Synthesis and Evaluation of Highly Tolerant Pd Electrocatalysts as Cathodes in Direct Ethylene Glycol Fuel Cells (DEGFC)

F Javier Rodríguez Varela,Sergio Fraire Luna,Oumarou Savadogo

doi:10.3390/en20400944

F Javier Rodríguez Varela, Sergio Fraire Luna + Show 1 more

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https://doi.org/10.3390/en20400944

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Journal: Energies	Publication Date: Oct 27, 2009
Citations: 44	License type: CC BY 3.0

Affiliation: Polytechnique Montréal

Abstract

Highly selective Pd electrocatalysts were synthesized by the formic acid (FA) method and evaluated as cathodes for DEGFC applications. In rotating disc measurements in acid medium, the Pd/C cathode showed important catalytic activity for the Oxygen Reduction Reaction (ORR). In the presence of ethylene glycol (EG, C2H6O2), Pd/C exhibited a noteworthy electrochemical behavior and full tolerance to the organic molecule. No current density peaks associated to the EG oxidation reaction emerged and the shift in onset potential for the ORR (Eonset) toward more negative potentials was negligible on this cathode. As a comparison, commercial Pt/C was tested under the same conditions showing a poor selectivity for the ORR when EG was present. The detrimental effect of EG on the Pt electrocatalysts resulted in high intensity current density peaks due to the oxidation of EG and a significant shift in Eonset. The evaluation of Pd/C in a DEGFC operating at 80 °C demonstrated its good performance as cathode material. Given these results, it is expected that highly efficient Pd-based cathodes can find application in DEGFCs.

Highlights

Direct Oxidation Fuel Cells (DOFCs) are an excellent alternative to H2/O2 PEMFCs in applications such as low-power electronic devices or stand-alone back up power systems.Nowadays, Direct Methanol and Ethanol Fuel Cells (DMFCs and DEFCs, respectively) are the most common fuel cells fueled with organic molecules, delivering high power densities at temperatures around 80 °C [1,2,3,4]
No current density peaks associated to the EG oxidation reaction emerged and the shift in onset potential for the Oxygen Reduction Reaction (ORR) (Eonset) toward more negative potentials was negligible on this cathode
We have shown that the catalytic activity of Pt-alone electrocatalysts for the ORR is significantly reduced by the presence of EG in acid solutions and the value of Eonset is remarkably displaced towards more negative potentials in the presence of relatively low concentrations of the liquid fuel [11,15,29]

Summary

Introduction

Direct Oxidation Fuel Cells (DOFCs) are an excellent alternative to H2/O2 PEMFCs in applications such as low-power electronic devices (laptops, PDAs, etc.) or stand-alone back up power systems. Direct Methanol and Ethanol Fuel Cells (DMFCs and DEFCs, respectively) are the most common fuel cells fueled with organic molecules, delivering high power densities at temperatures around 80 °C [1,2,3,4]. The loss of catalytic activity of Pt during the electro-oxidation of small organic molecules results in significantly high anode overpotentials and lower fuel cell performances. The crossover of relatively small amounts of liquid fuel and/or reaction intermediates to the cathode side of the MEA causes a significant increase in cathode overpotentials and a remarkable lower onset potential for the ORR when Pt-alone cathodes are used [1,2,3,4,5,6,7,8,9].

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