Coordination Engineering in Zirconium–Nitrogen-Functionalized Materials for N2 Reduction: A First-Principles Simulation

Coordination engineering was employed to optimize the coordination environment of the zirconium (Zr) atom anchored on the porphyrins (PP), serving as single-atom catalysts (SACs). Five promising ZrPP-A (A = C3O, N4, N2C2-o, C2O2-o, and C2O2-n) candidates as electrocatalysts for nitrogen reduction reaction (NRR) were identified through a "four-step" screening strategy, from a pool of 15 designed models. Performance evaluation of these candidates for NRR was conducted using first-principles calculations. A comprehensive examination of reaction pathways unveiled a predilection for a hybrid pathway when employing the selected catalysts for the NRR. The stability and notable catalytic activity of ZrPP-A stemmed from orbital hybridization and charge transfer mechanisms, occurring both between Zr and its coordinated atoms, as well as between ZrPP-A and the adsorbed N2 molecule. Zr played a pivotal role in orchestrating charge transfer during the NRR process. Simultaneously, coordinating atoms and the PP moiety collectively facilitated supplementary charge transfers to or from the adsorbate. Because of the robust coupling between O and its neighboring carbon atoms, no significant bonds were detected between the central Zr and the coordinating O atoms. An asymmetric coordination environment results in an uneven charge distribution within the substrate, inducing polarization of N2 molecules and their migration toward regions of asymmetric charge aggregation. This study underscores the significance of not only focusing on the single-atom catalyst itself but also its coordination environment when designing catalysts for enhanced efficiency.