Photocatalytic Activity Of CeO2 Research Articles

Influence of production method on the structure and photocatalytic activity of CeO<sub>2</sub>/Au nanocomposite

Two methods for preparing mesoporous CeO2/Au nanocomposites were compared: template synthesis and photochemical modification of fibrous cerium(IV) oxide with gold nanoparticles. The composition, structure, morphology of the obtained nanocomposites, as well as the specific surface area and pore size distribution were studied by a complex of physicochemical methods: X-ray phase analysis, X-ray spectral microanalysis, scanning electron microscopy, low-temperature nitrogen adsorption, and electron spectroscopy. The catalytic properties of the obtained nanocomposites were studied in methyl orange photodegradation reactions. It is shown that the CeO2/Au catalyst obtained by the photochemical modification method has the highest photocatalytic activity both under the action of UV and visible light.

The Relationship between Photoluminescence Emissions and Photocatalytic Activity of CeO2 Nanocrystals.

In this work, we focus on understanding the morphology and photocatalytic properties of CeO2 nanocrystals (NCs) synthesized via a microwave-assisted solvothermal method using acetone and ethanol as solvents. Wulff constructions reveal a complete map of available morphologies and a theoretical-experimental match with octahedral nanoparticles obtained through synthesis using ethanol as solvent. NCs synthesized in acetone show a greater contribution of emission peaks in the blue region (∼450 nm), which may be associated with higher Ce3+ concentration, originating shallow-level defects within the CeO2 lattice while for the samples synthesized in ethanol a strong orange-red emission (∼595 nm) suggests that oxygen vacancies may originate from deep-level defects within the optical bandgap region. The superior photocatalytic response of CeO2 synthesized in acetone compared to that of CeO2 synthesized in ethanol may be associated with an increase in long-/short-range disorder within the CeO2 structure, causing the Egap value to decrease, facilitating light absorption. Furthermore, surface (100) stabilization in samples synthesized in ethanol may be related to low photocatalytic activity. Photocatalytic degradation was facilitated by the generation of ·OH and ·O2- radicals as corroborated by the trapping experiment. The mechanism of enhanced photocatalytic activity has been proposed suggesting that samples synthesized in acetone tend to have lower e'─h· pair recombination, which is reflected in their higher photocatalytic response.

Effect of Pr, Fe, C Codoping on the Photocatalytic Activity of Ceo2

Effect of Pr, Fe, C Codoping on the Photocatalytic Activity of Ceo2

Plasma induced liquid-phase synthesis of Ce/Mo metal oxides as photocatalysts

Ce/Mo metal oxides were synthesized by plasma induced liquid-phase method and applied for photocatalysis. Compared with the traditional co-precipitation method and hydrothermal method, the Ce/Mo metal oxides prepared with plasma-assisted method had excellent UV-light photocatalytic properties. Ce/Mo metal oxides synthesized with plasma possessed regular micromorphology, good crystallinity, as well as oxygen vacancy, which were beneficial to photocatalytic performance. Compared with the photocatalytic activity of CeO2 and MoO2 alone, the photocatalytic activity enhancement of the Ce/Mo metal oxides could be ascribed to the efficient separation of the photogenerated electron-hole pairs. The degradation rate of 1000 mL (50 mg/L) methyl orange (MO) could reach 98% within 6 min under UV-light radiation. The reaction mechanism of the photocatalytic reaction process was deduced mainly as the coordinated oxidation process of superoxide radicals(O2−) and hydroxyl radicals(OH). The reusability experiments proved that Ce/Mo metal oxides exhibited prominent stability and repeatability. Ce/Mo metal oxides exhibited excellent photocatalytic performance for different dyes, and had potential application prospect in dye wastewater treatment.

Enhanced visible-light-driven photocatalytic degradation of acetaminophen over CeO2/I, K-codoped C3N4 heterojunction with tunable properties in simulated water matrix

• CeO 2 /IK-C 3 N 4 photocatalyst was synthesized for acetaminophen (ACT) photodegradation. • CeO 2 /IK-C 3 N 4 photocatalysts removed 98% ACT under visible light irradiation. • The photoactivity of CeO 2 /IK-C 3 N 4 is a function of pH, anions, CeO 2 amount and ACT concentration. • Active radicals including O 2 − and h + were identified and a type-II heterojunction mechanism was proposed. • CeO 2 /IK-C 3 N 4 showed excellent photocatalytic activity over ACT removal in three consecutive cycles. A novel visible-light-active photocatalyst consisting of CeO 2 nanoparticles and I, K-codoped graphitic carbon nitride (IK-C 3 N 4 ) was engineered using urea, potassium iodate and cerium nitrate as raw materials via a facile pyrolysis method. The CeO 2 /IK-C 3 N 4 composite was then applied for the rapid elimination of acetaminophen (ACT) under 465-nm visible light irradiation in aqueous solutions at different environmental parameters. The electronic images clearly showed that 5 – 20 nm CeO 2 can be tightly attached onto IK-C 3 N 4 . The charge imbalance of Ce element as well as oxygen vacancy of CeO 2 /IK-C 3 N 4 enhanced the photocatalytic activity of the composite. Moreover, the optical property and bandgap were easily tuned by changing the CeO 2 amounts. At optimum composition of 15 wt% CeO 2 , the bandgap of CeO 2 /IK-C 3 N 4 can narrow down to 2.38 eV. The photocatalytic activity of CeO 2 /IK-C 3 N 4 heterojunction toward ACT degradation is dependent on CeO 2 amounts and environmental parameters including pH, anions and initial ACT concentration. The calculated pseudo-first-order rate constants ranged from 0.039 to 0.051 min −1 . The radical species trapping experiments confirmed that O 2 − and h + play significant roles in ACT degradation. Thus, enhanced photodegradation of ACT is explained by type-II heterojunction mechanism. These findings provide a promising strategy of combining CeO 2 and doped g-C 3 N 4 for the effective removal of emerging pollutants under visible light irradiation, which can open a new route to synthesize novel heterojunction with high photoactivity for water purification and environmental sustainability.

Tuning the structural properties of CeO2 by Pr and Fe codoping for enhanced visible‐light catalytic activity

AbstractBACKGROUNDIron (Fe)3+ has much a smaller ion radius than cerium (Ce)4+ but praseodymium (Pr) ions have a similar radius to Ce ions with the same valence. Hence, it is interesting to tune the structural properties, including lattice deformation, band gap and oxygen vacancy (Ov), of CeO2 by Pr and Fe codoping for enhanced visible‐light catalytic activity.RESULTSA series of Ce1‐x‐yPrxFeyO2‐σ (x = 0∼0.012, y = 0.003∼0.031) nanoparticles were prepared by a simple one‐step sol‐gel method. The structural properties of CeO2, including crystal deformation (cell lattice from 5.4069 to 5.4195), band gap (from 2.20 to 2.93), oxygen vacancies (Ov from 0.15% to 9.03%), and peroxide species (O22− from 0.37% to 1.09%) can be finely tuned by Pr and Fe codoping. Among ten samples, Ce0.982Pr0.003Fe0.015O2‐σ with proper structural properties showed the highest photocatalytic activity towards the degradation of acid orange 7. The first reaction rate constant reaches 0.0687 min−1, 9.3 and 7.7 times that of Ce0.994Pr0.006O2‐σ and Ce0.985Fe0.015O2‐σ, respectively. The mechanism was found to involve ·OH, ·O2− and photogenerated holes.CONCLUSIONThe structural properties of CeO2 can be finely and easily tuned by Pr and Fe codoping. Thus, the photocatalytic activity of CeO2 under visible light irradiation was boosted. © 2019 Society of Chemical Industry

Effects of the Atmosphere in a Hydrothermal Process on the Morphology and Photocatalytic Activity of Cerium Oxide

AbstractThe hydrothermal method is widely applied in nanomaterials synthesis, and most of the influencing factors have already been taken into account. However, the effect of atmosphere in solution on the performance of nanomaterials has been underestimated for a long time. In this article, reaction solvents were saturated with three classical gases (argon, oxygen, and carbon dioxide), and then heated at 180 °C for 24 h to obtain the cerium dioxide (CeO2) nanoparticles. The properties of the three types of CeO2 are significantly different from that of the normal CeO2 (without gas saturation). The morphologies of the prepared CeO2 particles are different, even appear the hollow structure in CeO2−CO2 (synthesized in CO2 saturated condition). The more absorbing and meaningful thing is that the photocatalytic activity of CeO2−CO2 has been greatly improved. The concordance of the CO2 atmosphere (acid gas) and CeO2 (owning substantial content of basic sites) is the key point for the excellent photocatalytic performance.

Synthesis of CeO2/Ag/Ho nanostructures in order to improve photo catalytic activity of CeO2 under visible light

In one sun (Air mass 1.5), the amount of light that reaches earth’s surface is around 45% of visible and 3–5% of the UV. Therefore it is important to prepare visible driven photo-catalyst. CeO2 is highly potential photo-catalyst that its wide band gap limits its application in visible light. Here, its photo-catalytic activity was improved from 10 to 20% for methyl orange and Rhodamin B to 72 and 83%, respectively under visible light. In addition effect of different parameters such as surfactant and precipitating agent on the morphology of products were investigated.

Effect of hydrothermal conditions on microstructures of pure and doped CeO2 nanoparticles and their photo-catalytic activity: degradation mechanism and pathway of methylene blue dye

CeO2, Sm and Gd doped CeO2 were synthesized using the hydrothermal route. The influence of synthesis conditions on the crystal structure, particle size and microstructure was investigated. The prepared nanoparticles were characterized using X-ray powder diffraction, FT-Raman spectroscopy, transmission electron microscopy and scanning electron microscopy. The photo-catalytic degradation of methylene blue was examined under UV light using the prepared nanoparticles at different conditions (pH, dye concentration, catalyst dosage). The photo-catalytic activity of CeO2 was kinetically enhanced by trivalent cations (Gd+3 and Sm+3) doping. The results displayed the excellent catalytic activity of the Gd doped CeO2 as compared to that Sm doped CeO2 and the undoped one. The degradation pathways of MB were followed using liquid chromatography/mass spectroscopy (LC/MS), it was found that MB was degraded completely into safe byproducts. The total organic carbon content measurements confirmed the results obtained by LC/MS.

Microwave synthesis of pure and doped cerium (IV) oxide (CeO2) nanoparticles for methylene blue degradation.

Cerium (IV) oxide (CeO2), samarium (Sm) and gadolinium (Gd) doped CeO2 nanoparticles were prepared using microwave technique. The effect of microwave irradiation time, microwave power and pH of the starting solution on the structure and crystallite size were investigated. The prepared nanoparticles were characterized using X-ray diffraction, FT-Raman spectroscopy, and transmission electron microscope. The photocatalytic activity of the as-prepared CeO2, Sm and Gd doped CeO2 toward degradation of methylene blue (MB) dye was investigated under UV light irradiation. The effect of pH, the amount of catalyst and the dye concentration on the degradation extent were studied. The photocatalytic activity of CeO2 was kinetically enhanced by trivalent cation (Gd and Sm) doping. The results revealed that Gd doped CeO2 nanoparticles exhibit the best catalytic degradation activity on MB under UV irradiation. For clarifying the environmental safety of the by products produced from the degradation process, the pathways of MB degradation were followed using liquid chromatography/mass spectroscopy (LC/MS). The total organic carbon content measurements confirmed the results obtained by LC/MS. Compared to the same nanoparticles prepared by another method, it was found that Gd doped CeO2 prepared by hydrothermal process was able to mineralize MB dye completely under UV light irradiation.

UV-Light Absorption and Photocatalytic Properties of Zn-Doped CeO<sub>2</sub> Nanopowders Prepared by Ultrasound Irradiation

Ceria (CeO2) nanopowders doped with various Zinc (Zn) compositions were synthesized from solution by irradiating ultrasound waves. Ultrasound waves were irradiated to aqueous/isopropanol solution of cerium nitrate and zinc nitrate mixtures. Aqueous solution of ammonium hydroxide was droped into that solution until pH becomes 10. Dried precipitates were calcinated at 100°C to form CeO2 nanopowders. X-ray Diffraction (XRD) analysis shows the CeO2 nanopowder possess fluorite cubic structure. Ultrasound irradiation resulted in nanometric powder of CeO2 with spherical in shape. The addition of Zn into CeO2 reduces the particle size and shows strong absorbance in the ultra–violet (UV) region. Moreover, the addition of 20 mol% Zn is inhibiting photocatalytic activity of CeO2 under sunlight irradiation. These results suggest that Zn-doped CeO2 is more promising for UV radiation protection with no presence photocatalytic activity.

Enhanced photocatalytic activity of CeO2 using β-cyclodextrin on visible light assisted decoloration of methylene blue

An attempt has been made to enhance the photocatalytic activity of CeO(2) for visible light assisted decoloration of methylene blue (MB) dye in aqueous solutions by β-cyclodextrin (β-CD). The inclusion complexation patterns between host and guest (i.e., β-CD and MB) have been confirmed with UV-visible spectral data. The interaction between CeO(2) and β-CD has also been characterized by field emission scanning electron microscopy analysis. The photocatalytic activity of the catalyst under visible light was investigated by measuring the photodegradation of MB in aqueous solution. The effects of key operational parameters such as initial dye concentration, initial pH, CeO(2) concentration as well as illumination time on the decolorization extents were investigated. Among the processing parameters, the pH of the reaction solution played an important role in tuning the photocatalytic activity of CeO(2). The maximum photodecoloration rate was achieved at basic pH (pH 11). Under the optimum operational conditions, approximately 99.6% dye removal was achieved within 120 min. The observed results indicate that the decolorization of the MB followed a pseudo-first order kinetics.

CeO2 mediated photocatalytic degradation studies of C.I. acid orange 7

CeO2 nanoparticles were prepared by a simple precipitation method, followed by calcination treatment. By selecting photocatalytic degradation of acid orange 7 (AO7) as a probe reaction, the influences of calcination temperature of catalyst, the concentration of AO7, initial pH value of AO7 solution and catalyst dosage on the photocatalytic activity of CeO2 were studied. It was found that CeO2 calcined at 550°C shows the highest photocatalytic activity under visible light irradiation. It was revealed that under visible light irradiation the degradation of AO7 over CeO2 nanoparticles follows a dye self-sensitization mechanism. The degradation rate of AO7 increases with decrease in the initial pH value of the reaction solution, and degradation efficiency decreases with increase in the initial dye concentration. The optimal dosage of CeO2 in solution for AO7 degradation is 1 g/L.

Role of ZnO-CeO2 Nanostructures as a Photo-catalyst and Chemi-sensor

ZnO-CeO 2 nanostructures were synthesized by simple and efficient low temperature method. The structure and morphology of the ZnO-CeO 2 nanostructures were characterized by X-ray powder diffraction (XRD) and field emission scanning electron microscopy (FESEM), which revealed elongated shaped CeO 2 nanoparticles with diameters of 40–90 nm distributed on the surface of elongated ZnO nanostructures with diameters of 50–200 nm (edge-centre). Further the structure of the synthesized ZnO-CeO 2 nanostructure was supported by Raman spectra and Fourier transform infrared spectroscopy (FTIR). UV-vis absorption spectrum was used to confirm the optical properties of the CeO 2 doped ZnO nanostructures. Photo-catalytic activity of CeO 2 doped ZnO nanostructure was evaluated by degradation of acridine orange and methylene blue which degraded 84.55% and 48.65% in 170 min, respectively. ZnO-CeO 2 nanostructures also showed good sensitivity (0.8331 μA·cm −2 ·(mol/l) −1 ) in short response time (10 s) by applying to chemical sensing using ethanol as a target compound by I – V technique. These degradation and chemical sensing properties of ZnO-CeO 2 nanostructures are of great importance for the application of ZnO-CeO 2 system as a photo-catalyst and chemical sensor.

Preparation and photocatalytic activity of CeO 2/TiO 2 interface composite film

The CeO 2/TiO 2 and TiO 2/CeO 2 interface composite films were prepared on glass substrates by the sol–gel process via dip-coating and calcining technique. The scanning electron microscopy (SEM) revealed that the TiO 2 layer has a compact and uniformity glasslike surface with 200 nm in thickness, and the CeO 2 layer has a coarse surface with 240 nm in thickness. The X-ray diffractometer (XRD) analysis showed that the TiO 2 layer is made up of anatase phase, and the CeO 2 layer is structured by cubic fluorite phase. Through a series of photo-degradation experiments, the relationship of the photocatalytic activity with the constituents of the films was studied. In virtue of the efficient interfacial charge separation via the process of electron transfer from TiO 2 to CeO 2, the photocatalytic activity of the CeO 2/TiO 2 composite film is high. Contrarily, the photocatalytic activity of the TiO 2/CeO 2 composite film is low, due to its inert surface made up of CeO 2 with broad bandwidth. Apart from the effect of the film structure, the effect of film thickness on photocatalytic activity was also discussed.

Preparation, characterization and photocatalytic activity of CeO 2 nanocrystalline using ammonium bicarbonate as precipitant

CeO 2 nanocrystalline was obtained as a final decomposition product of hydrated cerium carbonate formed by using ammonium bicarbonate as precipitant. The decomposition course of hydrated cerium carbonate and the formation process of CeO 2 were studied by TG and XRD. Moreover, the effect of the dispersant on the dispersity of the CeO 2 powder was studied by SEM. The results show that hydrated cerium carbonate completely decomposes to CeO 2 at 300 °C for 2 h, and the crystallinity increases with increasing calcination temperature. The dispersity of the CeO 2 powder can be improved by the dispersant. For the first time, CeO 2 nanocrystalline was utilized as a photocatalyst for the photocatalytic degradation and decolorization of the dye Acidic Black 10B. The decolorizing rate can reach about 97% under appropriate conditions. Therefore, CeO 2 nanocrystalline possesses photocatalytic activity, and shows promising in dye wastewater treatment.

The Structure and Photocatalytic Activity of CeO<sub>2</sub> Doped TiO<sub>2</sub> Films Deposited onto Glass by Magnetron Sputtering

The Structure and Photocatalytic Activity of CeO<sub>2</sub> Doped TiO<sub>2</sub> Films Deposited onto Glass by Magnetron Sputtering