Synthesis and characterization of bismuth ferrite-based ternary composites for photocatalytic degradation of Congo red under visible light

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dc.contributor.authorMhamad, Shakhawan Ahmad
dc.date.accessioned2023-07-18T07:36:23Z
dc.date.available2023-07-18T07:36:23Z
dc.date.issued2021
dc.descriptionThesis (PhD. (Chemistry))
dc.description.abstractBismuth ferrite (BFO) is a well acquainted and significant semiconductor photocatalyst due to its vast solar radiation response in the visible region (band gap = 2.2 eV) and high chemical stability. In this study, bismuth ferrite was prepared by modified sol-gel auto-combustion method. The influences of chelating agents and fuel to metal nitrates ratios on the physicochemical properties of the synthesized samples were examined using various characterization techniques such as X-ray diffraction (XRD), field emission scanning electronic microscopy (FESEM), ultraviolet-visible spectroscopy-near infrared spectroscopy (UV-Vis-NIR), Brunauer-Emmett-Teller (BET) analysis, Fourier transformed infrared spectroscopy (FTIR), and photoluminescence (PL). The BFO-CA sample prepared in the presence of citric acid chelating agent showed the lowest peak intensity, which means the lowest electron charge recombination as well as it has the highest purity compared to BFO-EDTA and BFO-AA. So, BFO-CA was used to study the effect of fuel to metal nitrates molar ratios. Similarly, the PL and XRD of the BFO1:1 prepared in the presence of equal ratios of citric acid to metal nitrates showed superior properties. Therefore, this sample was used to prepare bismuth ferrite based ternary nanocomposite and its catalytic activity was measured in congo red (CR) degradation. The pure BFO (BFO1:1) exhibited low photocatalytic performance of CR degradation (61% in 60 minutes), which is ascribed to the fast recombination of charge carriers, and the low surface area (1.627 m2/g). Therefore, this research was extended to prepare novel ternary BFO/ZnO/BiOCl (BZB) and BFO/SnO2/BiOCl (BSB) nanocomposite by a facile one-pot sol-gel auto combustion method to improve BFO surface area and reduce the electron charge recombination by adding different amount (5, 10, and 15 %) of ZnCl2.2H2O and SnCl4.5H2O to BFO precursor solution. Preliminary photocatalytic activity testing of the prepared composites showed that BZB15 sample had the maximum degrading efficiency of up to 100% after 60 minutes, which was greater than that of BSB15 (99.5%) and pure BFO (61%). This is owing to the low electron charge recombination rate and large specific surface area of the BZB15 (15.1 m2/g) and BSB15 (11.49 m2/g) due to the formation of the p-n-p heterojunction between BFO, ZnO, or SnO2 and BiOCl. The photodegradation process of CR over BZB15 was further studied using in-situ capture study, total organic carbon (TOC), and high performance liquid chromatography (HPLC) analyses. In-situ capture studies revealed that the photogenerated superoxide radicals (•O2-) and holes (h+) were primarily active species in the photocatalytic system for the degradation of CR using BZB15, while the hydroxyl radical (•OH) plays a secondary role in the reaction. Similarly, the TOC studies revealed a removal of 99.5 % after 90 minutes. Meanwhile, HPLC analysis also confirmed the degradation of CR by BZB15 sample. Finally, the electron transfer mechanism was discussed, and a p-n-p electron transfer mechanism is proposed for the BZB15 composite system. The findings of this study would assist the researcher in selecting chelating agents in the auto-combustion method for the processing of nanoparticles for particular applications and provide a technique to improve the photocatalytic activity of photocatalysts through the processing of ternary p-n-p nanocomposites by reducing electron charge recombination and increasing the surface area.
dc.description.sponsorshipFaculty of Science
dc.identifier.urihttp://openscience.utm.my/handle/123456789/461
dc.language.isoen
dc.publisherUniversiti Teknologi Malaysia
dc.subjectPhotocatalysis
dc.subjectPhotochemistry
dc.subjectSemiconductors
dc.titleSynthesis and characterization of bismuth ferrite-based ternary composites for photocatalytic degradation of Congo red under visible light
dc.typeThesis
dc.typeDataset
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Calibration curve for CR absorption at 497 nm under visible light.
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HPLC profile of CR dye (a) before treatment and (b) after treatment with BZB15 catalyst for 90 min under visible light irradiation.
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