Construction of Ag SPR-Promoted S-Scheme SnNb₂O₆/Ag₃PO₄ Heterostructure for Enhanced Visible-Light-Driven Photocatalytic Activity

Ag surface plasmon resonance promoted step-scheme (S-scheme) SnNb₂O₆/Ag₃PO₄ heterojunctions were constructed via simple chemical deposition and precipitation. The samples were characterized by X-ray diffractometer, field-emission scanning electron microscope, high resolution transmission electron microscope, X-ray photoelectron spectrometer, UV-Vis diffuse reflectance spectrometer and photoluminescence spectrometer. The photocatalytic activities of SnNb₂O₆, Ag₃PO₄ and SnNb₂O₆/Ag₃PO₄ composites can be determined via degradation experiments. The results show that the SnNb₂O₆/Ag₃PO₄ composite possesses an optimum degradation performance in the photocatalytic degradation of methylene blue. Besides, the pseudo–first–order rate constant (K_app) of SnNb₂O₆/Ag₃PO₄ is 0.313 min^–1, which is 13.1 times and 4.8 times greater than that of SnNb₂O₆ and Ag₃PO₄, respectively. Also, Ag surface plasmon resonance–promoted SnNb₂O₆/Ag₃PO₄ S-scheme heterojunction can accelerate the separation of electron-hole pairs, thereby enhancing the redox reaction capability of the whole system.