Electrochemical Investigation of Pt-Co/MWCNT as an Alcohol-Tolerant ORR Catalyst for Direct Oxidation Fuel Cells

In this study, we investigated the behavior of a 30% Pt70-Co30/MWCNT electrocatalyst as oxygen reduction reaction (ORR) material in acid electrolyte without and with liquid fuels. The characterization was performed by rotating ring-disc electrode (RRDE) and electrochemical impedance spectroscopy (EIS). In the absence of organic molecules, the ORR on the alloy proceeds via a 4-electron transfer mechanism, with a negligible production of hydrogen peroxide, as indicated by the RRDE measurements. In the presence of the different liquid fuels (ethylene glycol, ethanol or 2-propanol), the alloy shows a high degree of tolerance, although this characteristic is dependent on the chemical composition of the molecule. The EIS measurements in solutions containing organic molecules suggest that at high polarization potentials, the competitive interaction of oxygen reduction and liquid fuels oxidation at the alloy catalytic sites leads to a faster reaction, as shown by the smaller charge transfer resistances (Rct) obtained from Nyquist plots, compared to the Rct values without organic molecules. The results obtained from the Pt-Co/MWCNT electrocatalyst are compared to those of a commercial Pt/C cathode.