Ammonia from Photothermal N-2 Hydrogenation over Ni/TiO2 Catalysts under Mild Conditions

Industrial ammonia production requires harsh conditions of high temperatures and high pressures. Exploring catalysts and approaches for ammonia synthesis under mild conditions is of great interest to reduce thermal energy input and to ensure apparatus safety. Herein, we report a new photothermal method for ammonia production over multifunctional Ni/TiO2 catalysts at low temperatures and ambient pressure. The oxygen vacancies on TiO2 adsorbed/activated N-2 molecules and trapped photoelectrons, while the Ni atoms dissociated H-2 molecules and hosted the holes. The synergy of photocatalysis and thermocatalysis of the Ni/TiO2 catalysts triggered photothermal N-2 hydrogenation to ammonia under mild conditions. The physicochemical and optical properties of the Ni/TiO2 catalysts were comprehensively studied and were applied to tentatively explain the photothermal performance of the N-2 hydrogenation reaction. The photothermal approach shows great potential for alternative ammonia synthesis and may be applied to other gas-solid reactions when using photocatalysts.