High Activity Ti3+-Modified Brookite TiO2/Graphene Nanocomposites with Specific Facets Exposed for Water Splitting

Effect of Process Parameters on the Microstructure and Performance of TiO2-Loaded Activated Carbon

In this study, the visible-light-driven photocatalytic regeneration performance of TiO2-loaded activated carbon (TiO2/AC) was effectively improved. By carefully controlling the activation condition at 700 °C for 2 h with a 60% H3PO4 concentration and 3:1 TBT (tetrabutyl titanate) impregnation ratio, 90.5% of methylene blue (50 mg/L) was removed within 2 h by a low-dose TiO2/AC (0.5 g/L), which was much higher than those obtained in previous studies on TiO2/AC. Moreover, the effects of process variables on the microstructure and performance of TiO2/AC were systematically investigated. The results showed that (1) the long period of activation time effectively inhibited the photogenerated charge carrier recombination and enhanced the regeneration performance of samples; (2) the photogenerated charge carrier recombination rate was lowered initially and then increased as the temperature ascended, whereas the pore volume showed an opposite variation tendency, and thus the adsorption and regeneration performances of samples were improved at 500-700 °C and then weakened at 800 °C; (3) the increase of H3PO4 concentration effectively inhibited the charge carrier recombination and had an improvement in the adsorption and regeneration performances of samples; and (4) the photogenerated charge carrier recombination rate and bandgap value of samples decreased initially and then increased with increasing TBT mass ratio, so the regeneration performances of samples were improved initially and then lowered.

Synthesis and Photocatalytic Activity of TiO2/CdS Nanocomposites with Co-Exposed Anatase Highly Reactive Facets

In this work, TiO2/CdS nanocomposites with co-exposed {101}/[111]-facets (NH4F-TiO2/CdS), {101}/{010} facets (FMA-TiO2/CdS), and {101}/{010}/[111]-facets (HF-TiO2/CdS and Urea-TiO2/CdS) were successfully synthesized through a one-pot solvothermal method by using [Ti4O9]2- colloidal solution containing CdS crystals as the precursor. The crystal structure, morphology, specific surface area, pore size distribution, separation, and recombination of photogenerated electrons/holes of the TiO2/CdS nanocomposites were characterized. The photocatalytic activity and cycling performance of the TiO2/CdS nanocomposites were also investigated. The results showed that as-prepared FMA-TiO2/CdS with co-exposed {101}/{010} facets exhibited the highest photocatalytic activity in the process of photocatalytic degradation of methyl orange (MO), and its degradation efficiency was 88.4%. The rate constants of FMA-TiO2/CdS was 0.0167 min-1, which was 55.7, 4.0, 3.7, 3.5, 3.3, and 1.9 times of No catalyst, CdS, HF-TiO2/CdS, NH4F-TiO2/CdS, CM-TiO2, Urea-TiO2/CdS, respectively. The highest photocatalytic activity of FMA-TiO2/CdS could be attributed to the synergistic effects of the largest surface energy, co-exposed {101}/{010} facets, the lowest photoluminescence intensity, lower charge-transfer resistance, and a higher charge-transfer efficiency.

rGO Functionalized ZnO–TiO2 Core-Shell Flower-Like Architectures for Visible Light Photocatalysis

Core-shell heterostructures with a complex, flower-like morphology, comprising a ZnO core and a TiO2 shell decorated with reduced graphene oxide (rGO) sheets by hydrothermal wrapping, are reported to extend the absorption properties of the semiconductors toward the visible light range. The ternary photocatalysts were characterized by X-ray diffraction, field emission scanning electron microscopy, Raman spectroscopy, diffuse reflectance UV–Vis, and attenuated total reflectance-Fourier transform infrared spectroscopy. Its photocatalytic performance was evaluated under visible light irradiation using methylene blue dye as a model pollutant. The rGO-modified ZnO–TiO2 photocatalyst exhibited superior photoactivity compared to that of the parent ZnO–TiO2 core-shell structures, which was dependent on its graphene content. The enhanced photocatalytic response was attributed to the higher absorption in the visible light range, as well as the pronounced electron and hole separation in the ternary system.

Araneose Ti3+ self-doping TiO2/SiO2 nanowires membrane for removal of aqueous MB under visible light irradiation

Araneose Ti³⁺ self-doped TiO₂/SiO₂ nanowires (RTiO₂/SiO₂) were prepared and anchored onto a polyethersulfone (PES) membrane. Careful characterizations and measurements indicated a covalent grafting of SiO₂ onto reduced TiO₂ (RTiO₂) through Ti-O-Si linkages, acquiring uniformed RTiO₂/SiO₂ nanowires of almost complete anatase and benign hydrophilicity. The RTiO₂/SiO₂-based PES membrane showed a significantly enhanced visible light-driven degradation rate of methylene blue (MB) (90.7%), compared with that on bare PES (11.1%) and PES-RTiO₂ (59.6%) membranes. The residual MB in filtered water was less than 5% after reusing three times. The normalized permeate flux of the modified membrane was 0.83, and the transmembrane pressure only increased by 0.4 MPa under irradiation of visible light. The improved performance of the PES-RTiO₂/SiO₂ was attributed to efficient intercept of MB molecular, light harvesting of visible light, and separation of charge carriers on araneose RTiO₂/SiO₂ nanowires.