Fine platinum nanoparticles supported on polyindole-derived nitrogen-doped carbon nanotubes for efficiently catalyzing methanol electrooxidation

Abstract

Carbon-based nanomaterials e.g. activated carbon powder, carbon nanotubes and graphene are often used as supports to sustain high performance of metal nanoparticles in electrochemical reactions. In principle, doping the carbon-based nanomaterials with hetero-atoms is an efficient approach to increase their catalytic aspects as catalyst supports. In this study, nitrogen-doped multi-walled carbon nanotubes (N-MWCNTs) are prepared for the first time by annealing the polyindole (PIn) coated acid treated MWCNTs, and then fine platinum nanoparticles (PtNPs) are deposited on them to design the Pt/N-MWCNTs catalyst for the anodic reaction of direct methanol fuel cells (DMFCs). The characterizations including Raman spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray energy dispersive spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) confirm that zero valent Pt metal is formed on the surfaces of N-MWCNTs with highly dispersion and uniformly fine sizes (ca. 2.11 nm). The Pt/N-MWCNTs exhibits the enhanced electro-catalytic efficacy, improved electrochemical stability and anti-CO poisoning capability compared to Pt/AO-MWCNTs (the precursor used to prepare Pt/N-MWCNTs) and commercially available Pt/C catalysts for methanol oxidation reaction (MOR) due to strong electronic interaction between the fine PtNPs and the N-MWCNT supports, as verified by electrochemical cyclic voltammetry and chronoamperometry methods.