Defect Pyrochlore-Type Mott-Schottky Photocatalysts for Enhanced Ammonia Synthesis at Low Pressure

The ambient ammonia synthesis coupled with distributed green hydrogen production technology can provide promising solutions for low-carbon NH3 production and H-2 storage. Herein, we reported Ru-loaded defective pyrochlore K2Ta2O6-x with remarkable visible-light absorption and a very low work function, enabling effective visible-light-driven ammonia synthesis from N-2 and H-2 at low pressure down to 0.2 atm. The photocatalytic rate was 2.8 times higher than that of the best previously reported photocatalyst and the photo-thermal rate at 425 K was similar to that of Ru-loaded black TiO2 at 633 K. Compared to perovskite-type KTaO3-x with the same composition, the pyrochlore exhibited a 3.7-fold increase in intrinsic activity due to a higher photoexcited charge separation efficiency and a higher conduction band position. The interfacial Schottky barrier and spontaneous electron transfer between K2Ta2O6-x and Ru further improve photoexcited charge separation and accumulate energetic electrons to facilitate N-2 activation.