A Z-scheme mechanism of the novel ZnO/CuO n-n heterojunction for photocatalytic degradation of Acid Orange 7

A series of novel ZnO/CuO n-n heterojunction photocatalysts were synthesized with a microwave assisted method. The structures, morphologies, optical properties, and chemical states of these prepared photocatalysts were systematically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-vis diffuse reflectance spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the crystalline structures and morphologies of ZnO and ZnO/CuO are both quasi-sphere shape wurtzite structures. The photocatalytic activities of ZnO/CuO heterojunction were evaluated by the degradation of Acid Orange 7 under simulated solar light irradiation. The results indicated that the ZnO/CuO n-n heterojunctions all have higher photocatalytic activities than the pure ZnO and the ZnO/CuO(2) sample with 2% of CuO exhibits the highest performance for degradation of Acid Orange 7. These could be due to the effective enhancement of electron-hole separation and weaken charge transfer resistance in ZnO/CuO n-n heterojunction, as indicated by their photoluminescences, the electrochemical impedance spectra, and photocurrent responses. Finally, Z-scheme electron transfer mechanism was proposed as the major photocatalytic mechanism of ZnO/CuO materials.