Preparation of CeO2/UiO-66-NH2 Heterojunction and Study on a Photocatalytic Degradation Mechanism

CeO₂/UiO-66-NH₂ (marked as Ce/UN) composites were in-situ synthesized by a hydrothermal method. The properties, photocatalytic aspects, and degradation mechanism of Ce/UN were studied carefully. SEM results show that Ce/UN have a 3D flower-like structure, where octahedral UiO-66-NH₂ nanoparticles are embedded in the two-dimensional sheet of CeO₂. TEM results demonstrate that CeO₂ and UiO-66-NH₂ are bonded interfacially to constitute a hetero-junction construction. Data obtained by electrochemical impedance spectroscopy and fluorescence spectroscopy established that Ce/UN has less charge shift resistance and luminescence intensity than these of two pure substances. When the ratio of Ce/UN is 1:1, and the calcination temperature 400 °C is used, the degradation efficiency of RhB in photocatalysis by obtained Ce/UN is about 96%, which is much higher than in the case of CeO₂ (4.5%) and UiO-66-NH₂ (54%). The improved photocatalytic properties of Ce/UN may be due to the formation of hetero-junction, which is conducive for most photo-carriers and thus the interfacial charge shift efficiency is enhanced. By the free radical capture test, it can be inferred that the major active substances involved in the degradation related to photocatalysis is H⁺ and · O2−.