Electrochemical and Catalytic Behaviors of Ni–YSZ Anode for the Direct Utilization of Ammonia Fuel in Solid Oxide Fuel Cells

In this study the electrochemical performances of Ni–YSZ anode in humidified H 2 , NH 3 and CH 4 fuels were compared under almost the same partial pressure of oxygen at 500–800°C. The cell performance was significantly affected by fuel species and operating temperature. The single cell exhibited higher performance in wet NH 3 as compared with that in CH 4 , which was caused by the difference in the catalytic activity of anode for the hydrogen production in wet NH 3 and CH 4 . Thus, it was clarified that NH 3 is a preferable fuel rather than CH 4 for the direct use in SOFCs. Furthermore, the kinetics study on ammonia decomposition over Ni–YSZ anode was conducted at 600°C. Although the ammonia decomposition increased with increasing ammonia concentration, the decomposition reduced in the presence of hydrogen in the reactant gas. Such a behavior was not confirmed at 850°C. These results indicated the inhibition effect of hydrogen for ammonia decomposition, which will be the key factor for the design of anode and the operating condition setting.