The n-type TiO2 semiconductor nanoparticles were coated on the p-type Ag2O nanoparticles deposited on SiO2 spherical particles through a simple sol-gel method for catalytic reduction of 4-nitrophenol. The as-prepared spherical composite abbreviated as SiO2/Ag2O@TiO2 was characterized by different techniques and tested as a catalyst towards 4-nitrophenol (4-NP) reduction into 4-aminophenol (4-AP) with NaBH4 as a reducing agent at room temperature. This work combines an interesting design with the n-type TiO2 rich in electrons outward and the p-type Ag2O rich in electronic holes inward to form the p/n junction for the purpose of efficiently separating the charge carrier to have a longer lifetime of outward electrons for catalytic reduction reactions. The SiO2/Ag2O@TiO2 composite catalyst showed the best performance in the reduction of 4-NP to 4-AP within 30 seconds. Our results reveal that the p-n junction combined composite sphere was superior and efficient in reduction of 4-nitrophenol without using the light source. The conversion mechanism is proposed here. Overall, the SiO2/Ag2O@TiO2 composite can be used as a cost-effective reduction catalyst for converting the toxic 4-NP into useful 4-AP, an industrial organic intermediate compound.
CuO–ZnO nanocomposites (NCs) were synthesized
using an aqueous
extract of
Verbascum sinaiticum
Benth.
(GH) plant. X-ray diffraction (XRD), spectroscopic, and microscopic
methods were used to explore the crystallinity, optical properties,
morphology, and other features of the CuO–ZnO samples. Furthermore,
catalytic performances were investigated for methylene blue (MB) degradation
and 4-nitrophenol (4-NP) reduction. According to the results, CuO–ZnO
NCs with 20 wt % CuO showed enhanced photocatalytic activity against
MB dye with a 0.017 min
–1
rate constant compared
to 0.0027 min
–1
for ZnO nanoparticles (NPs). Similarly,
a ratio constant of 5.925 min
–1
g
–1
4-NP reductions was achieved with CuO–ZnO NCs. The results
signified enhanced performance of CuO–ZnO NCs relative to ZnO
NPs. The enhancement could be due to the synergy between ZnO and CuO,
resulting in improved absorption of visible light and reduced electron–hole
(e
–
/h
+
) recombination rate. In addition,
variations in the CuO content affected the performance of the CuO–ZnO
NCs. Thus, the CuO–ZnO NCs prepared using
V.
sinaiticum
Benth. extract could make the material
a desirable catalyst for the elimination of organic pollutants.
The synthesis approach of the catalyst is simple and facile. The NiO/NiS catalyst is effective and universal towards reduction. NiS facilitates electron transfer for reduction reactions.
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