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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, C 2 H 6 O 2 ), 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 (E onset ) 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 E onset . 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.

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We studied the performance of carbon-supported Pd cathode electrocatalysts in O 2 -saturated acid solution containing ethanol. The Pd/C electrocatalysts showed an important selectivity toward the Oxygen Reduction Reaction (ORR), and a very high degree of tolerance to poisoning due to the presence of the alcohol. A negative shift in onset potential for the ORR of only 10 mV for a 20% Pd/C electrocatalyst in 0.5M H 2 SO 4 + 0.125M C 2 H 5 OH electrolyte was measured, whereas the shift for a 20% Pt/C electrocatalyst was of 398 mV in the same solution. Similar high tolerances were established at increasing C 2 H 5 OH concentrations for Pd/C.