Electrochemical behaviour of polycrystalline silver in 0·5M NaOH containing sulphide ions

Zaky, Ayman M.; Rehim, Sayed S. Abd El; Mohamed, B. M.

doi:10.1179/174327805x29903

Cited by 4 publications

(1 citation statement)

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“…However, negative slopes at potentials lower than 0.54 V RHE suggest that a cathodic reaction like reduction of contaminated oxygen is dominant. Potential of LPIG as a sulfide ion generation apparatus.-In general experiments to investigate a sulfidation of silver, Ag 2 S layer forms on the silver surface in the presence of sulfide ions-containing media such as H 2 S, K 2 S and Na 2 S. 1,4,7,[25][26][27] The sulfidized layer in this study by using Ag/Ag 2 S microelectrode (Fig. 8) is Ag 2 S. This result is not new findings.…”

Section: Resultsmentioning

confidence: 65%

Development of a Liquid-Phase Ion Gun and Its Application for Sulfidation of Silver Surface

Lee

Fushimi

Kitagawa

et al. 2015

J. Electrochem. Soc.

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7A system for safe generation of sulfide ions was established by using the microelectrode technique in order to investigate sulfidation of the metal surface of silver. Both silver microelectrode sulfidation and silver sulfide reduction on the microelectrode were reversible in Na 2 S solution and corresponded to Ag 2 S formation and HS − generation, respectively. Cathodic polarization of Ag 2 S, which covered the silver microelectrode, in pH 8.4 boric-borate buffer solution successfully generated HS − above a glass or silver substrate. Concentration of HS − in the vicinity of the substrate was dependent on the distance between the microelectrode and the substrate. The silver substrate was locally sulfidated by HS − generated from the microelectrode. However, at potentials higher than 0.14 V RHE , local sulfidation of the silver substrate was independent of the substrate potential. It is thought that mass transport of HS − is dominant for sulfidation of the silver substrate. A silver wire with a purity of 99.9% and a diameter of 500 μm was 69 embedded in a glass capillary with an outer diameter of 1 mm using 70 an epoxy resin. The cross section of the silver-glass capillary tip was 71 used as a silver microelectrode after mechanical polishing with SiC 72 papers down to 4000 grit and rinsing with distilled water. Figure 1 73 shows an optical microscopic image of the tip of the fabricated silver 74 microelectrode. A silver plate with a purity of 99.9% and a surface area 75 of 0.8 cm 2 was prepared as a substrate electrode. The silver substrate 76 was mounted in an epoxy resin mechanically ground with SiC papers 77 down to 800 grit and then rinsed with distilled water. 78Electrochemical experiments of using silver microelectrode and/or 79 the silver substrate electrode were carried out in a four-electrode 80 electrochemical cell of 100 cm 3 in volume with a platinum counter 81 electrode and an Ag/AgCl/sat. KCl reference electrode. However, 82 all the potentials in this study were with respect to the reversible 83 hydrogen electrode (RHE) potential. Cyclic voltammetry (CV) of the 84 silver microelectrode was conducted in a potential range between 0.38 85 and -0.06 V RHE in 0.1 mol dm -3 Na 2 S solution (pH 13.4) at a scan 86 rate of 20 mV s -1 . After a steady state had been obtained in CV, the 87 microelectrode was polarized at 0.3 V RHE in the same solution until the 88 electric charge of 10 mC, Q me.charge , was consumed. On the other hand, 89 potentiodynamic polarization of the silver substrate was performed in 90 a potential range from 0.7 to 1.1 V RHE at a scan rate of 1 mV s -1 in 91 pH 8.4 boric-borate buffer solution. 92Figure 2 schematically depicts the experimental setup for liquid-93 phase ion gun. An optical microscope with a resolution of ca. 5 μm 94 and a stepping motor stage (SGSP20-35, Sigma Koki) with an incre-95 mental motion of 0.1 μm were used to control the distance between 96 the microelectrode and substrate of a grass plate or silver electrode. 97 The silver microelectrode was positioned ab...

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