Effect of surface site interactions on potentiometric titration of hematite (α-Fe2O3) crystal faces

Chatman, Shawn; Zarzycki, Piotr; Preočanin, Tajana; Rosso, Kevin M.

doi:10.1016/j.jcis.2012.09.081

Cited by 37 publications

(88 citation statements)

References 55 publications

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“…The orientation of surface OH groups and the patterns they form influence solvent interaction processes like water splitting or crystal growth [22,79]. Figure 7 shows the most stable patterns for both the iron and the oxygen termination.…”

Section: Surface Oh Group Patternsmentioning

confidence: 99%

Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

Rudorff

Jakobsen

Rosso

et al. 2016

J. Phys.: Condens. Matter

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The atom-scale characterisation of interfaces between transition metal oxides and liquid water is fundamental to our mechanistic understanding of diverse phenomena ranging from crystal growth to biogeochemical transformations to solar fuel production. Here we report on the results of large-scale hybrid density functional theory-based molecular dynamics simulations for the hematite(001)-liquid water interface. A specific focus is placed on understanding how different terminations of the same surface influence surface solvation. We find that the two dominant terminations for the hematite(001) surface exhibit strong differences both in terms of the active species formed on the surface and the strength of surface solvation. According to present simulations, we find that charged oxyanions (-O−) and doubly protonated oxygens (-OH) can be formed on the iron terminated layer via autoionization of neutral -OH groups. No such charged species are found for the oxygen terminated surface. In addition, the missing iron sublayer in the iron terminated surface strongly influences the solvation structure, which becomes less well ordered in the vicinity of the interface. These pronounced differences are likely to affect the reactivity of the two surface terminations, and in particular the energetics of excess charge carriers at the surface.

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Section: Surface Oh Group Patternsmentioning

confidence: 99%

Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

Rudorff

Jakobsen

Rosso

et al. 2016

J. Phys.: Condens. Matter

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“…Another series of studies involved surface potential measurements. [67][68][69][70][71] The bulk part of the data suggests a broad plateau-like region in surface potential vs. pH curves with an increase at sufficiently low and a decrease at sufficiently high pH. Various interpretations of the data have been proposed.…”

Section: Introductionmentioning

confidence: 99%

Structure–charge relationship – the case of hematite (001)

et al. 2015

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We present a multidisciplinary study on the hematite (001)-aqueous solution interface, in particular the relationship between surface structure (studied via surface diffraction in a humid atmosphere) and the macroscopic charging (studied via surface- and zeta-potential measurements in electrolyte solutions as a function of pH). Upon aging in water changes in the surface structure are observed, that are accompanied by drastic changes in the zeta-potential. Surprisingly the surface potential is not accordingly affected. We interpret our results by increasing hydration of the surface with time and enhanced reactivity of singly-coordinated hydroxyl groups that cause the isoelectric point of the surface to shift to values that are reminiscent of those typically reported for hematite particles. In its initial stages after preparation the hematite surface is very flat and only weakly hydrated. Our model links the entailing weak water structure with the observed low isoelectric point reminiscent of hydrophobic surfaces. The absence of an aging effect on the surface potential vs. pH curves is interpreted as domination of the surface potential by the doubly coordinated hydroxyls, which are present on both surfaces.

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“…1a), which was composed of a single-crystal hematite electrode (SCrE), [18][19][20][21][22] a platinum electrode and the combined reference (Ag|AgCl)/glass electrode (Metrohm, US). The alkalimetric titration was performed by using a 665 Dosimat (Metrohm, US) assisted with/without the ultrasound mixing to avoid particle aggregation.…”

Section: Apparatusmentioning

confidence: 99%

“…[18][19][20][21][24][25][26] The natural hematite crystal was fixed in a plexiglass holder, and the surface was cleaned with ethanol and deionised water. [18][19][20][21][24][25][26] The natural hematite crystal was fixed in a plexiglass holder, and the surface was cleaned with ethanol and deionised water.…”

Section: Single-crystal Hematite Electrodementioning

confidence: 99%

Potentiometric and electrokinetic signatures of iron(ii) interactions with (α,γ)-Fe₂O₃

Toczydlowska

Kędra-Królik

Nejbert

et al. 2015

Phys. Chem. Chem. Phys.

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The electrochemical signatures of Fe(II) interactions with iron(III) oxides are poorly understood, despite their importance in controlling the amount of mobilized iron. Here, we report the potentiometric titration of α,γ-Fe2O3 oxides exposed to Fe(II) ions. We monitored in situ surface and ζ potentials, the ratio of mobilized ferric to ferrous, and the periodically analyzed nanoparticle crystal structure using X-ray diffraction. Electrokinetic potential reveals weak but still noticeable specific sorption of Fe(II) to the oxide surface under acidic conditions, and pronounced adsorption under alkaline conditions that results in a surface potential reversal. By monitoring the aqueous iron(II/III) fraction, we found that the addition of Fe(II) ions produces platinum electrode response consistent with the iron solubility-activity curve. Although, XRD analysis showed no evidence of γ-Fe2O3 transformations along the titration pathway despite iron cycling between aqueous and solid reservoirs, the magnetite formation cannot be ruled out.

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Effect of surface site interactions on potentiometric titration of hematite (α-Fe2O3) crystal faces

Cited by 37 publications

References 55 publications

Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

Structure–charge relationship – the case of hematite (001)

Potentiometric and electrokinetic signatures of iron(ii) interactions with (α,γ)-Fe₂O₃

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Effect of surface site interactions on potentiometric titration of hematite (α-Fe2O3) crystal faces

Cited by 37 publications

References 55 publications

Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

Hematite(001)-liquid water interface from hybrid density functional-based molecular dynamics

Structure–charge relationship – the case of hematite (001)

Potentiometric and electrokinetic signatures of iron(ii) interactions with (α,γ)-Fe2O3

Contact Info

Product

Resources

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Potentiometric and electrokinetic signatures of iron(ii) interactions with (α,γ)-Fe₂O₃