Facile synthesis of ternary heterojunction Bi2O3/reduced graphene oxide/TiO2 composite with boosted visible-light photocatalytic activity

In this work, a novel ternary heterojunction composite with bismuth oxide (Bi2O3), titanium dioxide (TiO2) and reduced graphene oxide (rGO) was produced via a one-step hydrothermal process. The prepared Bi2O3/rGO/ TiO2 (BRGT) composite possessed a strong visible-light responsiveness and a high separation efficiency of photogenerated carriers, with a specific surface area of 133.1 m(2)/g. The optimal degradation performance towards tetracycline (94.3% removal) was obtained by BRGT-10 with Bi/Ti molar ratio of 10% and mass ratio of graphene oxide/Ti of 5% following conditions of 0.1 g/L BRGT-10 at pH of 6.7. The degradation rate of tetra-cycline by BRGT was 4.5, 3.8, 1.4, and 1.28 times that of TiO2, TiO2/rGO, Bi2O3/TiO2, and Bi2O3/TiO2@rGO, respectively. O-center dot(2)- radicals and holes play the dominant roles in the photodegradation of tetracycline. Based on density function theory calculation and liquid chromatography-mass spectrometry identification of intermediates, the degradation pathways of tetracycline were mostly attributed to the breakage of carbon-carbon double bonds, nitrogen-carbon bonds and rearrangement of hydroxyl groups, and the decreased toxicity of the formed intermediates was evaluated. The BRGT-10 composite owned optimal reusability and applicability. This study explores a facile synthesis process of ternary heterojunction composite and provides insights into photo-degradation mechanism of refractory organics from water under visible-light.