p-n BiOI/Bi3O4Cl hybrid junction with enhanced photocatalytic performance in removing methyl orange, bisphenol A, tetracycline and Escherichia coli

It is urgent to design highly efficient and broad-spectrum photocatalysts for wastewater treatment. In this work, a new p-n BiOI/Bi3O4Cl hybrid junction was prepared by a simple ultrasonication method. The optimal BiOI/ Bi3O4Cl 30% composite could degrade 85.5% methyl orange in 90 min, 92.8% bisphenol A in 120 min and 73.5% antibiotic tetracycline in 180 min and thoroughly disinfect E. coli within 40 min. The results of transmission electron microscopy, photocurrent and electrochemical impedance spectrum confirmed the hybrid structure between BiOI and Bi3O4Cl, which promoted the separation of photoexcited electrons and holes in the semiconductor. Trapping experiments showed that holes (h+), superoxide anion radicals (center dot O-2(-)) and hydroxyl radicals (center dot OH) were active species for photocatalytic reaction, and h(+) played a more important role compared with center dot O-2(-) and center dot OH. The mechanism revealed that the Fermi level reached new equilibrium between p-type BiOI and n-Bi3O4Cl, which is favorable for the charge separation and enhancement of photoactivity. The enlarged surface area of BiOI/Bi3O4Cl composite and efficient charge separation contributed to the enhanced photo catalytic performance.