Publication: Investigation of kinetic growth and morphology evolution of silver/zinc oxide nanocomposites synthesized using direct heating method for photocatalyst application
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Date
2024-02-01
Authors
Le, Anh Thi
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Direct heating (DH) method is a rapid and simple approach for the growth of
ZnO nanostructures. Nevertheless, the morphology evolution and kinetic growth of
ZnO rods and Ag/ZnO nanocomposites immobilized on kanthal coils and kanthal
meshes in response to DH synthesis parameters have not been studied yet. In addition,
the degradation efficiency of RhB dye by ZnO rods synthesized by DH method was
relatively low. In this project, synthesis parameters of DH method, i.e., heating power,
heating duration, OH
–
2+
:Zn
molar ratio and zinc precursor concentration were studied
to evaluate the growth of ZnO rods on kanthal coils and kanthal meshes. The Ag/ZnO
nanocomposites were prepared by photo-reduction method. The structure,
morphology, elemental composition, optical properties of ZnO and Ag/ZnO
nanocomposite were characterized by XRD, FESEM, EDX, XPS, RTPL, Raman
analyses. Both ZnO/coil and ZnO/mesh had the same optimum synthesis conditions
including heating 50 W, heating duration 8 min, Zn
2+
concentration 0.02 M, and OH
–
2+
:Zn
molar ratio 32:1. The average surface coverage, diameter, and areal density of
ZnO/meshes were 77.8 ± 9.2 %, 160.8 ± 11.4 nm, and 4.4 ± 1.3 rod/µm
2
, respectively.
The crystal growth rate of ZnO/coil and ZnO/mesh were 0.27 and 0.11 µm/min,
respectively. After Ag deposition, the degradation efficiency of RhB dye by ZnO/coil
and ZnO/mesh were enhanced to 70.5 ± 4.1 % and 92.4 ± 0.3 %, respectively. The Ag
deposition enhanced the photocatalytic performance of ZnO rods via electron trapping mechanism and plasmonic effect. Both
•
2-
O
and
•
OH radicals were the dominant
reactive species responsible for degradation of RhB dye. The Ag/ZnO/mesh
nanocomposite could be used to treat up to 12 ppm of RhB dye with maximum removal
capability of 0.37 mg dye for 150 min of reaction. In conclusion, DH method is feasible
for the immobilization of ZnO rods on kanthal mesh in a larger scale. The immobilized
Ag/ZnO nanocomposite showed a remarkable stability to degrade RhB dye under UV
irradiation, which could be used as wastewater treatment module in industry.