Photoinduced Ammonia Synthesis over Lanthanum Oxyhydride-Supported Metal Nanoparticle Catalysts

High Resolution Image Download MS PowerPoint Slide Hydride materials have a significant ability to promote ammonia synthesis over supported transition metal (TM) nanoparticles due to the unique properties of lattice H – ions. Here, we report that lanthanum oxyhydride (LaH 3–2 x O x ) facilitates ammonia synthesis on the supported TM catalyst under visible light irradiation. Ru-loaded LaH 3–2 x O x exhibited an order of magnitude higher ammonia synthesis rate at 180 °C with an ∼18 kJ mol –1 lower activation energy under visible light irradiation (λ = 405 nm, 1.04 W cm –2 ) than that under dark conditions. The enhanced catalytic performance can be explained by photoionization of H – (H – → H 0 + e – ) constituting the valence band maximum (VBM) of LaH 3–2 x O x, in which photogenerated electrons are transferred to supported Ru, and neutral hydrogen (H 0 ) facilitates the hydrogenation of nitrogen species. Moreover, the photoexcitation of LaH 3–2 x O x enables shifting of the optimum TM catalyst from Ru to Ni in the volcano-shaped relationship between ammonia synthesis activity and metal–nitrogen binding energy.