Tackling the Scaling Relations in Ammonia Synthesis through Light-Driven Catalysis over LiH-Mediated Ru/TiN

Photothermal catalysis offers a promising pathway for sustainable ammonia synthesis under mild conditions. However, its performance is constrained by intrinsic scaling relations between dinitrogen activation and subsequent hydrogenation steps. To overcome this long-standing bottleneck, we design a Ru-LiH/TiN catalyst that enables a light-driven reaction cascade, wherein lithium hydride (LiH) serves as a dynamic “nitrogen mediator”. Under ambient pressure and illumination at 3.3 W·cm –2 , the catalyst achieves an unprecedented NH 3 production rate of 5574.3 μmol·g –1 ·h –1 (equivalent to 428.8 mmol·g Ru –1 ·h –1 ), representing a 31-fold improvement over its thermal-catalytic counterpart and a 52-fold enhancement relative to Ru/TiN. Notably, the Ru-LiH/TiN exhibits robust catalytic stability over 50 h, in stark contrast to the rapid deactivation (<1 h) commonly observed in thermal catalysis due to NH x ( x = 1–3) accumulation-induced adsorbate poisoning. Mechanistic studies reveal a relayed photothermal catalysis mechanism: photogenerated hot electrons facilitate N 2 activation on Ru sites, followed by nitrogen transfer to the LiH-TiN interface to form destabilized [Li–Ti–N-H] intermediates; subsequently, photoexcited LiH liberates reactive hydrogen species that participate in nitrogen hydrogenation. This work presents a new strategy that simultaneously weakens the strong adsorption of NH x on the catalyst and enables efficient NH 3 production under mild conditions.