Visible-Light Photocatalytic Activity and Deactivation Mechanism of Ag3PO4 Spherical Particles

Ag3PO4 spherical particles were synthesized by a facile precipitation method using silver nitrate and Na2HPO4 as precursors. The as-prepared samples had a high photocatalytic activity toward Rhodamine B (RhB) degradation under visible-light illumination. With increasing recycling times the photocatalytic activity first increased and then decreased. Based on systematic characterization of particles by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV/Vis absorption spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM), a possible mechanism responsible for the improvement and subsequent decline of the photocatalytic performance of Ag3PO4 is proposed. Ag3PO4 spherical particles recycled for four times showed the highest photocatalytic activity because, according to our mechanism, Ag nanoparticles deposited on Ag3PO4 acted as electron trapping centers to prevent photogenerated electron-hole pairs from recombination. A further increase in the recycle times decreases the photocatalytic activity owing to the shielding effect by Ag layers on the surface of Ag3PO4. The results presented herein shed new light on the photostability of Ag3PO4 spherical particles and are potentially applicable to other photocatalytically active composites.