Novel application of an in situ radiotracer method for the study of the formation of surface adlayers in the course of Cr(VI) reduction on a gold electrode

K. Varga, I. Szalóki, Lajos Gáncs, Réka Marczona

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12 Citations (Scopus)

Abstract

The electroreduction of Cr(VI) species to Cr(III) at noble metal electrodes in acidic solutions takes place via a ce (chemical-electron-transfer) mechanism where the heterogeneous chemical step which precedes the charge transfer involves anions (e.g. HSO4-/SO42-) leading to the formation of intermediate surface complexes. In this paper, we report some new findings obtained by in situ radiotracer and voltammetric studies of the simultaneous adsorption of anions (HSO4-/SO42- labeled with 35S, Cl- labeled with 36Cl) and Cr-containing species (labeled with 51Cr) on a gold electrode in the course of dichromate reduction in 1 mol dm-3 HClO4 supporting electrolyte. Moreover, special attention is paid to present a detection and calculation method elaborated for the quantitative evaluation of the surface excess of radiolabeled Cr species via measurement of the intensity of low energy X-rays (E=4.90 keV) emitted by 51Cr. From our experimental results it can be stated that: (i) at E4-/SO42-, ClO4-); (ii) no data indicating the embedding of Cl- ions into the surface film could be detected; (iii) the maximum surface excess of Cr-containing species (Γmax=1.2×10-9 mol cm-2) as well as the molar ratio between the Cr species and HSO4-/SO42- ions (m≈6 at E=0.8 V) attests that the coverage of the gold surface with intermediate complexes does not exceed one monolayer.

Original languageEnglish
Pages (from-to)168-175
Number of pages8
JournalJournal of Electroanalytical Chemistry
Volume524-525
DOIs
Publication statusPublished - May 3 2002

Fingerprint

Gold
Electrodes
Anions
Negative ions
Ions
Precious metals
Electrolytes
Charge transfer
Monolayers
chromium hexavalent ion
Adsorption
X rays
Electrons

Keywords

  • Cr(VI) reduction
  • In situ radiotracer 'foil' method
  • Induced adsorption of anions
  • Polycrystalline gold
  • X-ray

ASJC Scopus subject areas

  • Chemical Engineering(all)
  • Analytical Chemistry
  • Electrochemistry

Cite this

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title = "Novel application of an in situ radiotracer method for the study of the formation of surface adlayers in the course of Cr(VI) reduction on a gold electrode",
abstract = "The electroreduction of Cr(VI) species to Cr(III) at noble metal electrodes in acidic solutions takes place via a ce (chemical-electron-transfer) mechanism where the heterogeneous chemical step which precedes the charge transfer involves anions (e.g. HSO4-/SO42-) leading to the formation of intermediate surface complexes. In this paper, we report some new findings obtained by in situ radiotracer and voltammetric studies of the simultaneous adsorption of anions (HSO4-/SO42- labeled with 35S, Cl- labeled with 36Cl) and Cr-containing species (labeled with 51Cr) on a gold electrode in the course of dichromate reduction in 1 mol dm-3 HClO4 supporting electrolyte. Moreover, special attention is paid to present a detection and calculation method elaborated for the quantitative evaluation of the surface excess of radiolabeled Cr species via measurement of the intensity of low energy X-rays (E=4.90 keV) emitted by 51Cr. From our experimental results it can be stated that: (i) at E4-/SO42-, ClO4-); (ii) no data indicating the embedding of Cl- ions into the surface film could be detected; (iii) the maximum surface excess of Cr-containing species (Γmax=1.2×10-9 mol cm-2) as well as the molar ratio between the Cr species and HSO4-/SO42- ions (m≈6 at E=0.8 V) attests that the coverage of the gold surface with intermediate complexes does not exceed one monolayer.",
keywords = "Cr(VI) reduction, In situ radiotracer 'foil' method, Induced adsorption of anions, Polycrystalline gold, X-ray",
author = "K. Varga and I. Szal{\'o}ki and Lajos G{\'a}ncs and R{\'e}ka Marczona",
year = "2002",
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T1 - Novel application of an in situ radiotracer method for the study of the formation of surface adlayers in the course of Cr(VI) reduction on a gold electrode

AU - Varga, K.

AU - Szalóki, I.

AU - Gáncs, Lajos

AU - Marczona, Réka

PY - 2002/5/3

Y1 - 2002/5/3

N2 - The electroreduction of Cr(VI) species to Cr(III) at noble metal electrodes in acidic solutions takes place via a ce (chemical-electron-transfer) mechanism where the heterogeneous chemical step which precedes the charge transfer involves anions (e.g. HSO4-/SO42-) leading to the formation of intermediate surface complexes. In this paper, we report some new findings obtained by in situ radiotracer and voltammetric studies of the simultaneous adsorption of anions (HSO4-/SO42- labeled with 35S, Cl- labeled with 36Cl) and Cr-containing species (labeled with 51Cr) on a gold electrode in the course of dichromate reduction in 1 mol dm-3 HClO4 supporting electrolyte. Moreover, special attention is paid to present a detection and calculation method elaborated for the quantitative evaluation of the surface excess of radiolabeled Cr species via measurement of the intensity of low energy X-rays (E=4.90 keV) emitted by 51Cr. From our experimental results it can be stated that: (i) at E4-/SO42-, ClO4-); (ii) no data indicating the embedding of Cl- ions into the surface film could be detected; (iii) the maximum surface excess of Cr-containing species (Γmax=1.2×10-9 mol cm-2) as well as the molar ratio between the Cr species and HSO4-/SO42- ions (m≈6 at E=0.8 V) attests that the coverage of the gold surface with intermediate complexes does not exceed one monolayer.

AB - The electroreduction of Cr(VI) species to Cr(III) at noble metal electrodes in acidic solutions takes place via a ce (chemical-electron-transfer) mechanism where the heterogeneous chemical step which precedes the charge transfer involves anions (e.g. HSO4-/SO42-) leading to the formation of intermediate surface complexes. In this paper, we report some new findings obtained by in situ radiotracer and voltammetric studies of the simultaneous adsorption of anions (HSO4-/SO42- labeled with 35S, Cl- labeled with 36Cl) and Cr-containing species (labeled with 51Cr) on a gold electrode in the course of dichromate reduction in 1 mol dm-3 HClO4 supporting electrolyte. Moreover, special attention is paid to present a detection and calculation method elaborated for the quantitative evaluation of the surface excess of radiolabeled Cr species via measurement of the intensity of low energy X-rays (E=4.90 keV) emitted by 51Cr. From our experimental results it can be stated that: (i) at E4-/SO42-, ClO4-); (ii) no data indicating the embedding of Cl- ions into the surface film could be detected; (iii) the maximum surface excess of Cr-containing species (Γmax=1.2×10-9 mol cm-2) as well as the molar ratio between the Cr species and HSO4-/SO42- ions (m≈6 at E=0.8 V) attests that the coverage of the gold surface with intermediate complexes does not exceed one monolayer.

KW - Cr(VI) reduction

KW - In situ radiotracer 'foil' method

KW - Induced adsorption of anions

KW - Polycrystalline gold

KW - X-ray

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SN - 0022-0728

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