The effect of chloride on spatiotemporal dynamics in the electro-oxidation of sulfide on platinum

• Chloride results in enhancement of instability throughout the whole current–potential curve.
• Adsorption of chloride causes a new feedback loop for sulfide electro-oxidation.
• The characteristics of the oscillations and the morphology of patterns are modified by chloride.

The adsorption of poisonous species on the catalyst surface impacts electrocatalytic reactions to different extents and by distinct means. The impact of adsorbing anionic species on electrocatalytic reactions has generally been investigated in the non-oscillatory regime or, at most, with temporal oscillations. Here, we report on spatiotemporal pattern formation in the electro-oxidation of sulfide on a platinum disk perturbed with dissolved chloride. The spatiotemporal dynamics was followed simultaneously with an electrochemical workstation and a charge-coupled device (CCD) camera. Perturbing the system with chloride results in (a) enhancement of dynamic instabilities throughout the current–potential curve, including regions of both positive and negative slope; (b) emergence of several spatial patterns; and (c) decreasing the width of pulses with increasing [Cl−]. The results are interpreted in terms of surface poisoning by chloride adsorption.

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