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O. Yanushevska et al.
photocatalyst in nanoscale range complicates the further processing of suspensions,
and suspended nanoparticles remaining in the water can have harmful toxic effects
in the subsequent use of purified water.
Thus, titanium oxide (36 nm) was applied by using sol–gel method, adsorption,
and catalytic activity were evaluated in the process of adsorption and photodegradation of the Methylene blue dye in the UV irradiation range [18]. Four samples with
different TiO 2 content (12.3, 24.8, 40.7, and 48.3 wt%) were investigated, among
which the highest photocatalytic activity showed the sample with 40.7 wt% TiO 2 ,
which completely degraded the dye molecules within 60 min. It was also noted that
the adsorption capacity of the nanocomposite on the microspherical carrier to the
methylene blue dye was inversely proportional to the content of TiO 2 nanoparticles.
Instead, the photocatalytic efficiency of the nanocomposites under study showed a
direct correlation with the titanium (IV) oxide concentration. Surface electron microscope images of microspheres-based titanium-based photocatalysts indicate that an
excessive increase in the content of TiO 2 nanoparticles may also lead to the aggregation of microspheres and a decrease in light energy access to the catalyst surface
and, consequently, a decrease in their activity.
Similar studies were performed and presented in [19], in which synthesized TiO 2 -
based nanocomposites were investigated in the process of phenol photo-degradation
during irradiation in the visible light range (λ ≥ 420 nm). It was found that usage
of the 95 wt% TiO 2 content composite leads to the 68% photodegradation degree of
the pollutant.
Work [11] presented a simple and effective approach to increase the area available for light energy in photocatalyst based on dispersed TiO 2 particles and 1D ZnO
structures. The formation of nanostructured zinc rods dispersed on polymer titanium
nanoparticles, which serve as centers of crystallization and growth of ZnO nanostructures (21–24 nm), was realized. The efficiency of the obtained nanocomposite as
a photocatalyst is explained by a significant increase in the surface area available for
absorption of light energy, a high concentration of charge carriers, which minimizes
the number of recombination of electrons and «holes» in photocatalytic processes.
The obtained composite was studied in the degradation reaction of the organic dye
Rhodamine B when irradiated with UV and visible light. The degree of photodegradation was 90% for 70 min with the maximum dye absorption in the UV region of
the light spectrum. This indicates that there is a photo-synergistic effect due to the
interaction of two oxide semiconductors, but further studies have revealed that the
dominant effect on the photodegradation process still provides ZnO nanostructures.
Summarizing the above, it should be noted that the photocatalytic activity of
semiconductors (TiO 2 and ZnO), if used separately, is significantly reduced due to
one-electron recovery, a high degree of recombination of «electron–hole» transfers,
and a decrease in the specific surface area of light absorption. Therefore, it is much
more promising to use nanocomposite materials that combine photo-synergies, which
promotes the induction of multi-electron transmissions, increases the total contact
area of catalysts with light energy, and reduces recombinant effects.
In work [12], authors used photocatalysts based on TiO 2 nanotubes with sequential formation of the ZnO nanostructures on their surface by a chemical deposition
O. Yanushevska et al.
photocatalyst in nanoscale range complicates the further processing of suspensions,
and suspended nanoparticles remaining in the water can have harmful toxic effects
in the subsequent use of purified water.
Thus, titanium oxide (36 nm) was applied by using sol–gel method, adsorption,
and catalytic activity were evaluated in the process of adsorption and photodegradation of the Methylene blue dye in the UV irradiation range [18]. Four samples with
different TiO 2 content (12.3, 24.8, 40.7, and 48.3 wt%) were investigated, among
which the highest photocatalytic activity showed the sample with 40.7 wt% TiO 2 ,
which completely degraded the dye molecules within 60 min. It was also noted that
the adsorption capacity of the nanocomposite on the microspherical carrier to the
methylene blue dye was inversely proportional to the content of TiO 2 nanoparticles.
Instead, the photocatalytic efficiency of the nanocomposites under study showed a
direct correlation with the titanium (IV) oxide concentration. Surface electron microscope images of microspheres-based titanium-based photocatalysts indicate that an
excessive increase in the content of TiO 2 nanoparticles may also lead to the aggregation of microspheres and a decrease in light energy access to the catalyst surface
and, consequently, a decrease in their activity.
Similar studies were performed and presented in [19], in which synthesized TiO 2 -
based nanocomposites were investigated in the process of phenol photo-degradation
during irradiation in the visible light range (λ ≥ 420 nm). It was found that usage
of the 95 wt% TiO 2 content composite leads to the 68% photodegradation degree of
the pollutant.
Work [11] presented a simple and effective approach to increase the area available for light energy in photocatalyst based on dispersed TiO 2 particles and 1D ZnO
structures. The formation of nanostructured zinc rods dispersed on polymer titanium
nanoparticles, which serve as centers of crystallization and growth of ZnO nanostructures (21–24 nm), was realized. The efficiency of the obtained nanocomposite as
a photocatalyst is explained by a significant increase in the surface area available for
absorption of light energy, a high concentration of charge carriers, which minimizes
the number of recombination of electrons and «holes» in photocatalytic processes.
The obtained composite was studied in the degradation reaction of the organic dye
Rhodamine B when irradiated with UV and visible light. The degree of photodegradation was 90% for 70 min with the maximum dye absorption in the UV region of
the light spectrum. This indicates that there is a photo-synergistic effect due to the
interaction of two oxide semiconductors, but further studies have revealed that the
dominant effect on the photodegradation process still provides ZnO nanostructures.
Summarizing the above, it should be noted that the photocatalytic activity of
semiconductors (TiO 2 and ZnO), if used separately, is significantly reduced due to
one-electron recovery, a high degree of recombination of «electron–hole» transfers,
and a decrease in the specific surface area of light absorption. Therefore, it is much
more promising to use nanocomposite materials that combine photo-synergies, which
promotes the induction of multi-electron transmissions, increases the total contact
area of catalysts with light energy, and reduces recombinant effects.
In work [12], authors used photocatalysts based on TiO 2 nanotubes with sequential formation of the ZnO nanostructures on their surface by a chemical deposition