Jurzinsky, T.T.JurzinskyGomez Villa, Eduardo DanielEduardo DanielGomez VillaKübler, M.M.KüblerBruns, M.M.BrunsElsässer, P.P.ElsässerMelke, J.J.MelkeScheiba, F.F.ScheibaCremers, CarstenCarstenCremers2022-03-052022-03-052019https://publica.fraunhofer.de/handle/publica/25812610.1016/j.electacta.2018.12.1382-s2.0-85060886922In 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.en660541journal article