Photocatalytic reductive and oxidative ability study of pristine ZnO and CeO2-ZnO heterojunction impregnated with Cu2O

In the present work the Cu2O-ZnO heterosystem and the novel Cu2O-CeO2-ZnO triphasic heterojunction were synthesized impregnating the ZnO and the CeO2-ZnO system surfaces with 0.5% in weight of Cu2O, respectively. While X-ray powder diffraction (XRPD) evidenced any alteration in the matrix phases, the UV-vis and electron paramagnetic resonance (EPR) spectroscopy highlighted a drastic change in the optical and electronic behaviour respect to the non-impregnated samples. Deeply investigations allowed us identifying the photo-stability of the surface decorative Cu2O phase and the presence of additional copper species, namely Cu2+ and Cu(0), coming as "waste " from the employed impregnation route. The presented outcomes brought us to suggest a beneficial impact of these species promoting the overall photocatalytic process. Finally, both the oxidative and reductive photocatalytic activity of the produced materials has been evaluated by means the H-2 generation from the water photosplitting process and through the photodegradation of the tolytriazol molecule, respectively, where the novel Cu2O-CeO2-ZnO heterojunction exhibited the best performance upon UV-vis and purely visible irradiation.