“…ligand exchange, protonation, (de)sorption) can help identify surface groups. This approach has been applied to a wide range of inorganic materials, including catalytic alumina, 11,12 zinc oxides 13,14 and zeolites. 15 Single crystal surfaces 11 have moreover been highly beneficial in this area, by providing a priori knowledge of OH groups present, [16][17][18][19][20] constraining results obtained from otherwise uncharacterized, highly reactive, powdered materials.…”

Section: Introductionmentioning

confidence: 99%

“…This approach has been applied to a wide range of inorganic materials, including catalytic alumina, 11,12 zinc oxides 13,14 and zeolites. 15 Single crystal surfaces 11 have moreover been highly beneficial in this area, by providing a priori knowledge of OH groups present, [16][17][18][19][20] constraining results obtained from otherwise uncharacterized, highly reactive, powdered materials. Single FeOOH crystals are however of rarer occurrence than the nanoto micron-sized particles widely found in nature.…”

Section: Introductionmentioning

confidence: 99%

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Structural controls on OH site availability and reactivity at iron oxyhydroxide particle surfaces

Song

Boily

2012

Phys. Chem. Chem. Phys.

106

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Iron oxyhydroxides (FeOOH) are highly reactive minerals of widespread occurrence in natural and industrial settings. These minerals chiefly occur as nano- to submicron-sized particles and are covered by hydroxyl functional groups coordinated to one (-OH), two (μ-OH), or three (μ(3)-OH) underlying iron atoms. These groups are reaction centers for gases, solutes as well as solvents and thereby play important roles in the fate and transformation of natural and industrial compounds. In this work we provide tools to identify hydroxyl groups on distinct crystallographic planes of two important FeOOH polymorphs, namely lepidocrocite (γ-FeOOH) and goethite (α-FeOOH). Fourier transform infrared spectroscopy was used to monitor O-H stretching vibrations of groups on particles with well-defined and distinct morphologies. Spectral responses to proton loadings and thermal gradients were used to assign bands to hydroxyl groups. These efforts were facilitated by the extraction of pure spectral components obtained by multivariate curve resolution. Molecular dynamics simulations of dominant crystallographic planes of the particles guided band assignment procedures by identifying feasible hydrogen bond networks between surface groups. Our findings provide new possibilities for molecular-scale resolution of important gas-phase processes on the surfaces of these important minerals.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Structural controls on OH site availability and reactivity at iron oxyhydroxide particle surfaces

Song

Boily

2012

Phys. Chem. Chem. Phys.

106

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“…4,5 Thermally induced changes in both surface structure and stoichiometry have been found on sapphire crystal surfaces. 6,7 However, few studies have dealt with the interaction between heat-treated alumina surfaces and water or attempted to correlate the interactions with surface morphological changes. This is the focus of the present paper.…”

Section: Introductionmentioning

confidence: 99%

The unusual surface chemistry of α-Al2O3 (0001)

Yang

Krasowska

Sedev

et al. 2010

Phys. Chem. Chem. Phys.

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We report on the influence of heat treatment on the surface chemistry of an α-alumina crystal. We compare its electrical double layer behaviour with that of 150 nm diameter α-Al(2)O(3) particles. Surface spectroscopy and zeta potential studies are used to understand the changes in surface chemistry. The pH(pzc) of an α-Al(2)O(3) (0001) single crystal (∼4) is more acidic than that of α-Al(2)O(3) particles (8.5), a difference explained by the dominance of [triple bond, length as m-dash]Al(2)OH surface groups on the single crystals and their charging behaviour. Heat treatment of the alumina surface causes a substantial decrease in the number of surface OH groups. Heating at 500 °C decreases the surface density of hydroxyl groups. Heating at 1050 °C also affects surface morphology and surface chemistry. The increased magnitude of the zeta potential and the pH(pzc) shift to lower pH suggest a surface reconstruction and the appearance of more acidic aluminium sites.

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“…[2][3][4][5][6][7][8][9][10][11] Hematite ͑␣-Fe 2 O 3 ͒ is common in all geological formations considered for nuclear waste repositories and a highly reactive sorbent for cations such as the actinide ions. Unfortunately, interface selective nonlinear sum frequency spectroscopy at hematite is very difficult due to very strong absorption.…”

Section: Introductionmentioning

confidence: 99%

Theoretical investigation of the water/corundum (0001) interface

Polly

Schimmelpfennig

Flörsheimer

et al. 2009

The Journal of Chemical Physics

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For the reliable long-term modeling of the actinide migration in geological formations, the adsorption/desorption properties and the reactivity of mineral surfaces must be understood at the molecular level. The adsorption of radioisotopes at mineral surfaces of the aquifer is an important process that leads to the retention of contaminants such as radionuclides. Their transport by the ground water is either retarded or even completely inhibited by the presence of such a surface. Accordingly, this subject is of main importance for the safety assessment of nuclear waste repositories. As part of a joint theoretical/experimental effort, the interaction of water with the corundum (0001) surface is studied using several theoretical methods (Moller-Plesset perturbation theory, coupled cluster singles doubles with triplet corrections, as well as density functional theory). We focus in this study on the determination of the bond lengths and tilt angles of the surface OH species and their respective vibrational frequencies. The theoretical results are confirmed by subsequent simulation of the interface selective nonlinear sum frequency spectra. The excellent agreement of the simulated with the experimental spectra allows an assignment of the observed peaks in the sum frequency spectra of the water/corundum (0001) interface on the basis of our theoretical data. In this theoretical study we are able to give a unique interpretation of the observed sum frequency spectra of the water/corundum (0001) interface.

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High-temperature hydroxylation of alumina crystalline surfaces

Cited by 27 publications

References 20 publications

Structural controls on OH site availability and reactivity at iron oxyhydroxide particle surfaces

Structural controls on OH site availability and reactivity at iron oxyhydroxide particle surfaces

The unusual surface chemistry of α-Al2O3 (0001)

Theoretical investigation of the water/corundum (0001) interface

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