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Synthesis of novel ZnO/carbon xerogel composites: Effect of carbon content and calcination temperature on their structural and photocatalytic properties
摘要： This paper reports the development of new ZnO/carbon xerogel composites (XZn w) for photocatalytic applications. The use of black wattle tannin as a precursor to the carbon xerogel aimed at reducing costs and environmental impacts. The composites were characterized by di?use re?ectance spectroscopy (DRS), BET surface area, scanning electron microscopy (FEG-SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS), infrared spectroscopy (IR), and X-ray di?raction (XRD). The photocatalytic performance of the materials was evaluated in the decomposition process of methylene blue, a known toxic pollutant. The impacts of the catalyst dosage and calcination temperature on the photocatalytic process were also examined systematically. The X-ray pro?les of the XZn w evidenced the existence of the hexagonal structure of the zinc oxide (wurtzite) in the composites. The XPS and XRD analyses con?rmed the incorporation of carbon in the zinc oxide crystalline structure. The higher carbon content resulted in a larger surface area. All composites presented the ability to absorb radiation in less energetic wavelengths, contrary to pure zinc oxide that only absorbs radiation of wavelengths below 420 nm. The optimal dosage and calcination temperature were found to be 0.2 g L?1 and 300 °C. All the developed composites displayed signi?cant photocatalytic activities in the decomposition of methylene blue under both visible and solar light. The composites had superior photocatalytic e?ciency under visible light when compared to pure zinc oxide. The XZn 0.5 presented the best degradation e?ciency under visible radiation. All materials presented similar photocatalytic responses under solar light, evidencing the synergy between the carbon xerogel and the zinc oxide. The photocatalytic mechanism was evaluated by trapping experiments to be mainly controlled by the electron vacancies that are generated during the photoexcitation of the composites.
关键词： Zinc oxide,Methylene blue,Carbon xerogel,Tannin,Photocatalysis
更新于2025-09-10 09:29:36
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Novel and inexpensive Nb2O5/tannin-formaldehyde xerogel composites as substitutes for titanium dioxide in photocatalytic processes
摘要： This project studied the preparation of new Nb2O5/tannin-formaldehyde xerogel composites (XTF-wNb) for photocatalytical applications. The choice of tannin biomass and niobium recycled scraps as precursors is aimed at reducing costs and environmental impacts. The composites were characterized by diffuse re?ectance spectroscopy (DR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), infrared spectroscopy (IR), and X-ray diffraction (XRD). The photocatalytic properties of the composites were evaluated by methylene blue decomposition. The in?uence of the catalyst dosage and the initial concentration of dye in the adsorption and photocatalysis processes were studied. The X-ray pro?les of the XTF-wNb show the presence of niobic acid in the structure of the materials, proving the presence of the inorganic oxide in the matrix of these composites. The tannin/Nb ratio had a signi?cant in?uence on the morphology of the formed composites, causing changes in the shape and size of the particles composing each material. All materials have pHPZC < 5. The XTF-24Nb was the most effective photocatalyst, its photocatalytic ef?ciency superior to the one of titanium dioxide, evidencing the bene?cial effect of the xerogel coupling on the photocatalytic properties of the material.
关键词： Photocatalysis,Niobium oxide,Xerogel,Tannin
更新于2025-09-04 15:30:14