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Facile synthesis of α -Fe 2 O 3 nanodisk with superior photocatalytic performance and mechanism insight

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ABSTRACT

Intrinsic short hole diffusion length is a well-known problem for α-Fe2O3 as a visible-light photocatalytic material. In this paper, a nanodisk morphology was designed to remarkably enhance separation of electron-hole pairs of α-Fe2O3. As expected, α-Fe2O3 nanodisks presented superior photocatalytic activity toward methylene blue degradation: more than 90% of the dye could be photodegraded within 30 min in comparison with a degradation efficiency of 50% for conventional Fe2O3 powder. The unique multilayer structure is thought to play a key role in the remarkably improved photocatalytic performance. Further experiments involving mechanism investigations revealed that instead of high surface area, ·OH plays a crucial role in methylene blue degradation and that O·2− may also contribute effectively to the degradation process. This paper demonstrates a facile and energy-saving route to fabricating homogenous α-Fe2O3 nanodisks with superior photocatalytic activity that is suitable for the treatment of contaminated water and that meets the requirement of mass production.

No MeSH data available.


(a) MB degradation as a function of irradiation time with different as-synthesized samples; (b) the kinetic analysis (pseudo-first-order) of different as-synthesized samples; (c) the effect of MB concentration on MB degradation with a 200/30 sample; (d) UV/vis spectral changes of 20 ppm MB aqueous solution in the presence of a 200/30 sample and images (inset) of the aqueous solution recorded at different time intervals; (e) MB degradation as a function of irradiation time; (f) kinetic analysis (pseudo-first-order) for different durations of microwave irradiation during sample synthesis.
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Figure 5: (a) MB degradation as a function of irradiation time with different as-synthesized samples; (b) the kinetic analysis (pseudo-first-order) of different as-synthesized samples; (c) the effect of MB concentration on MB degradation with a 200/30 sample; (d) UV/vis spectral changes of 20 ppm MB aqueous solution in the presence of a 200/30 sample and images (inset) of the aqueous solution recorded at different time intervals; (e) MB degradation as a function of irradiation time; (f) kinetic analysis (pseudo-first-order) for different durations of microwave irradiation during sample synthesis.

Mentions: As revealed in the SEM and TEM images, the morphology changes with increasing synthesis temperature. Since absorption and electron transfer depend greatly on the surface structure of a nanocrystal, it is expected that the nanocrystals prepared at different temperatures should present different photocatalytic activities. Figure 5(a) shows the photocatalytic activities of samples with different synthesis temperatures. The degradation efficiency is defined as c/c0, where c0 and c are the initial (after equilibrium adsorption) and reaction concentrations, respectively, of MB at a specific time. It can be seen that, compared with the blank experiment (without addition of α-Fe2O3 photocatalyst but only H2O2), the as-synthesized and commercial samples show much better photocatalytic activities. Moreover, it is found that among all the samples, the 200 °C synthesized α-Fe2O3 nanodisk shows superior photocatalytic activity: more than 90% of MB can be degraded in 30 min, whereas the degradation efficiency of the commercial sample is only 50%. The reaction rate constant k of the as-synthesized and commercial samples is shown in figure 5(b) and table 1. It is evident that the 200 °C synthesized α-Fe2O3 nanodisk has the highest reaction rate constant, 0.087 min−1. When normalized to the Brunauer–Emmett–Teller surface areas (SBET), it is 15.08 × 10−3 min−1 Lm−2, which is also highest among all the samples (table 1). It is evident that the photocatalytic performance is comparable with previous reported α-Fe2O3 nanoplate structures (k = 0.008) or SnO2/α-Fe2O3 hierarchical nano-heterostructures (k = 0.011) [23, 28].


Facile synthesis of α -Fe 2 O 3 nanodisk with superior photocatalytic performance and mechanism insight
(a) MB degradation as a function of irradiation time with different as-synthesized samples; (b) the kinetic analysis (pseudo-first-order) of different as-synthesized samples; (c) the effect of MB concentration on MB degradation with a 200/30 sample; (d) UV/vis spectral changes of 20 ppm MB aqueous solution in the presence of a 200/30 sample and images (inset) of the aqueous solution recorded at different time intervals; (e) MB degradation as a function of irradiation time; (f) kinetic analysis (pseudo-first-order) for different durations of microwave irradiation during sample synthesis.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC5036498&req=5

Figure 5: (a) MB degradation as a function of irradiation time with different as-synthesized samples; (b) the kinetic analysis (pseudo-first-order) of different as-synthesized samples; (c) the effect of MB concentration on MB degradation with a 200/30 sample; (d) UV/vis spectral changes of 20 ppm MB aqueous solution in the presence of a 200/30 sample and images (inset) of the aqueous solution recorded at different time intervals; (e) MB degradation as a function of irradiation time; (f) kinetic analysis (pseudo-first-order) for different durations of microwave irradiation during sample synthesis.
Mentions: As revealed in the SEM and TEM images, the morphology changes with increasing synthesis temperature. Since absorption and electron transfer depend greatly on the surface structure of a nanocrystal, it is expected that the nanocrystals prepared at different temperatures should present different photocatalytic activities. Figure 5(a) shows the photocatalytic activities of samples with different synthesis temperatures. The degradation efficiency is defined as c/c0, where c0 and c are the initial (after equilibrium adsorption) and reaction concentrations, respectively, of MB at a specific time. It can be seen that, compared with the blank experiment (without addition of α-Fe2O3 photocatalyst but only H2O2), the as-synthesized and commercial samples show much better photocatalytic activities. Moreover, it is found that among all the samples, the 200 °C synthesized α-Fe2O3 nanodisk shows superior photocatalytic activity: more than 90% of MB can be degraded in 30 min, whereas the degradation efficiency of the commercial sample is only 50%. The reaction rate constant k of the as-synthesized and commercial samples is shown in figure 5(b) and table 1. It is evident that the 200 °C synthesized α-Fe2O3 nanodisk has the highest reaction rate constant, 0.087 min−1. When normalized to the Brunauer–Emmett–Teller surface areas (SBET), it is 15.08 × 10−3 min−1 Lm−2, which is also highest among all the samples (table 1). It is evident that the photocatalytic performance is comparable with previous reported α-Fe2O3 nanoplate structures (k = 0.008) or SnO2/α-Fe2O3 hierarchical nano-heterostructures (k = 0.011) [23, 28].

View Article: PubMed Central - PubMed

ABSTRACT

Intrinsic short hole diffusion length is a well-known problem for α-Fe2O3 as a visible-light photocatalytic material. In this paper, a nanodisk morphology was designed to remarkably enhance separation of electron-hole pairs of α-Fe2O3. As expected, α-Fe2O3 nanodisks presented superior photocatalytic activity toward methylene blue degradation: more than 90% of the dye could be photodegraded within 30 min in comparison with a degradation efficiency of 50% for conventional Fe2O3 powder. The unique multilayer structure is thought to play a key role in the remarkably improved photocatalytic performance. Further experiments involving mechanism investigations revealed that instead of high surface area, ·OH plays a crucial role in methylene blue degradation and that O·2− may also contribute effectively to the degradation process. This paper demonstrates a facile and energy-saving route to fabricating homogenous α-Fe2O3 nanodisks with superior photocatalytic activity that is suitable for the treatment of contaminated water and that meets the requirement of mass production.

No MeSH data available.