Enhanced photocatalytic degradation of tetracycline hydrochloride by Ag/AgI/WO 3 ·H 2 O composites

Novel visible light response Z-scheme Ag/AgI/WO3·H2O composite photocatalysts were synthesized using a two-step hydrothermal method followed by a photoreduction process without adding any surfactant. The synthesized Ag/AgI/WO3·H2O composite (AAW-2) with the Ag/WO3·H2O molar ratio of 0.8/1 showed the highest photodegradation activity for tetracycline hydrochloride (TCH) solution under visible light, and its rate constant was 24.6 times higher than that of WO3·H2O. The enhanced photocatalytic activity of the Ag/AgI/WO3·H2O composite can be due to the efficient separation of the electron–hole pairs through the Z-scheme Ag/AgI/WO3·H2O structure. The AAW-2 composite exhibited excellent stability toward TCH degradation after four successive circulations. Finally, the photocatalytic mechanism of the Ag/AgI/WO3·H2O composite was proposed based on the radical-trapping experiments, where h+ and •O2− were the main active species during the photocatalytic reaction.