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

Author(s)

Hartl, Fabian W. ^[1] ; Zulke, Alana A. ^[1] ; Fonte, Bruno J. ^[1] ; Varela, Hamilton ^[1]

Affiliation

^[1] Univ Sao Paulo, Inst Chem Sao Carlos, POB 780, BR-13560970 Sao Carlos, SP - Brazil

• Document type: Journal article
• Source: JOURNAL OF ELECTROANALYTICAL CHEMISTRY; v. 800, p. 99-105, SEP 1 2017.
• Web of Science Citations: 3

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 degrees C and 50 degrees C, in acidic media, and oscillations were not observed at 50 degrees 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. (C) 2016 Elsevier B.V. All rights reserved. (AU)

• FAPESP's process: 13/16930-7 - Electrocatalysis V: electrocatalytic processes of chemical and electrical energy interconversion
• Grantee: Edson Antonio Ticianelli
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 12/21204-0 - Temporal self-organization in electro-oxidation of small organic molecules: surface structure effect, water concentration and temperature
• Grantee: Bruno Alarcon Fernandes Previdello
• Support Opportunities: Scholarships in Brazil - Post-Doctoral
• FAPESP's process: 09/07629-6 - Electrocatalysis IV: fundamental and applied aspects of electrocatalytic processes, bio-electrocatalysis and kinetic instabilities
• Grantee: Edson Antonio Ticianelli
• Support Opportunities: Program for Research on Bioenergy (BIOEN) - Thematic Grants
• FAPESP's process: 14/08030-9 - Electrocatalysis under oscillatory regime: in situ IR spectroscopy in ATR-SEIRAS configuration
• Grantee: Fabian Hartl
• Support Opportunities: Scholarships in Brazil - Doctorate (Direct)