Pt-Covered Multiwall Carbon Nanotubes for Oxygen Reduction in Fuel Cell Applications

Recently one-dimensonal (1-D) Pt nanostructures have shown greatly enhanced intrinsic oxygen reduction reaction (ORR) activity (ORR kinetic current normalized to Pt surface area) and/or improved durability relative to conventional supported Pt catalysts. In this study, we report a simple synthetic route to create Pt-covered multiwall carbon nanotubes (Pt NPs/MVVNTs) as promising 1-D Pt nanostructured catalysts for ORR in proton exchange membrane fuel cells (PEMFCs). The average ORR intrinsic activity of Pt NPs/MVVNTs is similar to 0.95 mA/cm(2) Pt at 0.9 V(iR-corrected) versus reversible hydrogen electrode (RHE), similar to 3-fold higher than a commercial catalyst -46 wt % Pt/C (Tanaka Kikinzoku Kogyo) in 0.1 M HClO(4) at room temperature. More significantly, the mass activity of Pt NPs/MWNTs measured (similar to 0.48 A/mg(Pt) at 0.9 V(iR-corrected) vs RHE) is higher than other 1-D nanostructured catalysts and TKK catalysts. The enhanced intrinsic activity of 1-D Pt NPs/MWNTs could be attributed to the weak chemical adsorption energy of OH(ads)-species on the surface Pt NPs covering MWNTs.