Titanium dioxide modified with 3 wt% La was prepared via a green freeze-casting method, and its photocatalytic activity was tested in terms of its ability to degrade 4-chlorophenol (4-CP) and remove total organic carbon (TOC).

In this study, we describe synthesis and characterization of a floating photocatalyst for water treatment consisting of a light substrate coated by SiO2/TiO2 composite. Three supports of natural origin were used: natural cork, expanded clay (Liapor), and volcanic porous glass (Sorbix). The photoactivity of the coated supports was tested in a laboratory photoreactor, with Liapor being the most photoactive support with good mechanical stability. The corresponding rate constant for the degradation of a model pollutant, 4-chlorophenol, was 7.8 × 10−5 s−1. Detail characterization of the coated Liapor was obtained by XRF, SEM/EDX, and UV-Vis diffuse reflectance spectroscopy, and surface area measurements. Outdoor experiments were carried out with calcined Liapor and oxalic acid or methylene blue under sunlight on pilot reactors in the Czech Republic and Vietnam. We demonstrated satisfactory photocatalytic activity, long-term stability, and reusability of the new floating photocatalyst. The photoefficiency to mineralize oxalic acid in water under sunlight was estimated as 6.7% under the applied conditions.

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Ag-decorated TiO2 nanostructured materials are promising photocatalysts. We used non-standard cryo-lyophilization and ArF laser ablation methods to produce TiO2 nanosheets and TiO2 nanostructured thin films decorated with Ag nanoparticles. Both methods have a common advantage in that they provide a single multiply twinned Ag(0) characterized by {111} twin boundaries. Advanced microscopy techniques and electron diffraction patterns revealed the formation of multiply twinned Ag(0) structures at elevated temperatures (500 °C and 800 °C). The photocatalytic activity was demonstrated by the efficient degradation of 4-chlorophenol and Total Organic Carbon removal using Ag-TiO2 nanosheets, because the multiply twinned Ag(0) served as an immobilized photocatalytically active center. Ag-TiO2 nanostructured thin films decorated with multiply twinned Ag(0) achieved improved photoelectrochemical water splitting due to the additional induction of a plasmonic effect. The photocatalytic properties of TiO2 nanosheets and TiO2 nanostructured thin films were correlated with the presence of defect-twinned structures formed from Ag(0) nanoparticles with a narrow size distribution, tuned to between 10 and 20 nm. This work opens up new possibilities for understanding the defects generated in Ag-TiO2 nanostructured materials and paves the way for connecting their morphology with their photocatalytic activity.