Pramote Puengjinda

High-performance electrodes for reversible solid oxide fuel cell/solid oxide electrolysis cell: Ni–Co dispersed ceria hydrogen electrodes

Within the framework of developing reversible solid oxide fuel cells/solid oxide electrolysis cells (SOFCs/SOECs), we have engaged in the design of high-performance electrodes. Facile production of hollow spherical particles of samaria-doped ceria (SDC) decorated with Ni–Co alloy catalysts (Ni100−XCoX/SDC, X = 0–50 atom%), nanometers in size, was adopted. A distinctive microstructure was observed in the hydrogen electrode fabricated with this composite powder. The cobalt addition played a significant role in evolution of the microstructure and effectively enlarged the electrochemical reaction zone. Under SOFC/SOEC reversible operation, the optimal performance characterized by a comparatively low ohmic resistance and high electrocatalytic activity was achieved with the Ni80Co20/SDC composition. At 900 °C and an overpotential of 0.1 V, the current density reached remarkably high values of 0.18 and 0.37 A cm−2 in SOFC and SOEC operation, respectively.

Influence of Preparation Methods on the Carbon Deposition and Reduction Behavior of Ni–ScSZ Cermet

Nickel oxide and scandia-stabilized zirconia (NiO-ScSZ) composite powders were prepared through two different processes: mechanical powder mixing (PM) and coprecipitation (CP). The effect of calcination temperatures on the crystalline structure of as-prepared powders and the carbon deposition behavior over the cermets were investigated. Due to the finer precipitates obtained from the CP method, the solid-state reaction between NiO and ScSZ in the as-prepared powder was promoted even at low calcination temperatures, resulting in the stabilization of the cubic phase of ScSZ. The temperature-programmed reduction indicated the strong interaction between NiO and ScSZ in the composite subjected to high temperature treatment regardless of the preparation methods, CP and PM. Phase identification was also conducted for the composites after reduction treatment at high temperatures of 1000 and 1400°C. After reducing at 1400°C, a part of ScSZ in the composite from the CP method transformed from the cubic to the rhombohedral phase, whereas the cubic phase was stable for the composite from the PM method. In addition, the carbon deposition over the sample from the CP method was promoted due to the large surface area of Ni. However, the electrochemical performance of single cells was independent of the cermet anodes from different methods with a supply of both H 2 and CH 4 fuels.