Speciation modelling of the electroprecipitation of rare-earth cuprate and nickelate materials Speciation of aqueous solutions not at equilibrium

Monk, Paul; Janes, Robert R.; Partridge, Robert D.

doi:10.1039/a706095e

Cited by 14 publications

(8 citation statements)

References 25 publications

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“…Monk 13 was successful in electroprecipitating a mixture of copper and lanthanum, forming a mixed metal hydroxide species that was validated through speciation modeling. 13 However, surface pH changes near the electrode surface was not included in this study. Additionally, quantification of surface pH changes during electroprecipitation reactions may improve the preparation of lanthanide hydroxide-modified surfaces in the protection of surfaces/nanoparticles.…”

Section: D655mentioning

confidence: 98%

“…In the presence of nitrate, reduction to ammonia results in an increase in surface pH, but in the absence of nitrate ions, the hydrogen reduction reaction (HER) is responsible for the pH increase. 13 The alkaline conditions at the electrode surface result in metal ion hydrolysis and precipitation on the electrode surface. Therefore, to verify electroprecipitation as a possible mechanism, the surface pH changes near the electrode surface needs to be compared to the speciation of the analyte at that pH.…”

Section: D655mentioning

confidence: 99%

“…Therefore, to verify electroprecipitation as a possible mechanism, the surface pH changes near the electrode surface needs to be compared to the speciation of the analyte at that pH. Monk 13 was successful in electroprecipitating a mixture of copper and lanthanum, forming a mixed metal hydroxide species that was validated through speciation modeling. 13 However, surface pH changes near the electrode surface was not included in this study.…”

Section: D655mentioning

confidence: 99%

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Electrochemical Preconcentration Mechanism of Trivalent Lanthanum

Medina

Ivory

Wall

et al. 2018

J. Electrochem. Soc.

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The goals of this work were 1) to demonstrate lanthanum preconcentration/deposition on electrodes, 2) to elucidate the mechanism of deposition, and 3) to use electrodeposition to detect lanthanum on carbon fiber microelectrodes. Lanthanum was preconcentrated via electroprecipitation on carbon electrodes using unbuffered electrolyte. To measure the amount of La deposited on the surface, we used eQCM to observe the mass change (quantified as frequency change) while La precipitated on the surface of the electrode. The chemical state of the deposited film was determined using X-ray photoelectron spectrometry and Auger electron spectrometry. We used a pH microelectrode with a tip diameter of less than 20 μm near the electrode surface to determine surface pH changes. We found that lanthanum preconcentration on electrodes is a result of pH changes at the electrode surface due to water electrolysis. La(OH) 3 was determined to be the predominant state of the film, with La and O atoms colocalized in the precipitates. Based on this discovery, the current responses to lanthanum electroprecipitation on carbon fiber microelectrodes and a mercury-filmed carbon fiber microelectrode were compared. We found that both microelectrode responses were concentration-dependent.

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Section: D655mentioning

confidence: 98%

Section: D655mentioning

confidence: 99%

Section: D655mentioning

confidence: 99%

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Electrochemical Preconcentration Mechanism of Trivalent Lanthanum

Medina

Ivory

Wall

et al. 2018

J. Electrochem. Soc.

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“…At 2.5 and 3 mA cm Ϫ2 , the potential decrease is non-negligible but moderate, confirming the small resistance cell drop due to the hydrated nature of electroprecipitated hydroxide films in spite of their insulating properties. 54 A parallel examination of current and potential transients has allowed to us to confirm the progressive evolution of the overall deposition process with variable parameters. When either the overpotential or the cathodic current density is increased, the corresponding position of the experimental conditions on the cathodic polarization curve is shifted from the top right to the bottom left part ͑Fig.…”

Section: Resultsmentioning

confidence: 97%

“…46 On our own, we confirmed unambiguously these latter results in dimethylsulfoxide ͑DMSO͒ solutions containing residual water, thereby showing that the hydrogen evolution reaction is of prime importance for cathodic base generation. 47 Despite the occasional publication of interesting studies about peculiar single or composite oxides of technological interest, 27,34,[50][51][52][53][54] the link in this field between fundamental research and material optimization appears to be scarce as a general rule, and current methodologies are mostly empirical. There is a deep need to rationalize the way of determining the best experimental conditions for obtaining good quality oxide materials by electrodeposition, as for semiconductor chalcogenides.…”

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confidence: 99%

Electrochemical Codeposition of Copper-Strontium Hydroxide Films from Dimethylsulfoxide Solutions

Lepiller

Poissonnet

Bonnaillie

et al. 2004

J. Electrochem. Soc.

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The cathodic electrodeposition technique has been applied to the binary Cu͑II) ϩ Sr͑II) system in nitrate-dimethylsulfoxide solution, with use of voltammetry as a prerequisite to thin-film synthesis. The electrochemical study was performed under diffusion and convection regimes as a function of the concentration ratio r ϭ ͓Sr͑II͔͒/͓Cu͑II)] and resulted in the choice of a solution with r ϭ 5 for deposition experiments. Films were grown potentiostatically and galvanostatically at room temperature on silver tapes. Electrolytic deposition was followed by annealing for 4 min in air at 880°C. Both series were then analyzed by chronoamperometry, X-ray diffraction, electron microprobe analysis, and scanning electron microscopy. Inside the parameter ranges determined by electrochemistry, as-grown and annealed films were homogeneous, pinhole-free, and adherent. The best quality was seen in the galvanostatic mode due to accurate control of the overall deposition rate. Copper was electrodeposited as a metal by diffusion-limited reduction of Cu͑II͒ ions, while strontium was precipitated as a hydroxide by electrogeneration of base in the water reduction range. Codeposition was found to give rise to separated phases, involving a microcrystalline strontium hydroxide layer surrounding a nanocrystalline copper underlayer, which was surrounded by copper surface clusters. Annealed films were composed of various mixtures of strontium cuprate phases, whose composition was directly related to the strontiumcopper atomic ratio in the precursor films.

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