TY - JOUR

T1 - Autonomous Voltage Oscillations in a Direct Methanol Fuel Cell

AU - Nogueira, Jéssica A.

AU - Peña Arias, Ivonne K.

AU - Hanke-Rauschenbach, Richard

AU - Vidakovic-Koch, Tanja

AU - Varela, Hamilton

AU - Sundmacher, Kai

N1 - Funding information: J.A.N. and H.V. acknowledge São Paulo Research Foundation (FAPESP) for the scholarship (grant #2015/09295-9) and financial support (grants #2012/21204-0, and #2013/16930-7). J.A.N. acknowledges Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) and the support by the Max Planck Society during her internship in Magdeburg , which enabled this cooperation. H.V. (#306151/2010-3) acknowledges Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for financial support. I.K.P.A and R.H.R. gratefully acknowledge financial support from Deutsche Forschungsgemeinschaft , Grant No. HA 6841/1-1 .

PY - 2016/9/10

Y1 - 2016/9/10

N2 - Proton exchange membrane fuel cells fed with H2/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.

AB - Proton exchange membrane fuel cells fed with H2/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.

KW - DMFC

KW - electrocatalysis

KW - fuel cells

KW - methanol

KW - oscillations

KW - FAFC

KW - Electrodissolution

KW - DMFC

KW - electrocatalysis

KW - fuel cell

KW - Methanol

KW - oscillations

UR - http://www.scopus.com/inward/record.url?scp=84978786387&partnerID=8YFLogxK

U2 - 10.1016/j.electacta.2016.07.050

DO - 10.1016/j.electacta.2016.07.050

M3 - Article

AN - SCOPUS:84978786387

VL - 212

SP - 545

EP - 552

JO - Electrochimica acta

JF - Electrochimica acta

SN - 0013-4686

ER -