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 LnOx (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 5.0 nm in the Pt3-(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 LnOx modified Pt/C electrocatalysts (except for the Pt3-(ScOx)1/C electrocatalyst) displayed the typical character of Pt face centered cubic (fcc) phase, whereas the Pt3-(ScOx)1/C electrocatalyst contained the diffraction pattern of Pt face centered cubic and Sc2O3 phase. LnOx 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 LnOx (except for NdOx) modified the Pt/C electrocatalysts gave higher catalytic activity and stability than Pt/C. In particular, the Pt3-(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 Pt3-(PrOx)1/C and Pt1-(PrOx)1/C catalysts showed better catalytic activity and stability than the Pt5-(PrOx)1/C, Pt1-(PrOx)3/C and Pt/C catalysts. The Pt3-(PrOx)1/C and Pt1-(PrOx)1/C catalysts had high catalytic activity and good stability, which could be used as novel electrocatalysts for direct methanol fuel cell.