Srinivasan Anandan

Highly Active Rare-Earth-Metal La-Doped Photocatalysts: Fabrication, Characterization, and Their Photocatalytic Activity

Efficient La-doped TiO2 photocatalysts were prepared by sol-gel method and extensively characterized by various sophisticated techniques. The photocatalytic activity of La-doped TiO2 was evaluated for the degradation of monocrotophos (MCPs) in aqueous solution. It showed higher rate of degradation than pure TiO2 for the light of wavelength of 254 nm and 365 nm. The rate constant of TiO2 increases with increasing La loading and exhibits maximum rate for 1% La loading. The photocatalytic activities of La-doped TiO2 are compared with La-doped ZnO; the reaction rate of the former is ~1.8 and 1.1 orders higher than the latter for the lights of wavelength 254 nm and 365 nm, respectively. The relative photonic efficiency of La-doped TiO2 is relatively higher than La-doped ZnO and commercial photocatalysts. Overall, La-doped TiO2 is the most active photocatalyst and shows high relative photonic efficiencies and high photocatalytic activity for the degradation of MCP. The enhanced photocatalytic activity of La-doped TiO2 is mainly due to the electron trapping by lanthanum metal ions, small particle size, large surface area, and high surface roughness of the photocatalysts.

SYNTHESIS AND CHARACTERIZATION OF A HIGHLY CRYSTALLINE NOVEL MESOPOROUS C- AND N-CODOPED TiO2 NANOPHOTOCATALYST

Here we report, for the first time, the synthesis of highly crystalline novel mesoporous carbon/nitrogen (C/N)-codoped TiO2 (MCNT) using ethylene diamine and carbon tetrachloride as the source for nitrogen and carbon, KIT-6 as the template, and titanium tetraisopropoxide as the TiO2 source. The obtained material has been unambiguously characterized by various sophisticated techniques. XRD and TEM analysis revealed that the MCNT material possesses highly crystalline 3D structure with a continuous network of mesoporous channels as well as structure corresponding to TiO2. UV-DRS analysis indicated that light absorption shifted to lower energy and stronger absorption in the visible light region. XPS revealed that C and N were doped effectively and C or N dopants might be present in the chemical environment of Ti–O–N or Ti–O–C. It has been found that the material is highly crystalline and possesses high surface area, pore volume and uniform pore size distribution. Owing to its textural characteristics, it could be useful for various applications, such as photocatalysis, fuel cells, bulky biomolecule adsorption and nanotechnology.

Surface X-ray diffraction study and photocatalytic activity of HF-treated single crystal rutile TiO2(001) surface

The photocatalytic activity of a hydrogen fluoride (HF)-treated rutile TiO2(001) surface for the decomposition reaction of linoleic acid was lower than that of an as-received (polished) rutile TiO2(001) surface. The surfaces of as-received TiO2(001) and HF-treated TiO2(001) were investigated using low-energy electron diffraction (LEED) and surface X-ray diffraction (SXRD) to elucidate differences in their photocatalytic activities. The as-received (polished) surface did not yield good LEED patterns, which implied that the surface was not well-ordered and was thus not examined using SXRD. In contrast, the HF-treated surface produced good LEED patterns with a 1 × 1 structure and was thus studied using SXRD. The analysis of crystal truncation rods indicated that all atoms in the four layers of the surface moved toward the bulk and that the HF-treated surface was (101)-faceted with terraces. On average, the facet was found to be four layers deep. The difference in the condition of the surface influences the photocatalytic activity of the surface.

Effect of Multiple Parallel Grooves on the Photocatalytic Activity of Rutile TiO2 Surfaces

The effect of the surface conditions of (001) and (100) rutile TiO2 surfaces on the photocatalytic decomposition of linoleic acid was investigated. The rate of decomposition was observed by measuring the weight of the remaining linoleic acid. The as-received (polished) (001) surface showed a higher photocatalytic activity than the (100) surface, but the activity was greatly reduced when the surface was treated by HF solution and heated to 400°C. Condition of the surface strongly affects the photocatalytic activity. The heated (001) surface partially regained its activity after multiple parallel grooves were introduced along the [110] direction. However, the surface did not regain its activity if these grooves were instead introduced along the [1-10] or [100] directions.

Hydrogen production using mesoporous titanium dioxide

Abstract Mesoporous C/N doped TiO2 (MCNT) samples were prepared, and Pt was deposited on their surfaces. The hydrogen production capability of this material was investigated by irradiating it with UV light at two different wavelengths. It was found that MCNT could be used to produce hydrogen gas. The highest hydrogen production rate was obtained when 0·003 mol Pt was deposited on the surface of 1 mol MCNT. Since this optimal Pt concentration is the same as that for P-25, it was concluded that the mesopore surface was not directly deposited with Pt. More hydrogen was produced when Pt deposited MCNT was irradiated with 350 nm wavelength UV light than with 370 nm wavelength UV light at similar intensity. This implies that the wavelength of UV light strongly affects hydrogen production.