High-temperature electrolysis using Solid Oxide Cells (SOC) is a promising approach for renewable energy storage. A special feature that distinguishes SOCs from other types of electrolysis cells is that via electrochemical splitting of CO₂ and H₂O in SOCs, the production of carbon neutral fuels is possible. Composite materials like Gd doped Ceria (GDC) combined with metallic Ni show great potential as fuel electrode materials in SOCs, since they offer high catalytic activity, and stability against redox cycling. Key degradation issues of Ni/GDC electrodes include morphological changes of the porous structure like the dewetting of Ni after many hours of operation, which impairs electrolysis performance and therefore hinders the commercialisation of this technology. To better understand this dewetting phenomenon, we monitor the morphological changes of thin film based Ni-GDC model electrodes via in-situ surface sensitive techniques like electrochemical oxygen activity control Auger electron microscopy (EXACT-AEM) and x-ray photoelectron spectroscopy (EXACT-XPS). The distinctive advantage of the so-called EXACT technique is that it allows in-situ characterization of a model-SOC working electrode, without the presence of an atmosphere. This becomes possible, as the oxygen activity of the studied electrode (Ni/GDC thin film in the present case) can be tuned using electrochemical biasing versus an oxygen buffering counter electrode. Therefore, in-situ measurements using analysis techniques, which depend on (ultra-) high vacuum (like AEM), become possible. This way, the oxygen activity dependence of both, the morphology changes as well as the surface composition distribution of the Ni-GDC composite, can be analysed at high temperatures while preventing the influence of a gas phase. Utilizing this approach, we can isolate effects coming from metal/oxide interface. Simultaneously, electrochemical impedance spectroscopy (EIS) measurements are carried out revealing insights into the point defect chemistry of the material. The obtained results show that upon a sequence of oxidation and reduction (redox-cycling), the Ni layer undergoes redox transitions at the Ni/GDC interface, whereby the Ni surface appears to remain unaffected. Furthermore, Ni-dewetting is dramatically enhanced after redox-cycling. This phenomenon can also be reproduced in porous symmetrical Ni-GDC cells during steam electrolysis, demonstrating that findings from model cells can also be transferred to more realistic electrolysis cells, underscoring the broader relevance and applicability of our model-based approach.