Ellipsometric measurements of the Pt-aqueous electrolyte interface, in the absence and in the presence of specific anionic adsorption

Hyde, Peter Alden; Maggiore, C.J.; Redondo, Antonio; Srinivasan, S.; Gottesfeld, S.

doi:10.1016/0368-1874(85)85772-5

Cited by 19 publications

(7 citation statements)

References 28 publications

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“…Therefore, it can be considered that the adsorption of H20 occurs on the pair sites of the C02-and H20-desorbing oxides until the crossing point in the qst curve is attained, as discussed in the cases of G-10006 and HG-1000. 7 In spite of the variety of C02 content, 0.035, 0.011, and 0.097 molecules/nm2 on three samples, G-1000,6 HG-1000,7 and OG-1000, respectively, the crossing point of the qBt curve with the Hl level agrees well with the C02 content on each sample. After these sites are completely occupied by the adsorbed H20 molecules, the adsorption of H20 will take place on the oxide sites which can expel only H20 on pyrolysis, and further adsorption onto the preadsorbed H20 molecules will result in the formation of clusters.…”

Section: Discussionmentioning

confidence: 76%

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Adsorption sites for water on graphite. 3. Effect of oxidation treatment of sample

Miura¹,

Morimoto²

1986

Langmuir

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The adsorption isotherms of H20 were measured on graphite samples which were partially burnt in an H20-02 mixture and then outgassed at higher temperatures. On these samples, the gas content and acidic surface functional groups were determined. The isosteric heat of adsorption of H20, qst, calculated from the second adsorption isotherms, decreases more steeply when the pretreatment temperature of graphite is raised. The qBt curve on the 1000 °C treated sample reveals a distinct minimum, at which the qst value is very small compared with the heat of liquefaction of H20. It has been found that these phenomena depend on the variety and quantity of surface oxides on graphite and that the qBt minimum appears when each amount of the H20-, C02-, and CO-desorbing oxides is extremely small.

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Section: Discussionmentioning

confidence: 76%

“…The same feature was observed in the cases of the G6 and HG samples. 7 As described above, the content of H20 and C02 on OG-1000 comes from regenerated surface oxides (Table I). Therefore, it is reasonable to infer that the adsorbed H20 molecules interact with the regenerated surface oxides.…”

Section: Discussionmentioning

confidence: 92%

Adsorption sites for water on graphite. 3. Effect of oxidation treatment of sample

Miura¹,

Morimoto²

1986

Langmuir

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“…One of the earliest measurements of bromide adsorption was carried out on polycrystalline platinum by Kazarinov et al 7 using the radiotracer method, but in light of later studies, the reported bromide coverages appear to be too small. Subsequently, Hyde et al 8 employed ellipsometry, showing qualitatively an optical signature of the bromide adsorption isotherm without determining actual coverages. Neither of the above studies succeeded in establishing a value of the electrosorption valency, γ.…”

Section: Introductionmentioning

confidence: 99%

“…using the radiotracer method, but in light of later studies, the reported bromide coverages appear to be too small. Subsequently, Hyde et al . employed ellipsometry, showing qualitatively an optical signature of the bromide adsorption isotherm without determining actual coverages.…”

Section: Introductionmentioning

confidence: 99%

Bromide Adsorption on Pt(111): Adsorption Isotherm and Electrosorption Valency Deduced from RRD_Pt(111)E Measurements

1996

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The rotating ring-disk electrode technique with a Pt(111) single crystal in the disk position is used to establish, for the first time, both the bromide adsorption isotherm and its electrosorption valency on Pt(111). In 0.1 M HClO4 with ≈10 -4 M Br -, bromide adsorption begins at ca. -0.15 V (SCE) and reaches a coverage of ≈0.42 ML at 0.5 V; the electrosorption valency is essentially unity. By subtracting the bromide flux from the Pt(111)-disk current, we were able to deconvolute hydrogen adsorption/desorption processes in the presence of bromide. The major peak in the voltammetry at ca. -0.1 V is the simultaneous desorption/adsorption of hydrogen and adsorption/desorption of bromide. Furthermore, we demonstrated that the saturation coverage of adsorbed hydrogen on Pt( 111) is ≈160 µC/cm 2 .

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“…in Figure ID: ®Br = Q(complete Br reduction) -Q(partial Br reduction) i v i d u a l n o t d i r e c t l y a s s o c i a t e d w i t h s c i t e i s p r o h i b i t e d .Graphed at the right side is the fractional surface area not occupied by adsorbed OH, calculated from the coulometric charge for peak 1 of FigureIF:-packed OH layer) -Q(partial OH layer)(7) …”

mentioning

confidence: 99%

Structure and composition of a platinum(111) surface as a function of pH and electrode potential in aqueous bromide solutions

Salaita¹,

Stern²,

Lu³

et al. 1986

Langmuir

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Hl value. As shown in Figure 5, the shape of the qst curve on OG-400 and OG-25 is very similar to that on OG-700, the only difference being the fact that the break point slightly shifts to higher coverage of H20 from OG-700 to OG-400 and further to OG-25. Admittedly, there is a great difference between the qst curves on OG-700 and OG-IOOO.The reason why such a difference appears can be attributed to the fact that the CO content on OG-700 is as much as those on OG-25 and OG-400, in contrast to a smaller value on OG-IOOO (Table I). Walker and Janov have reported that the CO-desorbing oxides on Graphon act as the sites for adsorption of H20, which give the heat of adsorption similar to the HL value.22 Thus, the H20 molecules will be adsorbed on the CO-desorbing oxides of OG-25, OG-400, and OG-700 after the sites, such as the C02-and H20-desorbing oxides, have been completely covered with H20.thank the Ministry of Education (Japan) for the financial support granted for this research.

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Ellipsometric measurements of the Pt-aqueous electrolyte interface, in the absence and in the presence of specific anionic adsorption

Cited by 19 publications

References 28 publications

Adsorption sites for water on graphite. 3. Effect of oxidation treatment of sample

Adsorption sites for water on graphite. 3. Effect of oxidation treatment of sample

Bromide Adsorption on Pt(111): Adsorption Isotherm and Electrosorption Valency Deduced from RRD_Pt(111)E Measurements

Structure and composition of a platinum(111) surface as a function of pH and electrode potential in aqueous bromide solutions

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Ellipsometric measurements of the Pt-aqueous electrolyte interface, in the absence and in the presence of specific anionic adsorption

Cited by 19 publications

References 28 publications

Adsorption sites for water on graphite. 3. Effect of oxidation treatment of sample

Adsorption sites for water on graphite. 3. Effect of oxidation treatment of sample

Bromide Adsorption on Pt(111): Adsorption Isotherm and Electrosorption Valency Deduced from RRDPt(111)E Measurements

Structure and composition of a platinum(111) surface as a function of pH and electrode potential in aqueous bromide solutions

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Bromide Adsorption on Pt(111): Adsorption Isotherm and Electrosorption Valency Deduced from RRD_Pt(111)E Measurements