A Computational Study of the Heterogeneous Synthesis of Hydrazine on Co(3)Mo(3)N

ABSTRACT: Periodic and molecular density functional theory calculations have been applied to elucidate the associative mechanism for hydrazine and ammonia synthesis in the gas phase and hydrazine formation on Co(3)Mo(3)N. We find that there are two activation barriers for the associative gas phase mechanism with barriers of 730 and 658 kJ/mol, corresponding to a hydrogenation step from N(2) to NNH(2) and H(2)NNH(2) to H(3)NNH(3), respectively. The second step of the mechanism is barrierless and an important intermediate, NNH(2), can also readily form on Co(3)Mo(3)N surfaces via the Eley–Rideal chemisorption of H(2) on a pre-adsorbed N(2) at nitrogen vacancies. Based on this intermediate a new heterogeneous mechanism for hydrazine synthesis is studied. The highest relative barrier for this heterogeneous catalysed process is 213 kJ/mol for Co(3)Mo(3)N containing nitrogen vacancies, clearly pointing towards a low-energy process for the synthesis of hydrazine via a heterogeneous catalysis route. GRAPHICAL ABSTRACT: [Image: see text] ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1007/s10562-017-2080-y) contains supplementary material, which is available to authorized users.