Halide adsorption effect on methanol electro-oxidation reaction studied by dynamic instabilities

• Published in: Journal of electroanalytical chemistry (Lausanne, Switzerland) Vol. 856; p. 113657
• Main Authors: Fiori, I.A., Melle, G.B., Sitta, E.
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01-01-2020; Elsevier Science Ltd
• Subjects: Adsorption; Anion adsorption; Dynamic instabilities; Electro-oxidation; Methanol; Oscillations; Oxidation; Platinum; Poisoning; Temperature effects; Oscillations; Anion adsorption; Platinum; Electro-oxidation; Dynamic instabilities; Methanol
• ISSN: 1572-6657; 1873-2569
• DOI: 10.1016/j.jelechem.2019.113657

The effect of halide anion adsorption on methanol electro-oxidation reaction in acid media was studied by means of thermal effects on both cyclic voltammograms (CV) and oscillations in galvanostatic time series (GTS). While increasing the chloride concentration we observed a monotonically current decrease followed by an increase of apparent activation energy (Ea) in CV, GTS increases the maximum potential (Emax) and decreases both the oscillation frequency (w) and Ea. Poisoning/Freeing rates (dE/dt) increase for a very small Cl− amount but decreases for higher concentrations. Changing Cl− by Br−, albeit observing similar behaviors for currents on CV and w, Emax and Ea changes suggest that Br− probably plays a dual role, i.e. poisoning the surface by its adsorption but also interacting with adsorbed methanol residues. Finally, increasing the pH to 5.6 in a nonadsorbing electrolyte (HClO4/NaF) several oscillations patterns were mapped with a lesser Cl− influence on both CV and GTS.
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