Selectively attaching Pt-nano-clusters to the open ends and defect sites on carbon nanotubes for electrochemical catalysis

Pt nano-clusters (nano-Pt) have been selectively attached to the open ends and defect sites of mildly oxidized multi-wall carbon nanotubes (MWCNTs) on a glassy carbon electrode (GCE) by a cyclic voltammetry (CV) electrodeposition method. The nano-Pt functionalized MWCNTs were characterized by XPS, XRD, FE-SEM and electrochemical techniques. The catalytic activity of the nano-Pt functionalized MWCNTs were tested by an oxygen reduction reaction (ORR) and a methanol oxidation reaction (MOR). Taking the ORR as an example, we found that the electrocatalytic activity of the nano-Pt functionalized MWCNTs can be well tuned by varying the cycle number and the PtCl₆²⁻ concentration of the deposition conditions. The average size of the nano-Pt was 123 nm, and it was constituted of nano-crystallite of an average size of 10.8 nm. Though the large nano-Pt particles (100-150 nm) were only attached on the open ends and defect sites of the MWCNTs, which were very different from the highly dispersed small Pt nanoparticles (<10 nm) on carbon nanotubes reported by other research groups. In our method, excellent electrocatalytic activity of the nano-Pt functionalized MWCNTs for ORR and MOR can be obtained. The mechanisms for nano-Pt deposition are proposed.