Carbon-supported ternary PtSnIr catalysts for direct ethanol fuel cell

Binary PtIr, PtSn and ternary PtSnIr electrocatalysts were prepared by the Pechini–Adams modified method on carbon Vulcan XC-72, and these materials were characterized by TEM and XRD. The XRD results showed that the electrocatalysts consisted of the Pt displaced phase, suggesting the formation of solid solutions between the metals Pt/Ir and Pt/Sn. However, the increase in Sn loading promoted phase separation, with the formation of peaks typical of cubic Pt3Sn. The electrochemical investigation of these different electrode materials was carried out as a function of the electrocatalyst composition, in a 0.5 mol dm−3 H2SO4 solution, with either the presence or the absence of ethanol. Cyclic voltammetric measurements and chronoamperometric results obtained at room temperature showed that PtSn/C and PtSnIr/C displayed better electrocatalytic activity for ethanol electrooxidation compared to PtIr/C and Pt/C, mainly at low potentials. The oxidation process was also investigated by in situ infrared reflectance spectroscopy, to identify the adsorbed species. Linearly adsorbed CO and CO2 were found, indicating that the cleavage of the CC bond in the ethanol substrate occurred during the oxidation process. At 90 °C, the Pt89Sn11/C and Pt68Sn9Ir23/C electrocatalysts displayed higher current and power performances as anode materials in a direct ethanol fuel cell (DEFC).