Concerning “An Opinion on the Heterogeneous Photoreduction of N 2 with H 2 O”: Second Letter

The synthesis of ammonia from nitrogen and water by irradiation in the presence of certain metal oxide powders as catalysts has been published a number of times since 1977 but was called into question last year by Edwards et al. ( Angew. Chem. Int. Ed. Engl. 1992 , 31, 480). Criticism of those arguments and the authors' reply should allow our readers to draw their own conclusions. This discussion is welcome in view of the importance of the reaction, whose apparently simple stoichiometry is even open to debate.