Synergetic tuning charge dynamics and potentials of Ag3PO4 photocatalysts with boosting activity and stability by facile in-situ fluorination

Abstract

Exploiting advanced silver phosphate (Ag3PO4) photocatalyst with excellent activity and durability is highly desirable for developing practical environmental photocatalytic techniques. In this study, fluorine (F)-doped Ag3PO4 photocatalysts with significantly improved activity and stability are successfully synthesized by a facile in-situ fluorine ion mediated co-precipitation route. The microstructures and physicochemical properties of as prepared samples are characterized by a series of advanced optical and electronic spectroscopy together with systematic photoelectrochemical measurements (including transient photocurrent responses, electrochemical impedance spectroscopy and Mott-Schottky plots). All the F-doped Ag3PO4 photocatalysts prepared with different initial F/Ag molar ratio (RF) exhibit higher efficiency than pure Ag3PO4 for degrading rhodamine B (RhB) as a typical organic pollutant. In particular, F-doped Ag3PO4 prepared with RF = 0.5 exhibits the best photocatalytic activity and stability. Most fluorine ions were doped into the lattice of Ag3PO4 by substituting O, as suggested by the XRD and XPS results. Significantly, the in-situ F-doping enhances the degree of crystallinity and conductivity, introduces more surface oxygen vacancies and elevates the conduction band levels, which together significantly increase the charge separation and transfer efficiency, as supported by systematic photoelectrochemical measurements. Scavenger studies suggest that photogenerated hole (h+) and H2O2 are the dominant reactive oxidation species (ROSs) responsible for the elimination of organic pollutants. After F-doping in Ag3PO4, the elevated conduction band position endows the photogenerated e− with stronger reduction ability, and the enriched surface oxygen vacancies favor for surface O2 capture, together facilitating two-electron mediated surface O2 activation to yield more H2O2. More photogenerated electrons playing a role in photocatalytic reactions in F-doped Ag3PO4 not only enhance the photocatalytic activity, but also promote photocatalytic durability by inhibiting electron-induced self-corrosion. This study demonstrates that F-doping is a facile and feasible method to enhance the photocatalytic activity and stability of Ag3PO4 by synergetic tuning the charge potentials and dynamics.