Hydrogen attracts more and more interest, since it is considered as one of the most promising future energy carriers owing to the possibility of its sustainable production as well as its application as fuel for low-emission power generation. Solid oxide fuel and electrolyser cells (SOFC and SOEC) are highly efficient technologies for the conversion and generation of hydrogen, respectively. However, the high operating temperatures of 600-850 °C cause significant degradation effects of the materials used, resulting in a continuous deterioration of cell performance during long-term operation. The aim of this work is the installation and optimisation of a test stand for the investigation of SOFC and SOEC button cells. With this setup, valuable information about the suitability of novel compounds as electrode materials may be obtained and long-term studies can be performed, without requiring elaborately produced cells with industry-relevant dimensions. After the successful implementation of the experimental setup, extensive tests and parameter studies were performed, focusing on the gas tightness and temperature distribution at the cell. Further, nine button cells were characterized by means of electrochemical impedance spectroscopy and current-voltage curves, with focus on the influence of different water contents in the fuel feed. Moreover, post-test analyses using scanning electron microscopy and energy-dispersive X-ray spectroscopy give information about the microstructure and chemical composition of the different cell layers, which is used as feedback for optimisation of the test setup and materials development. The results show that for all investigated cells, the polarisation resistance decreases with increasing temperature and increasing water content in the fuel feed. Cells with air electrodes fabricated from the mixed ionic-electronic conductor La1-xSrxCoO3-δ exhibit the best performance due to small area-specific resistances and low degradation. Cells with the novel air electrode material La0.8Ca0.2FeO3-δ do currently not achieve the high cell performance observed with standard materials (La1-xSrxMnO3±δ, La1-xSrxCoO3-δ). Based on the results of post-test analyses, operation with high water contents in the fuel feed during an extended period of time, is identified as an especially critical factor, which may lead to delamination and thus to failure of the cells.