Highly photoactive anatase foams prepared from lyophilized aqueous colloids of peroxo-polytitanic acid

Ce ion surface-modified TiO2 aerogel powders: a comprehensive study of their excellent photocatalytic efficiency in organic pollutant removal

The surface modification of TiO₂ aerogel powders by cerium ions has led to enhanced photoinduced properties.

Influence of Inorganic Bases on the Structure of Titanium Dioxide-Based Microsheets

Laboratory synthesis of microsheets of titanium dioxide from titanyl sulfate involves the use of ammonia solution, whereas another inorganic base is most likely to be employed at the industrial level, as ammonia is a toxic agent and therefore should be avoided according to European Union (EU) regulations. Selected nontoxic bases such as sodium, potassium, and lithium hydroxides have been tested as an alternative to ammonia solution to obtain amorphous and crystalline TiO₂-based microsheets. The final products obtained at each step of the procedure (samples lyophilized and annealed at 230 and 800 °C) were analyzed with electron and atomic force microscopy, X-ray powder diffraction, thermal analysis, and Fourier transform infrared (FTIR) and Raman spectroscopies to determine their morphology and phase composition. The differences in the morphology of the obtained products were described in detail as well as phase and structural composition throughout the process. It was found that, in the last step of the synthesis, microsheets annealed at 800 °C were built of small rods and oval or platy crystalline particles depending on the base used. The temperature of formation of anatase, rutile, and alkali-metal titanates in correlation with the ionic radius of the alkali metal present in the sample was discussed.

Controlling the growth of nanosized titania via polymer gelation for photocatalytic applications

Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides).

The relationship between microstructure and photocatalytic behavior in lanthanum-modified 2D TiO2 nanosheets upon annealing of a freeze-cast precursor

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). Under annealing conditions, the freeze-cast precursor was transformed into an La-modified anatase with a well-defined 2D TiO₂ nanosheet morphology. Rietveld refinement of the X-ray diffraction patterns confirmed the substitutional nature of the La cation that induced local structural variations and involved subtle ion displacement in the TiO₂ lattice due to the ionic size effect. Despite nearly identical tetragonal structures, replacement of Ti with La alters the photocatalytic activity through a reduction in band gap energies and an increase in charge carrier mobility. Material annealed at 650 °C exhibited the highest photocatalytic performance and achieved efficient TOC removal. Upon annealing at 800 °C, nanoscale lanthanum-enriched regions were generated due to the diffusive migration of La cations and phase transition from anatase to rutile. The La³⁺ cation, acting as a structural promoter, supported 2D TiO₂ growth with well controlled crystallite size, surface area and porosity. La³⁺ could be regarded as a potential electronic promoter that can reduce the band gap of 2D TiO₂ nanosheets and can provide a signature of the electron transfer and carrier charge separation. Both methods, kinetics of degradation of 4-CP and TOC, provided similar results, revealing that the photocatalytic activity under UV light irradiation increased in the order 950C < 500 °C < 800 °C < 650 °C < TiO₂-P25.

Synergistic effect of nanocavities in anatase TiO2 nanobelts for photocatalytic degradation of methyl orange dye in aqueous solution

Nanocavities are empty voids exposed on the surface of one dimensional TiO2 nanostructured material. Often, they exhibited beneficial optical and electrical properties that leads to efficient photocatalytic reactions. This study reports formation of nanocavities on anatase TiO2 nanobelts (TNB) through dehydroxylation of surface hydroxyl groups during calcination process (350-600°C). The morphological and crystal structure analysis of TNB-500, -550 and -600 displayed the nanobelts shape with high density of nano-size cavities and increase in average diameter with calcination temperature. The SAED patterns confirm the anatase TiO2 phase. The enhanced light absorption properties of biphasic anatase/TiO2-B and anatase TiO2 than H2Ti3O7 are attributed to transformation of crystal structure upon calcination process. The catalytic activity was evaluated for degradation of methyl orange dye in aqueous solution under solar light irradiation. The reaction variables such as calcination temperature, amount of catalyst and pH of the methyl orange dye solution were studied and discussed in detail. Under optimal experimental conditions TNB-550 photocatalyst displayed highest degradation performance about 8 folds higher than H2Ti3O7. The high performance is explained as due to synergistic properties of one dimensional anatase TiO2 with high density of nanocavities leading to one dimensional transfer of electrons and high absorption co-efficient in UV-A spectrum are suitable for efficient red-ox reactions.