Abstract:

Ag₃PO₄ polyhedrons were synthesized by a facile hydrothermal route using polyethylene glycol-6000 (PEG-6000). The effects of hydrothermal temperature, reaction time, and PEG-6000 dosage on the morphologies and structures of the products were systematically investigated. The photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet-visible diffuse reflectance spectra (UV-Vis DRS), and photoluminescence (PL) spectra. The hydrothermal temperature and the PEG dosage are key factors in the production of Ag₃PO₄ polyhedrons with oriented {110} facets. The Ag₃PO₄ polyhedrons evolve via Ostwald ripening, and exhibit superior visible-light photocatalytic degradation of Rhodamine B (RhB) relative to Ag₃PO₄ samples without oriented {110} facets and Ag₃PO₄ nanoparticles prepared by anion-exchange. The reaction rate constant of the Ag₃PO₄ polyhedrons was 8.3 times that of the Ag₃PO₄ nanoparticles. Total organic carbon (TOC) analysis and cycling experiments revealed that the polyhedrons have better mineralization efficiency and exhibit good circulation runs. Holes (h+) and hydroxyl radicals (·OH) are confirmed to be the dominant active species in the presence of radical scavengers and in N₂-saturated solution. Given the redox potential of the active species and the band structure of Ag₃PO₄ polyhedron, the separation and migration mechanism of photogenerated electron-hole (e^--h⁺) pairs at the photocatalytic interface was proposed.

Key words: Silver phosphate, PEG-6000, Hydrothermal route, Photocatalysis, Active species, Separation of photogenerated carriers