Pronounced synergetic effect of the nano-sized PtSnNi/C catalyst for ethanol oxidation in direct ethanol fuel cell

Abstract

Abstract Carbon supported well-dispersed Pt, Pt90Sn10, Pt90Ni10 and Pt80Sn10Ni10 nanoparticles were synthesized by co-reduction using Bonnemann's colloidal precursor method. X-ray diffraction (XRD) analysis showed that catalysts have the Pt face centred cubic (fcc) structure and their crystallite size are in the range 2–6 nm. Regarding the ternary Pt80Sn10Ni10/C catalyst, its lattice parameter is larger than that of Pt90Ni10/C and smaller than that of Pt90Sn10/C. The size of catalyst nanoparticles was observed via Transmission electron microscopy (TEM) and showed an average diameter of 3 nm. X-ray photon electron spectroscopy (XPS) results indicate that the surface of Pt90Sn10/C catalyst is enriched in Sn as compared to bulk composition, whereas Pt80Sn10Ni10/C catalyst is Pt-enriched. The onset potentials for ethanol oxidation on Pt90Sn10/C and Pt80Sn10Ni10/C catalysts were significantly lower than that of Pt/C and Pt90Ni10/C. Single direct ethanol fuel cell (DEFC) performances obtained for the Pt80Sn10Ni10/C is promising when compared to that obtained with Pt90Sn10/C catalyst. The effect of Ni by promoting the C C bond cleavage is confirmed by in situ IR measurements. These results suggest the presence of Ni in the Pt80Sn10Ni10/C catalyst can facilitate C C bond cleavage reaction on its Pt-rich surface; however, Sn oxide species activates the adsorbed CO on the surface providing the necessary OH species for oxidation of ethanol at lower potentials.