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Functionalization of multi-walled carbon nanotubes with indazole

: Jurzinsky, T.; Gomez-Villa, E.D.; Kübler, M.; Bruns, M.; Elsässer, P.; Melke, J.; Scheiba, F.; Cremers, C.


Electrochimica Acta 298 (2019), S.884-892
ISSN: 0013-4686
Bundesministerium für Bildung und Forschung BMBF (Deutschland)
Fraunhofer ICT ()

In this work, the functionalization of carbon nanotubes (CNTs) with indazole groups covalently bound to the CNTs’ surface is reported. The novel material was structurally characterized via near edge X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray photoelectron spectroscopy (XPS) and successful functionalization was proven. As the novel material is a potential candidate for catalyst support application in high-temperature proton-exchange membrane fuel cells (HT-PEMFCs), thermal and electrochemical stability of the novel material was investigated. Measurements via thermogravimetric analysis coupled to a mass spectrometer (TGA-MS) showed that the indazole-functionalized CNTs are thermally stable until a temperature of approx. 300 °C is reached. The thermal degradation of the functional group was tracked by monitoring the evolution of NOX gases. Furthermore, electrochemical stability of the novel material was evaluated using high-temperature differential electrochemical mass spectrometry (HT-DEMS) under gas-phase conditions. Compared to unmodified CNTs, it was shown that the functionalization leads to a slightly increased electrochemical carbon corrosion. However, the indazole-functionalized CNTs show a higher electrochemical stability than carbon black (Vulcan XC72R) typically used as catalyst support in HT-PEMFCs. In comparison to unmodified CNTs, functionality tests of the indazole-functionalized CNTs showed a better dispersibility in water and a lower contact angle with concentrated H3PO4, which is the electrolyte in HT-PEMFCs. Ultimately, ion exchange capacity measurements showed that the indazole-functionalized CNTs are able to bind protons in the catalyst layer and, therefore, potentially improve the catalyst-electrolyte interface as well as the proton conductivity in the catalyst layer.