396
A.Y.S. Malkhasian / Journal of Alloys and Compounds 649 (2015) 394e399
AgVO3 nanowires. A Nova 2000 series Chromatech apparatus was
used to measure the BET surface area of -AgVO3 and Pt/ -AgVO3
b
b
nanowires before measurements the samples were heated under
vacuum for 3 h at 200 ꢀC. A UV/Vis/NIR spectrophotometer (V-570,
JASCO, Japan) was used to measure the band gap energy of
and Pt/ -AgVO3 nanowires. A JEOL-JEM-1230 microscope was used
to determine the shape and particle size of -AgVO3 and Pt/b-
b-AgVO3
b
b
AgVO3 nanowires. Before measurement, the samples were
dispersed in ethanol for 30 min. Then, a small portion of the
samples were placed on a carbon-coated copper grid. A Thermo
Scientific K-ALPHA, X-ray photoelectron spectroscope (XPS), En-
gland, was used to determine the elemental nature of the sample.
The photoluminescence emission spectra of
b-AgVO3 and Pt/b-
AgVO3 nanowires were measured using a Shimadzu RF-5301
fluorescence spectrophotometer.
2.4. Photocatalytic activity
The photocatalytic performance was measured under visible
light irradiation via the photooxidation of atrazine. A 300-W
Xenon lamp was used as the irradiation source, and it was
completely covered with an optical cut-off filter to remove any
light that has a wavelength below 420 nm. An aqueous solution of
100 ppm atrazine was kept in the dark for 30 min prior to the
illumination step to ensure complete adsorptionedesorption
equilibrium was reached. The change in the concentration of
atrazine was measured using high-pressure liquid chromatog-
raphy (Shimadzu LC 20 A) with a C18 column UV detector. To
confirm the complete oxidation of atrazine into carbon dioxide,
chloride, and nitrate ions, the concentrations of chloride and ni-
trate ions were measured using ion chromatography (DX-300)
with a CDM-II conductivity detector and an AS4A-SC column. To
confirm the presence of carbon dioxide gas as one of the final
products from the photocatalytic oxidation of atrazine, the gases
that were obtained from the photocatalytic reaction were passed
over a 0.2 M NaOH solution. Then, a barium nitrate solution was
added to them, and the white precipitate produced was analyzed
using XRD.
3. Results and discussion
Fig. 3. TEM images of b-AgVO3 sample (A) and 0.6 wt % Pt/b-AgVO3 sample (B).
3.1. Characterization of
b
-AgVO3 and Pt/
b
-AgVO3 nanowires
-AgVO3 and Pt/b-AgVO3
AgVO3 samples. The results reveal that shape of
AgVO3 is nanowire as shown in Fig. 3A and B respectively. Also, Pt
was well dispersed into surface of -AgVO3 as shown in Fig. 3B.
Table 1 shows the BET surface area of -AgVO3 and Pt/ -AgVO3
samples. The results reveal that the BET of Pt/ -AgVO3 samples is
smaller than that of -AgVO3 sample, due to blocking of some pores
of -AgVO3 by Pt doping.
UVeVis spectra of
b-AgVO3 and Pt/b-
Fig. 1 shows the XRD patterns of
nanowires with different Pt weight percentages. The results reveal
that the characteristic peak for -AgVO3 appeared in all samples.
There is no peak for Pt due to the low Pt content or good dispersion
of Pt on the surface of -AgVO3. Additionally, increasing the weight
percentage of Pt increased the broadening of the characteristic peak
of -AgVO3, which means that increasing the weight percentage of
Pt decreases the crystalline size of -AgVO3.
Fig. 2 shows the XPS spectra of 0.6 wt % Pt/
b
b
b
b
b
b
b
b
b
b
b-AgVO3 and Pt/b-AgVO3 samples with
b
different weight percentages of Pt are shown in Fig. 4. The results
reveal that increasing the weight percentage of Pt from 0.2% to 0.6%
b
-AgVO3 nanowires.
The results reveal the presence of oxygen in the sample by the
presence of peak for O1s at 531.1 eV, as shown in Fig. 2A. Fig. 2B
shows the XPS for V2P. The results reveal that the peaks at 517.6 and
525.1 eV is attributed to V2p3/2 and V2p1/2, respectively. Fig. 2C
shows the XPS for Ag3d. The results reveal that the peaks at 368.4
and 374.5 eV are attributed to Ag3d5/2 and Ag3d3/2 bonding en-
ergies, respectively, which confirms the presence of Agþ. Therefore,
moved the absorption edges of
However, increasing the weight percentage of Pt on the surface of
-AgVO3 to above 0.6% has no significant effect on absorption edge
b-AgVO3 to longer wavelengths.
b
Table 1
BET surface area and band gap of b-AgVO3 and Pt-b-AgVO3 nanowires.
Sample
SBET (m2/g)
Band gap, eV
above XPS peaks confirm the presence of b-AgVO3 as obtained from
XRD results. Fig. 2D shows the XPS for Pt4f. The results reveal that
the peaks at 70.0 and 73.3 eV are attributed to Pt4f7/2 and Pt4f5/2
bonding energies, respectively, which confirms the presence of Pt
metal.
b
-AgVO3
30.00
28.00
26.00
24.00
22.00
2.43
2.29
2.22
2.04
1.97
0.2 wt % Pt-
0.4 wt % Pt-
0.6 wt % Pt-
0.8 wt % Pt-
b
b
b
b
-AgVO3
-AgVO3
-AgVO3
-AgVO3
Fig. 3 shows the TEM images of b-AgVO3 and 0.6 wt % Pt/b-