Platinum-Coated Palladium Nanotubes as Oxygen Reduction Reaction Electrocatalysts

Platinum (Pt) coated palladium (Pd) nanotubes (Pt/PdNTs) with a wall thickness of 6 nm, outer diameter of 60 nm, and length of 5-20 mu m are synthesized via the partial galvanic displacement of Pd nanotubes. Pt coatings are controlled to a loading of 9 (PtPd 9), 14 (PtPd 14), and 18 (PtPd 18) wt % and estimated to have a thickness of 1.1, 1.7, and 2.2 Pt atoms, respectively, if a uniform and continuous coating is assumed. Oxygen reduction experiments have been used to evaluate Pt/PdNTs, Pt nanotubes, Pd nanotubes, and supported Pt nanoparticle activity for proton exchange membrane fuel cell cathodes. The dollar and area (specific surface area) normalized ORR activities of Pt/PdNTs exceed the United States Department of Energy (DOE) targets. PtPd 9, PtPd 14, and PtPd 18 produce dollar activities of 10.4, 9.4, and 8.7 A$(-1), respectively; PtPd 9 exceeds the DOE dollar activity target (9.7 A$(-1)) by 7%. Pt/PdNTs further exceed the DOE area activity target by 40-43%.