Platinum deposition on multiwalled carbon nanotubes by ion-exchange method as electrocatalysts for oxygen reduction

Platinum supported on multiwalled carbon nanotubes (MWNTs) as electrocatalysts were prepared by the ion exchange method. The support was functionalized to create surface functional groups for the ion exchange reaction. The ion exchange was repeated for increased Pt loading. For comparison, the same loading of Pt catalyst supported on carbon nanotubes was prepared by the borohydride method. The electrocatalysts were characterized by energy dispersive analysis of X-ray, transmission electron microscopy, and X-ray photoelectron spectra. It was found that Pt/MWNTs with a high dispersion were obtained by the ion exchange method. The electrocatalytic properties of the Pt/MWNTs for oxygen reduction reaction (ORR) were investigated by cyclic voltammetry and linear sweep voltammetry. Compared with the electrocatalysts prepared by the borohydride method, Pt/MWNTs prepared with the ion exchange method showed a higher performance toward ORR and a higher Pt utilization efficiency. Furthermore, in spite of a low Pt loading (15.4 wt %), they showed a higher catalytic activity than 20 wt % E-TEK Pt/C catalyst. Thus, the ion exchange technique can provide a method for the reduction of Pt usage in Pt-based catalyst. (C) 2007 The Electrochemical Society.