New Application and Excellent Performance of Ag/KNbO3 Nanocomposite in Photocatalytic NH3 Synthesis

The present work was designed to synthesize Ag/KNbO3 nanocomposite for efficient photocatalytic conversion of N-2 to NH3. KNbO3 was prepared in a low KOH concentration solution at 260 degrees C, while Ag nanoparticles (NPs) were loaded on KNbO3 by a photodeposition procedure. The as-synthesized nanocomposite presented excellent performance in photocatalytic N-2 fixation. Under simulated sunlight, the NH3 generation rate reaches 385.0 mu mol.L(-1)g(-1)-h(-1), which is 4 times higher than that of pure KNbO3. Additionally, the Ag/KNbO3 composite also showed good photoactivity under visible light. Multiple techniques, including XRD, Raman, XPS, SEM, TEM, DRS, PL, EIS, PC, and LSV, were performed to reveal the origin of the high performance. The results indicated that a low KOH concentration is beneficial to formation of nanosize KNbO3, while a high hydrothermal temperature endowed KNbO3 high crystallinity which boosted the bulk charge separation. The Ag NPs' decoration further increased the surface separation of charge carriers via trapping the electrons from KNbO3. The significantly elevated efficiency in charge separation is believed to be the origin of the high performance of the Ag/KNbO3 composite. Additionally, the surface plasmon resonance effect of Ag NPs also awarded the composite the capability in absorbing visible light, which resulted in its visible-light-driven photocatalytic activity. Interestingly, under simulated sunlight, a competition between the photosensitization mechanism and the electron-trapping mechanism existed, and the latter dominated the photocatalytic process on Ag/KNbO3. Besides the photocatalytic N-2 fixation, the Ag/KNbO3 composite also performed well in photocatalytic H-2 evolution and RhB degradation, indicating its great potential in practical photocatalytic application.