Pt-Sn Nanoparticles Decorated Carbon Nanotubes as Electrocatalysts with Enhanced Catalytic Activity

The catalytic activities of Pt-Sn alloy nanoparticles with different Pt:Sn atomic ratios, prepared by a pulse microwave-assisted polyol (MP) method, in the oxygen reduction reaction and oxidation of methanol and formic acid have been examined by using cyclic voltammetry. The pulse MP approach enables the formation of Pt-Sn alloy nanoparticles with well-defined atomic ratios over the surface of carbon nanotubes. The as-prepared Pt-Sn nanoparticles display a homogeneous dispersion with a narrow crystalline size in the range of 2.72-3.66 nm. An appropriate amount of Sn dopants (25 at. 96) facilitates not only the catalytic activity but also the long-term antipoisoning ability as compared with pure Pt catalyst. The improved performance of Pt-Sn alloy catalyst is attributed to the bifunctional mechanism of bimetallic catalysts; that is, CO adsorption mainly occurs on Pt sites, while OH formation would take place preferentially on the Sn sites. Thus, the introduction of Sn offers one pathway to strip CO from the Pt-CO sites, thereby raising the CO tolerance. Without any treatment, the pulse MP synthesis emerges as a feasible method to prepare Pt-Sn catalysts with excellent catalytic activity and long-term durability for fuel cell applications.