One pot direct hydrothermal growth of photoactive TiO2 films on glass

Photocatalytic Degradation of Quinoline Yellow over Ag3PO4

In this study, the ability of Ag3PO4 to achieve the photocatalytic degradation of quinoline yellow (QY) a hazardous and recalcitrant dye, under UVA and visible light was investigated. The photocatalyst Ag3PO4 was synthesized through a precipitation method, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), BET Brunauer–Emmett-Teller (BET) analysis, UV-Differential Reflectance Spectroscopy (DRS) and Fourier transform infrared spectroscopy (FTIR). Ag3PO4 could successfully induce the photocatalytic degradation of QY under UVA and visible light. Optimal parameters were 0.5 g·L−1 of the catalyst, 20 ppm of QY and pH~7. Ag3PO4 was 1.6-times more efficient than TiO2 Degussa P25 under UVA light in degrading QY. Total organic carbon (TOC) analyses confirmed the almost complete QY mineralization. At least eight intermediate degradation products were identified by liquid chromatography coupled to high resolution mass spectrometry. The stability of Ag3PO4 was satisfactory as less than 5% Ag metal appeared in XRD analyses after 3 reuse cycles. These results show that under optimized conditions Ag3PO4 can efficiently achieve quinolone yellow mineralization.

Catalytic oxidation of dibromomethane over Ti-modified Co3O4 catalysts: Structure, activity and mechanism

Ti-modified Co₃O₄ catalysts with various Co/Ti ratios were synthesized using the co-precipitation method and were used in catalytic oxidation of dibromomethane (CH₂Br₂), which was selected as the model molecule for brominated volatile organic compounds (BVOCs). Addition of Ti distorted the crystal structure and led to the formation of a Co-O-Ti solid solution. Co₄Ti₁ (Co/Ti molar ratio was 4) achieved higher catalytic activity with a T₉₀ (the temperature needed for 90% conversion) of approximately 245°C for CH₂Br₂ oxidation and higher selectivity to CO₂ at a low temperature than the other investigated catalysts. In addition, Co₄Ti₁ was stable for at least 30h at 500ppm CH₂Br₂, 0 or 2vol% H₂O, 0 or 500ppm p-xylene (PX), and 10% O₂ at a gas hourly space velocity of 60,000h^-1. The final products were CO_x, Br₂, and HBr, without the formation of other Br-containing organic byproducts. The high catalytic activity was attributed to the high Co³⁺/Co²⁺ ratio and high surface acidity. Additionally, the synergistic effect of Co and Ti made it superior for CH₂Br₂ oxidation. Furthermore, based on the analysis of products and in situ DRIFTs studies, a receivable reaction mechanism for CH₂Br₂ oxidation over Ti-modified Co₃O₄ catalysts was proposed.

Integrated Nano- and Macroscale Investigation of Photoinduced Hydrophilicity in TiO2 Thin Films

The hydrophilicity of titanium dioxide has been investigated for films, deposited on glass by e-beam evaporation, being exposed to UV radiation and subjected to thermal annealing. The wettability alteration has been showed to depend upon both treatments, and insights into how to introduce more stable hydrophilicity into these films have been presented for the sake of boosting their commercial value. Observations from multiple length scales to assess the wetting behavior of as-deposited and high-temperature annealed samples were assessed through macroscopic measurements, i.e., water contact angle measurements, showing that the annealed crystalline samples, treated at 500 °C, are much more hydrophilic (SCA ≈ 20°) than as-deposited TiO₂ films (SCA ≈ 90°), and the nanoscopic experiments performed by amplitude modulation (AM) atomic force microscopy (AFM) indicated that this increased hydrophilicity is related to an enhanced adhesion force and surface energy, resulting in the partial crystallization of TiO₂ and the consequent formation of crystals on its surface rather than being related to morphologic differences. XRD and Raman measurements have highlighted that the crystallinity of the TiO₂ film is crucial in determining its hydrophilicity, in good agreement with the AFM study. The results also indicated that, after irradiation, the samples treated at 500 °C preserve their hydrophilicity for a significant time compared to previous studies.