Segregated Pt on Pd nanotubes for enhanced oxygen reduction activity in alkaline electrolyteElectronic supplementary information (ESI) available: Experimental details, XAS results, and Tafel plots. See DOI: 10.1039/c5cc05706j

Nanoscaled Pt domains were integrated with Pd nanotubes via vapor deposition to yield a highly active electrocatalyst for the oxygen reduction reaction (ORR) in alkaline media. The surface-area-normalized ORR activity of these bi-metallic Pt-on-Pd nanotubes (PtPdNTs) was nearly 6× the corresponding carbon-supported Pt nanoparticle (Pt/C) activity at 0.9 V vs. RHE (1.5 vs. 0.24 mA cm metal −2 , respectively). Furthermore, the high specific activity of the PtPdNTs was achieved without sacrificing mass-normalized activity, which is more than twice that of Pt/C (0.333 A mg PtPdNT −1 vs. 0.141 A mg Pt/C −1 ) and also greater than that of Pd/C (0.221 A mg Pd/C −1 ). We attribute the enhancements in specific and mass activity to modifications of the segregated Pt electronic structure and to nanoscale porosity, respectively. Nanoscaled Pt domains were integrated with Pd nanotubes via vapor deposition to yield a highly active electrocatalyst for the oxygen reduction reaction (ORR) in alkaline media.