Structure of hydrated Zn2+ at the rutile TiO2 (110)-aqueous solution interface: Comparison of X-ray standing wave, X-ray absorption spectroscopy, and density functional theory results

Zhan Zhang, Paul Fenter, Shelly D. Kelly, Jeffery G. Catalano, Andrei V. Bandura, James D. Kubicki, Jorge Osvaldo Sofo, David J. Wesolowski, Michael L. Machesky, Neil C. Sturchio, Michael J. Bedzyk

Research output: Contribution to journalArticle

43 Citations (Scopus)

Abstract

Adsorption of Zn2+ at the rutile TiO2 (110)-aqueous interface was studied with Bragg-reflection X-ray standing waves (XSW), polarization-dependent surface extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) calculations to understand the interrelated issues of adsorption site, its occupancy, ion-oxygen coordination and hydrolysis. At pH 8, Zn2+ was found to adsorb as an inner-sphere complex at two different sites, i.e., monodentate above the bridging O site and bidentate between two neighboring terminal O sites. EXAFS results directly revealed a four or fivefold first shell coordination environment for adsorbed Zn2+ instead of the sixfold coordination found for aqueous species at this pH. DFT calculations confirmed the energetic stability of a lower coordination environment for the adsorbed species and revealed that the change to this coordination environment is correlated with the hydrolysis of adsorbed Zn2+. In addition, the derived adsorption locations and the occupancy factors of both sites from three methods agree well, with some quantitative discrepancies in the minor site location among the XSW, EXAFS, and DFT methods. Additional XSW measurements showed that the adsorption sites of Zn2+ were unchanged at pH 6. However, the Zn2+ partitioning between the two sites changed substantially, with an almost equal distribution between the two types of sites at pH 6 compared to predominantly monodentate occupation at pH 8.

Original languageEnglish (US)
Pages (from-to)4039-4056
Number of pages18
JournalGeochimica et Cosmochimica Acta
Volume70
Issue number16
DOIs
StatePublished - Aug 15 2006

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X ray absorption spectroscopy
standing wave
atomic absorption spectroscopy
rutile
X-ray spectroscopy
Density functional theory
aqueous solution
Adsorption
X rays
X ray absorption
adsorption
Hydrolysis
Extended X ray absorption fine structure spectroscopy
hydrolysis
Ions
Polarization
Oxygen
occupation
comparison
titanium dioxide

All Science Journal Classification (ASJC) codes

  • Geochemistry and Petrology

Cite this

Zhang, Zhan ; Fenter, Paul ; Kelly, Shelly D. ; Catalano, Jeffery G. ; Bandura, Andrei V. ; Kubicki, James D. ; Sofo, Jorge Osvaldo ; Wesolowski, David J. ; Machesky, Michael L. ; Sturchio, Neil C. ; Bedzyk, Michael J. / Structure of hydrated Zn2+ at the rutile TiO2 (110)-aqueous solution interface : Comparison of X-ray standing wave, X-ray absorption spectroscopy, and density functional theory results. In: Geochimica et Cosmochimica Acta. 2006 ; Vol. 70, No. 16. pp. 4039-4056.
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title = "Structure of hydrated Zn2+ at the rutile TiO2 (110)-aqueous solution interface: Comparison of X-ray standing wave, X-ray absorption spectroscopy, and density functional theory results",
abstract = "Adsorption of Zn2+ at the rutile TiO2 (110)-aqueous interface was studied with Bragg-reflection X-ray standing waves (XSW), polarization-dependent surface extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) calculations to understand the interrelated issues of adsorption site, its occupancy, ion-oxygen coordination and hydrolysis. At pH 8, Zn2+ was found to adsorb as an inner-sphere complex at two different sites, i.e., monodentate above the bridging O site and bidentate between two neighboring terminal O sites. EXAFS results directly revealed a four or fivefold first shell coordination environment for adsorbed Zn2+ instead of the sixfold coordination found for aqueous species at this pH. DFT calculations confirmed the energetic stability of a lower coordination environment for the adsorbed species and revealed that the change to this coordination environment is correlated with the hydrolysis of adsorbed Zn2+. In addition, the derived adsorption locations and the occupancy factors of both sites from three methods agree well, with some quantitative discrepancies in the minor site location among the XSW, EXAFS, and DFT methods. Additional XSW measurements showed that the adsorption sites of Zn2+ were unchanged at pH 6. However, the Zn2+ partitioning between the two sites changed substantially, with an almost equal distribution between the two types of sites at pH 6 compared to predominantly monodentate occupation at pH 8.",
author = "Zhan Zhang and Paul Fenter and Kelly, {Shelly D.} and Catalano, {Jeffery G.} and Bandura, {Andrei V.} and Kubicki, {James D.} and Sofo, {Jorge Osvaldo} and Wesolowski, {David J.} and Machesky, {Michael L.} and Sturchio, {Neil C.} and Bedzyk, {Michael J.}",
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Structure of hydrated Zn2+ at the rutile TiO2 (110)-aqueous solution interface : Comparison of X-ray standing wave, X-ray absorption spectroscopy, and density functional theory results. / Zhang, Zhan; Fenter, Paul; Kelly, Shelly D.; Catalano, Jeffery G.; Bandura, Andrei V.; Kubicki, James D.; Sofo, Jorge Osvaldo; Wesolowski, David J.; Machesky, Michael L.; Sturchio, Neil C.; Bedzyk, Michael J.

In: Geochimica et Cosmochimica Acta, Vol. 70, No. 16, 15.08.2006, p. 4039-4056.

Research output: Contribution to journalArticle

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T1 - Structure of hydrated Zn2+ at the rutile TiO2 (110)-aqueous solution interface

T2 - Comparison of X-ray standing wave, X-ray absorption spectroscopy, and density functional theory results

AU - Zhang, Zhan

AU - Fenter, Paul

AU - Kelly, Shelly D.

AU - Catalano, Jeffery G.

AU - Bandura, Andrei V.

AU - Kubicki, James D.

AU - Sofo, Jorge Osvaldo

AU - Wesolowski, David J.

AU - Machesky, Michael L.

AU - Sturchio, Neil C.

AU - Bedzyk, Michael J.

PY - 2006/8/15

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N2 - Adsorption of Zn2+ at the rutile TiO2 (110)-aqueous interface was studied with Bragg-reflection X-ray standing waves (XSW), polarization-dependent surface extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) calculations to understand the interrelated issues of adsorption site, its occupancy, ion-oxygen coordination and hydrolysis. At pH 8, Zn2+ was found to adsorb as an inner-sphere complex at two different sites, i.e., monodentate above the bridging O site and bidentate between two neighboring terminal O sites. EXAFS results directly revealed a four or fivefold first shell coordination environment for adsorbed Zn2+ instead of the sixfold coordination found for aqueous species at this pH. DFT calculations confirmed the energetic stability of a lower coordination environment for the adsorbed species and revealed that the change to this coordination environment is correlated with the hydrolysis of adsorbed Zn2+. In addition, the derived adsorption locations and the occupancy factors of both sites from three methods agree well, with some quantitative discrepancies in the minor site location among the XSW, EXAFS, and DFT methods. Additional XSW measurements showed that the adsorption sites of Zn2+ were unchanged at pH 6. However, the Zn2+ partitioning between the two sites changed substantially, with an almost equal distribution between the two types of sites at pH 6 compared to predominantly monodentate occupation at pH 8.

AB - Adsorption of Zn2+ at the rutile TiO2 (110)-aqueous interface was studied with Bragg-reflection X-ray standing waves (XSW), polarization-dependent surface extended X-ray absorption fine structure (EXAFS) spectroscopy, and density functional theory (DFT) calculations to understand the interrelated issues of adsorption site, its occupancy, ion-oxygen coordination and hydrolysis. At pH 8, Zn2+ was found to adsorb as an inner-sphere complex at two different sites, i.e., monodentate above the bridging O site and bidentate between two neighboring terminal O sites. EXAFS results directly revealed a four or fivefold first shell coordination environment for adsorbed Zn2+ instead of the sixfold coordination found for aqueous species at this pH. DFT calculations confirmed the energetic stability of a lower coordination environment for the adsorbed species and revealed that the change to this coordination environment is correlated with the hydrolysis of adsorbed Zn2+. In addition, the derived adsorption locations and the occupancy factors of both sites from three methods agree well, with some quantitative discrepancies in the minor site location among the XSW, EXAFS, and DFT methods. Additional XSW measurements showed that the adsorption sites of Zn2+ were unchanged at pH 6. However, the Zn2+ partitioning between the two sites changed substantially, with an almost equal distribution between the two types of sites at pH 6 compared to predominantly monodentate occupation at pH 8.

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