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 H2 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.