Vapor Synthesis and Thermal Modification of Supportless Platinum–Ruthenium Nanotubes and Application as Methanol Electrooxidation Catalysts

Metallic, mixed-phase, and alloyed bimetallic Pt–Ru nanotubes were synthesized by a novel route based on the sublimation of metal acetylacetonate precursors and their subsequent vapor deposition within anodic alumina templates. Nanotube architectures were tuned by thermal annealing treatments. As-synthesized nanotubes are composed of nanoparticulate, metallic platinum and hydrous ruthenium oxide whose respective thicknesses depend on the sample chemical composition. The Pt-decorated, hydrous Ru oxide nanotubes may be thermally annealed to promote a series of chemical and physical changes to the nanotube structures, including alloy formation, crystallite growth, and morphological evolution. Annealed Pt–Ru alloy nanotubes and their as-synthesized analogs demonstrate relatively high specific activities for the oxidation of methanol. As-synthesized, mixed-phase Pt–Ru nanotubes (0.39 mA/cm2) and metallic alloyed Pt64Ru36NTs (0.33 mA/cm2) have considerably higher area-normalized activities than PtRu black (0.22 mA/cm2) at 0.65 V vs RHE.