High performance rare earth oxides LnOx (Ln = Sc, Y, La, Ce, Pr and Nd) modified Pt/C electrocatalysts for methanol electrooxidation

In this paper, the LnO. (Ln = Sc, Y, La, Ce, Pr and Nd) modified Pt/C catalysts were prepared by wet precipitation and reduction method. The catalysts were characterized by transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD). TEM showed that the Pt-PrOx, nanoparticles were uniformly dispersed on carbon with an average particle size of 5.0mn in the Pt-3-(PrOx)(1)/C catalyst. EDX showed that Pt and Pr were successfully loaded on the carbon support without obvious loss. XRD showed that all the Pt/C and LnO(x) modified Pt/C electrocatalysts (except for the Pt-3-(ScOx)(1)/C electrocatallyst) displayed the typical character of Pt face centered cubic (fcc) phase, whereas the Pt-3-(ScOx)(1)/C electrocatalyst contained the diffraction pattern of Pt face centered cubic and Sc2O3 phase. LnO(x) modified Pt/C electrocatalysts were compared with Pt/C in terms of the electrochemical activity and stability for methanol electrooxidation using cyclic voltammetry (CV) and chronoamperometry (CA) in 0.5 M H2SO4 + 0.5 M CH3OH solutions. The results showed that all the LnO(x) (except for NdOx) modified the Pt/C electrocatalysts gave higher catalytic activity and stability than Pt/C. In particular, the Pt-3-(PrOx)(1)/C eloctrocatalyst was found to be superior than others. Under this respect, several Pt-PrOx/C catalysts with different atomic ratio of Pt/Pr were also identically prepared and characterized. It was found by CV and CA that the Pt-3-(PrOx)(1)/C and Pt-1-(PrOx)(1)/C catalysts showed better catalytic activity and stability than the Pt-5-(PrOx)(1)/C, Pt-1-(PrOx)(3)/C and Pt/C catalysts. The Pt-3-(PrOx)(1)/C and Pt-1-(PrOx)(1)/C catalysts had high catalytic activity and good stability, which could be used as novel electrocatalysts for direct methanol fuel cell. (c) 2006 Elsevier B.V. All rights reserved.