Synthesis of large surface area LaFeO3 nanoparticles by SBA-16 ...

J Nanopart Res
a
La3d
50
Intensity (a.u.)
800°C
3d 5/2
3d 3/2
DRS (%)
40
30
20
10
900°C
800°C
700°C
600°C
b
Intensity (a.u.)
Intensity (a.u.)
820 830 840 850 860
Binding energy (eV)
c
700°C
800°C
700°C
2p 3/2
2p 1/2
700 710 720 730
Binding energy (eV)
800°C
700°C
524 528 532 536
Binding energy (eV)
Fe2p
wavelength range from 300 to 550 nm, with a SPS peak
at about 390 nm, which can be attributed to the
photoinduced electronic transitions from the valence
band to conduction band (O 2p ? Fe 3d ) (Li et al. 2000).
O L
O L
O H
O H
O1s
Fig. 6 XPS spectra of La3d (a), Fe2p (b), and O1s (c) of
LaFeO 3 samples calcined at 700 and 800 °C
0
300 350 400 450 500 550 600 650 700
Wavelength (nm)
Fig. 7 UV–Vis DRS spectra of LaFeO 3 samples calcined at
different temperature
Moreover, the SPS response becomes much stronger
with increasing calcination temperature, which is close
related to the increase in the crystallinity of the LaFeO 3 .
The high crystallinity makes electronic band perfect so
as to enhance the built-in field strength, which can
promote charge separation, meanwhile leading to the
decrease of the defect amounts, which is also favorable
for charge separation (Jing et al. 2006). According to the
SPS method principles, it can be expected that the
stronger is the SPS signal, the higher is the photoinduced
charge separation rate. Thus, it can be supposed
that the high crystallinity is favorable for the photoinduced
charge separation and then improve the photocatalytic
activity further.
Photocatalytic activity evaluation
The activity of the as-prepared LaFeO 3 was evaluated
by photocatalytic degradation of Rhodamine B solution
under visible light. Figure 9 shows the RhB
degradation rate of photocatalytic reaction under
visible irradiation and adsorption in the dark on the
different LaFeO 3 samples and internationally commercial
P-25 TiO 2 . As the calcination temperature is
enhanced, it can be noticed that the photocatalytic
activity of the as-prepared LaFeO 3 gradually increases,
and the LaFeO 3 calcined at 900 °C exhibits excellent
photocatalytic activity. Interestingly, all the LaFeO 3
samples display higher visible activity than P25 TiO 2
and those LaFeO 3 samples prepared via the citrate
method (Li et al. 2007). Based on the above discussion,
the high photocatalytic activity is mainly explained
from the following two aspects. One is the large surface
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