Deciphering the Nitrogen Activation Mechanisms on Group VIII Single Atoms at MoS.

The activation of nitrogen (N) is vital for sustainable ammonia production and nitrogen fixation technologies. This study employs density functional theory (DFT) to investigate the nitrogen activation and reduction capabilities of Group VIII single-atom catalysts anchored on MoS. Among these, osmium anchored on MoS (Os@MoS) emerged as the most promising catalyst, exhibiting the highest N activation and the lowest nitrogen reduction reaction (NRR) overpotential (0.624 V). A pronounced "electron drift" effect was observed for Os@MoS, leading to significant charge redistribution that weakens the N ≡ N triple bond, facilitating its activation. The N-N dissociation energy barrier at the *N-NH intermediate was calculated to be only 0.82 eV, confirming Os@MoS's superior catalytic efficiency. Detailed analyses, including electrostatic potential maps, electron localization functions, spin density, and charge transfer, revealed the pivotal role of orbital interactions in driving N activation. Interestingly, the trends in adsorbed N bond energies and NRR overpotentials showed a consistent diagonal pattern across the Group VIII catalysts, emphasizing the importance of electronic and geometric factors. This work offers valuable insights into nitrogen activation mechanisms and provides a framework for designing efficient catalysts, highlighting Os@MoS's potential in sustainable ammonia synthesis.