Preparation of high-performance PdPt–Pt core–shell catalyst with shortened carbon nanotubes as support

Shortened carbon nanotubes (SCNTs) obtained by ball milling of carbon nanotubes (5–10 μm) with the assistance of ethanol are used as supports for fabrication of core–shell structured PdPt@Pt/SCNTs via a successive colloidal reduction approach. The catalysts are characterized by X-ray diffraction (XRD) analysis, Transmission electron microscopy, and X-ray photoelectron spectroscopy. The active particles are found to disperse on the shortened carbon nanotubes with an average particle size of 3.1 nm. PtPd nanoparticles, rather than single Pd nanoparticles, are used as core materials for prevention of possible agglomeration and better dispersion. Using this catalyst, we investigate methanol oxidation reactions (MOR) and oxygen reduction reactions (ORR). The catalysts show excellent activity to anodic MOR, 2.87 times higher than that of commercial Johnson Matthey 40 wt.% Pt/C catalyst. The ratio of forward current Ifto backward current Ib is as high as 1.41 for the oxidation of methanol relative to that of 0.74 for the commercial Pt/C catalyst, an indication of better CO tolerance of the former. In the ORR, the reaction is found to proceed via an overall four-electron transfer process.

Graphical abstractThe activity of the core–shell structured PdPt@Pt/SCNTs (PPPS) catalyst supported on shortened carbon nanotubes is found to be 2.87 times and 1.5 times of that of Pt/C (JM4100) and 40 wt.% PtRu/C catalysts, respectively. This catalyst shows superior activity to Pt/C and PtRu/C catalysts for the anodic oxidation of methanol. The If/Ib of the PPPS catalyst (1.41) is higher than that of the JM Pt/C (0.74) and 40 wt.% PtRu/C (1.12) catalysts, showing the high activity toward anodic oxidation of methanol of core–shell structured PPPS catalyst with good tolerance to poisoning species on the catalyst surface.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Shortened carbon nanotubes are used as supports for core–shell PdPt@Pt/SCNTs catalyst. ► The mass activity for PdPt@Pt/SCNTs catalyst is 2.87 times higher than JM 40 wt% Pt/C catalyst. ► The catalyst shows better poisoning tolerance than PtRu/C catalyst. ► The enhanced activity observed did not alter the ORR pathway.