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Influence of crystal structure of nanosized ZrO2 on photocatalytic degradation of methyl orange.

Basahel SN, Ali TT, Mokhtar M, Narasimharao K - Nanoscale Res Lett (2015)

Bottom Line: The structural and textural properties of the samples were analyzed by X-ray diffraction, Raman spectroscopy, TEM, UV-vis, X-ray photoelectron spectroscopy (XPS), and N2 adsorption measurements.The characterization results revealed that monoclinic ZrO2 nanoparticles possessed high crystallinity and mesopores with diameter of 100 Å.The higher activity of the monoclinic ZrO2 sample for the photocatalytic degradation of methyl orange can be attributed to the combining effects of factors including the presence of small amount of oxygen-deficient zirconium oxide phase, high crystallinity, large pores, and high density of surface hydroxyl groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Faculty of Science, King Abdulaziz University, P. O. Box, 80203, Jeddah, 21589 Kingdom of Saudi Arabia.

ABSTRACT
Nanosized ZrO2 powders with near pure monoclinic, tetragonal, and cubic structures synthesized by various methods were used as catalysts for photocatalytic degradation of methyl orange. The structural and textural properties of the samples were analyzed by X-ray diffraction, Raman spectroscopy, TEM, UV-vis, X-ray photoelectron spectroscopy (XPS), and N2 adsorption measurements. The performance of synthesized ZrO2 nanoparticles in the photocatalytic degradation of methyl orange under UV light irradiation was evaluated. The photocatalytic activity of the pure monoclinic ZrO2 sample is higher than that of the tetragonal and cubic ZrO2 samples under optimum identical conditions. The characterization results revealed that monoclinic ZrO2 nanoparticles possessed high crystallinity and mesopores with diameter of 100 Å. The higher activity of the monoclinic ZrO2 sample for the photocatalytic degradation of methyl orange can be attributed to the combining effects of factors including the presence of small amount of oxygen-deficient zirconium oxide phase, high crystallinity, large pores, and high density of surface hydroxyl groups.

No MeSH data available.


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Structural forms of methyl orange under acidic and basic conditions.
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Fig10: Structural forms of methyl orange under acidic and basic conditions.

Mentions: It is also known that the photocatalytic redox reaction mainly takes place on the surface of the photocatalysts and so the surface properties significantly influence the efficiency of catalyst [60]. Additionally, the surface hydroxyl groups of ZrO2 are acidic to a certain degree, and the proportion of transformed azo structure increases into quinoid structure under acidic conditions (Figure 10). It is also reported that quinoid structure is more likely to be degraded than azo structure [61]. From the XRD patterns, it is clear that the m-ZrO2 sample has the highest crystallinity (sharpest peaks, largest crystals). This is also reflected in the Raman spectra. A higher crystallinity is usually believed to be beneficial for photocatalysis because of the amount of defect sites in the structure (which usually act as recombination centers). In comparison, the m-ZrO2 sample synthesized in this work possessed relatively high pore volume, pore size, and high density of hydroxyl groups.Figure 10


Influence of crystal structure of nanosized ZrO2 on photocatalytic degradation of methyl orange.

Basahel SN, Ali TT, Mokhtar M, Narasimharao K - Nanoscale Res Lett (2015)

Structural forms of methyl orange under acidic and basic conditions.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385125&req=5

Fig10: Structural forms of methyl orange under acidic and basic conditions.
Mentions: It is also known that the photocatalytic redox reaction mainly takes place on the surface of the photocatalysts and so the surface properties significantly influence the efficiency of catalyst [60]. Additionally, the surface hydroxyl groups of ZrO2 are acidic to a certain degree, and the proportion of transformed azo structure increases into quinoid structure under acidic conditions (Figure 10). It is also reported that quinoid structure is more likely to be degraded than azo structure [61]. From the XRD patterns, it is clear that the m-ZrO2 sample has the highest crystallinity (sharpest peaks, largest crystals). This is also reflected in the Raman spectra. A higher crystallinity is usually believed to be beneficial for photocatalysis because of the amount of defect sites in the structure (which usually act as recombination centers). In comparison, the m-ZrO2 sample synthesized in this work possessed relatively high pore volume, pore size, and high density of hydroxyl groups.Figure 10

Bottom Line: The structural and textural properties of the samples were analyzed by X-ray diffraction, Raman spectroscopy, TEM, UV-vis, X-ray photoelectron spectroscopy (XPS), and N2 adsorption measurements.The characterization results revealed that monoclinic ZrO2 nanoparticles possessed high crystallinity and mesopores with diameter of 100 Å.The higher activity of the monoclinic ZrO2 sample for the photocatalytic degradation of methyl orange can be attributed to the combining effects of factors including the presence of small amount of oxygen-deficient zirconium oxide phase, high crystallinity, large pores, and high density of surface hydroxyl groups.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Faculty of Science, King Abdulaziz University, P. O. Box, 80203, Jeddah, 21589 Kingdom of Saudi Arabia.

ABSTRACT
Nanosized ZrO2 powders with near pure monoclinic, tetragonal, and cubic structures synthesized by various methods were used as catalysts for photocatalytic degradation of methyl orange. The structural and textural properties of the samples were analyzed by X-ray diffraction, Raman spectroscopy, TEM, UV-vis, X-ray photoelectron spectroscopy (XPS), and N2 adsorption measurements. The performance of synthesized ZrO2 nanoparticles in the photocatalytic degradation of methyl orange under UV light irradiation was evaluated. The photocatalytic activity of the pure monoclinic ZrO2 sample is higher than that of the tetragonal and cubic ZrO2 samples under optimum identical conditions. The characterization results revealed that monoclinic ZrO2 nanoparticles possessed high crystallinity and mesopores with diameter of 100 Å. The higher activity of the monoclinic ZrO2 sample for the photocatalytic degradation of methyl orange can be attributed to the combining effects of factors including the presence of small amount of oxygen-deficient zirconium oxide phase, high crystallinity, large pores, and high density of surface hydroxyl groups.

No MeSH data available.


Related in: MedlinePlus