Photodegradation of phenol using reconstructed Ce doped Zn/Al layered double hydroxides as photocatalysts

ZnAlCe layered double hydroxides (LDH) with different content of Ce (3.5, 5.0 and 10.0% mol) were successfully synthesized in one step by the co-precipitation technique. The partial incorporation of cerium into the layers of the material can be appreciated in the XRD diffraction patterns, showing some deformation in the crystallographic direction (1 1 0) of the ZnAlCe LDHs. In the samples calcined at 400 °C, the UV-vis-DRS study showed a shift of the absorption edge toward the blue region of the spectra as a result of the cerium incorporation to the ZnAl LDH; the analysis of XPS confirms the co-existence of Ce⁴⁺ and Ce³⁺ in the ZnAlCe LDHs. The photodegradation and mineralization of phenol under UV irradiation was remarkably improved in the sample containing 5% mol of Ce. A mechanism where cerium in the layered material promotes the separation of the photogenerated electron-hole pairs is proposed. In this mechanism, Ce⁴⁺ acts as electron scavenger, facilitating the electron transfer toward adsorbed O₂ and an accumulation of holes, increasing the generation of radicals OH.