Developments in ammonia synthesis have also made it possible to take a more rational approach to research on ammonia decomposition. It has been found that the optimal catalyst for ammonia synthesis is never the optimal catalyst for ammonia decomposition, which is almost counter-intuitive in catalysis research. The approach taken for ammonia synthesis/decomposition could be useful for many other systems and lead to a more rational development of new and improved catalysts and catalytic processes. (c) 2004 Elsevier Inc. All rights reserved.