Surface segregation in Pt-Au alloys studied using Auger electron spectroscopy

Hörnström, Sven Erik; Johansson, L. I.; Flodström, Anders

doi:10.1016/0169-4332(86)90050-4

Cited by 28 publications

(15 citation statements)

References 14 publications

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“…For the Ag-Au (62,69) and Pd-Au (68) alloys a number of experimental studies indicate that no surface segregation occurs, in contradiction with other experimental data for Ag-Au alloys (57,75,76,83,84), PdAu alloys (79), and Pt-Au alloys (81,85) as well as most theoretical models. This absence of segregation may be due to a lack of thermodynamic equilibrium (69) or substantial preferential sputtering of Au atoms from the surface (68).…”

Section: Predicting and Observing Segregationmentioning

confidence: 60%

“…Most alloys containing gold that have been used in surface segregation studies were prepared by melting the constituent metals together (26, 54, 56-57, 62-63, 67-68, 73-77), polishing, typically using diamond or alumina grit down to 1 pm grit size or less (51,54,56,57,77,78), chemically treating (74,75,79), and annealing (56,62,63,67,68,73,74,76,79). Chemical treatments were often combined with the annealing of the gold alloy samples since the samples were not always annealed in just vacuum (63,73), or argon (62,74,76,77), but in hydrogen (68,75,77,80) and oxygen (79,81) as well. Following the preparation of the goldcontaining alloy, the sample is then placed in ultra-high vacuum and further efforts are made to remove the residual contamination from the surface.…”

Section: Preparation Of Gold Alloy Surfacesmentioning

confidence: 99%

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Surface segregation from gold alloys

1987

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Among the properties of alloys affected by surface segregation are corrosion resistance and strength. In this paper, the surface segregation phenomenon is reviewed, with particular attention given to gold-containing alloys. A brief discussion of the various thermodynamic models for surface segregation is provided. The results of experimental investigations of surface segregation for gold-containing alloys are summarized and explained in terms of some of the thermodynamic models.

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Section: Predicting and Observing Segregationmentioning

confidence: 60%

Section: Preparation Of Gold Alloy Surfacesmentioning

confidence: 99%

Surface segregation from gold alloys

1987

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“…This value is much higher than that of 2.5:1 obtained from EDS data for the coating composition, indicating a further significant enrichment of the surface with Au. Au surface segregation in Au-Pt bimetallics is predicted both by thermodynamic considerations and DFT calculations (taking into account the difference in the atomic radii and lattice parameters of the two metals [16]) and kinetic reasoning (based on the higher mobility of Au atoms [50][51][52]). This has also been found experimentally [15,[53][54][55], especially in cases of continuous potential cycling between hydrogen and oxygen evolution [15].…”

Section: Surface Electrochemistry Of Aupt(ni)/gc Electrodes In Acidmentioning

confidence: 99%

Mixed platinum–gold electrocatalysts for borohydride oxidation prepared by the galvanic replacement of nickel deposits

Tegou

Armyanov

Valova

et al. 2009

Journal of Electroanalytical Chemistry

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“…The alloys were studied using Auger electron spectroscopy. 24 The results obtained unambiguously showed the detrimental impact of gold on the electrocatalytic activity of platinum. Hence, gold is a poor choice as a support material for platinum to be used as a cathode catalyst in a PEMFC.…”

Section: Resultsmentioning

confidence: 83%

Alternative Catalyst Supports Deposited on Nanostructured Thin Films for Proton Exchange Membrane Fuel Cells

Garsuch

Stevens

Sanderson

et al. 2010

J. Electrochem. Soc.

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A series of platinum-coated underlayer materials, alumina, gold, titanium carbide, and titanium disilicide, deposited by a high throughput magnetron sputtering method have been investigated as cathode catalyst supports in fuel cells. Orthogonal thickness gradients of the underlayer materials ͑0-100 nm planar equivalent͒ and the platinum top layer ͑0-75 nm planar equivalent͒ made up the 76 ϫ 76 mm libraries. The resulting catalyst films were characterized by surface profilometry, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. The electrochemical properties of the catalyst composition spreads were investigated simultaneously in 64-electrode proton exchange membrane fuel cells with emphasis placed on the determination of the electrochemical surface area ͑ECSA͒ as a function of underlayer thickness and chemistry. The present study shows that gold and titanium disilicide used as underlayers on 3M's nanostructured thin film supports lead to a loss of ECSA during operation. Migration and surface accumulation were observed when gold was used as underlayer material. For titanium disilicide, alloying and the generation of platinum silicide phases occurred. Alumina and titanium carbide were found to be potentially acceptable underlayer materials as well as alternative support materials on the basis of their influence on the catalyst surface area.Polymer electrolyte membrane fuel cells ͑PEMFCs͒ are promising power sources for automotive applications in the future. 1 The main environmental advantage of using PEMFCs in vehicles is the reduction of carbon dioxide emissions, pollutants, and consumption of fossil fuels. 2 To fully commercialize PEMFCs for automotive vehicles, their high production cost needs to be reduced while improving performance and durability. The core of a PEMFC, the membrane electrode assembly ͑MEA͒, consists of two electrocatalyst electrodes ͑anode and cathode͒ with gas diffusion layers ͑GDLs͒ on either side of the proton-conducting ion-exchange membrane. Each of these MEA components contributes to the overall performance, stability durability, robustness, and cost of a PEMFC, and thus research efforts have been focused on the improvement of the electrocatalyst and membrane properties. 3 Platinum or platinum alloys are commonly used as the catalyst on the anode side for the hydrogen oxidation reaction ͑HOR͒ and on the cathode side for the oxygen reduction reaction ͑ORR͒ in a PEMFC. These catalysts may consist of highly dispersed platinum particles ͑2-3 nm͒ supported on carbon blacks, activated carbon, or carbon nanotubes. A range of factors 4 are known to contribute to the significant performance degradation of PEMFCs that can occur during long-term operation or as a result of adverse operating conditions ͑e.g., fuel starvation on the anode side during start-up and shutdown 5 ͒. These include Pt-catalyzed corrosion of the carbon support, 6 oxidation and decomposition of the GDL, 7 dissolution or poisoning of the Pt catalysts on the cathode and anode side, 8 and degr...

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Surface segregation in Pt-Au alloys studied using Auger electron spectroscopy

Cited by 28 publications

References 14 publications

Surface segregation from gold alloys

Surface segregation from gold alloys

Mixed platinum–gold electrocatalysts for borohydride oxidation prepared by the galvanic replacement of nickel deposits

Alternative Catalyst Supports Deposited on Nanostructured Thin Films for Proton Exchange Membrane Fuel Cells

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