The influence of temperature on the anodic oxidation/dissolution of uranium dioxide

Broczkowski, Michael E.; Noël, James J.; Shoesmith, David W.

doi:10.1016/j.electacta.2007.06.027

Cited by 14 publications

(17 citation statements)

References 17 publications

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“…Consequently, and again, it is the relative invariance of ΔE s‐p (Fig. ), even in mixed valence U compounds, that strongly constrains the fit and lessens the dependence of interpreting oxidation states on BEs.…”

Section: Mixed Valence Systemsmentioning

confidence: 99%

“…For example, it is of great interest to the environmental chemistry community whether U is present in the tetravalent or hexavalent state in the subsurface as oxidation state is a primary control on U solubility and hence its ultimate fate and transport in the environment. However, recent work has provided evidence that U(V) can be a long lived intermediate during fuel corrosion, oxidation of colloidal UO 2 , reduction in Fe(II)–Fe(III) systems, and as an artifact of beam induced reduction of U(VI) …”

Section: Introductionmentioning

confidence: 99%

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XPS determination of uranium oxidation states

Ilton

Bagus

2011

Surface & Interface Analysis

217

118

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This contribution is both a review of different aspects of X-ray photoelectron spectroscopy that can help one determine U oxidation states and a personal perspective on how to effectively model the X-ray photoelectron spectroscopy of complicated mixed-valence U phases. After a discussion of the valence band, the focus lingers on the U4f region, where the use of binding energies, satellite structures, and peak shapes is discussed in some detail. Binding energies were shown to be very dependent on composition/structure and consequently unreliable guides to oxidation state, particularly where assignment of composition is difficult. Likewise, the spin orbit split 4f 7/2 and 4f 5/2 peak shapes do not carry significant information on oxidation states. In contrast, both satellite-primary peak binding energy separations, as well as intensities to a lesser extent, are relatively insensitive to composition/structure within the oxide-hydroxide-hydrate system and can be used to both identify and help quantify U oxidation states in mixed valence phases. An example of the usefulness of the satellite structure in constraining the interpretation of a complex multivalence U compound is given. Copyright © 2011 John Wiley & Sons, Ltd.Keywords: XPS; uranium; oxidation states IntroductionOne of the great strengths of X-ray photoelectron spectroscopy ( XPS) is its ability to elucidate the valence state of a wide range of elements at the near-surface of materials. Although many features of interest concern bulk properties, it is the surface and the near-surface that has immediate contact with its surroundings and consequently mediates most reactions. With the renewed interest in nuclear energy, characterizing the surface composition and chemical state of actinide-containing materials is important for both industrial applications and understanding the fate and transport of actinides in the environment. This perspective article is focused on uranium as the data set is by far the most comprehensive of all the actinides where an appreciable literature on the XPS of U compounds dates back to the beginnings of the commercialization of XPS in the 1970s. For an early paper on the XPS of a broad range of actinide oxides we refer the reader to Veal et al.[1] A basic understanding of XPS principles is assumed throughout and will not be reviewed.On one level, determining oxidation states with XPS would appear to be a simple exercise of comparing the binding energies (BEs) of core levels to well characterized standards; so why bother? However, interpreting the oxidation states of samples with mixed valence, unknown structures, and complicated or different compositions can pose a challenge, as with any analytical technique. In fact, composition can strongly affect uranium core-level BEs and potentially confuse the determination of oxidation states. For example, perhaps one is working in an oxidizing system and only expects U(VI), yet the U4f 7/2 line has a peak at 382.0 eV and a shoulder at 380.5 eV. Does the shoulder represent a reduced species, po...

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Section: Mixed Valence Systemsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

XPS determination of uranium oxidation states

Ilton

Bagus

2011

Surface & Interface Analysis

217

118

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“…Numerous studies have focused on redox reactions of uranium compounds [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17]. A subset of these efforts [9][10][11][12][13][14][15][16][17] has made use of X-ray photoelectron spectroscopy (XPS) to quantify systematic changes in the intensities of U IV , U V and U VI components.…”

Section: Introductionmentioning

confidence: 99%

“…A subset of these efforts [9][10][11][12][13][14][15][16][17] has made use of X-ray photoelectron spectroscopy (XPS) to quantify systematic changes in the intensities of U IV , U V and U VI components. For example, in a previous study by the present authors [16] a constant high flux of monochromatic Al Ka X-rays was used to reduce uranyl sorbed on a mica substrate, to a mixture of U IV -U V -U VI oxidation states (Fig.…”

Section: Introductionmentioning

confidence: 99%

An independent confirmation of the correlation of Uf4 primary peaks and satellite structures of UVI, UV and UIV in mixed valence uranium oxides by two-dimensional correlation spectroscopy

Boily

Ilton

2008

Surface Science

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“…The threshold for the onset of anodic dissolution (640 mV vs. SHE) was shown not to change significantly between 20°C and 60°C. However the oxidation of the surface U 4+ to the U 5+ intermediate, and the rate of dissolution of the U 6+ species are appreciably increased in rate at 60°C, with higher anodic (dissolution) currents observed, as expected, when the temperature is raised (Broczkowski et al, 2007). Electrochemical studies on UO 2.0 films have shown that alkaline solutions could lead to the presence of a UO 2.33 layer, which is not observed in acidic solutions, and this most likely contributes to the differences in dissolution rates between acidic and basic solutions (Miserque et al, 2001).…”

Section: Effect Of E Hmentioning

confidence: 52%