Ceria Based Nano-composite Synthesis for Direct Alcohol Fuel Cells


TAPAN N. A. , Cacan U. B. , VARIŞLI D.

INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE, vol.9, no.8, pp.4440-4464, 2014 (Journal Indexed in SCI) identifier identifier

  • Publication Type: Article / Article
  • Volume: 9 Issue: 8
  • Publication Date: 2014
  • Title of Journal : INTERNATIONAL JOURNAL OF ELECTROCHEMICAL SCIENCE
  • Page Numbers: pp.4440-4464

Abstract

Ethanol electro-oxidation activities of electrocatalysts for direct alcohol fuel cells (DAFC), prepared by impregnation-hydrothermal method were investigated by cyclic voltammetry, chronoamperometry, chronopotentiometry and fuel cell tests. In addition, the relation between activity and morphology, chemical and physical structure were determined by spectroscopic techniques. X-ray photoelectron spectroscopy showed that the surface oxygen content of electrocatalysts can be arranged in order as: Pt/NiCeOx> Pt/PdCeOx> Pd/PtCeOx> Ni/PtCeOx> Pt/FeCeOx> Fe/PtCeOx. Comparison of XPS and ICP-OES (bulk and surface analysis) indicate that; after hydrogen reduction Pt and Ni in Pt/NiCeOx or Ni/PtCeOx segregate to the surface. The same behavior was also seen for Pt and Pd in Pt/PdCeOx or Pd/PtCeOx. However, in the case of Pt and Fe, surface segregation of Fe is higher than Pt. Diffraction analysis show that, after hydrothermal synthesis, Fe was in the form of Fe3O4 in the support phase but Pt and Ni may incorporate into the ceria matrix. Although metallic Pt, Pd and Ni are seen in ceria phase, Fe and Ni may also appear as a different oxide phase (Fe2O3 or NiO) beside ceria. Both XRD and TEM analysis support the existence of Fe and Ni oxides. Cyclic voltammograms indicate that all home made catalysts exhibit typical ethanol electro-oxidation peaks, magnitudes of oxidation current densities can be arranged in order as Fe/PtCeOx> Pt/PdCeOx> PtRu/C. When anodic polarizations at 0.5 mA are compared from lowest to highest, it was seen that, Fe/PtCeOx< Pt/PdCeOx Pd/PtCeOx>PtRu/C approximate to Pt/PdCeOx. Although, power densities of home-made electro-catalysts are close to that of commercial PtRu/C at 40 degrees C, because of the intense kinetic effect in PtRu/C, the performances of home-made electro-catalysts fall behind PtRu/C at 60 and 80 degrees C. After physically mixing home-made electro-catalysts with the commercial PtRu/C, fuel cell performances drastically improved and even higher power densities than PtRu/C could be obtained for Ni/PtCeOx+PtRu/C, Pt/FeCeOx+PtRu/C and Pt/PdCeOx+PtRu/C.