Photocatalytic and photo-fenton catalytic degradation activities of Z-scheme Ag 2 S/BiFeO 3 heterojunction composites under visible-light irradiation

Abstract

Z-scheme Ag 2 S/BiFeO 3 heterojunction composites were successfully prepared through a precipitation method. The morphology and microstructure characterization demonstrate that Ag 2 S nanoparticles (30–50 nm) are well-decorated on the surfaces of polyhedral BiFeO 3 particles (500–800 nm) to form Ag 2 S/BiFeO 3 heterojunctions. The photocatalytic and photo-Fenton catalytic activities of the as-derived Ag 2 S/BiFeO 3 heterojunction composites were evaluated by the degradation of methyl orange (MO) under visible-light irradiation. The photocatalytic result indicates that the Ag 2 S/BiFeO 3 composites exhibit much improved photocatalytic activities when compared with bare Ag 2 S and BiFeO 3 . The optimum composite sample was observed to be 15% Ag 2 S/BiFeO 3 with an Ag 2 S mass fraction of 15%. Furthermore, the addition of H 2 O 2 can further enhance the dye degradation efficiency, which is due to the synergistic effects of photo-and Fenton catalysis. The results of photoelectrochemical and photoluminescence measurements suggest a greater separation of the photoexcited electron/hole pairs in the Ag 2 S/BiFeO 3 composites. According to the active species trapping experiments, the photocatalytic and photo-Fenton catalytic mechanisms of the Ag 2 S/BiFeO 3 composites were proposed and discussed.