Ternary Layered Double Hydroxides (LDHs) Based on Co-, Cu-Substituted ZnAl for the Design of Efficient Photocatalysts

Co-, Cu-substituted ZnAl ternary layered double hydroxides (LDHs) were synthesized and explored as efficient photocatalysts for dye degradation. LDH materials were fully characterized with various methods including elemental analysis, X-ray diffraction, infrared spectroscopy, Raman spectroscopy, and transmission electron microscopy, which revealed that LDH materials were well crystallized without any amorphous phase as impurity. In addition, the plates of LDH were well dispersed, one plate being easily distinguished from another plate, and their size could also be controlled by varying the Co, Cu substitution ratio. As an application, the adsorption characteristics and photocatalytic degradation of orange II, a model pollutant, were investigated. In particular, Co-substituted LDHs exhibit an excellent photocatalytic activity with the optimal Co/Zn substitution ratio of 1:3. Interestingly, LDH materials having a higher ratio didn't show any improvement of the photocatalytic activity, suggesting that the amount of Zn is the crucial factor. Furthermore, the photocatalytic performance of Zn1.5Co0.5Al1 (Co/Zn = 1:3) was compared with other materials such as metal oxides prepared by heat or microwave treatment, and the result could prove the efficiency of LDH materials of this work. Therefore, Co, Cu substitution in ZnAl ternary LDHs could be a straightforward approach for designing efficient photocatalysts with various potential applications such as the remediation of wastewater.