Efficient removal of ammonia with a novel graphene-supported BiFeO3 as a reusable photocatalyst under visible light

Graphene-supported BiFeO 3 (rG-BiFeO 3 ) was synthesized by the hydrothermal method and used for the efficient removal of ammonia under visible light. X-ray diffraction, transmission electron mi-croscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, and ultraviolet-visible diffuse reflectance spectroscopy were conducted to characterize the rG-BiFeO 3 . The specific surface area of the rG-BiFeO 3 catalyst was 48.6 m 2 /g, larger than that of BiFeO 3 (21.0 m 2 /g). When used as a heterogeneous photocatalyst, rG-BiFeO 3 achieved 91.20% degradation of a NH 3 -N solution (50 mg/L) at pH=11 under visible-light irradiation in the absence of hydrogen peroxide. The degrada-tion of ammonia followed pseudo-first-order kinetics, and the catalyst retained high photocatalytic activity after seven reaction cycles. Study of the mechanism showed that the holes, superoxide ani-on radicals, and hydroxyl radicals, arising from the synergy between graphene and BiFeO 3 , oxidized NH 3 directly to N 2 .