Dynamic electrochemical impedance study of methanol oxidation at Pt at elevated temperatures

Date

2019

Authors

Holm, Thomas
Dahlstrøm, Per Kristian
Sunde, Svein
Seland, Frode
Harrington, David A.

Journal Title

Journal ISSN

Volume Title

Publisher

Electrochimica Acta

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.

Description

Keywords

Electrochemical impedance spectroscopy, Methanol oxidation, Temperature, Reaction mechanism

Citation

Holm, T., Dahlstrøm, R.K., Sunde, S., Seland, F. & Harrington, D.A. (2019). Dynamic electrochemical impedance study of methanol oxidation at Pt at elevated temperatures. Electrochimica Acta, 295, 139-147. https://doi.org/10.1016/j.electacta.2018.10.071