Research activities in the field of renewable energies are increasingly focusing on the use of hydrogen as the energy source of the future. There are various approaches to harnessing the chemical energy bound in hydrogen. One promising technology is the solid oxide cell, which can be operated both as a fuel cell and as an electrolysis cell, depending on the direction of the current. In this master's thesis, solid oxide cells with ceramic composites as an active layer in air electrodes were investigated. For this purpose, both symmetrical cells and anode-supported full cells were prepared and tested at 800°C. Electrode performance was characterized by means of electrochemical impedance spectroscopy and current-voltage analyses. To characterize the electrode microstructure and the quality of the electrode-electrolyte interface, cross-sections were made of all tested cells and then examined under a scanning electron microscope. The results clearly show that air electrodes with a current collector layer perform significantly better than those without. It was also tested whether different procedures for applying and sintering the layers have an influence on the electrode performance. It was found that co-sintering of the active layer and the current collector layer yields the best results. The findings from tests on symmetrical cells were transferred to anode-supported full cells and the objective of a current density of at least 1 A/cm² at 800°C in electrolysis mode was achieved. In future activities, current collectors with a more porous microstructure are to be produced and tested, e.g. by using coarser powder or pore-forming agents.