Cerium dioxide (CeO2, ceria) is becoming an ubiquitous constituent in catalytic systems for a variety of applications. 2016 sees the 40th anniversary since ceria was first employed by Ford Motor Company as an oxygen storage component in car converters, to become in the years since its inception an irreplaceable component in three-way catalysts (TWCs). Apart from this well-established use, ceria is looming as a catalyst component for a wide range of catalytic applications. For some of these, such as fuel cells, CeO2-based materials have almost reached the market stage, while for some other catalytic reactions, such as reforming processes, photocatalysis, water-gas shift reaction, thermochemical water splitting, and organic reactions, ceria is emerging as a unique material, holding great promise for future market breakthroughs. While much knowledge about the fundamental characteristics of CeO2-based materials has already been acquired, new characterization techniques and powerful theoretical methods are dee...

Fundamentals and Catalytic Applications of CeO2-Based Materials

Preparation of bismuth vanadate and cerium dioxide (BiVO4/CeO2) nanocomposites as visible-light photocatalysts was successfully obtained by coupling a homogeneous precipitation method with hydrothermal techniques. The BiVO4/CeO2 nanocomposites with different mole ratios were synthesized and characterized by X-ray diffraction (XRD), Raman spectroscopy, and transmission electron microscopy (TEM). Absorption range and band gap energy, which are responsible for the observed photocatalyst behavior, were investigated by UV–vis diffuse reflectance (UV–vis DR) spectroscopy. Photocatalytic activities of the prepared samples were examined by studying the degradation of model dyes Methylene Blue, Methyl Orange, and a mixture of Methylene Blue and Methyl Orange solutions under visible-light irradiation (>400 nm). Results clearly show that the BiVO4/CeO2 nanocomposite in a 0.6:0.4 mol ratio exhibited the highest photocatalytic activity in dye wastewater treatment.

BiVO(4)/CeO(2) nanocomposites with high visible-light-induced photocatalytic activity.

p–n junction Cu2O/BiVO4 heterogeneous nanostructures for enhancement of visible-light photocatalytic properties of BiVO4 nanocrystals have been successfully prepared through coupling a hydrothermal process with polyol strategy. The assembly of p-type Cu2O nanoparticles produces a large number of nano p–n junction heterostructures on the surface of the BiVO4 nanocrystals, where Cu2O and BiVO4 form p- and n-type semiconductors, respectively. The experimental results reveal that these p–n junction Cu2O/BiVO4 heterogeneous nanostructures exhibit much higher visible-light photocatalytic activities than the individual BiVO4 nanocrystals for the degradation of model dyes methylene blue and colorless organic phenol under visible light irradiation. The enhanced photocatalytic efficiencies are attributed to the charge transfer from n-type BiVO4 to the attached p-type Cu2O nanoparticles, which effectively reduces the recombination of electrons and holes, leading to the enhancement of the photocatalytic properties of the heterostructure nanostructures. These new p–n junction heteronanostructures are expected to show considerable potential applications in solar-driven wastewater treatment.

Preparation of p–n junction Cu2O/BiVO4 heterogeneous nanostructures with enhanced visible-light photocatalytic activity

A novel Ag3PO4/CeO2 composite was fabricated by in situ wrapping CeO2 nanoparticles with Ag3PO4 through a facile precipitation method. The photocatalytic properties of Ag3PO4/CeO2 were evaluated by the photocatalytic degradation of MB and phenol under visible light and UV light irradiation. The photocatalytic activity of the composite is much higher than that of pure Ag3PO4 or CeO2. The rate constant of MB degradation over Ag3PO4/CeO2 is more than 2 times and 20 times than those of pure Ag3PO4 and CeO2 under visible light irradiation, respectively. The Ag3PO4/CeO2 composite photocatalyst also shows higher photocatalytic activity for the colorless phenol degradation compared to pure Ag3PO4. Moreover, the Ag3PO4/CeO2 sample has almost no loss of photocatalytic activity after five recycles under the irradiation of visible light and UV light, indicating that the composite has good photocatalytic stability. The excellent photocatalytic activity of the Ag3PO4/CeO2 composite is closely related to the fast transfer and efficient separation of electron–hole pairs at the interfaces of the two semiconductors derived from the matching band positions between CeO2 and Ag3PO4. This newly constructed Ag3PO4/CeO2 composite, with promising and fascinating visible light-driven photocatalytic activity as well as good stability, could find potential applications in environmental purification and solar energy conversion.

Novel Ag3PO4/CeO2 composite with high efficiency and stability for photocatalytic applications

An over review on recently developed techniques, mechanisms and intermediate involved in the advanced azo dye degradation for industrial applications

CeO 2 –Bi 2 O 3 composite was synthesized via a two-stage process. The precursors were prepared from Ce(NO 3 ) 3 ·6H 2 O, Bi(NO 3 ) 3 ·5H 2 O and CO(NH 2 ) 2 with different molar ratio through the hydrothermal process, and then was completed by carrying out the precursors for 4 h at 600 °C under flowing air atmosphere. Techniques of X-ray diffraction (XRD), transmission electron microscopic (TEM) and diffuse reflectance ultraviolet–vis spectra (UV-DRS) were employed to characterize the as-synthesized materials. The results showed that the microstructure and morphology of CeO 2 –Bi 2 O 3 composite were similar in spite of different inverse proportion. We also investigated improved photocatalytic activity in the case of CeO 2 –Bi 2 O 3 composite catalyst compared to the catalytic activity of pure Bi 2 O 3 or CeO 2 powder. The suppression of charge recombination in the composite CeO 2 –Bi 2 O 3 catalyst led to higher catalytic activity for the degradation of RhB. The CeO 2 10%/Bi 2 O 3 photocatalyst exhibited maximum photocatalytic activity. The photocatalytic activity is in close relation with the inverse proportion between reactants.

Lingzhi Li

Papers

CeO2–Bi2O3 nanocomposite: Two step synthesis, microstructure and photocatalytic activity