Ethanol electrooxidation on PdIr/C electrocatalysts in alkaline media: electrochemical and fuel cell studies

PdIr/C electrocatalysts in different atomic ratios (Pd:Ir 90:10, 70:30, and 50:50), Pd/C and Ir/C supported on Vulcan XC 72 carbon were tested for ethanol electrooxidation in alkaline media. The electrocatalysts were prepared by borohydride reduction method. The electrocatalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), cyclic voltammetry (CV), and chronoamperometry (CA). The XRD measurements suggested the PdIr alloy formation. EDS analyses showed the real atomic ratios similar to the nominal ones. TEM showed the average particle diameter between 4.6 and 5.8 nm for all compositions prepared. The catalytic activity for ethanol electrooxidation in alkaline medium investigated by CV and CA at room temperature showed that PdIr/C (90:10) exhibited higher performance for ethanol oxidation in comparison with others PdIr/C compositions, Pd/C and Ir/C, while the experiments on a single direct ethanol alkaline fuel cell at 70 A degrees C showed higher performance for PtIr (70:30). The best results obtained using PdIr/C electrocatalysts may be associated to the electronic effect between Pd and Ir that might cause a decrease of poisoning on catalyst and the occurrence of bifunctional mechanism.