&nbsp; Study on photocatalytic properties of (Na 1- x La x )(Ta 1- x Fe x )O 3 solid solutions under visible light irradiation <br>

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Journal of Nanjing University(Natural Sciences) ›› 2010, Vol. 46 ›› Issue (6) : 697-704.

Study on photocatalytic properties of (Na 1- x La x )(Ta 1- x Fe x )O 3 solid solutions under visible light irradiation

Jiang Xiao J un 1, 2 , Li Zhaon Sheng 1, 2 , Li Guo Qiang 3 , H uang X ian Li 2 , Zou Zhi Gang 2

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Abstract

In order to develop new visible light-driven photocatalytic materials, a series of ( Na 1- x La x ) (T a 1- x Fe x ) O 3 ( 0 < x < 1) solid ?solution photocatalysts were prepared by a solid state reaction method. X ray diffraction
( XRD) , ultraviolet-visible spectroscopy ( UV-vis), specific surface area and porosity analyzer were employed to investigate the crystal structures, absorption and surface area properties of the series of ( Na 1- x La x ) ( Ta 1- x Fe x )O 3
solid solutions. T he XRD results show that with the increasing value of x , the crystal structures of the series of solid solutions gradually transform from monoclinic structure to cubic structure and the cell volumes of the samples
increase until x= 0 8, and then decrease when x > 0 8 for the substitution of different ion radii. According to the diffuse reflection spectra of the solid solutions, the absorption edges of the ( Na 1- x La x ) ( Ta 1- x Fe x )O 3 samples red
shift as the value of x increases, that is to say with the increase of LaFeO 3 in component the light absorption edgesof the solid solutions extend from ultraviolet region to visible region. The band gaps estimated from the onsets of the
absorption edges of the solid solutions decrease from 3- 3 to 2 -2 eV, when x decreases from 0 - 05 to 0 8. It means that the band gaps of the obtained series of solid solutions can be tuned by the variation in component of NaT aO 3 and
LaFeO 3 . T he photocatalytic results show that the prepared solid solutions ( 0< x < 1) exhibit the activities of H 2 evolution from the aqueous CH 3 OH solution under visible light irradiation(!420 nm) , but no H 2 evolution for the
NaT aO 3 sample. Among the samples, ( Na 0 -2 La 0 8 ) ( T a 0 2 Fe 0 8 ) O 3 ( x = 0 -8) solid solution shows the highest activity. Dark experiment excludes the possibility of mechanocatalysis effect and blank experiment excludes the
possibility of photolysis effect. There is no noticeable variation in the XRD patterns of the solid solutions before and after the photocatalytic H 2 evolution, suggesting that the structures of solid-solution photocatalysts are stable. The
wavelength dependence of the H 2 evolution of the (Na 0-2 La 0 - 8 )( Ta 0-2 Fe 0?8 ) O 3 photocatalyst exhibits that the rates of H 2 evolution decrease with the increase in cutoff wavelength, which is in good agreement with the UV-vis diffuse
reflectance spectra of ( Na 0 - 2 La 0?8 ) ( Ta 0-2 Fe 0?8 ) O 3 photocatalyst. This phenomenon indicates the present catalytic reaction is indeed driven by a visible light absorption. T he standard CAST EP package was also used to calculate the
bandstructure. The first principle calculation reveals that incorporation of LaFeO 3 into the solid solutions not only pushes down the CB bottom but also pushes up the VB top, thus making the band gap of the solid solutions narrower.

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Jiang Xiao J un 1, 2 , Li Zhaon Sheng 1, 2 , Li Guo Qiang 3 , H uang X ian Li 2 , Zou Zhi Gang 2
. Study on photocatalytic properties of (Na 1- x La x )(Ta 1- x Fe x )O 3 solid solutions under visible light irradiation
[J]. Journal of Nanjing University(Natural Sciences), 2010, 46(6): 697-704

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