Dynamic electrochemical impedance study of methanol oxidation at Pt at elevated temperatures. (1st February 2019)

• Record Type: Journal Article
• Authors: Holm, Thomas; Dahlstrøm, Per Kristian; Sunde, Svein; Seland, Frode; Harrington, David A.
• Is Part Of: Electrochimica acta. Volume 295(2019)
• Page Start: 139
• Page End: 147
• Publication Date: 2019-02-01
• Subjects: Electrochemical impedance spectroscopy -- Methanol oxidation -- Temperature -- Reaction mechanism; Electrochemistry -- Periodicals; Electrochemistry, Industrial -- Periodicals; 541.37
• DOI: 10.1016/j.electacta.2018.10.071
• Languages: English
• ISSNs: 0013-4686

Abstract

Abstract: The methanol oxidation reaction (MOR) is studied at temperatures up to 140 °C by a combination of cyclic voltammetry, chronoamperometry, and dynamic electrochemical impedance spectroscopy (dEIS). A mechanistic analysis of the reaction is done based on the Tafel relation, the calculated activation energy, and the fitting of dEIS data. At the fuel cell relevant potentials, 0–0.80 V vs RHE, the MOR mechanism is similar at all temperatures. The rate-determining step is the adsorption of water at low overpotentials (< 0.50 V vs RHE), a combination of the methanol adsorption reaction and the surface reaction between adsorbed CO and OH at intermediate potentials (0.50–0.65 V vs RHE), and the methanol adsorption reaction at high potentials (> 0.65 V vs RHE). The shoulder on the oxidation peak at 0.60–0.65 V vs RHE corresponds well with where the CO coverage approaches zero. Graphical abstract: Image 1 Highlights: Methanol oxidation on Pt is studied at temperatures up to 140 °C. Dynamic electrochemical impedance spectra are correlated with voltammetry. A reaction mechanism is suggested based on the experimental results. The reaction mechanism is similar at all temperatures. Three potential regions with different rate-determining steps are identified.