Fabrication of a La-doped BiVO4@CN step-scheme heterojunction for effective tetracycline degradation with dual-enhanced molecular oxygen activation

Abstract

• Both La doping and La-BiVO 4 @CN heterojunction promoted electron-hole separation. • Dual methods for O 2 − formation have been achieved by heterojunction and La doping. • O 2 − and h + were determined to be dominant active species for TC degradation. • La-BiVO 4 @CN revealed boosted visible-light photocatalytic TC degradation rate. • A possible photocatalytic mechanism of the S-scheme La-BiVO 4 @CN was proposed. A self-assembly method has been used to construct g-C 3 N 4 -nanosheets (CNNS)-wrapped lanthanum-doped bismuth vanadate (La-BiVO 4 @CN) heterojunction. The interaction between La-BiVO 4 and CNNS could broaden the light absorption region and facilitate photogenerated carrier separation and interfacial charge transfer. Theoretical and experimental results proved that the enhancement of the photocatalytic activity was ascribed to the following two reasons: (i) La atoms could localize excess electrons and adsorb free O 2 to promote the formation rate of superoxide radical ( O 2 − ) in photocatalyst, (ii) La-BiVO 4 @CN, S-scheme heterojunction photocatalyst, could further overcome the photo-induced charge carriers of BiVO 4 with poor redox ability, activated the dissolved oxygen to create more reactive oxygen species (ROS) with high oxidation capacity, which was beneficial for photocatalytic activity. La-BiVO 4 @CN also exhibited better recyclability after five cycles. Meanwhile, this work clarified the charge carriers transport pathway and proposed the photocatalytic reaction mechanism, providing a feasible strategy to design oxidation catalysts by increasing reactive oxygen species generation.