The reduction of N2 to ammonia in industry requires extreme conditions to break the strong N≡N triple bond. In past few decades, much effort has been made to develop new catalysts and to explore efficient processes for N_2 activation. Ruthenium-based catalysts have been found to have fairly high activity after osmium and iron. Steps on the ruthenium surface are generally shown more active than terraces, where an ensemble of five Ru atoms on stepped surface, i.e. so-called B_5-type sites, are responsible for the high activity. In the present work, we carried out DFT investigations on N_2 dissociation over the B_5-type sites of Ru, Os, and Fe cluster models. Possible electronic aspects of such high activity of the step as well as the activity tendency of the B_5-type sites for different metals are discussed.
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