催化学报

催化学报 ›› 2012, Vol. 33 ›› Issue (2): 267-274.DOI: 10.1016/S1872-2067(11)60331-8

• 研究论文 • 上一篇    下一篇

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

Fereydoon GOBAL, Laleh MAJARI KASMAEE   

  1. Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran
  • 收稿日期:2011-08-25 修回日期:2011-10-20 出版日期:2012-02-20 发布日期:2015-07-27

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

Fereydoon GOBAL, Laleh MAJARI KASMAEE   

  1. Department of Chemistry, Sharif University of Technology, P.O. Box 11365-9516, Tehran, Iran
  • Received:2011-08-25 Revised:2011-10-20 Online:2012-02-20 Published:2015-07-27

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摘要： 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.

关键词: L-ascorbic acid, polysulfide, electrode poisoning, silver, electro-oxidation

Abstract: 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.

Key words: L-ascorbic acid, polysulfide, electrode poisoning, silver, electro-oxidation