Closed Pt nanowire arrays as nanostructured microreactors for catalysis

In recent years, the advantages of microstructured devices for chemical reactions have been demonstrated most impressively. The application of microstructured reactors has gained significant importance in chemical synthesis and analysis [1]. The spectrum of chemical conversions, carried out successfully in microstructured reactors, includes many catalytic reactions. Supportless onedimensional nanostructures were recently recognized as durable catalysts [2]. Due to their low diameter, nanowires provide a very large surface area without the need for a high-surface-area support. Moreover, it is expected that these structures can reduce all degradation pathways discussed for nanoparticles such as Ostwald ripening. To use their full potential in applications, however, nanowires need to be integrated efficiently in different device architectures. Our approach to a durable catalyst suitable for device integration is based on parallel metal nanostructures. We synthesized closed platinum nanowire arrays (PtNWAs) by template electrodeposition using track-etched polycarbonate (PC) membranes [3]. One side of the irradiated membrane was coated with a conductive Au layer and then electrochemically reinforced by Cu. After etching in NaOH, the wires were grown in the nanopores. The concept of reverse-pulsed plating was adopted to compensate for the slow diffusion-driven transport in high-aspect materials. The deposition was continued until the caps forming on the top of each nanowire coalesced. Finally, an additional metal layer was deposited on the caps to increase the mechanical stability. Afterwards, the polymer matrix was dissolved in dichloromethane.