Double-Walled Ag–Pt Nanotubes Fabricated by Galvanic Replacement and Dealloying: Effect of Composition on the Methanol Oxidation Activity
Abstract
The synthesis of bimetallic nanostructures using galvanic replacement displays a versatile route toward efficient catalysts for fuel cell reactions. We show that electrolessly plated Ag nanotubes (NTs) are a unique template for the synthesis of double-walled Ag–Pt NTs. After replacement reaction, different dealloying protocols are applied to adjust the residual Ag content. The structures were thoroughly characterized by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy, providing evidence of a hollow tube structure composed of Ag–Pt alloy. Experiments under harsh conditions reveal, that a significant amount of Ag remain in the NTs, which strongly affects the methanol oxidation performance. With optimized Ag–Pt ratio, the specific activity of Pt/C catalysts can be outperformed. From the obtained results, we emphasize that each effort using galvanic replacement should be accompanied by detailed compositional analysis.
