Relative stabilities of Ce(IV) and Ce(III) limiting carbonate complexes at 5–50°C in Na+ aqueous solutions, an electrochemical study

Larabi-Gruet, Nathalie; Chaussé, A.; Legrand, Ludovic; Vitorge, Pierre

doi:10.1016/j.electacta.2006.08.046

Cited by 13 publications

(13 citation statements)

References 23 publications

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“…As discussed in our prior work, when using cerium(III) carbonate in an acid solution, the carbonate will react with the available protons to form CO 2 which is vented out of the solution with sufficient N 2 sparging. The redox potentials of cerium carbonate complexes range from 0.198 to 0.2595 V versus SHE, whereas the redox potentials we measured during kinetic measurements ranged between 1.39 and 1.49 V versus SHE, which is consistent with cerium complexation in H 2 SO 4 . We previously demonstrated that the Ce 3+ UV–vis peaks did not change significantly whether Ce 3+ were prepared from Ce 2 (CO 3 ) 3 or Ce(CF 3 SO 3 ) 3 , suggesting that Ce 3+ is predominantly coordinated by the same species in each of these, that is, water .…”

Section: Experimental and Computational Methodssupporting

confidence: 73%

Unveiling the Cerium(III)/(IV) Structures and Charge-Transfer Mechanism in Sulfuric Acid

Buchanan

Herrera

Balasubramanian

et al. 2022

JACS Au

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The Ce3+/Ce4+ redox couple has a charge transfer (CT) with extreme asymmetry and a large shift in redox potential depending on electrolyte composition. The redox potential shift and CT behavior are difficult to understand because neither the cerium structures nor the CT mechanism are well understood, limiting efforts to improve the Ce3+/Ce4+ redox kinetics in applications such as energy storage. Herein, we identify the Ce3+ and Ce4+ structures and CT mechanism in sulfuric acid via extended X-ray absorption fine structure spectroscopy (EXAFS), kinetic measurements, and density functional theory (DFT) calculations. We show EXAFS evidence that confirms that Ce3+ is coordinated by nine water molecules and suggests that Ce4+ is complexed by water and three bisulfates in sulfuric acid. Despite the change in complexation within the first coordination shell between Ce3+ and Ce4+, we show that the kinetics are independent of the electrode, suggesting outer-sphere electron-transfer behavior. We identify a two-step mechanism where Ce4+ exchanges the bisulfate anions with water in a chemical step followed by a rate-determining electron transfer step that follows Marcus theory (MT). This mechanism is consistent with all experimentally observed structural and kinetic data. The asymmetry of the Ce3+/Ce4+ CT and the observed shift in the redox potential with acid is explained by the addition of the chemical step in the CT mechanism. The fitted parameters from this rate law qualitatively agree with DFT-predicted free energies and the reorganization energy. The combination of a two-step mechanism with MT should be considered for other metal ion CT reactions whose kinetics have not been appropriately described.

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Section: Experimental and Computational Methodssupporting

confidence: 73%

Unveiling the Cerium(III)/(IV) Structures and Charge-Transfer Mechanism in Sulfuric Acid

Buchanan

Herrera

Balasubramanian

et al. 2022

JACS Au

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“…In the present study, we investigated the redox behavior of Ce(IV)/Ce(III) in the presence of NTA by cyclic voltammetry to help predict the effect of complexation on the redox behavior of An(IV)/An(III) [13,14], since the ionic radii of Ce(IV) and Ce(III) are comparable to those of An(IV) and An(III), respectively [15]. Both Ce(IV) and An(IV), especially Pu(IV), show strong hydrolysis tendency and form polymeric species even in highly acidic solutions [16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Redox behavior of Ce(IV)/Ce(III) in the presence of nitrilotriacetic acid: A surrogate study for An(IV)/An(III) redox behavior

2010

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Using cyclic voltammetry, we investigated the redox behavior of Ce(IV)/Ce(III), which is a surrogate for An(IV)/An(III) (An=actinides), in a solution of nitrilotriacetic acid (NTA) at 25 °C. The cyclic voltammogram of Ce in a 0.1 M NTA solution at pH 6 showed a reversible one-electron redox reaction for Ce(IV)/Ce(III) at 0.51 V vs. Ag/AgCl. This redox potential was much lower than that obtained in 1 M nitric acid, indicating that Ce(IV) was preferentially stabilized by complexation with NTA. The redox potential in the NTA solution was independent of the Ce concentration from 2 to 20 mM, NTA concentration from 5 to 200 mM and pH between 3 and 7. These results indicated that no polymerization and no additional coordination of NTA and OH− to the Ce(III)-NTA complex took place during the redox reaction. As the speciation calculation of Ce(III) in the NTA solution showed that the predominant species was CeIII(nta)2 3− (H3nta=NTA), the redox reaction of the Ce-NTA complex was expressed by the following: CeIV(nta)2 2−+e−⇋CeIII(nta)2 3−. The logarithm of the stability constant of CeIV(nta)2 2− was calculated to be 38.6±0.8 for I=0 from the redox potential shift of Ce(IV)/Ce(III) in the NTA solution. The value was in good accordance with the stability constant of the NpIV(nta)2 2− complex, demonstrating that the aqueous coordination chemistry of Ce(IV) with NTA is quite similar to that of An(IV). These results strongly suggest that a negative shift of the Pu(IV)/Pu(III) redox potential in the NTA solution should make Pu(IV) more stable than Pu(III) even in a reducing environment.

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“…Due to their similar chemical behaviors and redox states, lanthanides are commonly used as analogues of these actinides in studies of radionuclide migration. − Ce specifically has been used as an analogue of trivalent and tetravalent actinides, − as its +III and +IV oxidation states make it a good analogue for Pu . This study therefore aimed to elucidate the impacts of intrinsic colloid formation through precipitation of radionuclides with carbonates on the migration and recovery of radionuclides through a chalk fracture, using Ce as an analogue for redox active actinides such as Pu.…”

Section: Introductionmentioning

confidence: 99%

Influence of Intrinsic Colloid Formation on Migration of Cerium through Fractured Carbonate Rock

Tran

Klein-BenDavid²,

Teutsch

et al. 2015

Environ. Sci. Technol.

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Migration of colloids may facilitate the transport of radionuclides leaked from near surface waste sites and geological repositories. Intrinsic colloids are favorably formed by precipitation with carbonates in bicarbonate-rich environments, and their migration may be enhanced through fractured bedrock. The mobility of Ce(III) as an intrinsic colloid was studied in an artificial rainwater solution through a natural discrete chalk fracture. The results indicate that at variable injection concentrations (between 1 and 30 mg/L), nearly all of the recovered Ce takes the form of an intrinsic colloid of >0.45 μm diameter, including in those experiments in which the inlet solution was first filtered via 0.45 μm. In all experiments, these intrinsic colloids reached their maximum relative concentrations prior to that of the Br conservative tracer. Total Ce recovery from experiments using 0.45 μm filtered inlet solutions was only about 0.1%, and colloids of >0.45 μm constituted the majority of recovered Ce. About 1% of Ce was recovered when colloids of >0.45 μm were injected, indicating the enhanced mobility and recovery of Ce in the presence of bicarbonate.

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Relative stabilities of Ce(IV) and Ce(III) limiting carbonate complexes at 5–50°C in Na+ aqueous solutions, an electrochemical study

Cited by 13 publications

References 23 publications

Unveiling the Cerium(III)/(IV) Structures and Charge-Transfer Mechanism in Sulfuric Acid

Unveiling the Cerium(III)/(IV) Structures and Charge-Transfer Mechanism in Sulfuric Acid

Redox behavior of Ce(IV)/Ce(III) in the presence of nitrilotriacetic acid: A surrogate study for An(IV)/An(III) redox behavior

Influence of Intrinsic Colloid Formation on Migration of Cerium through Fractured Carbonate Rock

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