Highly transparent pure and Au doped TiO2 thin films are successfully deposited by using simple chemical spray pyrolysis technique. The effect of Au doping onto the structural and physicochemical properties has been investigated. The PEC study shows that, both short circuit current (Isc) and open circuit voltage (Voc) are (Isc=1.81mA and Voc=890mV) relatively higher at 3at.% Au doping percentage. XRD study shows that the films are nanocrystalline in nature with tetragonal crystal structure. FESEM images show that the film surface covered with a smooth, uniform, compact and rice shaped nanoparticles. The Au doped thin films exhibit indirect band gap, decreases from 3.23 to 3.09eV with increase in Au doping. The chemical composition and valence states of pure and Au doped TiO2 films are studied by using X-ray photoelectron spectroscopy. The photocatalytic degradation effect is 49% higher in case 3at.% Au doped TiO2 than the pure TiO2 thin film photoelectrodes in the degradation of benzoic acid. It is revealed that Au doped TiO2 can be reused for five cycles of experiments without a requirement of post-treatment while the degradation efficiency was retained.

Photoelectrocatalytic degradation of benzoic acid using Au doped TiO2 thin films

In recent years, the photochemistry of nano-semiconductor particles has been one of the fastest growing research areas in the physical chemistry field TiO2 is considered as the most thoroughly investigated semiconductor in the literature, due to its photocatalytic activity, excellent functionality, thermal stability, and non-toxicity It seems to be the most promising for the photocatalytic destruction of organic pollutants The challenge for scientific materials is to find a processing method in which the crystalline phase as well as the size and morphology of TiO2 nanocrystals can be controlled The concept of the present paper consists of a comprehensive study regarding the level of knowledge in the synthesis of TiO2-based nanopowders and their application in the advanced degradation of aromatic nitrocompounds The objectives are related to: critical analysis of the synthesis techniques of the TiO2-based nanopowders, underlining the importance of using the sol–gel method evaluation of the morphological and structural specific characterization of these techniques; and a comprehensive study of the operational parameters of the pollutant photocatalytic degradation The relative simple sol–gel method is the most widely used, being considered as a versatile means of developing catalytic materials, as well as an important experimental tool in understanding their physical and chemical properties In order to enhance TiO2 photocatalysis and to extend the response into the visible domain, titanium has been doped with metals, nonmetals, and ionic components A recent literature survey concerning some transition metals-doping (Fe, Co, and Ni) of TiO2 nanopowders by the sol–gel method was also included

TiO2-based Nanomaterials with Photocatalytic Properties for the Advanced Degradation of Xenobiotic Compounds from Water. A Literature Survey

Flower-like anatase TiO 2 hierarchical spheres assembled by nanosheets were synthesized by glycine assistant via a simple hydrothermal approach and after-annealing process. These flower-like spheres are about 2 μm in diameter with sheet thickness about 20 nm. Results showed reaction time, temperature, solution pH and glycine dosage all played an important role in control of shape and size of the as-synthesized TiO 2 nanocrystals. The photocatalytic activity of this nano-TiO 2 was evaluated by the photocatalytic oxidation decomposition of methyl orange under sunlight illumination in the presence of hydrogen peroxide (H 2 O 2 ). The photocatalytic activity of the obtained TiO 2 was higher than that of commercial TiO 2 .

Glycine assisted synthesis of flower-like TiO2 hierarchical spheres and its application in photocatalysis

Ag-doped TiO2 with Ag content ranging from 1 to 7 mol% was synthesized by a modified sol–gel route, and its performance as the photoanode of dye-sensitized solar cells (DSSCs) was compared with undoped TiO2 photoanode. Titanium(IV)isopropoxide was used as precursor and hexamethylenetetramine as the capping agent. XRD results show the formation of TiO2 nanoparticles with an average crystallite size of 5 nm (1 % Ag-doped TiO2) and 9 nm (undoped TiO2), respectively. The TiO2 nanopowder was used to prepare its thin film photoelectrode using doctor’s blade method. Significant improvement in light-to-energy conversion efficiency was achieved when thin films of 1 % Ag-doped TiO2 were applied as photoanode in DSSC taking N719 as the sensitizer dye. As evidenced by EIS measurements, the electron lifetime of DSSC with Ag-doped TiO2 increased from 1.33 (for undoped TiO2) to 2.05 ms. The short-circuit current density (J
 sc), open-circuit voltage (V
 oc), fill factor (FF) and the overall energy conversion efficiency (η) were 1.07 mA cm−2, 0.72 V, 0.73 and 0.40 %, respectively, with the use of 1 % Ag-doped TiO2 photoanode, whereas with undoped TiO2 under similar conditions, J
 sc = 0.63 mA cm−2, V
 oc = 0.70 V, fill factor 0.45 and conversion efficiency 0.14 % could be obtained. Therefore, compared with the reference DSSC containing an undoped TiO2 photoanode, the power conversion efficiency of the cell based on Ag-doped TiO2 has been remarkably enhanced by ~70 %. The substantial improvement in the device performance is attributed to the reduced band-gap energy, retarded charge recombination and greater surface coverage of the sensitizing dye over Ag-doped TiO2, which ultimately resulted in improved IPCE, J
 SC and η values.

Improved performance of Ag-doped TiO 2 synthesized by modified sol–gel method as photoanode of dye-sensitized solar cell

An effective process based on the photocatalytic reduction of CO2 to face on the one hand, the crucial problem of environmental pollution, and, on the other hand, to propose an efficient way to product clean and sustainable energy sources has been developed in this work. Particular attention has been paid to the sustainability of the process by using a green reductant (water) and TiO2 as a photocatalyst under very mild operative conditions (room temperature and atmospheric pressure). It was shown that the efficiency in carbon dioxide photoreduction is strictly related to the process parameters and to the catalyst features. In order to formulate a versatile and high performing catalyst, TiO2 was modified by oxide or metal species. Copper (in the oxide CuO form) or gold (as nanoparticles) were employed as promoting metal. Both photocatalytic activity and selectivity displayed by CuO-TiO2 and Au-TiO2 were compared, and it was found that the nature of the promoter (either Au or CuO) shifts the selectivity of the process towards two strategic products: CH4 or H2. The catalytic results were discussed in depth and correlated with the physicochemical features of the photocatalysts.

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Andrei Năstuţă

Papers

Structural study of sol–gel Au/TiO2 films from nanopowders