EXAFS study of the nickel oxide electrode

McBreen, J.; O’Grady, W.E.; Pandya, K. I.; Hoffman, R. W.; Sayers, D. E.

doi:10.1021/la00075a027

Cited by 177 publications

(122 citation statements)

References 8 publications

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“…The remainder was delivered at a plateau voltage of 1.2V. The discharge curve is shown elsewhere (5). This type of behavior has been seen in battery electrodes (12) and is more common in electrodes with graphite as the conductive diluent (13).…”

Section: Resultsmentioning

confidence: 91%

“…Electrochemical cell--The electrochemical cell has been described in detail elsewhere (5,7). The cell body consisted of two machined acrylic plastic blocks (76 • 76 x 19 ram) with a hole (40 x 10 ram) machined at the center of each block.…”

Section: Methodsmentioning

confidence: 99%

“…Extended x-ray absorption fine structure (EXAFS) technique can be used to study the average local structure of systems that do not possess long range order. A previous paper has presented preliminary results of an in situ EXAFS study of a nickel oxide electrode (5). This work has shown that the EXAFS spectroscopy can be used to study electro-…”

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confidence: 94%

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In Situ X‐Ray Absorption Spectroscopic Studies of Nickel Oxide Electrodes

Pandya

Hoffman

McBreen

et al. 1990

J. Electrochem. Soc.

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117

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In situ transmission x-ray absorption spectroscopy was used to investigate changes in the structure of Ni(OH)2 as it was cycled as a nonsintered nickel oxide electrode in concentrated alkali. Results were obtained for dry as-prepared electrodes and electrodes that were charged or discharged. Changes were observed in the (0001) plane of the Ni(OH)2 as a function of cycling. In the charged material there was a contraction in the Ni-O and Ni-Ni distances. The EXAFS results and the XANES spectra strongly indicate that the Ni-O coordination is symmetrical in Ni(OH)2, whereas the coordination is asymmetric in the charged material.The nickel oxide electrode, also known as the nickel or nickel hydroxide electrode (NOE), is used in batteries, fuel cells, and electrolyzers. Other possible uses are in electrochromic and switching devices. Because of its many applications it has been the subject of numerous investigations and reviews (1-4). In spite of this, the electrode processes remain an enigma. Much of this confusion is due to the amorphous nature of the reactants and products. Extended x-ray absorption fine structure (EXAFS) technique can be used to study the average local structure of systems that do not possess long range order. A previous paper has presented preliminary results of an in situ EXAFS study of a nickel oxide electrode (5). This work has shown that the EXAFS spectroscopy can be used to study electro- chemical systems under working conditions (in situ).The present paper is a more extensive report of the previous work which includes analysis of higher shells and x-ray absorption near edge structure (XANES). ExperimentalElectrode fabrication.--In order to obtain high quality x-ray absorption data, samples of good uniformity and an absorption step (h~x) of -1.5 at the nickel K absorption edge are required (6). From the data interpretation point of view, the data analysis procedure is considerably simplified if only a single compound of the element of interest is present in the sample. For this reason, nonsintered electrodes were fabricated in which nickel was present only in the hydroxide form. Details of the electrode fabrication process are given elsewhere (7,8). The electrodes consisted of ~-Ni(OH)2, cobalt hydroxide, graphite powder, chopped vitreous carbon fibers, and a polyvinylidene fluoride plastic binder. The electrodes were circular and were 25.4 mm in diam and 0.25 mm thick. The electrode composition was 69.1 mg Ni(OH)2, 5.4 mg Co(OH)2, 32.4 mg graphite, ll,6mg carbon fibers, and 12.4mg polyvinylidene fluoride. The theoretical electrode capacity was 20 mAh. Excellent utilization was obtained with these electrodes.Electrochemical cell--The electrochemical cell has been described in detail elsewhere (5, 7). The cell body consisted of two machined acrylic plastic blocks (76 • 76 x 19 ram) with a hole (40 x 10 ram) machined at the center of each block. Acrylic windows (76 x 76 x 0.75 mm) were glued to one face of each block. The cell was clamped between each window. The cell consisted of the ...

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Section: Resultsmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

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In Situ X‐Ray Absorption Spectroscopic Studies of Nickel Oxide Electrodes

Pandya

Hoffman

McBreen

et al. 1990

J. Electrochem. Soc.

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117

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“…13 The working electrodes consisted of pellets formed with the dispersed catalysts agglutinated with PTFE (ca. 40 wt.…”

Section: Methodsmentioning

confidence: 99%

Electrochemical performance of dispersed Pt-M (M =V, Cr and Co) nanoparticles for the oxygen reduction electrocatalysis

Lima¹,

Giz²,

Ticianelli³

2005

J. Braz. Chem. Soc.

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A cinética da reação de redução de oxigênio (RRO) foi estudada em eletrólito de KOH em eletrodos de camada ultra fina, formados por eletrocatalisadores de Pt-V, Pt-Cr e Pt-Co dispersos em pó de carbono (Pt-M/C). As características eletrônicas e estruturais dos eletrocatalisadores foram estudadas por XANES (X-ray Absorption Near Edge Structure) e EXAFS (Extended X-ray Absorption Fine Structure) in situ. Voltametria cíclica e curvas de polarização do estado estacionário para a RRO foram obtidas usando a técnica de disco/anel rotatório. Os resultados de XANES para as ligas no estado oxidado mostraram um aumento na ocupação da banda 5d da Platina, enquanto que os resultados de EXAFS mostraram uma pequena redução na distância interatômica Pt-Pt em relação à Pt/C. As medidas eletroquímicas indicaram que o mecanismo via 4 elétrons é principalmente seguido para a RRO nas ligas de platina. A maior atividade eletrocatalítica foi atingida pela liga Pt-V/ C, depois de tratamento térmico a 850 o C em atmosfera de hidrogênio.The kinetics of the oxygen reduction reaction (ORR) was studied in KOH electrolyte on ultra thin layer electrodes formed by Pt-V, Pt-Cr and Pt-Co electrocatalysts dispersed on a carbon powder (Pt-M/C). The electronic and structural features of the materials were studied by in situ XANES (Xray Absorption Near Edge Structure) and EXAFS (Extended X-ray Absorption Fine Structure). Cyclic voltammograms and steady state polarization curves for the ORR were obtained using the rotating ring/disk electrode technique. The XANES results for the composites in the oxidized state have shown an increase of the occupancy of the Pt 5d band while the EXAFS analyses showed some reduction of the Pt-Pt interatomic distance in the different metal alloys compared to Pt/C. The electrochemical measurements indicated that the 4-electrons mechanism is mainly followed for the ORR in these platinum alloys. The highest electrocatalytic activity was shown by the Pt-V/C alloy, after treated at 850 o C under hydrogen atmosphere.Keywords: oxygen reduction, platinum alloys, X-ray absorption IntroductionSeveral studies have been carried out in the last years aiming to increase the platinum electrocatalytic performance for the oxygen reduction reaction (ORR). 1-3Some authors have reported that on Pt alloys, Pt-V, P-Co, Pt-Cr, Pt-Fe, etc, there is an increase of the kinetics of the ORR electrocatalysis compared to pure Pt, and this fact has been attributed to changes in the Pt-Pt bond distance, number of Pt nearest neighbors, electronic density of states of the Pt 5d band, and nature and coverage of surface oxide layers.Toda et al. 4 explained the improvement of catalytic activity based on the increases by the Pt 5d band vacancy, leading to a stronger Pt-O 2 -interaction. This causes weakening and lengthening of the O-O bond and its easier scission, resulting in an increase of the reaction rate. Arico et al. 5 and Shukla et al. 6 have attributed the increase of the catalytic activity to a decrease of the coverage of surface oxides and an enri...

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“…Details of the electrochemical cell, which is a modified version of that described in ref. 38, are given elsewhere 37 . The data acquired by both the electrochemical and thermal cells were processed and analysed by Athena and Artemis software 39 .…”

Section: Mea Testmentioning

confidence: 99%

Highly stable Pt monolayer on PdAu nanoparticle electrocatalysts for the oxygen reduction reaction

et al. 2012

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stability is one of the main requirements for commercializing fuel cell electrocatalysts for automotive applications. Platinum is the best-known catalyst for oxygen reduction in cathodes, but it undergoes dissolution during potential changes while driving electric vehicles, thus hampering commercial adoption. Here we report a new class of highly stable, active electrocatalysts comprising platinum monolayers on palladium-gold alloy nanoparticles. In fuel-cell tests, this electrocatalyst with its ultra-low platinum content showed minimal degradation in activity over 100,000 cycles between potentials 0.6 and 1.0 V. under more severe conditions with a potential range of 0.6-1.4 V, again we registered no marked losses in platinum and gold despite the dissolution of palladium. These data coupled with theoretical analyses demonstrated that adding a small amount of gold to palladium and forming highly uniform nanoparticle cores make the platinum monolayer electrocatalyst significantly tolerant and very promising for the automotive application of fuel cells.

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EXAFS study of the nickel oxide electrode

Cited by 177 publications

References 8 publications

In Situ X‐Ray Absorption Spectroscopic Studies of Nickel Oxide Electrodes

In Situ X‐Ray Absorption Spectroscopic Studies of Nickel Oxide Electrodes

Electrochemical performance of dispersed Pt-M (M =V, Cr and Co) nanoparticles for the oxygen reduction electrocatalysis

Highly stable Pt monolayer on PdAu nanoparticle electrocatalysts for the oxygen reduction reaction

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