The effect of sunlight induced surface defects on the photocatalytic activity of nanosized CeO 2 for the degradation of phenol and its derivatives (original) (raw)
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Journal of Rare Earths, 2018
CeO 2 nanoparticles (NPs) were synthesized in alkaline medium via the homogeneous precipitation method and were subsequently calcined at 80 °C/24h (assigned as CeO 2-80) and 500 °C/2 h (assigned as CeO 2-500). The as-prepared materials and the commercial ceria (assigned as CeO 2-com) were characterized using TGA-MS, XRD, SEM-EDX, UVvis DRS and IEP techniques. The photocatalytic performances of all obtained photocatalysts were assessed by the degradation of Congo red azo-dye (CR) under UVA-light irradiation at various environmental key factors (e.g., reaction time and calcination temperature). Results reveal that CeO 2 compounds crystalize with cubic phase. CeO 2-500 exhibits smaller crystallite size (9 nm vs 117 nm) than that of bare CeO 2-com. SEM analysis shows that the materials are spherical-like in shape NPs with strong assembly of CeO 2 NPs observed in the CeO 2-500 NPs. EDX analysis confirms the stoichiometry of CeO 2 NPs. UV-vis DRS measurement reveals that, CeO 2-500 NPs exhibits a red-shift of absorption band and a more narrow bandgap (2.6 eV vs 3.20 eV) than that of bare CeO 2-com. On the contrary, Urbach energy of Eu is found to be increased from 0.12 eV (CeO 2-com) to 0.17 eV (CeO 2-500), highlighting an increase of crystalline size and internal microstrain in the CeO 2-500 NPs sample. Zeta potential (IEP) of CeO 2-500 NPs is found to be 7.2. UVAlight-responsive photocatalytic activity is observed with CeO 2-500 NPs at a rate constant of 10 × 10-3 min-1 , which is four times higher than that of CeO 2-com (K app =2.4 × 10-3 min-1) for the degradation of CR. Pseudo-first-order kinetic model gives the best fit. On the basis of the energy band diagram positions, the enhanced photocatalytic performance of CeO 2-500 nano-catalyst can be ascribed to O 2 •− , • OH and R •+ as the primary oxidative species involved in the degradation of RC under UVA-light irradiation. Key word: CeO 2 NPs, Congo red, photocatalytic activity, Bandgap, Urbach energy of Eu, band theory.
Synthetic CeO 2 Nanoparticle Catalysis of Methylene Blue Photodegradation: Kinetics and Mechanism
CeO 2 nanocrystals were synthesized by a simple precipitation method and calcination at 600 °C. (NH 4) 2 Ce(NO 3) 6 and ammonia were used as precursors. The CeO 2 nanoparticles were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy, and N 2 adsorption. The photodegradation of methylene blue catalyzed by CeO 2 nanoparticles was studied under UV and sunlight irradiation. The highest degradation was obtained with 1.0 g/L CeO 2 at pH 11 within 125 min. The pseudo first order rate constants of dye bleaching were calculated as 16.2 × 10 −3 and 15.7 × 10 −3 min −1 under UV and sunlight irradiation, respectively. The effect of iso-PrOH, iodide ion, and H 2 O 2 was studied to predict the pathway of dye degradation. The obtained results indicate the effect of photogen-erated holes in the degradation mechanism of the dye. Also, the photocatalytic activity of the prepared photocatalyst was studied in the presence of several negative ions.
Undoped CeO2 and 0.50–5.00 mol% Fe-doped CeO2 nanoparticles were prepared by a homogeneous precipitation combined with homogeneous/impreganation method, and applied as photocatalyst films prepared by a doctor blade technique. The superior photocatalytic performances of the Fe-doped CeO2 films, compared with undoped CeO2 films, was ascribed mainly to a decrease in band gap energy and an increase in specific surface area of the material. The presence of Fe31 as found from XPS analysis, may act as electron acceptor and/or hole donor, facilitating longer lived charge carrier separation in Fe-doped CeO2 films as confirmed by photoluminescence spectroscopy. The 1.50 mol% Fe-doped CeO2 film was found to be the optimal iron doping concentration for MO degradation in this study.
Materials Science in Semiconductor Processing, 2019
TiO 2 is a semiconductor widely used in photocatalytic degradation of organic pollutants due to its band gap energy. However, its absorption range is restricted only to UV radiation that is less than 10% of solar light. With the aim of increasing the adsorption area on TiO 2 nanoparticles a modified sol-gel method was used to produce a smaller particle size, and to extend the absorption range to the visible spectrum, TiO 2 nanoparticles were synthesized with different CeO 2 contents to generate semiconductor heterojunction between them. The crystallographic, morphological, and optoelectronic characteristics of these TiO 2-CeO 2 nanoparticles were studied, and two crystalline phases were differentiated: anatase for TiO 2 and fluorite for CeO 2. An increase in the CeO 2 content produced crystallite sizes between 6.5 nm and 12.0 nm. TiO 2-CeO 2 nanoparticles showed morphological properties such as small particle size, heterogeneous surface and high BET surface area compared to bare commercial TiO 2. These features involve a positive effect of CeO 2 in TiO 2 nanoparticles surface, thus TiO 2-CeO 2 nanoparticles exhibit enhanced optoelectronic properties caused by a decrease in the effective band gap and redshift in the electromagnetic spectrum. In addition, methylene blue degradation showed that TiO 2-CeO 2 nanoparticles are suitable for high photocatalytic activity application under visible light.
Desalination and Water Treatment, 2021
In this study, CeO 2 /TiO 2 nanocomposites (NCs) were synthesized by adopting a straightforward two steps method comprising, first, the synthesis of CeO 2 and TiO 2 nanoparticles by wet chemical precipitation method and second, the heterostructure CeO 2 /TiO 2 NCs by solid-state reaction process. The CeO 2 /TiO 2 NCs were characterized by X-ray diffraction, N 2 adsorption-desorption isotherm analysis, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and UV-vis diffuse reflectance spectroscopy. Regardless of CeO 2 content, the bandgap energies of CeO 2 / TiO 2 NCs were lower than that of pure TiO 2. Photocatalytic activity of the synthesized photocatalysts was assessed by degrading a model dye methylene blue under the illumination of UV light. The CeO 2 /TiO 2 NCs containing 2 wt% CeO 2 exhibited higher photocatalytic degradation efficiency compared to reference TiO 2 (P25), pure TiO 2 , and CeO 2 /TiO 2 NCs containing CeO 2 other than 2 wt%. The alkaline environment was favorable for photocatalytic decomposition of cationic dye methylene blue (MB). The enhanced degradation efficiency of CeO 2 /TiO 2 NCs was substantiated in terms of vectorial charge separation and the reduction of photogenerated charge carriers owing to the band offsets existing at the interface between CeO 2 and TiO 2 NPs. Finally, no significant change in the degradation efficiency of CeO 2 /TiO 2 NCs after successive uses evidenced the stability and reusability of the photocatalysts. Therefore, it can be concluded that the synthesized CeO 2 /TiO 2 heterostructure photocatalyst would be a promising candidate for application in wastewater treatment.
Visible light induced degradation of methylene blue using CeO 2 /V 2 O 5 and CeO 2 /CuO catalysts
This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: http://www.elsevier.com/authorsrights In the present study, the nanocatalysts CeO 2 , V 2 O 5 , CuO, CeO 2 /V 2 O 5 and CeO 2 /CuO were synthesized by thermal decomposition method. This method is simple, fast and cost effective compared with other preparation methods. The synthesized catalysts were characterized by different techniques. The XRD and XPS results confirmed the structure and the oxidization states of the nanocomposite materials. DRS results suggested that the prepared CeO 2 /V 2 O 5 and CeO 2 /CuO nanocomposites can generate more electrons and holes under visible light irradiation. The photocatalytic activities of prepared catalysts were evaluated using the degradation of aqueous methylene blue solution as a model compound under visible light irradiation. In addition, the nanocomposite (CeO 2 /V 2 O 5 and CeO 2 /CuO) materials were employed to degrade the textile effluent under visible light condition.
Photocatalytic activity of biosynthesized CeO2 nano particles
SN Applied Sciences
This paper focuses on a cost effective and environment friendly technique for green synthesis of cerium oxide (CeO 2) nano particles from cerium (III) nitrate hexahydrate solution by co-precipitation method using the leaf extract of different species of Artemisia pallens which acts as reducing and capping agent. The prepared CeO 2 nano particles were characterized by XRD, TEM, FTIR, UV-Vis spectroscopy. The Photocatalytic activity of the prepared ceria powders was determined by their ability to degrade Methylene blue solution under UV-light radiation. The photo degradation result observed with 10 mg/L ceria at pH = 11 for 180 min have highest output and pseudo 1st order rate constant was 0.983.
Materials Chemistry and Physics, 2017
CeO 2 nanoparticles have been prepared by gel combustion method. The as-prepared nanoparticles were calcined at 500, 550 and 600 C. The crystallite size of the nanoparticles has been determined using X-ray diffraction. Catalytic activity has been studied by measuring the Tafel slope in oxygen reduction reaction in cyclic voltammetery. The nanoparticles samples showed higher catalytic activity than bulk ceria sample. Surprisingly, smaller size nanoparticles with large surface area showed less catalytic activity than larger size nanoparticles. Positron annihilation, X-ray photo electron spectroscopy and photoluminescence studies indicated the presence of oxygen vacancies as well as larger surface defects. It has been found that surface defect concentration increased with the increase in calcination temperature and the catalytic activity of the nanoparticles is directly correlated to the surface defect concentrations.
Materials Science and Engineering C
journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues. Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. In most cases authors are permitted to post their version of the article (e.g. in Word or Tex form) to their personal website or institutional repository. Authors requiring further information regarding Elsevier's archiving and manuscript policies are encouraged to visit: In the present study, the nanocatalysts CeO 2 , V 2 O 5 , CuO, CeO 2 /V 2 O 5 and CeO 2 /CuO were synthesized by thermal decomposition method. This method is simple, fast and cost effective compared with other preparation methods. The synthesized catalysts were characterized by different techniques. The XRD and XPS results confirmed the stru...
Coatings
Removal of hazardous organic dyes from polluted water bodies requires the introduction of strong adsorbents and photocatalysts to industrial wastewaters. Herein, photocatalytic CeO2 nanoparticles and CeO2/CuO nanocomposite were synthesized following a co-precipitation method for low cost elution of methylene blue (MB) from water. The crystallinity and surface structure of the as-prepared materials have been analyzed using characterization techniques including X-ray powder diffraction (XRPD), field emission scanning electron microscopy (FE-SEM), energy-dispersive spectroscopy (EDS), ultra-violet visible spectroscopy (UV–Vis), and Fourier-transform infrared spectroscopy (FTIR). The average particle size of both the nano scaled samples were approximately 20–30 nm. The photocatalytic properties of CeO2/CuO were investigated under visible light against methylene blue (MB). The results showed 91% photodegradation of MB organic pollutant in 3 h as monitored by UV–Vis spectroscopy. Absorban...