Pt-rare earth catalysts for ethanol electrooxidation: modification of polyol synthesis

Pt–Ln/C (Ln = La, Ce, Pr, and Eu) catalysts were obtained by using a modification of the polyol method and tested for ethanol oxidation. Transmission electron microscopy (TEM) results showed that the Pt–Ln/C catalysts had particles with average size of 3 nm, which is the smallest particle size reported for Pt–rare earth catalysts; and the particles are homogeneously distributed on the carbon support. X-ray diffraction analysis showed no alloy formation between Pt and rare earth elements, and X-ray photoelectron spectroscopy (XPS) confirmed that Ln is present in its oxide form. X-ray absorption spectroscopy (XAS) results confirmed that the presence of the second metal affects the Pt electronic structure. CO oxidation in the presence of rare earths takes place mostly through the lower-potential pathway, and these catalysts showed better activity toward ethanol oxidation than Pt/C with the same particle size. Durability tests performed by repetitive potential cycling under an Ar atmosphere revealed good structural stability of the Pt–Ln/C catalysts.