Rainer Ostermann

Controlled electrochemically-assisted deposition of sol-gel biocomposite on electrospun platinum nanofibers.

The modification of platinum nanofibers by silica using the electrochemically-assisted deposition is reported here. Pt nanofibers are obtained by electrospinning and deposited on a glass substrate. The electrochemically-assisted deposition of the sol-gel material then gives the unique possibility to finely tune the silica film thickness around these nanofibers. It also allows the successful encapsulation of a biomolecule (glucose oxidase was chosen here as a model) while retaining its biological activity, as pointed out via the electrochemical monitoring of H(2)O(2) produced upon addition of glucose in the medium. This silica-glucose oxidase composite offers the possibility of comparing systematically the influence of the deposition time on the bioelectrode response and to compare it with the particular features of the deposits. It was found that the film first grew uniformly around the nanofibers and then started to deposit between them, covering the whole sample (fibers and glass substrate), and tended to fully embed the nanofibers for prolonged deposition. The thickness of the silica film is critical for the electroactivity of the biocomposite, the best response being obtained for a silica layer thickness in the range of the fiber diameter (∼50 nm).

Electrospun Metal Oxide Nanofibres for the Assessment of Catalyst Morphological Stability under Harsh Reaction Conditions

Long‐term stability is a major issue in heterogeneous catalysis and is often related to structural instabilities, which are difficult to assess in the early stage of catalyst screening. However, studies of morphological transformations in catalytic systems can greatly benefit from a well‐defined starting morphology and microstructure of the catalyst to be analysed. The present study suggests the use of catalysts in the form of 1 D nanofibres (NFs) as a conceptual methodology to assess catalyst stability, which is exemplified for the HCl oxidation reaction. These nanostructured model catalysts are synthesised by electrospinning, a versatile method to produce metal oxide NFs. We have studied the stability of RuO2‐ and CeO2‐based materials in the harsh HCl oxidation reaction (Deacon process). At 573 K pure RuO2 NFs have shown to be morphologically unstable, whereas mixed RuO2‐TiO2 NFs are stable. The stability of CeO2‐based NFs in the HCl oxidation was studied at 703 K. Under HCl lean conditions CeO2 NFs are stable, whereas under HCl rich conditions pure CeO2 NFs disintegrate by recrystallisation, forming (hydrated) Ce‐chloride. If CeO2 is doped with 20 % of Zr, the resulting mixed oxide Zr0.20Ce0.80O2 NFs have shown to be stable even under HCl rich reaction conditions and are similarly active as pure CeO2. These are the first activity experiments of mixed oxide ZrxCe1−xO2 in the Deacon process. The versatility of electrospun NFs as model catalysts has been demonstrated for testing catalyst stability in terms of morphology changes, thus serving as a proof‐of‐principle study.