Highly improved photocatalytic degradation of rhodamine B over Bi 2 Ga 4- x Fe x O 9 solid solutions under visible light irradiation.

In this work, Bi 2 Ga 4- x Fe x O 9 (0 ≤ x ≤ 1.2) solid solutions were prepared via the traditional high-temperature solid-state reaction. The Le Bail fitting on the powder X-ray diffraction patterns shows that these solid solutions were successfully synthesized. Scanning electron microscopy showed that the Bi 2 Ga 3.2 Fe 0.8 O 9 sample was composed of sub-micron particle crystallites. Energy dispersive spectroscopy analysis and X-ray photoelectron spectroscopy were used to identify that the Fe element is trivalent when doping into the crystal structure. Ultraviolet-visible diffused reflectance spectra suggested that the bandgap of Bi 2 Ga 3.2 Fe 0.8 O 9 is narrower than that of the undoped Bi 2 Ga 4 O 9 sample. Three strategies, including Fe 3+ doping, addition of H 2 O 2 , and loading of the cocatalyst, were utilized to improve the photocatalytic degradation activity. The optimum photocatalytic performance was obtained over 2.5 wt% Cu/Bi 2 Ga 3.2 Fe 0.8 O 9 sample in 20 ppm RhB aqueous solution (containing 1.5 mL H 2 O 2 ) under visible light irradiation. Its photodegradation rate is 8.0 times that of Bi 2 Ga 4 O 9 containing 0.5 mL H 2 O 2 . The 2.5 wt% Cu/Bi 2 Ga 3.2 Fe 0.8 O 9 photocatalyst remained stable and active even after four cycles. Also, its photocatalytic conversion efficiency for RhB was nearly 100%, which was achieved in 3 hours. The photocatalytic mechanism indicated that ·OH and h + played an important role in the photocatalytic degradation reaction.