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

Abstract

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.

Kinetic and Isotherm Study of As(III) Removal from Aqueous Solution by PET Track-Etched Membranes Loaded with Copper Microtubes

“…Nowadays, TeMs are used as filtration membranes for water purification [ 20 , 21 ] or effective adsorbents and are commercially available. Combining the inherent advantages of TeMs and metal nanostructures provides composite membranes that are excellent candidates in a variety of promising material science applications, such as biotechnology [ 22 , 23 ], catalysis [ 24 , 25 , 26 , 27 , 28 ], medicine [ 29 , 30 ], sensors [ 21 , 31 ], and radiation resistive and magnetic materials [ 32 , 33 ]. In our previous study, we created Cu/CuO in the nanochannels and surface of poly(ethylene terephthalate) (PET) TeMs by electroless template-assisted deposition of copper and subsequent low-temperature annealing process.…”

Electroless Nano-Plating in Ion-track Etched Polymers: Iridium- and Bismuth-coated Membranes for Catalysis and Sensing Applications

“…[9], [10] Recently, we showed that nanoscale electroless Ir plating is possible as long as the choice of metal precursor, complexing agent and reducing agent is carefully considered. [7] In this case, either citrate or ethylene diamine (EDA) proved to be suitable stabilizers, when NaBH4 is used as reducer. Figure 1a shows SEM images of Ircoated ion-track etched polycarbonate membranes, prepared using a citrate stabilized plating bath.…”

“…XPS and XRD measurements on a similar deposit have confirmed that metallic Ir is deposited predominantly. [7] However, small amounts of surface oxides are to be expected, due to the comparatively high oxygen affinity of Ir. Interestingly, the presence of both Ir and IrOx has been linked to an increased catalytic activity of the material.…”

“…for various hydrogenation reactions such as the reduction of 4-NP or the degradation of organic dyes, such as methyl orange or rhodamine B. In our case, we assessed the activity of the deposit by utilizing it in the reduction of 4-NP [7] as well as the degradation of methyl orange (shown here). The coated membranes can be used in a flow-through configuration, in which the reaction solution is pumped through the membrane, as well as in a more conventional way, by simply submerging the catalyst in the solution under constant agitation.…”

“…Ir and Bi coated membranes are fabricated by procedures developed in our group [7], [8] by electroless plating on commercially available ion-track etched polycarbonate membranes (ipPORE™, it4ip, Belgium) with a nominal pore diameter and membrane thickness of 400 nm and 25 µm, respectively. In the case of Ir, the coated membranes are then used for catalyzing the degradation of methyl orange in the presence of NaBH4, while the Bi coated polymer is used as a proofof-concept device to detect Pb in water.…”