LiH/FePcG-Catalyzed Ammonia Synthesis via Interfacial Hydride-Mediated Dinitrogen Activation

Abstract Ammonia synthesis under mild conditions remains challenging because of the inertness of the N≡N bond and the limited ability of conventional catalysts to couple efficient dinitrogen activation with rapid hydrogenation. Here, we report a LiH/FePcG catalyst in which strong interfacial coupling between LiH and Fe–N–C sites enable efficient ammonia synthesis. Comprehensive characterization, including structural analysis, kinetic study, isotopic-labelling, gas-phase mass spectrometry, and in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) reveal that the catalytic activity originates from interfacial active sites. Under reaction conditions, structural nitrogen atoms within the Fe–Nx moieties undergo reversible consumption and reconstruction, demonstrating the dynamic participation of the Fe–N–C framework in ammonia synthesis. Concurrently, hydridic hydrogen supplied by LiH directly participates in the initial hydrogenation steps, while the LiH/Fe–N–C interface generates Fe-centered multicomponent hydride species essential for N2 binding and activation. An inverse H/D kinetic isotope effect, an H2-promoted 28N2/30N2 exchange rate, in situ spectroscopic evidence, and density functional theory (DFT) calculations collectively support a non-classical, hydrogen-assisted pathway for dinitrogen activation rather than the conventional direct N≡ bond cleavage. These findings establish interfacial hydride chemistry as a cooperative mechanism for efficient ammonia synthesis and provide a strategy for designing advanced catalysts under mild conditions.