Direct utilization of ammonia in intermediate-temperature solid oxide fuel cells

Ammonia is considered to be one of the most promising candidates as the fuel for solid oxide fuel cells (SOFCs). In this work, nitrogen oxide formation was thermodynamically determined as a function of ammonia conversion rate and temperature. The result showed that more NO was formed at higher temperature. Therefore, ammonia was experimentally investigated as the fuel for an intermediate-temperature SOFC (IT-SOFC) consisted of a Ni-Ce0.8Sm0.2O1.9 (SDC) anode, an SDC (50 mu m) electrolyte, and an Sm0.5Sr0.5CoO3-delta (SSC)-SDC cathode. The components of anode off-gas were analyzed both theoretically and experimentally, especially for the possibility of nitrogen oxide formation. Performances of the cells fueled with ammonia and hydrogen were quite similar at the same temperatures. Maximum power densities were 168.1 and 191.8 mW cm(-2) at 600 degrees C with ammonia and hydrogen as the fuels, respectively. The electrode polarization resistances and electrolyte resistances of cells fueled by ammonia and hydrogen were characterized by AC impedance spectroscopy. The long-term endurance of cells in ammonia was also tested. (c) 2006 Elsevier B.V. All rights reserved.