Constructing a plasmonic p-n heterojunction photocatalyst of 3D Ag/Ag6Si2O7/Bi2MoO6 for efficiently removing broad-spectrum antibiotics

Abstract The extensive production and consumption of pharmaceutical antibiotics are bringing serious environmental issues. Photocatalytic reaction has been emerging as an environment-friendly and effectively means for treating virous pollutants. Herein, we developed an effective photocatalytic system involving a novel plasmonic p-n heterojunction catalyst of Ag/Ag6Si2O7/Bi2MoO6 to efficiently eliminate environmental pharmaceutical pollutants, where the catalyst was synthesized via the in-situ growth of Ag/p-Ag6Si2O7 nanoparticles on n-Bi2MoO6 microspheres during a controlled precipitation-photoreduction process. As we predicted, the optimized plasmonic p-n heterojunction of Ag/Ag6Si2O7/Bi2MoO6 (AASO/BMO-3) shows a remarkable improved photocatalytic performance in eliminating ciprofloxacin (CIP) and tetracycline hydrochloride (TC). The reasons behind this fact is (1) the formation of p-n heterojunction between Ag6Si2O7 and Bi2MoO6 and (2) the precipitation of Ag nanoparticles with a plasmonic effect on Ag6Si2O7/Bi2MoO6, which made Ag/Ag6Si2O7/Bi2MoO6 possess a better capacity to efficiently separate the photogenerated carriers and utilize the visible-light. Moreover, superoxide free radicals (•O2–) and photo-excited holes (h+) were determined to be the main active species in degrading antibiotics by the results of quenching and ESR tests. In addition, relevant experiment results indicated that the direct contact between AASO/BMO-3 and antibiotics also played an important role in the efficient elimination of antibiotics. This work gives a new plasmonic p-n heterojunction of Ag/Ag6Si2O7/Bi2MoO6 with an effective degradation and mineralization ability towards broad-spectrum antibiotics in aqueous solutions, further enriching the possibility of applying photocatalytic technology to treat wastewater containing pharmaceutical antibiotics.