Natascha Weidler

Template-based synthesis of metallic Pd nanotubes by electroless deposition and their use as catalysts in the 4-nitrophenol model reaction

The method of electroless plating offers a facile synthesis route to high-aspect ratio metal nanotubes. Despite the simplicity of the method, the traditional approach involves hazardous and toxic chemicals; to change this Green Chemistry has come into play. Since both, nanotechnology and Green Chemistry, have become important research topics, the combination of these offers new opportunities. According to the concept of Green Chemistry, Pd nanotubes were produced by using nonhazardous chemicals. The challenge was to rebuild the sensitisation and activation process of electroless plating and to find green reaction parameters for controlling the auto-catalysed heterogeneous nucleation of Pd. The produced Pd nanotubes were characterised by SEM and EDX. Furthermore TEM characterisation was done for determining the structural properties of Pd NTs. The efficiency of the reaction was quantified by ICP-OES and XPS measurements. To illustrate that green synthesized nanomaterials can be compared with conventionally prepared catalysts, the Pd nanotubes were tested in a model reaction to determine their catalytic activity. For this purpose the reduction of 4-nitrophenol to 4-aminophenol with NaBH4 was chosen, which also finds application in the synthesis of acetaminophen.

Exploring Active Sites in Multi-Heteroatom-Doped Co-Based Catalysts for Hydrogen Evolution Reactions

Today, metal-N- as well as metal-S-doped carbon materials are known to catalyze the hydrogen evolution reaction (HER). However, especially N- and S-co-doped catalysts reach highest activity, but it remains unclear if the activity is related to MNx or MSy (M=metal) sites. In this work we apply a simple method for multi-heteroatom doping and investigate the effect of cobalt content on the HER in acidic medium. The CoNx and CoSy sites were evidenced on the basis of structural characterization by Raman, X-ray induced photoelectron spectroscopy, and TEM. The presence of sulfur enables the formation of a larger number of CoNx sites. Structure-performance relationship proves that the HER activity is dominated by CoNx rather than CoSy sites. The most active catalysts also exhibit an excellent stability under galvanostatic conditions making them of interest for electrolyser application.