Production of H₂ by electrochemical conversion of H₂O, through electrolysis can be achieved without expensive catalysts using Solid Oxide Electrolysis cells (SOECs). SOEC shows great dynamics to become commercially competitive against other electrolysis technologies (AEL, PEMEL), which are better established but more expensive and less efficient. On the other hand, SOECs are less mature and have issues regarding performance and durability that are currently important issues that need to be addressed. Indicatively, the latest State-of-the-Art (SoA) cells with NiO/YSZ and LSM as cathode and anode electrodes, respectively, show that the performance decreases for the H₂O electrolysis reaction, whereas for the H₂O/ CO₂ co-electrolysis process, the situation is even worse and the technology level is much behind than the commercialization thresholds. In this respect, SElySOs project focuses on understanding the degradation and lifetime fundamentals on both SOFC electrodes. New electrode materials are developed, and the degradation mechanisms are investigated during the project. Overall, the target is to improve the stability, minimize the degradation and achieve better performance during H₂O electrolysis and CO₂ electrolysis. This paper presents short-term stability testing of large ESCs comprising Au-Mo-modified NiO/GDC compared with unmodified Ni-GDC as fuel electrode and LSCF as air electrode, under steam electrolysis operating conditions. The cells are tested in short stack configuration with metallic interconnects and sealing. The two stacks are operated with 0.5 A/ cm2 at 835oC. The results show a positive effect of the Au-Mo modified cell stack on the degradation rates during the stability tests. The observed degradation rate for the 3Au-3Mo-modified fuel electrode stack was 300 mV/kh as compared to 700 mV/kh with the non-modified Ni/GDC stack.