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In the present work, two H evolution photocatalysts were prepared by employing two different oxides, TiO and zirconium titanate (ZrTiO), as the support of various copper phases. For both the supports the same Cu loading (0.5% w/w) was adopted, but two different impregnation procedures have been followed, leading to different forms of Cu in the final composite material that are: (i) Cu(II) species dispersed on the oxide surface and (ii) CuO particles dispersed on the oxide surface. The present paper based on the parallel use of photocatalytic test and spectroscopic analysis performed in catalytic conditions illustrates the evolution of photocatalytic systems occurring during the H evolution reaction tests, pointing out that the as-prepared materials represent a pre-catalyst and they are modified during irradiation leading to the real working systems different from the starting ones. The herein presented spectroscopic analysis aims to contribute to the living debate on the oxidation state of copper in mixed Cu/oxide materials and on its role in hydrogen evolution under photocatalytic conditions.

We prepared via hydrothermal synthesis zinc oxide samples doped with cerium. The samples were characterized via powder X Ray Diffraction measurements, Diffuse Reflectance UV Vis spectroscopy, Scanning Electron Microscopy and Transmission Electron Microscopy with EDX (Energy Dispersive X‐Ray spectroscopy) analysis, and BET (Brunauer–Emmett–Teller) surface area analysis. XRD measurements reveal the formation of highly crystalline materials; wurtzite is the most important. All materials were tested using phenol as model molecule and their performances were compared with TiO2 P25. The material showing the best performance, namely Ce‐doped ZnO, was then used to abate some emerging pollutants. We chose three iodinated X‐ray contrast agent (ICM), iopromide, iopamidol and diatrizoate, known to be recalcitrant to traditional advanced oxidation processes. In the presence of TiO2 P25, all ICM exhibited a slow degradation, with t1/2 ranging from 30 min (iopamidol) to 120 min (diatrizoate) and several hours are required for their complete disappearance. The employment of Ce‐doped ZnO leads to a sharp increase in their disappearance, with t1/2 obtained within 15 min (iopamidol) or 25 min (diatrizoate) and the complete abatement is achieved within 2 h.

Polycrystalline zirconium titanate, ZrTiO4, has been prepared via sol–gel chemistry and its properties both as a semiconducting oxide and as a photoactive system have been investigated by experimental and computational techniques. The oxide exhibits a structure analogous to those of the main TiO2 polymorphs with a slightly higher band gap of 3.65 eV. Theoretical results explain this small difference in terms of composition of the lower part of the conduction band, which is based on Ti 3d orbitals. Interestingly zirconium titanate is much less reducible than TiO2 upon annealing under a vacuum in the range between room temperature and 673 K. Over this temperature the system releases O2, forming oxygen vacancies and trapping excess electrons on tetravalent Ti ions as firmly indicated by both electron paramagnetic resonance (EPR) and computational results. Irradiating the solid with UV photons a charge separation is observed by EPR and the photogenerated carriers easily reach the surface where they react with gas phase molecules. ZrTiO4 shows, therefore, a photochemical behavior very similar to that of TiO2. Its band potentials, however, slightly differ from those of titania (in particular, the conduction band potential is more negative of about 0.20 eV), making the solid of potential interest for further photocatalytic investigations.

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