CeO2 Nanosheets Research Articles

Bismuth single atom supported CeO2 nanosheets for oxidation resistant photothermal reverse water gas shift reaction

Bi single atoms supported on CeO2 nanosheets combined with a Ti2O3 based photothermal device showed oxidation resistance and outperforming weak solar driven RWGS with a CO production rate of 31.00 mmol g−1 h−1 under 3 sun units of irradiation.

Robust Photoelectrochemical Route for the Ambient Fixation of Dinitrogen into Ammonia over a Nanojunction Assembled from Ceria and an Iron Boride/Phosphide Cocatalyst.

The nitrogen reduction reaction is of great scientific significance as a hydrogen fuel carrier as well as a source of value-added products; in context to this, photoelectrochemical (PEC) nitrogen fixation emerges as an effective and environmentally benign strategy to meet the need. Hence, the current work reports an effective catalytic system containing a low-cost iron boride-based cocatalyst onto the CeO2 nanosheet matrix for photoelectrochemical nitrogen reduction reaction. The harmonized electronic property and the ensemble effect of phosphorus and boron in FeB/P with unsaturated metal sites make it a site-selective cocatalyst for nitrogen adsorption and its polarization. Furthermore, the low Fermi level of iron borophosphide enhances the trapping of photogenerated electrons from CeO2 and productively provides it to the adsorbed nitrogen species. The observed peculiar photocurrent behavior confirms the interaction of photogenerated electrons with adsorbed nitrogen species and its subsequent reduction by the surrounding protonic environment. The optimized CeO2-FeB/P photoelectrocatalyst exhibited an excellent NH3 yield velocity, i.e., 9.54 μg/h/cm2 at -0.12 V vs RHE with a solar-to-chemical conversion efficiency of 0.046% under ambient conditions. The same catalyst is also very active under near-zero biasing conditions and possesses impressive durability even after multiple uses. This work might strategically direct a promising way for the exploration of new photoelectrocatalytic systems for effective PEC-nitrogen reduction reaction.

One-pot synthesis of plate-like CeO2 nanosheets for sensing NH3 gas at room temperature

Plate-like CeO2 nanosheets were fabricated through a one-pot polyvinylpyrrolidone-assisted polyol process using the cerium–glycolate complex as the precursor at a low reaction temperature, followed by calcination. The morphology, phase composition, crystalline structure, specific surface area, and pore size distributions of plate-like CeO2 nanosheets were analyzed by scanning electron microscopy coupled with energy-dispersive X-ray elemental mapping, X-ray diffractometry, and N2 adsorption–desorption testing. The formation process of plate-like CeO2 nanosheets was discussed in detail. The mesoporous structure of plate-like CeO2 nanosheets synthesized at 50 °C resulted in larger specific surface area of 99.77 m2/g and more pore size of 20 Å than those of were synthesized at 190 °C, which was beneficial to the absorption of NH3 gas. The NH3 gas sensor that was fabricated using the plate-like CeO2 nanosheets synthesized at 50 °C showed a high response (11.8%) even at a low concentration of NH3 of 0.1 ppm, a low detection limit (50 ppb) and good linearity (R2 = 0.9279) over the range of 0.1–100 ppm of NH3 gas at room temperature.

Construction of Z–scheme 1D CdS nanorods/2D ultrathin CeO2 nanosheets toward enhanced photodegradation and hydrogen evolution

The synthesis of semiconductor-based photocatalytic materials has been developed rapidly because of the wide application potential in solving environmental pollution and energy crises. In this study, a noval Z–scheme heterojunction by in situ assembly of two-dimensional (2D) ceria nanosheets and one-dimensional (1D) cadmium sulfide nanorods (CdS/CeO2) was constructed and employed for effective photocatalytic degradation of contaminant and hydrogen production under irradiation. The morphologies and physicochemical properties of as-synthesized nanostructures were analyzed by a series of characterizations. The optimized CdS/CeO2 showed more superior degradation efficiency of tetracycline than the most CdS-based materials as reported, and exhibited about 1.8 folds higher hydrogen evolution efficiency than pristine CdS. A direct Z–scheme charge transfer mechanism was proposed by combining radicals trapping experiments and electron paramagnetic resonance spectra, which accelerated the efficient transport of photo-induced charge carriers. The present work demonstrates that CdS/CeO2 nanomaterial with high photocatalytic performance has a promising application in the environmental treatment and green energy production.

Metal-organic framework-derived CeO2 nanosheets confining ultrasmall Pd nanoclusters catalysts with high catalytic activity

An in-situ assembly method was successfully constructed to encapsulate Pd clusters within CeMOF matrix. This method involved the protection of nanoclusters with PVP and the assembly of CeMOF around Pd nanoclusters under mild condition. The small size and high dispersion resulting from physical confinement effect were inherited in the derivates as CeO2 nanosheets confining Pd nanoclusters catalysts. The relative position of Pd and Ce was regulated via varying pyrolysis parameter, which determined the confinement state of Pd clusters. A critical state was found where Pd clusters were maintained at high dispersion and possessed unlimited accessibility for CO. The specific confining structure and low surface concentration depressed the oxygen supply, resulting in the formation of substoichiometric PdOx, which interacted with CeO2 and formed Pd–Ce–O(s) clusters. With the improved dispersion and high content of Pd–Ce–O(s) clusters, the catalyst converted 100% CO at 63 °C with a Pd loading of 1.07%. The reaction followed Mars-van Krevelen mechanism, in which CO adsorbed on Pd–Ce–O(s) clusters and reacted with the highly active oxygen species.

Facile tree leaf-templated synthesis of mesoporous CeO2 nanosheets for enhanced sensing detection of p-xylene vapors

The fabrication of nano-structured 2D metal oxide materials using simple, low-cost, pollution-free and general method has been still challenging. Herein, mesoporous CeO2 nanosheets were prepared by simple cerium nitrate impregnation and calcination using tree leaves as template. Meanwhile, the influence of calcination temperature on microstructure and gas-sensing properties was also investigated. The CeO2-550 nanosheets calcinated at 550 °C are assembled by cross-linking nanoparticles with small size, which possess homogeneously mesoporous distribution, relatively large surface area and oxygen vacancies originated from Ce3+ ions, as well as the synergism of surface coordination unsaturated lattice oxygen and imprinting effect from bio-template. The CeO2-550 sensor exhibits high response (S = 16.5) and selectivity towards 100 ppm p-xylene vapors at 170 °C, and also presents low detection limit of 1 ppm, which are all significantly better than those of reported CeO2-based sensors. Therefore, mesoporous CeO2-550 nanosheets could be utilized as candidate for detecting trace p-xylene vapors.

Electron structure and reaction pathway regulation on porous cobalt-doped CeO2/graphene aerogel: A free-standing cathode for flexible and advanced Li-CO2 batteries

Li-CO2 batteries present considerable prospects both in resourcing CO2 and remedying the unsatisfied performance of current energy storage devices. Herein, a porous self-supporting cathode for Li-CO2 battery is fabricated through straightforward anchoring of two-dimensional (2D) cobalt-doped CeO2 nanosheets on graphene aerogel, bypassing the addition of binder and the complicated manufacturing process. The combination of CeO2 and Co3O4 results in the reorganization of electronic structure by strongly coupled nanointerfaces, enhancing the reversible formation and decomposition of Li2CO3. Meanwhile, the unique porous structure facilitates the diffusion of CO2 and electrolyte in Li-CO2 batteries. The as-assembled Li-CO2 battery achieves a superior discharge capacity (7860 mAh/g) and competitive cycling stability (>100 cycles). In particular, a flexible Li-CO2 battery is developed with the freestanding cathode, which can provide a stable power output during multi-angle bending and folding. The improved conductivity, CO2 adsorption ability and the electrochemical reaction pathway are revealed by density functional theory (DFT) calculations in detail. This work sheds new light on the development of advanced and flexible Li-CO2 batteries for wearable electronics.

Engineering surface oxygen vacancy of mesoporous CeO2 nanosheets assembled microspheres for boosting solar-driven photocatalytic performance

Surface oxygen vacancy defects of mesoporous CeO2 nanosheets assembled microspheres (D-CeO2) are engineered by polymer precipitation, hydrothermal and surface hydrogenation strategies. The resultant D-CeO2 with a main pore diameter of 9.3 nm has a large specific surface area (~102.3 m2/g) and high thermal stability. The mesoporous nanosheets assembled microsphere structure prevents the nanosheets from aggregation, which is beneficial to effective mass transfer and shortens the migration distance of charge carriers. After surface hydrogenation, the photoresponse extends to long wavelength region, combing with the band gap from 2.63 eV reduced to 2.39 eV. Under AM 1.5 G radiation, the photocatalytic degradation rate of tetracycline (TC) can be up to 99.99%, which is three times as high as that of pristine CeO2 microspheres. The excellent solar-driven photocatalytic performance can be attributed to the efficient surface oxygen vacancy engineering and the mesoporous nanosheets assembled microsphere structure, which narrows the band gap, shortens the migration distance of carriers, promotes the spatial separation of photogenerated electron-hole pairs and favors mass transfer. The strategy provides new insights for fabricating other high-efficient oxide photocatalysts .

Defect engineering for high-selection-performance of NO reduction to NH3 over CeO2 (111) surface: A DFT study

To reduce the greenhouse effect caused by the surgery of nitrogen-oxides concentration in the atmosphere and develop a future energy carrier of renewables, it is very critical to develop more efficient, controllable, and highly sensitive catalytic materials. In our work, we proposed that nitric oxide (NO), as a supplement to N2 for the synthesis of ammonia, which is equipped with a lower barrier. And the study highlighted the potential of CeO2 (111) nanosheets with La doping and oxygen vacancy (OV) as a high-performance, controllable material for NO capture at the site of Vo site, and separation the process of hydrogenation. We also reported that the Eads of -1.12 eV with horizontal adsorption and the Bader charge of N increasing of 0.53|e| and O increasing of 0.17|e| at the most active site of reduction-OV predicted. It is worth noting that ΔG of NORR (NO reduction reaction) shows good performance (thermodynamically spontaneous reaction) to synthesize ammonia and water at room temperature in the theoretical calculation.

Facile one-step hydrothermal fabrication of Allium giganteum-like superhydrophobic coating on Mg alloy with self-cleaning and anti-corrosion properties

Superhydrophobic coating can act as the anti-corrosion layer for Mg alloy due to its water-repellency. The construction of such coating is dominated by the roughness and surface energy, which is expected to achieve in one-step to improve the weak adsorption phenomenon of surface modification during traditional approaches. Therefore, a superhydrophobic coating composed of CeO2 and cerium stearate (Ce(CH3(CH2)16COO)3) is fabricated via a facile hydrothermal method. The synthesis of Ce(CH3(CH2)16COO)3 passivates the surface of CeO2 nanosheets, leading to a reduction of surface energy and the formation of an Allium giganteum-like structure which presents a micro-nano hierarchical roughness. This unique structure with high roughness and low surface energy is responsible for the excellent superhydrophobic behavior of coating which has high water contact angle (WCA) of 164° and low rolling angle (RA) of 4.1°. The superhydrophobic coating also displays an outstanding self-cleaning behavior due to its low surface adhesion. The corrosion rate of prepared coating in 3.5 wt% NaCl aqueous solution is approximately two orders of magnitude lower than that of bare Mg alloy. This remarkably enhanced corrosion resistance arises from the decrease in contact area between the corrosion solution and sample due to the water-repellency of coating.

Ambient sunlight-driven photothermal methanol dehydrogenation for syngas production with 32.9 % solar-to-hydrogen conversion efficiency

SummaryMethanol dehydrogenation is an efficient way to produce syngas with high quality. The current efficiency of sunlight-driven methanol dehydrogenation is poor, which is limited by the lack of excellent catalysts and effective methods to convert sunlight into chemicals. Here, we show that atomically substitutional Pt-doped in CeO2 nanosheets (Pts-CeO2) exhibit excellent methanol dehydrogenation activity with 500-hr level catalytic stability, 11 times higher than that of Pt nanoparticles/CeO2. Further, we introduce a photothermal conversion device to heat Pts-CeO2 up to 299°C under 1 sun irradiation owning to efficient full sunlight absorption and low heat dissipation, thus achieving an extraordinarily high methanol dehydrogenation performance with a 481.1 mmol g−1 h−1 of H2 production rate and a high solar-to-hydrogen (STH) efficiency of 32.9%. Our method represents another progress for ambient sunlight-driven stable and active methanol dehydrogenation technology.

Photocatalytic degradation of organic dye and tetracycline by ternary Ag2O/AgBr\u2013CeO2 photocatalyst under visible-light irradiation

In this work, CeO2 nanosheets decorated with Ag2O and AgBr are successfully fabricated via a simple sediment-precipitation method. The as-prepared ternary Ag2O/AgBr–CeO2 composite with double Z-scheme construction was analyzed by various analytical techniques. Ag nanoparticles (NPs) used as the electron medium could reduce the recombination of photoelectrons and holes, thus leading to the improvement of photocatalytic performance of these catalysts. Due to the unique structure and composite advantages, the optimal Ag2O/AgBr–CeO2 photocatalysts exhibit the superior tetracycline (TC) degradation efficiency of 93.23% and favorable stability with near-initial capacity under visible light irradiation. This ternary Z-scheme structure materials will be the well-promising photocatalysts or the purification of antibiotic wastewater.

Ultrathin CeO2 nanosheets as bifunctional sensing materials for humidity and formaldehyde detection

Issues like morphology control and further multifunctional applications are of significant importance for rare earth nano-oxides, e.g., cerium dioxide (CeO2) nanostructures, however, relevant results in this respect are rather limited up to now. In the present work, ultrathin CeO2 nanosheets were synthesized through a facile low-temperature hydrothermal method. The structure, morphology and specific surface area of these CeO2 nanosheets were characterized by X-ray diffraction (XRD), field emission scanning electron microscope (FESEM) and N2 adsorption–desorption. Significantly, CeO2 nanosheets have the potential as bifunctional sensing materials to detect both humidity and formaldehyde vapor. The CeO2 nanosheet humidity sensor exhibited excellent sensing characteristics in the relative humidity range of 11%–97% with the response value as high as 3.1 × 104. Meanwhile, the CeO2 nanosheet gas sensor showed superior sensitivity and repeatability with fast response/recovery speed toward formaldehyde vapor at 300 °C. Finally, the humidity and formaldehyde sensing mechanism were discussed as well.

Comparative Studies of Phosphate-Modified CeO2 and Al2O3 for Mechanistic Understanding of Dichloromethane Oxidation and Chloromethane Formation

A phosphate-modified CeO2 nanosheet as a promising catalyst presenting high activity, durability, and selectivity for catalytic oxidation of chlorinated volatile organic compounds (CVOCs) was used ...

Synthesis of Novel Kaolin-Supported g-C3N4/CeO2 Composites with Enhanced Photocatalytic Removal of Ciprofloxacin.

Herein, novel ternary kaolin/CeO2/g-C3N4 composite was prepared by sol-gel method followed by hydrothermal treatment. The self-assembled 3D “sandwich” structure consisting of kaolin, CeO2 and g-C3N4 nanosheets, was systematically characterized by appropriate techniques to assess its physicochemical properties. In the prerequisite of visible-light irradiation, the removal efficiency of ciprofloxacin (CIP) over the kaolin/CeO2/g-C3N4 composite was about 90% within 150 min, 2-folds higher than those of pristine CeO2 and g-C3N4. The enhanced photocatalytic activity was attributed to the improved photo-induced charge separation efficiency and the large specific surface area, which was determined by electrochemical measurements and N2 physisorption methods, respectively. The synergistic effect between the kaolin and CeO2/g-C3N4 heterostructure improved the photocatalytic performance of the final solid. The trapping and electron paramagnetic resonance (EPR) experiments demonstrated that the hole (h+) and superoxide radicals (•O2−) played an important role in the photocatalytic process. The photocatalytic mechanism for CIP degradation was also proposed based on experimental results. The obtained results revealed that the kaolin/CeO2/g-C3N4 composite is a promising solid catalyst for environmental remediation.

Honeycomb-like g-C3N4/CeO2-x nanosheets obtained via one step hydrothermal-roasting for efficient and stable Cr(VI) photo-reduction

Graphitic carbon nitride (g-C3N4)-based materials are regarded as one of the most potential photocatalysts for utilizing solar energy. In this work, we reported a facile one step in-situ hydrothermal-roasting method for preparing honeycomb-like g-C3N4/CeO2 nanosheets with abundant oxygen vacancies (g-C3N4/CeO2-x). The hydrothermal-roasting and incomplete-sealed state can (i) generate an in-situ reducing atmosphere (CO, N2, NH3) to tune the concentration of oxygen vacancies in CeO2; (ii) beneficial to prevent continuous growth of g-C3N4 and results in honeycomb-like g-C3N4/CeO2-x hybrid nanosheets. What is more, the g-C3N4/CeO2-x photocatalyst exhibited extended photoresponse range, increased specific surface area and obviously enhanced separation efficiency of photogenerated electron-hole pairs. As a proof-of-concept application, the optimized g-C3N4/CeO2-x nanosheets could achieve 98% removal efficiency for Cr(VI) under visible light irradiation (λ ≥ 420 nm) within 2.5 h, which is significantly better than those of pure g-C3N4 and CeO2. This work provides a new idea for more rationally designing and constructing g-C3N4-based catalysts for efficient extended photochemical application.

Solvothermal Synthesis of Humic Acid-Supported CeO₂ Nanosheets Composite as High Performance Adsorbent for Congo Red Removal.

Surface properties and structures of materials are essential for their adsorption of pollutants in water. Humic acids (HA)-supported CeO₂ nanosheet composites are synthesised by solvothermal method. The size of CeO₂ nanosheets are approximately 100-500 nm. The obtained composite exhibits superior adsorption ability for Congo Red (CR) in water, which can be attributed to its unique structure and highly dispersed CeO₂ nanosheet. The composite's adsorption behaviour of CR follows a pseudo-second-order mode and Langmuir adsorption model well, and the maximum adsorptive capacity for CR achieves 260 mg g-1. The presence of CeO₂ nanosheets enhances surface area and enriches the mesoporous structure of the composites, thereby promoting CR adsorption capacity.

Promoting Formation of Oxygen Vacancies in Two-Dimensional Cobalt-Doped Ceria Nanosheets for Efficient Hydrogen Evolution.

As an alternative for depleting fossil fuel energy, hydrogen economy desires low-cost and efficient hydrogen production from water splitting. In order to explore a cheap, abundant, active, and durable catalyst for the electrocatalytic hydrogen evolution reaction (HER), two-dimensional (2D) ceria nanosheets are produced through a thermal decomposition exfoliation method from CeCO3OH with a layer-stacked structure. The additional cobalt dopant promotes formation of oxygen vacancies in ceria nanosheets and, in turn, optimizes hydrogen binding/water dissociation and increases the active sites. As a result, the 2D Co-doped CeO2 nanosheets exhibit an excellent catalytic performance in alkaline HER such that the overpotential is as low as 132 and 215 mV to deliver a high current density of 100 and 500 mA cm-2, respectively, outperforming Pt. Such 2D Co-doped CeO2 nanosheets are also durable HER electrocatalysts, as the activity loss during an extended period of operation is nearly negligible.

Hollow β-Bi2O3@CeO2 heterostructure microsphere with controllable crystal phase for efficient photocatalysis

Herein, a two-step hydrothermal synthesis is used to successfully prepare a Bi2O3 microsphere coated with CeO2 nanosheets on the surface. The resultant core/shell Bi2O3@CeO2 microsphere is calcined at different temperatures, yielding a series of Bi2O3@CeO2-t hollow microspheres. It is found that, with the increasing calcination temperature, the Kirkendall effect occurred can impel the interior Bi2O3 to gradually diffuse outward the Bi2O3@CeO2 microsphere, meanwhile the crystal structure of Bi2O3 transforms from the metastable tetragonal phase (β) to the stable monoclinic phase (α) at 350 °C. Phase-controllable preparation of the Bi2O3@CeO2-350 composite with the highly active β-Bi2O3 is pursued to obtain the high electron-transfer efficiency between β-Bi2O3 and CeO2, thus exhibiting superior photocatalytic performance in the photocatalytic degradation of tetracycline (TC) under visible light irradiation. Therefore, Kirkendall effect can be exploited as a new methodology to effectively improve the photocatalytic performance of heterojunction photocatalysts.

Enhanced Visible-Light Photocatalytic Activity of Ag QDs Anchored on CeO2 Nanosheets with a Carbon Coating.

Ag quantum dots (QDs) anchored on CeO2 nanosheets with a carbon coating (Ag/CeO2@C) (composites) were prepared via an in situ reduction approach for the photocatalytic degradation of Cr(VI) and tetracycline hydrochloride (TCH) in the visible-light region. The photocatalytic activity of Ag/CeO2@C was greatly affected by carbon content, Ag-doping content, Cr(VI) concentration, pH value, and inorganic ions. Enhanced photocatalytic activity was obtained by Ag/CeO2@C (compared to CeO2 and CeO2@C), of which 3-Ag/CeO2@C-2 with an Ag-doping content of 5.41% presented the best removal efficiency and the most superior stability after five cycles. ·O2− and ·OH radicals were crucial for the photocatalytic capacity of 3-Ag/CeO2@C-2. The combined effect of the surface plasma resonance (SPR) of Ag QDs, an electron trapper of carbon shells, and the redox activity of the Ce(III)/Ce(IV) coupling induced efficient charge transfer and separation, suppressing the recombination of electron–hole pairs.