Polysulfide Poisoning of Ag Electrocatalyst during L-Ascorbate Ion Electro-oxidation in Alkaline Solution

L-Ascorbate anion electro-oxidation on a silver electrode in hydroxide solution in the absence and presence of sodium polysulfide of concentrations from 1 × 10-5 to 4.5 × 10-4 mol/L was studied using cyclic voltammetry and electrochemical impedance spectroscopy.Both hydroxide and polysulfide ions in...

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Bibliographic Details
Published in:Chinese journal of catalysis 2012-02, Vol.33 (2), p.267-274
Main Authors: GOBAL, Fereydoon, MAJARI KASMAEE, Laleh
Format: Article
Language:English
Subjects:
electro-oxidation
electrode poisoning
Electrodes
Hydroxides
Impedance
L-ascorbic acid
Oxidation
Poisoning
polysulfide
Polysulfides
Silver
Voltammetry
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Summary:L-Ascorbate anion electro-oxidation on a silver electrode in hydroxide solution in the absence and presence of sodium polysulfide of concentrations from 1 × 10-5 to 4.5 × 10-4 mol/L was studied using cyclic voltammetry and electrochemical impedance spectroscopy.Both hydroxide and polysulfide ions inhibited L-ascorbate ion oxidation,with the poisoning effect of polysulfide ion being more pronounced in the potential range of-0.3 to-0.2 V/SCE.The time constants for L-ascorbate ion oxidation in the absence and presence of polysulfide were,10-3 to 1 × 10-2 s and 1 × 10-4 to 1 × 10-2 s,respectively depending on the potential used for the impedance analysis.Based on the cyclic voltammetry findings,a mechanism for L-ascorbate oxidation in the presence of polysulfide ions was proposed.Impedance calculations based on the kinetic analysis can account for the occurrence of a negative impedance in a potential region around-0.2 V/SCE in the Nyquist polts.
ISSN:0253-9837
1872-2067
1872-2067
DOI:10.1016/S1872-2067(11)60331-8