A brief study on the boosted photocatalytic activity of AgI/WO3/ZnO in the degradation of Methylene Blue under visible light irradiation

A novel visible-light-driven AgI/WO 3 /ZnO nanocomposite was synthesized for the photodegradation of methylene blue (MB).The composite was characterized by XRD, UV-Vis DRS, SEM, BET, electrochemical impedance spectroscopy (EIS) and photoluminescence (PL) techniques.PL results confirmed lower PL intensity for the composite confirming a lower e -/h + recombination for it.Both PL intensity and photodegradation activity of the resulted composites depended on the mole ratio of AgI, WO 3 and ZnO in the composite.The composite with a mole ratio of 2:1:1 (AgI:WO 3 :ZnO) showed a broad PL peak at 698 nm which is 11.3 times weaker than that of WO 3 and ZnO and 3 times weaker than that of AgI alone.Among the composites with different mole ratios, this composite had also the lowest PL intensity.Initial photodegradation experiments showed that about 21%, 36%, 56% and 69% of MB molecules can remove by single ZnO, WO 3 , AgINps and the composite (with a mole ratio of 1:1:1), respectively.The composite with a mole ratio of 2:1:1 showed also the best photodegradation efficiency and it removed about 79% of MB molecules during 40 min photodegradation process.MB solutions before and after photodegradation process were subjected to FTIR analysis and the results showed appearance of new peaks at 3452 and 1655 cm -1 , confirming degradation of MB molecules into the smaller fragments.The pseudo-first order reaction rate constants of 0.055 and 0.025 min -1 were estimated based on COD and UV-Vis results based on the Hinshelwood model.The catalyst showed good reusing applicability after 4 successive runs.