Electrooxidation of sulfide by cobalt pentacyanonitrosylferrate film on glassy carbon electrode by cyclic voltammetry

Despite the fact that the majority of the catalytic electro-oxidation of small organic molecules presents oscillatory kinetics under certain conditions, there are few systematic studies concerning the influence of experimental parameters on the oscillatory dynamics. Of the studies available, most are devoted to C1 molecules and just some scattered data are available for C2 molecules. We present in this work a comprehensive study of the electro-oxidation of ethylene glycol on polycrystalline platinum surfaces and in alkaline media. The system was studied by means of electrochemical impedance spectroscopy, cyclic voltammetry, and chronoamperometry, and the impact of parameters such as applied current, ethylene glycol concentration, and temperature were investigated. As in the case of other parent systems, the instabilities in this system were associated with a hidden negative differential resistance, as identified by impedance data. Very rich and robust dynamics were observed, including the presence of harmonic and mixed mode oscillations and chaotic states, in some parameter region. Oscillation frequencies of about 16 Hz characterized the fastest oscillations ever reported for the electro-oxidation of small organic molecules. Those high frequencies were strongly influenced by the electrolyte pH and far less affected by the EG concentration. The system was regularly dependent on temperature under voltammetric conditions but rather independent within the oscillatory regime.

Complex kinetics, high frequency oscillations and temperature compensation in the electro-oxidation of ethylene glycol on platinum

For the first time, potential oscillations are observed during the electrochemical oxidation of urea on Ni catalyst in alkaline medium. Electrochemical measurements, in combination with in situ time-resolved surface enhanced Raman (SER) spectroscopy studies, revealed that the potential oscillations might be caused by the periodic reduction and oxidation of the electrochemically active NiOOH catalyst to its inactive Ni(OH)2 state and vice versa. Cyclic voltammetry and rotating disc electrode voltammetry suggests that mass transfer of urea to the double layer region due to local convection caused by oxygen evolution reaction does not play a role in the potential oscillation mechanism.

Experimental Investigation of Potential Oscillations during the Electrocatalytic Oxidation of Urea on Ni Catalyst in Alkaline Medium

This paper treats the electrochemical oxidation of sulfide ions on platinum using cyclic voltametry An electrolyte of 35% 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 -01, 0475 and 10 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

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Liangqin Xu

Papers

Nonlinear phenomena in the electrochemical oxidation of sulfide

Oscillations and period-doubling bifurcations in the electrochemical oxidation of thiourea