Characterization of the β-Ni(OH)2/β-NiOOH system by positron lifetime spectroscopy

Süvegh, Károly; Horányi, T.S.; Vértes, A.

doi:10.1016/0013-4686(88)80195-6

Cited by 12 publications

(9 citation statements)

References 12 publications

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“…In our earlier work, we confirmed the outlined mechanism of the oxidation-reduction process on electrochemically treated samples with the help of positron lifetime spectro-scopy and observed the formation of a positron trap in the heterogeneous range [4]. In this work, we give the results of measurements performed on chemically oxidised samples and compare these results with those of electrochemical oxidation.…”

Section: Introductionsupporting

confidence: 67%

“…Of the lifetimes, z3 is the only identifiable one. On the basis of our earlier measurements on fine-grained and rough-grained pure Ni(OH), [4], we related it to the annihilation of oxidised positronium atoms trapped at the surface of Ni(OH)*. Therefore, the decrease in Z3 indicates the decreasing Ni(OH)* content of the surfaces of grains.…”

Section: Resultsmentioning

confidence: 98%

“…To obtain good electrical contact during the electrochemical treatment, the samples were mixed with 20% graphite. The detailed description of the sample preparation and the electrochemical oxidation-reduction process can be found in [4].…”

Section: Methodsmentioning

confidence: 99%

“…Spectra were evaluated as three components by the POSITRONFIT EXTENDED computer program [5]. However, these components were scarcely identifiable because of the two lifetimes of the graphite and the three lifetimes of the pure material [4].…”

Section: Methodsmentioning

confidence: 99%

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Oxidation of βl-Ni(OH)₂: positron lifetime study of a heterogeneous solid

Süvegh

Horányi²,

Vértes

1989

J. Phys.: Condens. Matter

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Positron lifetime spectroscopy was used to characterise the P-Ni(OH),/P-NiOOH electrode system. The lifetime parameters for both chemically and electrochemically treated samples are presented. Three different stages in the oxidation-reduction process were observed and identified. For intermediate-oxidation states the samples were assumed to be heterogeneous and the interface between the differently oxidised phases proved to be an effective positron trap. The positron lifetime parameters provided valuable information about the oxidation processes occurring in different ways in the chemically and the electrochemically treated samples.

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Section: Introductionsupporting

confidence: 67%

Section: Resultsmentioning

confidence: 98%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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Oxidation of βl-Ni(OH)₂: positron lifetime study of a heterogeneous solid

Süvegh

Horányi²,

Vértes

1989

J. Phys.: Condens. Matter

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“…According to Barnard's work, − it was generally assumed that the reversible transformation of β-II into β-III occurs in three definite steps: an initial β-II solid solution region up to NEE = 0.25, a biphasic domain up to NEE = 0.75, and a final β-III solid solution region up to NEE = 1. Such assumptions were later confirmed by other techniques, such as thermal analysis and positron lifetime spectroscopy . However, later on, by studying chemically prepared samples with controlled oxidation degree, Tessier et al pointed out that at least the β-II solid solution region could be much smaller than expected.…”

Section: Resultsmentioning

confidence: 94%

In Situ Neutron Powder Diffraction of a Nickel Hydroxide Electrode

et al. 2004

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The redox processes occurring at the nickel oxyhydroxide electrodes were followed by in situ neutron diffraction. The aim was to get a deeper insight into the existing phases and the reactivity mechanisms involved in the reduction process, paying special attention to the so-called “second plateau” phenomenon, occasionally appearing during electrochemical reduction at a potential of 0.8 V vs Hg/HgO. Chemically prepared protonated or deuterated nickel hydroxides, having different phase compositions, oxidation state, and particle size were studied to serve as reference samples. The electrochemically driven structural evolution of four samples upon discharge and charge was followed by in situ neutron powder diffraction using a specially designed cell. For both γ and β-NiOOH phases, the neutron diffraction results evidenced a direct and continuous structural transformation into the β-Ni(OH)2 phase upon reduction, on both the first and the second plateau, with no discontinuity when encountering the second plateau. This confirms that the second plateau phenomenon is not due to any intrinsic structural properties of the active material but is related to its surface properties being prone to be strongly dependent upon the electrode preparation.

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The Nickel Group (Nickel, Palladium, and Platinum)

Inzelt

Horányi

2006

Encyclopedia of Electrochemistry

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The sections in this article are Nickel Fundamentals Surface Changes at Atomic Level as a Function of Potential Adsorption Studies Spontaneous Reduction of Anions at Ni Surface Electrochemical Oscillation during Nickel Dissolution New Findings on the Dissolution/Deposition Processes Nickel–Hydrogen Systems Nickel Oxide and Nickel Hydroxide Palladium Fundamentals New Findings on the Dissolution and Deposition of Palladium Hydrogen and Oxygen Sorption in/at Palladium Electrodes Electrosorption and Electrocatalytic Processes Platinum Fundamentals Effect of Adsorption and Surface Structure on the Voltammetric Behavior of Platinum Electrodes Adsorption of Hydrogen, Oxygen, and Anions Well‐defined Platinum Surfaces Faceted and Platinized Platinum Electrodes Surface Structure and Reactivity Acknowledgment

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Characterization of the β-Ni(OH)2/β-NiOOH system by positron lifetime spectroscopy

Cited by 12 publications

References 12 publications

Oxidation of βl-Ni(OH)₂: positron lifetime study of a heterogeneous solid

Oxidation of βl-Ni(OH)₂: positron lifetime study of a heterogeneous solid

In Situ Neutron Powder Diffraction of a Nickel Hydroxide Electrode

The Nickel Group (Nickel, Palladium, and Platinum)

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Characterization of the β-Ni(OH)2/β-NiOOH system by positron lifetime spectroscopy

Cited by 12 publications

References 12 publications

Oxidation of βl-Ni(OH)2: positron lifetime study of a heterogeneous solid

Oxidation of βl-Ni(OH)2: positron lifetime study of a heterogeneous solid

In Situ Neutron Powder Diffraction of a Nickel Hydroxide Electrode

The Nickel Group (Nickel, Palladium, and Platinum)

Contact Info

Product

Resources

About

Oxidation of βl-Ni(OH)₂: positron lifetime study of a heterogeneous solid

Oxidation of βl-Ni(OH)₂: positron lifetime study of a heterogeneous solid