Preparation and photo-electrochemical characterization of KAlPO4F: application to photodegradation of methyl violet under sunlight

The oxyfluorophosphate KAlPO4F compound was synthesized by hydrothermal route at 453 K and the physical and photo-electrochemical properties were reported for the first time. The as- prepared compound crystallizes in an orthorhombic system (Space Group: Pnna) with the refined lattice constants: a = 12.612(5) angstrom, b = 10.172(3) angstrom, c = 6.205(0) angstrom. The direct optical transition of 4.93 eV, determined from the diffuse reflectance, is assigned to the charge transfer F-: 2p -> K+: 4 s. The electrochemical measurement in Na2SO4 electrolyte gives a flat band potential (E-fb) of + 0.28 V-SCE. The single crystal exhibits an intrinsic behavior with a donor density of 10(15) cm(-3) and a valence band deriving mostly from F-: 2p orbital. The electrochemical impedance spectroscopy shows a semicircle attributed to the bulk property, an intrinsic comportment. The photocatalytic performance was successfully tested through the degradation under solar light of methyl violet (MV), a hazardous and persistent dye. A total discoloration was obtained after 5 h illumination and a reaction mechanism is proposed.

Automated summary

The oxyfluorophosphate KAlPO4F compound was synthesized and its physical and photo-electrochemical properties were reported for the first time, including crystal structure, optical transition, and electrochemical performance. Additionally, the photocatalytic performance for methyl violet degradation under solar light was successfully tested, achieving complete discoloration after 5 hours of illumination.