Deciphering the Nitrogen Activation Mechanisms on\nGroup VIII Single Atoms at MoS<sub>2</sub>

The\nactivation of nitrogen (N<sub>2</sub>) is vital for sustainable\nammonia production and nitrogen fixation technologies. This study\nemploys density functional theory (DFT) to investigate the nitrogen\nactivation and reduction capabilities of Group VIII single-atom catalysts\nanchored on MoS<sub>2</sub>. Among these, osmium anchored on MoS<sub>2</sub> (Os@MoS<sub>2</sub>) emerged as the most promising catalyst,\nexhibiting the highest N<sub>2</sub> activation and the lowest nitrogen\nreduction reaction (NRR) overpotential (0.624 V). A pronounced “electron\ndrift” effect was observed for Os@MoS<sub>2</sub>, leading\nto significant charge redistribution that weakens the N ≡ N\ntriple bond, facilitating its activation. The N–N dissociation\nenergy barrier at the *N–NH<sub>2</sub> intermediate was calculated\nto be only 0.82 eV, confirming Os@MoS<sub>2</sub>’s superior\ncatalytic efficiency. Detailed analyses, including electrostatic potential\nmaps, electron localization functions, spin density, and charge transfer,\nrevealed the pivotal role of orbital interactions in driving N<sub>2</sub> activation. Interestingly, the trends in adsorbed N<sub>2</sub> bond energies and NRR overpotentials showed a consistent diagonal\npattern across the Group VIII catalysts, emphasizing the importance\nof electronic and geometric factors. This work offers valuable insights\ninto nitrogen activation mechanisms and provides a framework for designing\nefficient catalysts, highlighting Os@MoS<sub>2</sub>’s potential\nin sustainable ammonia synthesis.