Ultrafine platinum nanoparticles uniformly dispersed on arrayed CN _x nanotubes with high electrochemical activity

The structure and electrochemical properties of arrayed nitrogen-containing carbon nanotube (CM _x NT)-platinum nanoparticle (Pt NP) composites directly grown on Si substrates have been investigated. The CN _x nanotube arrays were grown by microwave-plasma-enhanced chemical vapor deposition first and then acted as the template and support for Pt dispersion in the following sputtering process. Under the same sputtering conditions, it was found that well-separated Pt NPs would form with an average diameter of 2 nm on the arrayed NTs while a continuous Pt thin film was observed on the bare Si substrate. X-ray photoelectron spectroscopy (XPS), X-ray diffraction, and electron microscopy were employed to study bonding and structure changes with increasing deposition time. Implications of the C1s and N1s bonding changes in XPS and their possible relation to the NT-Pt composite structures with self-limited size distribution are discussed. Cyclic voltammograms show well-behaved curves in methanol oxidation, suggesting an efficient electronic conduction mechanism from the substrate via CN _x NTs to reach individual Pt NPs is in operation. Such an integrated nanocomposite approach possesses a high potential for micro direct methanol fuel cell applications.