Photocatalytic degradation of methylene blue with a nanocomposite system: synthesis, photocatalysis and degradation pathways

Three different composites, including a calcined FeOOH supported ZnAl layered double hydroxide (FeOOH-LDO), a calcined ZnAl layered double hydroxide (ZnAl-LDO) and a calcined ZnFeAl layered double hydroxide (ZnFeAl-LDO), were synthesized via a sol-gel method, and their activity for the visible light photocatalytic degradation of methylene blue (MB) was studied. The composites were characterized by PXRD, SEM, and BET techniques, confirming the formation of highly crystalline structures. The activity performance of MB degradation was in the following order: FeOOH-LDO (similar to 95%) > ZnFeAl-LDO (similar to 60%) > ZnAl-LDO (similar to 23%). In addition, a possible photocatalytic degradation reaction mechanism for MB was also proposed. Moreover, the frontier electron densities on the atoms of MB were calculated, which were in satisfactory agreement with the postulated mechanism.