Photocatalytic Degradation of Tetracycline Activated by Visible Light Using the In ₂ O ₃ /g-C ₃ N ₄ Composite Photocatalyst with the S-scheme Heterojunction

Tetracycline (TC) is difficult to degrade and is widely used, seriously threatening the environment and human health. This paper employed the two-step hydrothermal synthesis process to combine the different loading of urchin-like In 2 O 3 with laminar g-C 3 N 4 . After a series of experiments, it was proved that the 10.0 wt.% In 2 O 3 /g-C 3 N 4 is the optimal ratio. Its decompose efficiency of TC could reach 86.1%, and the apparent rate constant of degradation was 0.01655 min −1 simultaneously. This result is attributed to the S-scheme heterojunction structure within the In 2 O 3 /g-C 3 N 4 composite material. Through this mechanism, useless electrons and holes were eliminated via recombination, while the highly reactive photogenerated electrons in the g-C 3 N 4 ’s CB and the holes in the In 2 O 3 ’s VB were reserved for photocatalytic reactions and generated a substantial quantity of reactive species (RSs) that effectively degraded TC. This work provides several useful insights for removing TC or other organic pollutants from the water environment.