A nearly complete decomposition of MO, TC and OFX over a direct Z-scheme p-n heterojunction g-C3N4/La-Bi2O3 composite

To find a photocatalyst for photodegrading different pollutants, a direct Z-scheme p-n heterojunction g-C3N4/La-Bi2O3 (LBOCN) composite was prepared in this study. The composite was characterized by XRD, SEM, HRTEM, UV-vis DRS, M-S, XPS, EIS and PL. The photocatalytic activity of LBOCN was evaluated by photodegrading methyl orange (MO), ofloxacin (OFX) and tetracycline (TC). Many nanodots in the as-prepared LBOCN were clearly observed in the HRTEM images, which could drastically accelerate the transfer of photogenerated charges since their size is 4-5 nm, shortening the transfer route of photogenerated carriers from the inner part to the outside. The p-n junction strengthened the Z-scheme to separate the photogenerated electrons and holes, therefore improving the photocatalytic property of LBOCN. In the photodegradation of MO, the photoreaction rate of LBOCN is approximately 13 times that of Bi2O3 (BO), 12 times that of g-C3N4 (CN), 3 times that of La-Bi2O3 (LBO) and 2 times that of g-C3N4/Bi2O3 (BOCN). Moreover, LBOCN can also completely photodegrade OFX within 60 min. Finally, this work demonstrates if a p-n-type Z-scheme heterojunction structured composite can generate superoxide radicals or hydroxyl radicals under light irradiation, the refractory antibiotics, such as ofloxacin, can be completely decomposed into small molecules under the synergistic effects of effective separation of photogenerated electron-hole pairs driven by the p-n junction and strong redox ability of the photogenerated carriers. (C) 2022 Elsevier B.V. All rights reserved.