Influences of silver halides AgX (X = Cl, Br, and I) on magnesium bismuth oxide photocatalyst in methylene blue degradation under visible light irradiation

AgX/MgBi2O6 composites (X = Cl, Br, and I), prepared from the hydrothermal procedure combined with a co-precipitation method, display unique visible light responsive photocatalytic activity. The catalytic performance of the AgX/MgBi2O6 composites were evaluated through the photodegradation of methylene blue (MB, 15 ppm) under white-light light-emitting diode irradiation (2.5 W, power density: 0.38 Wcm(-2)). Among the AgX/MgBi2O6 composites, the AgI/MgBi2O6 composite, with molar ratio of AgI to MgBi2O6 as 3:1, exhibited the highest photocatalytic performance within 20 min (degradation efficiency: 99.5 %) while MgBi2O6, AgCl/MgBi2O6, and AgBr/MgBi2O6 composites achieved degradation efficiency of 14.9 %, 24.9 % and 56.1 % respectively. The main reason of superior photocatalytic activity in AgI/MgBi2O6 composite attributes to the pn junction between AgI nanoparticles and MgBi2O6 effectively enhancing the charge separation efficiency and reducing the recombination rate of electron-hole pairs. This study revealed that hydroxyl and oxygen radicals are the major species involved in the degradation of MB from the photoactivated AgI/MgBi2O6 composite. To develop a practical application of this new material, the samples of AgI/MgBi2O6 composite have demonstrated excellent photocatalytic performance in degradation of various dyestuffs (92.3 %-99.5 % degradation within 10 min) under visible light irradiation and 99.8 % MB degradation under sunlight irradiation within 6 min.