Ultralow Pt amount of Pt–Fe alloys supported on ordered mesoporous carbons with excellent methanol tolerance during oxygen reduction reaction

Abstract

The synthesis of ordered mesoporous carbons supported various atomic ratios of Pt–Fe nanoparticles (PtxFe100−x/OMC) with low Pt loading and high Pt–Fe alloying extent is reported. The resultant PtxFe100−x/OMC have been thoroughly characterized by a variety of different spectroscopic techniques and used as electrocatalysts during oxygen reduction reaction (ORR) for direct methanol fuel cell (DMFC) at cathode. Results obtained from X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) indicate that the Pt metal in the PtxFe100−x/OMC is formed in the face-centered cubic (fcc) crystalline structure and composed of Pt(0) and Pt oxides. By using N2 adsorption/desorption isotherms, transmission electron microscopy (TEM), it was found that Pt–Fe alloy nanoparticles (3–5 nm) homogeneously dispersed on the mesoporous carbon supports with high surface areas (>1000 m2 g−1) and regular pore channels (ca. 3.4 nm) for all PtxFe100−x/OMC. Further studies by X-ray absorption spectroscopy (XAS) reveal that the Pt-richshell–Fe-richcore microstructure with a higher Pt–Fe alloying state is accountable for the superior ORR performance observed for the PtxFe100−x/OMC, as compared to the commercial electrocatalysts. Among the various PtxFe100−x/OMC catalysts, the Pt45Fe55/OMC exhibits the highest ORR performance, methanol-tolerant capability and ultralow Pt content, which should have potential applications as cathodic catalysts in DMFC.