In-situ TEM reduction of a solid oxide cell with NiO/YSZ and NiO/BZCY materials for fuel electrode

Increasing the durability of solid oxide cells is one of the main goals for achievingwider industrial application. The quality of the electrode plays a major role in theperformance and durability of a fuel and electrolysis cells. Ni/YSZ or Ni/BZCY (BZCY staysfor the state-of-the-art proton conducting ceramic material BaZr1-x(Ce,Y)xO3-d) electrodes ofsolid oxide cells are commonly reduced from NiO/YSZ or NiO/BZCY under hydrogenatmosphere at high temperatures, prior to operation. It is known from commissioning thate.g. reduction temperature and H2 pressure influence the initial performance of the fuelelectrode by governing Ni particle size and shape.With in-situ TEM we are able to observe the reduction of NiO in real time whileexposing the sample to hydrogen gas and heat [28]. We studied the electrode reduction atthe H2 pressures up to 1 atmosphere and temperatures 200-850 °C. Grain boundaries andtriple junctions between NiO and YSZ or BZCY are determined as the starting points of thereduction process at lower temperatures. We also showed that the initial temperature ofthe reduction is crucial to achieve a high number of electrochemically active triple phaseboundaries between e.g. ... mehrNi/YSZ and gas. In-situ results go in good agreement with ex-situresults obtained from a bulk cell reduced in a test bench.