Autonomous Voltage Oscillations in a Direct Methanol Fuel Cell

Author(s)

Nogueira, Jessica A. ; Arias, Ivonne K. Pena ; Hanke-Rauschenbach, Richard ; Vidakovic-Koch, Tanja ; Varela, Hamilton ; Sundmacher, Kai

• Document type: Journal article
• Source: Electrochimica Acta; v. 212, p. 545-552, SEP 10 2016.
• Web of Science Citations: 7

Abstract

Proton exchange membrane fuel cells fed with H-2/CO mixtures at the anode have a considerably lower performance than fuel cells fed with pure hydrogen. However, when operated in an autonomous oscillatory regime, the overall voltage loss decreases due to a self-cleaning mechanism. Another molecule, also widely used as feed in the fuel cell and susceptible to kinetic instabilities, is methanol. To the best of our knowledge, there are no reports on autonomous voltage oscillations in the direct methanol fuel cell (DMFC). The purpose of this work was to explore if such instabilities also occur in the DMFC system. Initially, half-cell experiments with a gas diffusion electrode were performed. Then, a DMFC was operated under current control and studied by means of electrochemical impedance spectroscopy. The half-cell measurements revealed that the induction period for oscillations depends on the mass transfer conditions, where on stagnant electrode the induction time was shorter than in the case of forced convection. The DMFC showed also autonomous voltage oscillations above a certain threshold current. The results obtained by electrochemical impedance spectroscopy give evidence of a negative differential resistance in the fuel cell, hitherto not described in the literature, which can be related to the appearance of oscillations during galvanostatic methanol electro-oxidation. These results open the possibility to evaluate the performance of low-temperature fuel cells fed with carbon-containing fuels under oscillatory operating conditions. (C) 2016 Elsevier Ltd. All rights reserved. (AU)

• 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: 15/09295-9 - Dynamic behavior in low-temperature fuel cells based on oxidation of small organic molecules
• Grantee: Jéssica Alves Nogueira
• Support Opportunities: Scholarships in Brazil - Doctorate
• 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