posted on 2020-06-01, 17:36authored byKe Ye, Min Hu, Qin-Kun Li, Yulan Han, Yi Luo, Jun Jiang, Guozhen Zhang
The
production of ammonia from nitrogen reduction reaction (NRR)
under mild conditions is one of the most challenging issues in modern
chemistry. The linear scaling relationship between the adsorption
energies of −N2H and −NH2 on a
single active site is a well-established bottleneck. By investigating
a series of densely monodispersed Mo–N–C sites embedded
in graphene using first-principles calculations, we found that previously
underappreciated neighboring effects between adjacent active sites
may help break the limit: they not only improve the energetics of
potential determining steps of NRR but also promote an alternative
associative mechanism based on a cooperative bridge-on adsorption
of N2 by two Mo–N–C sites of ∼6 Å
apart. Further, a barrier of 0.71 eV for N–N bond dissociation
is achieved by proper ratio of coordinated C/N atoms of Mo. Our work
suggests the cooperation of two adjacent active sites may offer an
alternative strategy of nitrogen fixation.