ForSt C-TNT

Formation and stabilisation mechanisms of defects in carbon-doped and self-doped titanate nanotubes

In this project, funded by the German Research Foundation, details of the defect structure of titanate nanotubes are being investigated. Such nanotubes have potential applications in hydrogen technology. For example, the material could function as a catalyst carrier, i.e., as a substrate for the platinum particles in PEM fuel cells. To this end, it should have a highly specific surface area and be electronically conductive. Currently, carbon black is used as a catalyst carrier, which meets these requirements, but is not stable in the long-term under the electrochemical conditions in a fuel cell. The degradation of the catalyst carrier leads to agglomeration or even discharge of platinum particles, which leads to a loss of active surface in the cell. Using a material that has an adequately high specific surface area, is electronically conductive, and is also stable against oxidation processes could be a solution to this problem. At the end of the 1990s, a Japanese research group showed that a tubular nanomaterials, titanate nanotubes, can be produced from titanium dioxide using a relatively simple process. As this material is already in oxidised form, it is expected to have better stability compared to carbon black in fuel cells. Without further modification, however, titanate nanotubes are not sufficiently conductive. Therefore, a process has been developed at the Ohm to introduce carbon into the structure without losing the high specific surface area. Electrical characterisations show that the nanotubes display a significantly improved conductivity, which is within the magnitude-range required for fuel cells.

However, it has not yet been researched in detail, to what this conductivity can be attributed. One conjecture is that during the production process Ti⁴⁺ is reduced to Ti³⁺, which is stabilised by carbon. The project aims to investigate whether such defect states exist and whether they cause electrical conductivity by specifically modifying the material and by comparing carbon-containing and pure, undoped titanate nanotubes. X-ray diffraction, scanning electron microscopy, thermal analysis methods, and spectroscopic procedures are used as methods for investigation. The project will run over three years (2021-2024). Doctoral candidates will carry the research out. The research associates will be supported by student assistants, who will benefit from the opportunity to gain insight into research and development early in their academic careers.

Project leader: Prof. Uta Helbig

Researchers: Dominik Eitel, M.Sc.

Funded by the German Research Foundation

Funding period: March 2021 - March 2024