Enhanced photocatalytic performances of hierarchical ZnO/ZnAl2O4 microsphere derived from layered double hydroxide precursor spray-dried microsphere.

Layered double hydroxides (LDHs), also called hydrotalcites, have been widely investigated for degradation of dye molecules, in the forms of direct photocatalysts, supports or precursors to ZnO-containing photocatalysts. LDH precursor-derived ZnO/ZnAl2O4 photocatalytic nanostructures have hitherto been created, involving ZnO/ZnAl2O4 powder and templated hierarchical frameworks with laboratory-scale preparations. We herein report a scalable preparation of ZnO/ZnAl2O4 microsphere derived from ZnAl-LDH precursor spray-dried microsphere. Survey of textural properties shows that ZnO/ZnAl2O4 microspheres maintain the hierarchically spherical feature and the relatively large surface area. Photocatalytic evaluation under UV irradiation shows that the ZnO/ZnAl2O4 microspheres exhibit highly enhanced photodegradation performance to methylene blue (MB) in comparison with the commercial ZnO powder. A preferential photodegradation to methyl orange (MO) of the MO/MB mixture was also observed, which was illustrated experimentally in terms of the favorable interaction and distribution between basic MO molecules and the acidic-site ZnO/ZnAl2O4 photocatalyst. Our results may initiate large-scale production of microspheres with promising photocatalytic performances.