The use of carbon nanotubes coated with a porous nitrogen-doped carbon layer with embedded Pt for the methanol oxidation reaction

An exceptionally durable and highly active Pt catalyst has been prepared by embedding Pt nanoparticles inside the pores of a nitrogen-doped porous carbon layer coated on carbon nanotubes (denoted as Pt@NC-CNT). The aforementioned material, under different carbonization temperatures, is characterized by transmission electron microscopy, N-2 adsorption and desorption isotherms, X-ray photoelectron spectroscopy, and Raman spectroscopy. The maximum current density (I-max) during the methanol oxidation reaction (MOR) observed for Pt@NC-CNT (13.2 mA cm(-1)) is 20% higher than that of the commercial Pt/XC-72 (10.8 mA cm(-1)) catalyst. In the accelerated durability test, the I-max after 2000 cycles for Pt@NC-CNT-600 decreased from 13.2 to 6.9 mA cm(-2) (48% decreased) compared with Pt/XC-72, which showed a decrease from 10.8 to 0.46 mA cm(-2) (96% decreased). This indicates that the Pt@NC-CNT catalyst has extremely stable electrocatalytic activity for MOR owing to its unique structure, whereby Pt is protected by being embedded inside the pores of the nitrogen-doped carbon layer. Pt@NC-CNT's superior durability properties are further verified by observing the changes of the Pt particle sizes using TEM images before and after accelerated durability tests, as compared with Pt/XC-72. (C) 2011 Elsevier B.V. All rights reserved.