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

Abstract

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.