Effect of W on PtSn/C catalysts for ethanol electrooxidation

Binary and ternary Pt-based catalysts were prepared by the Pechini–Adams modified method on carbon Vulcan XC-72, and different nominal compositions were characterized by TEM and XRD. XRD showed that the electrocatalysts consisted of the Pt displaced phase, suggesting the formation of a solid solution between the metals Pt/W and Pt/Sn. Electrochemical investigations on these different electrode materials were carried out as a function of the electrocatalyst composition, in acid medium (0.5 mol dm⁻³ H₂SO₄) and in the presence of ethanol. The results obtained at room temperature showed that the PtSnW/C catalyst display better catalytic activity for ethanol oxidation compared to PtW/C catalyst. The reaction products (acetaldehyde, acetic acid and carbon dioxide) were analyzed by HPLC and identified by in situ infrared reflectance spectroscopy. The latter technique also allowed identification of the intermediate and adsorbed species. The presence of linearly adsorbed CO and CO₂ indicated that the cleavage of the C–C bond in the ethanol substrate occurred during the oxidation process. At 90 °C, the Pt₈₅Sn₈W₇/C catalyst gave higher current and power performances as anode material in a direct ethanol fuel cell (DEFC).