  Coordination engineering was employed to optimize the coordination
environment of the Zr atom anchored on the porphyrins (PP). Five promising
ZrPP-A candidates as electrocatalysts for nitrogen reduction reaction (NRR)
were identified through a four-step screening strategy. First-principles
calculations were utilized to evaluate the performance of the candidate
electrocatalysts for NRR. A comprehensive search for reaction pathways revealed
that NRR reactions with these selected catalysts tend to follow a hybrid
pathway. It is found that orbital hybridization and charge transfer between Zr
and its coordination atoms, as well as between ZrPP-A and the adsorbed N2
ensured the stability and high catalytic activity of these selected ZrPP-A. Zr
plays a crucial role in coordinating charge transfer during the NRR process.
Simultaneously, the coordinating atoms and the PP moiety jointly provide
additional charge transfers to or from the adsorbate. An asymmetric
coordination environment results in an asymmetric charge distribution of the
substrate, causing the adsorbed polarized N2 molecule oriented toward the
asymmetric charge aggregation region. Our work underscores the importance of
considering not only the single-atom catalyst itself but also its coordination
environment for the rational design of efficient catalysts.
