Détermination du mécanisme de dégagement d'hydrogène sur le niobium en milieu alcalin

Vijayan, Cherubala P.; Piron, Dominique-Louis

doi:10.1139/v77-057

Cited by 3 publications

(4 citation statements)

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“…Energy conversion from electricity to hydrogen during the electrolysis of water does, however, require increased efficiency for the success of a hydrogen economy. It is the object of the present investigation to contribute to a better knowledge of materials that can be used as electrocatalysts.The hydrogen evolution reaction on niobium has been studied quite intensively at low hydrogen overvoltage (3)(4)(5). Under high hydrogen overvoltage, the niobium electrode undergoes some modification, and the current associated with the hydrogen evolution reaction increases as was shown earlier (2, 3).…”

mentioning

confidence: 88%

“…The hydrogen evolution reaction on niobium has been studied quite intensively at low hydrogen overvoltage (3)(4)(5). Under high hydrogen overvoltage, the niobium electrode undergoes some modification, and the current associated with the hydrogen evolution reaction increases as was shown earlier (2,3).…”

mentioning

confidence: 93%

“…65~ and accelerates the erosion of the electrode. 5. The film on the as-polished Nb is very close to the oxide Nb205, but the one on the cathodically treated Nb is postulated to be an oxyhydroxide in which the oxidation state of Nb is slightly lower than Nb~ +.…”

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confidence: 95%

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Changes in the Niobium Electrode Surface Induced by Strong Cathodic Polarization

Sugimoto

Bélanger

Piron

1979

J. Electrochem. Soc.

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The cathodic polarization characteristics of the Nb electrode were measured in 25% KOH solutions at 24~The changes in the morphology and composition of the surlace of the electrode under cathodic polarization were examined. It was found that two kinds of layers were formed on the surface of the electrode: a black film-like layer, which is the outer layer, and a layer with a needle-like structure, which is the inner layer. Both layers are thought to be mobium hydrides with different H/~b ratios. At high temperatures, the outer layer became thick and powdery. 'lhis caused an increase in the hydrogen overpotential above b5~ as well as erosion of the electrode. The x-ray photoelectron spectra of the cathodically polarized emctrode indicate a change in the chemical nature of the surIace; the oxide layer undergoes partial reduction and OH entities are detected.Over recent years, there has been a growing interest in the use of hydrogen for the storage and transportation of energy (1, 2). Energy conversion from electricity to hydrogen during the electrolysis of water does, however, require increased efficiency for the success of a hydrogen economy. It is the object of the present investigation to contribute to a better knowledge of materials that can be used as electrocatalysts.The hydrogen evolution reaction on niobium has been studied quite intensively at low hydrogen overvoltage (3)(4)(5). Under high hydrogen overvoltage, the niobium electrode undergoes some modification, and the current associated with the hydrogen evolution reaction increases as was shown earlier (2, 3). The hydrogen evolution overpotential under certain prepolarization treatment can reach values comparable to nickel electrodes now used in commercial electrolyzers. Such dramatic improvements are worth investigating by surface analytical techniques. Therefore in this investigation, the behavior of niobium in 25% KOH solution under high cathodic polarization was studied by electrochemical, spectroscopic, and microscopic techniques to follow the changes in the surface properties and characteristics when the electrode sustains the I-IER. ExperimentalTwo kinds of pure Nb rods were used for electrodes: a spectrographically pure Nb rod (main impurities, in ppm: Fe 3, Si 3, Mg < 1, Ag < 1) which had a diameter of 4.2 ram, and a 99.9% Nb rod (main impurities in ppm: C 25, O 210, N 60, Ta 480, Ti 30), which had a diameter of 6.4 ram. The former was used for microscopic observations and analyses by x-ray photoelectron spectroscopy (XPS). The cross sections of both rods were used as the electrode surfaces. The surfaces were polished with 0.05 ~m alumina suspension. The side of the rod was insulated by winding a vinyl adhesive tape around the rod and then coating epoxy resin over it. Electrode surfaces were degreased with ethyl alcohol, washed with distilled 9 Electrochemical Society Active Member.water, and then etched in HF solution for 1 rain at room temperature just before using.A 25% KOH solution (pH 14.2) was used as the electrolyte. Solutions were deaerat...

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Changes in the Niobium Electrode Surface Induced by Strong Cathodic Polarization

Sugimoto

Bélanger

Piron

1979

J. Electrochem. Soc.

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“…Aprks refroidissement et solidification, le l'klectrolvse de l'eau en milieu alcalin. le niobium a bouton d'alliage ainsi forme a ete retourne et refondu pour kt6 ktudik par notre groupe (1)(2)(3)(4)(5). L~ &canisme du assurer une homog6neit6 complkte a l'etat solide de I'alliage.…”

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Polarisation cathodique en milieu alcalin des alliages Nb–Co

Umetsu¹,

Piron²,

Bélanger³

1981

Can. J. Chem.

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NbCo alloys were prepared and their composition characterized by optical microscopy. These alloys were evaluated for their electrochemical activity towards the hydrogen evolution reaction (HER) at 25 °C in a 25% KOH solution. The alloys between 20 and 70wt% Co showed an increased activity compared to their parent metals. However the activity is below the one observed for pure Ni. As for the NbNi alloys, the NbCo undergo some surface degradation under prolonged (6 h) cathodic polarization at 400–700 mA cm−2. This disintegration of the surfaces is observed for alloys below 50% in Co. Above this proportion, the alloys remain stable towards the RDH. This degradation is associated with the presence of the δ phase in the alloy: this phase is the solid solution of Nb in the alloy.

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