Reduction of dinitrogen to ammonia on doped three-atom clusters Nb₂M (M = Sc to Cu & Y to Ag)

Catalytic reduction of dinitrogen to ammonia under mild conditions remains an attractive topic for the purpose of lowering energy consumption. Three-atom metal clusters have been proved an ideal model to explore highly efficient catalysts taking advantage of unique geometric/electronic structures and cooperative active sites. Here a study of N₂ activation and reduction on seventeen bimetallic Nb₂M (M = Sc to Cu, and Y to Ag) clusters was reported. Three key processes for ammonia fixation (namely nitrogen activation, hydrogenation, and ammonia desorption) are fully studied, and three preferred systems (Nb₂Ni, Nb₂Rh and Nb₂Pd) are highlighted with outstanding catalytic performance. The d-σ and d-π* orbital hybridizations between these metal clusters and N₂ were demonstrated and the internal association with the N≡N bond activation was unveiled. By examining the ammonia synthesis on four chosen Nb₂M clusters (M = Fe, Ni, Rh and Pd), it can be elucidated that the distal pathway is more favorable than the alternative pathway in these systems. This work not only clarifies the N₂ reduction on the bimetallic Nb₂M clusters, but also guides efficient bimetallic catalyst design.