Electroless Nanoplating of Iridium: Template‐Assisted Nanotube Deposition for the Continuous Flow Reduction of 4‐Nitrophenol

Electroless plating is a powerful tool in nanofabrication and is available for many of the noble transition metals. There is, however, a striking lack of electroless plating procedures for the rarer platinum‐group metals. In this work, two plating baths for nanoscale iridium coatings are developed and their conformality and nanofabrication potential are showcased by coating ion‐track‐etched polycarbonate membranes, creating Ir nanotubes in the process. Both plating solutions yield morphologically different deposits, indicating that the microstructure of the film can be tuned by adjusting the composition of the plating bath. The catalytic performance of the deposited materials is investigated by using membrane‐embedded nanotubes as catalysts for the reduction of 4‐nitrophenol and methyl orange by borohydride, showing remarkable activity and stability. Operation in flow‐through configuration, in which the metallized membrane is implemented as a microreactor greatly enhances the interaction with the catalyst surface, considerably increasing product yield. The results highlight the potential of Ir nanoplating for realizing sophisticated nanostructures and heterogeneous catalysts, but also illustrate the intricacies related to the complex chemistry of electroless Ir plating baths.