Development of TiO2 nanostructure modification for photocatalysis
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COVALIOV, Victor, COVALIOVA, Olga. Development of TiO2 nanostructure modification for photocatalysis. In: Materials Science and Condensed Matter Physics, Ed. 7, 16-19 septembrie 2014, Chișinău. Chișinău, Republica Moldova: Institutul de Fizică Aplicată, 2014, Editia 7, p. 342.
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Materials Science and Condensed Matter Physics
Editia 7, 2014
Conferința "Materials Science and Condensed Matter Physics"
7, Chișinău, Moldova, 16-19 septembrie 2014

Development of TiO2 nanostructure modification for photocatalysis


Pag. 342-342

Covaliov Victor, Covaliova Olga
 
Moldova State University
 
Disponibil în IBN: 23 martie 2019


Rezumat

The methods of heterogeneous catalysis for water treatment containing the organic pollutants, using the disperse metal oxide particles, among them TiO2 with nanotubular structure, are being actively developed in the last years. Their photocatalytic activity is connected with the fact that the light quanta under the UV-irradiation with the wavelength l<385 nm, excite electrons from the valency zone to conductivity zone, forming the electron-hole pairs, i.e. TiO2 + hν → TiO2(е-+h+). This promotes the formation of high reactive oxygen-containing radicals such as 'OH, 'О2-, 'НО2, 'О2- etc. in water environment [1]. The result of photocatalytical treatment of water containing the chemically stable organic substances, is their mineralization due to the development of the redox processes with the involvement of active radicals. This leads to the formation of simple non-toxic compounds following the general view reaction: ОН + О2 + СnOmH(2n-2m+2) → nCO2 + (n-m+1)H2O.  The improved methods of nanostructured TiO2 electrochemical synthesis were proposed, both in the form of deposits strongly attached to the Ti base, and separate particles formation in water environment [2]. The mechanism of nano-tubular TiO2 structure formation has been discussed from the point of view of the structural-geometric theory. The role of the barrier layer formation, destruction and renewal processes is mentioned, which determine the character of tubular structure formation of the anodic deposits on Ti. It is shown that, independently on the anodic treatment regime, the ratio of elementary cell and applied voltage is maintained: W = 2SE + D = 2L + D, where W – cell dimension (diameter); E – oxide forming voltage; D – pore diameter; S – relative thickness of cell wall, characterizing the thickness share per each V of forming voltage; L – cell wall thickness.   Dependence of barrier layer (Т) and elementary cell wall thickness is expresses by the formula: T = 1,2 L. The following expression gives correlation between the pores diameter, cell diameter and thickness of barrier layer: D = W – 1,67 T. The specific amount of nanotubes elementary cells, calculated on the base of cell dimensions, makes (3-5)∙108 in 1 сm2 and is changing in inverse proportion to voltage.  A new principle of flow-through photocatalytic reactor on the base of nano-tubular TiOhas been proposed [3]. The possibility to produce composites on its basis was considered [4]. In particular, there is information that the TiO2 nano-tubes massive under the solar irradiation can transform a mixture of СО2 and water vapour into the natural gas, which can help to resolve the greenhouse gases emissions in future. The equipment is proposed, making it possible to cover the nano-tubes surface with copper by chemical-catalytic reduction, which in the perspective could help to radically increase the rate of CO2 conversion in natural gas.