Photocatalytic activity and degradation mechanism of in-situ reduction Bi-doped self-assembled 3D flower-sphere UiO-66-NH2/BiOBr

Abstract

The 3D flower-sphere UiO-66-NH2/Bi/BiOBr with good photocatalytic performance was successfully prepared by in-situ reduction and self-assembly process. The formation of semi-metal Bi was identified by XRD, XPS, HR-TEM and other methods. Transient photocurrent response and EIS spectra proved that compared with BiOBr nanosheets, the 3D flower-sphere structure, the reduction of metal Bi and the construction of Z-scheme heterojunction significantly improved the separation efficiency of photogenerated carriers in composite materials. The degradation rates of 50% UiO-66-NH2/Bi/BiOBr on tetracycline (30 mg/L TC) and norfloxacin (10 mg/L NOR) reached about 80% and 100%, respectively. Cycling experiments and XRD and XPS characterization results before and after the photocatalytic reaction verified that the composite had excellent reusability and stability. The experiment of free radical trapping agent and EPR spectrum analysis showed that in the UiO-66-NH2/Bi/BiOBr system, superoxide radical (·O2-) was the major active substance in the photocatalytic reaction, and Z-scheme degradation mechanism using metal Bi as electron conduction bridge was surmised.