Unraveling the Photocatalytic Mechanism of N Fixation on Single Ruthenium Sites.

Photocatalytic N fixation offers promise for ammonia synthesis, yet traditional photocatalysts encounter challenges such as low efficiency and short carrier lifetimes. Atomically precise ligand-metal nanoclusters emerge as a solution to address these issues, but the photophysical mechanism remains elusive. Inspired by the synthesis of AuRu NCs, we investigate the mechanism behind N activation on AuRu, focusing on photoactivity and carrier dynamics. Our results reveal that vibration of the Ru-N bond in the low-frequency domain suppresses the deactivation process leading to a long lifetime of the excited N. By the strategy of isoelectronic substitution, we identify the single Ru sites as the active sites for N activation. Furthermore, these ligand-protected MRu (M = Au, Ag, Cu) NCs show robust thermal stability in explicit solvation and decent photochemical activity for N activation and NH production. These findings have significant implications for the optimization of catalysts for sustainable ammonia synthesis.