Nitrogen-doped carbon nanotubes for high-performance platinum-based catalysts in methanol oxidation reaction

Nitrogen-doped carbon nanotubes (CNx-NTs), platinum (Pt)-based catalysts supports, were prepared by pyrolysis of polypyrrole nanotubes (PPy-NTs), which were synthesized using a self-degraded template method. The morphology, structure and physicochemical properties of CNx-NTs supports and Pt/CNx-NTs catalysts were investigated by scanning electron microscope, Brunauer-Emmett-Teller surface area, transmission electron microscopy, X-ray diffraction, and X-Ray photoelectron spectroscopy. Fine Pt nanoparticles are uniformly deposited onto the CNx-NTs supports, which possess well-defined nanotube morphology. The Pt/CNx-NTs catalysts, especially Pt/CNx-NTs-800 catalyst (CNx-NTs prepared at pyrolysis temperature of 800 °C), exhibit outstanding electrochemical performance toward methanol oxidation reaction (MOR), compared with commercial Pt/C catalyst, which is attributed to high nitrogen content and nanotube morphology of the support. High nitrogen content can better disperse and anchor Pt nanoparticles, and nanotube structure may provide an open network around the active catalysts for facilitating the mass transfer. Under the same electrocatalytic activity, the Pt loading of the Pt/CNx-NTs-800 catalyst is reduced by 56.3% comparing with commercial Pt/C catalyst. The results indicate that the CNx-NTs-800 as support greatly reduces the loading of noble metal platinum, further promoting the commercialization process of proton exchange membrane fuel cells (PEMFCs).