Magneto-optical Spectra in Pd/Co Multilayers and Related Alloys.

Tosaka, Yasuhiro; Ikekame, H.; Urago, K.; Kurosawa, Shunsuke; Sato, K.; Shin, Shung-Chul

doi:10.3379/jmsjmag.18.389

Cited by 10 publications

(5 citation statements)

References 4 publications

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“…Toda et al claimed that the growth of “Pt-skin” on Pt−Fe, Pt−Ni, and Pt−Co may be limited within few monolayers, and hence the sufficient modification of its electronic property by that of the underlying bulk alloy appears. Such a long-range interaction more than 10 Å distance from the alloy has been reported in several studies. , However, the effect must be reduced with increasing the thickness of the “Pt-skin”, resulting in the lower enhancement effect by alloying.…”

Section: Resultsmentioning

confidence: 75%

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An Investigation of Structure−Catalytic Activity Relationship for Pt−Co/C Bimetallic Nanoparticles toward the Oxygen Reduction Reaction

et al. 2007

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Carbon-supported Pt−Co alloy nanoparticle catalysts of nominal atomic composition but with different alloying extents were prepared via a modified Watanabe process by employing microwave heating. Their structure was studied by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) techniques. Transmission electron microscopy (TEM) images indicated that the in-house-prepared Pt−Co alloy nanoparticles (sample-1 and sample-2) were well dispersed on the surface of the carbon support with narrow particle size distribution which is consistent with XRD grain size values. The catalyst composition obtained from XAS was nearly the same as that of the nominal value (1:1). The alloying extent values of Pt calculated from XAS measurements for sample-2 is similar to that of the commercial E-tek Pt−Co/C. This observation demonstrates the practical viability of our preparation protocol for Pt−Co/C catalysts. A comparative study was made for the oxygen reduction reaction (ORR) using a thin-film rotating disk electrode method to evaluate the catalytic behavior of Pt−Co/C and Pt/C catalyst with similar metal loadings and particle sizes. As compared to the Pt/C catalyst, the bimetallic Pt−Co/C of sample-2 exhibited an enhancement factor of 3 in mass activity at 0.95 V toward ORR. The enhancement in activity of sample-2 is similar in magnitude to that of the commercial E-tek Pt−Co/C catalyst. It is found that that the samples possessing a high alloying extent of Pt in the cluster enhances the activity of the bimetallic Pt−Co/C toward ORR. This observation confirms that the alloying extent of Pt is an important parameter by which one can have control over the fine-tuning of the catalytic activities of bimetallic nanoclusters. This activity enhancement may originate from the favorable electronic effects of a well mixed alloy underneath a thin “Pt-rich skin” structure of the Pt−Co bimetallic nanoparticles. This kind of thin “Pt-rich skin” is created by the dissolution of Co oxide on Pt−Co bimetallic nanoparticles while washing in acidic electrolyte before being subjected to ORR.

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Section: Resultsmentioning

confidence: 75%

“…Such a long-range interaction more than 10 Å distance from the alloy has been reported in several studies. 51,52 However, the effect must be reduced with increasing the thickness of the "Pt-skin", resulting in the lower enhancement effect by alloying.…”

Section: Resultsmentioning

confidence: 99%

An Investigation of Structure−Catalytic Activity Relationship for Pt−Co/C Bimetallic Nanoparticles toward the Oxygen Reduction Reaction

et al. 2007

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“…For example, the experimental and theoretical studies on artificially grown Pt and Co multilayers revealed the significant modification of the electronic state of Pt layers more than 6 Å distant from Co layers. 21,22 Furthermore, layers of 3d metals such as Fe, Co, and Ni cause the change in the state of conductive electrons in layers of noble metals over a few tens of angstrom. 23,24 The positive chemical shifts in such inner-core orbitals of Pt as 4d or 4f strongly suggests a lowering of the Fermi level, or an increase of the d vacancy, in the valence band 5d orbital at the skin Pt.…”

Section: Enhancement Of the Orr By Alloyingmentioning

confidence: 99%

Enhancement of the Electroreduction of Oxygen on Pt Alloys with Fe, Ni, and Co

Toda

Igarashi

Uchida

et al. 1999

J. Electrochem. Soc.

1,366

1,148

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Electrocatalytic activity of Pt alloys with Ni, Co, and Fe, formed by sputtering, was investigated with regard to the oxygen reduction reaction (ORR) in perchloric acid solution. Hydrodynamic voltammograms with rotated electrodes were used to measure the electrocatalytic activity. Maximum activity was observed at ca. 30, 40, and 50% content of Ni, Co, and Fe, respectively, by which 10, 15, and 20 times larger kinetic current densities than that of pure Pt were attained. X‐ray photoelectron spectroscopy analysis of the surfaces after the reaction indicated that the active surfaces were covered by a few monolayers of Pt. We present an enhancing mechanism for the ORR based on an increased d‐electron vacancy of the thin Pt surface layer caused by underlying alloy. Results of this work contribute in development of new active cathode catalysts for fuel cells used as power sources of electric vehicles, etc. © 1999 The Electrochemical Society. All rights reserved.

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“…This suggests that Au, Pt, or Ta affects the electronic structure of PtCo underneath the capping layer. We believe that this can happen, since it is known that the metallic multilayer has a peculiar electronic structure that cannot be merely explained by assuming the stack of metals observed in Pd/Co and Fe/Au multilayers 7,8) .…”

Section: Optical Constants Of Gmr Structuresmentioning

confidence: 97%

Magneto-optical Spectra of Pt/Co GMR Structures with Capping Layers

et al. 2012

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The MO spectra of GMR structures with capping layers, Si/SiO2/bottom electrode/TbFeCo (9 nm)/Cu (4 nm)/ Co (0.1 nm)/Pt (1.1 nm)/(Pt (1.1 nm)/Co (6 nm)!4)/cap (cap = Ta, Au, Pt (3 nm)), were studied. We found that the optical constants and Kerr spectra exhibited different behaviors for all samples. The differences in the optical constants of these samples were analyzed by means of optical simulation. The MO spectrum is discussed in terms of simulation carried out by the virtual optical constant method for (PtCo)/cap (cap = Ta, Au, Pt (3 nm)).

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Magneto-optical Spectra in Pd/Co Multilayers and Related Alloys.

Cited by 10 publications

References 4 publications

An Investigation of Structure−Catalytic Activity Relationship for Pt−Co/C Bimetallic Nanoparticles toward the Oxygen Reduction Reaction

An Investigation of Structure−Catalytic Activity Relationship for Pt−Co/C Bimetallic Nanoparticles toward the Oxygen Reduction Reaction

Enhancement of the Electroreduction of Oxygen on Pt Alloys with Fe, Ni, and Co

Magneto-optical Spectra of Pt/Co GMR Structures with Capping Layers

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