The Promoting Effect of Europium on PtSn/C Catalyst for Ethanol Oxidation

Well-dispersed PtSnEu/C and PtSn/C catalysts were prepared by the impregnation-reduction method using formic acid as a reductant and characterised by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersion X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The synthesised catalysts with different atomic ratios of Pt/Sn/Eu have the Pt face centered cubic (fcc) structure and their particle sizes are 3-4 nm. The PtSnEu/C catalyst is composed of many Pt (0), SnO2, Eu(OH)(3), a small amount of Pt(II) and partly alloyed PtSn, but no metallic Eu. The electrochemical measurements indicate that in comparison with Pt3Sn1/C catalyst, the Pt3Sn1Eu1/C catalyst for ethanol oxidation has more negative onset potential, smaller apparent activation energy and lower electrochemical impedance so that it exhibits very high catalytic activity. Its peak current density increases by 135% and 40%, compared with Pt3Sn1/C and Pt1Ru1/C (JM) catalysts, respectively. This is because the Eu(OH) 3 formed by adding Eu to PtSn/C catalyst can provide the OH group which is in favour of the removal of adsorbed intermediates and ethanol oxidation.