Abstract
This paper treats the electrochemical oxidation of sulfide ions on platinum using cyclic voltametry. An electrolyte of 3.5% NaCl containing sulfide ions was used as the testing medium. The effects of scan rate, concentration of sulfide ions and temperature on the cyclic voltamograms were investigated. Cyclic voltamograms show small currents in the absence of sulfide ions. In the presence of sulfide ions, the magnitude of the anodic currents in the forward sweep is much more than these in the reverse sweep. Cyclic voltamograms show three features appear in the forward sweep at potentials of -0.1, 0.475 and 1.0 V vs Ag/AgCl, respectively. Peaks currents are increased upon the increase of either the scan rate or temperature. These peaks are explained to show the possible formed species and the possible electrochemical oxidation reactions at the electrode surface.
Highlights
March, 2010 electrode was polished successively down to 0.3 and 0.05 μm alumina and cleaned for using acetone in an ultrasonic bath for 10 min
Cyclic voltamograms of polycrystalline platinum were measured in 3.5% NaCl solution in the absence and in the presence of sulfide ions
The range of potentials for this CV was chosen to avoid hydrogen and oxygen evolution. This figure reveals some important features: 1) The anodic currents measured in the absence of sulfide ions are negligibly small compared to those measured in its presence, at all potentials
Summary
2010 electrode was polished successively down to 0.3 and 0.05 μm alumina and cleaned for using acetone in an ultrasonic bath for 10 min. Measurements were performed in an electrolyte of 3.5% (0.58 M) NaCl containing different concentrations of sodium sulfide. This supporting electrolyte maintains the ionic strength of the electrolyte nearly constant and minimizes double layer effects on the kinetic parameter. The test solutions were prepared from deionized water, NaCl (BDH) and Na2S (BDH). The temperature of the test electrolyte was controlled by flowing hot water around the cell through its double jacketed walls. The platinum electrodes were tested using cyclic voltametry method. The potential of the working electrode was scanned from cathodic towards anodic potentials using a Gamry (PC4/750 Potentiostat/Galvanostat/ZRA). The electrodes surfaces were examined using an X-ray photoelectron spectrometer, FISONS Instruments, Model ESCA–Lab 200 (VG Instruments)
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