Temperature dependence of the evolving oscillations along the electrocatalytic oxidation of methanol

Hartl, Fabian W. and Aragon Zulke, Alana Aragon and Fonte, Bruno J. and Varela, Hamilton (2017) Temperature dependence of the evolving oscillations along the electrocatalytic oxidation of methanol. Journal of Electroanalytical Chemistry, 800. pp. 99-105. ISSN 0022-0728

Abstract

Despite the constancy of all controllable experimental parameters, most natural and artificial oscillators are known to slowly evolve over time. In electrochemical systems, this spontaneous evolution has been ascribed to the surface deactivation that gently drives the system and acts a bifurcation parameter. We investigate the effect of temperature on the electro-oxidation of methanol on platinum, with focus on the potential oscillations and its spontaneous temporal evolution. The study was performed at comparable applied currents (normalized with respect to the oscillatory window) at nine temperatures between 10 °C and 50 °C, in acidic media, and oscillations were not observed at 50 °C. The main results were discussed in connection with voltammetric data, which were deconvoluted into three regions according to the electrode potential. While the frequency of potential oscillations followed a regular Arrhenius-like dependence, the size of the oscillatory window was found to remain nearly unaffected by temperature. From the mechanistic point-of-view, these dependencies were attributed to the existence of more than one Langmuir–Hinshelwood (LH) step that consumes adsorbed oxygenated species. This fact was corroborated by voltammetric data. The relative magnitude of the activation energies of the LH processes were estimated as higher than that of the deactivation process, as previously suggested.