Refining active sites and hydrogen spillover for boosting visible-light-driven ammonia synthesis at room temperature

Abstract

It is highly desirable to develop a low-pressure, low-temperature ammonia synthesis process. Although this process is, in principle, thermodynamically feasible under ambient conditions, it remains a big challenge to find ideal catalysts with favorable kinetic pathways. Here, we demonstrate that efficient ammonia synthesis (>3700 μg h⁻¹ g_cat.⁻¹) from N₂ and H₂ gases can proceed at room temperature using Mo, Pt modified TiO_2−x under visible light irradiation up to 800 nm. The doped Mo(V) species nearby surface oxygen vacancies (V_O) offer coordinatively unsaturated sites for N₂ activation with strong adsorption energy and excellent electron back-donation ability. Distinctively, a small amount of surface-loaded Pt nanoparticles trigger hydrogen spillover from Pt to V_O, enabling facile NH₃ assembly and desorption, as well as increasing free Mo(V) active sites. The incorporation of Mo and Pt also synergistically optimizes the light-harvesting ability and the band structure of TiO₂, greatly facilitating the photoexcited N₂ reduction and H₂ oxidation.