PtSb/C electrocatalysts for glycerol oxidation in alkaline electrolyte

Abstract

Pt/C and PtSb/C catalysts in various atomic ratios were synthesized by the sodium borohydride reducing method and their activity for the glycerol oxidation reaction (GOR) was evaluated in alkaline media. Transmission Electron Microscopy (TEM) images showed that Pt particle size increases with increasing Sb content in the catalyst. X-ray photoelectron spectroscopy (XPS) showed that the ratio of Pt and Sb is close to that expected. By XPS measurements, the presence of Sb2O5 in Pt70Sb30/C and Pt50Sb50/C was observed. X-ray diffraction (XRD) analysis revealed the presence of the face-centered cubic (FCC) structure of Pt and PtSb and of some others phases that could be identified as Sb oxides. By linear sweep voltammetry (LSV) measurements, Pt80Sb20/C showed the highest activity for the GOR in alkaline media for potentials >−0.35 V vs. Ag/AgCl, while Pt50Sb50/C showed the highest GOR activity in the potential range between −0.60 and −0.35 V vs. Ag/AgCl. The direct glycerol fuel cells with Pt80Sb20/C as the anode catalyst showed the best performance. These results attest the beneficial effect of Sb addition to platinum: the activity enhancement in the presence of Sb atoms has to be ascribed to both a bifunctional mechanism related to the presence of Sb oxides, and an electronic effect between platinum and antimony in the PtSb alloy.