Eco-friendly nanostructured Zn-Al layered double hydroxide photocatalysts with enhanced photocatalytic activity

Zn-Al layered double hydroxides (Zn-Al LDHs) with various reaction times were synthesized by a hydrothermal method at constant pH, and they were tested for the removal of RhB with or without post-calcination treatment. The effect of reaction time and calcination treatment on the structures, morphologies, chemical compositions and photocatalytic properties of Zn-Al LDHs was analyzed by XRD, TG/DSC, SEM, XPS, FTIR, Raman, PL and UV-vis DRS in detail. The optimized Zn-Al LDHs with a book page morphology had good crystal quality and the sample morphology changed to irregular flakelets with increasing calcination temperature. The RhB photodegradation results showed that the photocatalytic activity of Zn-Al LDHs was enhanced with increasing reaction time due to the improved crystal quality and the better separation of photogenerated electron-hole pairs. It was found that the calcination temperature was also an important factor for the c-Zn-Al-LDH samples, and the c-Zn-Al-LDH-24-300 sample exhibited the best photocatalytic activity due to the highest efficiency of photogenerated electron-hole separation, especially the formation of a new phase. A pseudo first order rate and recycling experiments were also used to analyze the photocatalytic activity.