Olga Chernyayeva

Sonophotodeposition of bimetallic photocatalysts Pd-Au/TiO2 : application to selective oxidation of methanol to methyl formate.

The aim of this work is to develop bimetallic Pd-Au/TiO2 P90 systems, which are highly active and selective for the photocatalytic oxidation of methanol to form methyl formate. Modification of commercial TiO2 P90 with Pd-Au nanoparticles was successfully achieved for the first time by means of a sonophotodeposition (SPD) method. The prepared materials were characterized by TEM, UV/Vis spectroscopy, X-ray photoelectron spectroscopy, and powder XRD. The Pd-Au bimetallic nanoparticles supported on titania exhibited remarkably enhanced catalytic activity in selective methanol oxidation to form methyl formate due to the synergism of Au and Pd particles, as well as the strong interaction between TiO2 and Pd-Au. SPD is a green methodology that can be used to prepare well-defined bimetallic surfaces on semiconductor supports with great promise for catalytic applications, in which selectivity can be tuned through adjustment of the surface composition.

Sonication‐Assisted Low‐Temperature Routes for the Synthesis of Supported Fe–TiO2 Econanomaterials: Partial Photooxidation of Glucose and Phenol Aqueous Degradation

Fe‐doped TiO2‐supported photocatalytic materials prepared by the use of a mild ultrasound‐assisted protocol have been found to possess excellent selectivities in glucose oxidation and total phenol mineralization. These materials were characterized by a number of techniques such as XRD, diffuse reflectance UV/Vis spectroscopy, N2 physisorption, X‐ray photoelectron spectroscopy, SEM with X‐ray microanalysis, HRTEM, and flame atomic absorption spectroscopy. The proposed synthesis method was found to have a significant effect on textural properties, morphology, and visible‐light responsiveness of nanophotocatalysts. The dopant agent was found to be in the form of Fe3+ ions. The effects of the textural properties, together with the Fe presence and the adsorption ability of the material (acidic properties), seem to be involved in the optimum photocatalytic activities found for Fe–TiO2 supported on zeolite. In phenol photodegradation, although Fe doping demonstrated the detrimental effect on the conversion rate, an improvement in the direct mineralization of phenol to CO2 and water, particularly for the SiO2‐supported photocatalyst, with a negligible content of toxic byproducts in water has been observed in comparison with commercially available Evonik P25.

Iron‐Containing Titania Photocatalyst Prepared by the Sonophotodeposition Method for the Oxidation of Benzyl Alcohol

The sonophotodeposition method was applied in the synthesis of an iron‐containing titania photocatalyst. This procedure enables the use of sustainable energy sources, such as sonication and light, and eliminates the use of hazardous reducing agents. For the first time an ultrasonic horn and sun‐imitating Xenon lamp were used in this method. The following techniques: diffuse reflectance UV/Vis spectroscopy, high‐resolution transmission electron microscopy with X‐ray microanalysis (HRTEM‐EDS), X‐ray photoelectron spectroscopy (XPS) and energy‐dispersive X‐ray fluorescence (EDXRF) were applied for the characterization of the prepared material. The photocatalytic oxidation of benzyl alcohol into benzaldehyde under sun‐imitating Xenon lamp irradiation was applied as a test reaction. The photocatalyst prepared by the sonophotodeposition method showed better results, in terms of alcohol conversion and yield of benzaldehyde, in comparison with the photocatalyst prepared by an ordinary wet‐impregnation method.

Insight into the synthesis procedure of Fe3+/TiO2-based photocatalyst applied in the selective photo-oxidation of benzyl alcohol under sun-imitating lamp

Fe3+/TiO2/zeolite Y photocatalyst synthesized by using sonophotodeposition method was compared with photocatalysts prepared by simple photodeposition and sonodeposition methods in order to clarify the role of light irradiation and ultrasounds while they are used simultaneously. To gain an insight into the mechanism of this method a detailed characterization of the photocatalysts was carried out by means of the following techniques: UV-vis diffuse reflectance spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, Mössbauer measurements and photocatalytic test reaction. Basing on the results from these techniques the chemical role of light and mainly mechanical role of ultrasound were observed. The selective photocatalytic oxidation of benzyl alcohol into benzaldehyde in liquid phase was a test reaction verifying the utility of the prepared materials. The best photocatalytic efficiency in this reaction was performed by photocatalyst synthesized using compilation of ultrasound energy with photoexcitation.