Mesoporous CeO2 Research Articles

Oxidation of Toluene over the Pt-Embedded Mesoporous CeO2 Hollow Nanospheres with Advanced Catalytic Performances.

In this study, the novel Pt-embedded mesoporous CeO2 hollow nanospheres (Pt-MS-CeO2-H) with varying Pt contents (0.5-3.0 wt %) were facilely prepared. The Pt nanoparticles were one-pot embedded within the mesoporous shell of Pt-MS-CeO2-H and assisted with the reduction Ostwald ripening process. The traditional preparation methods often face challenges, such as the uneven distribution or aggregation of nanoparticles, as well as difficulty in maintaining high catalytic activity at low Pt content. Compared with the traditional supported Pt/MS-CeO2 catalyst, the embedding strategy facilitated precise control over the position, distribution, and uniformity of Pt nanoparticles within the CeO2 mesoporous shell. Additionally, the encapsulation process of Pt nanoparticles played a pivotal role in generating oxygen vacancies and activating surface chemical adsorption of oxygen. Resultantly, the toluene oxidation performances of 1Pt-MS-CeO2-H catalyst showed much lower T90 (171 °C) than 1Pt/MS-CeO2 (311 °C). To elucidate the underlying reasons, in situ diffuse reflectance infrared Fourier transform spectroscopy of toluene oxidation was employed to identify the reaction intermediates and pathways over these catalysts. In summary, the Pt-embedded mesoporous CeO2 hollow nanosphere catalysts were considered as potential candidates when designing high-performance toluene catalytic oxidation catalysts.

Nanocasting synthesis of mesoporous CeO2 particle abrasives from mesoporous SiO2 hard templates for enhanced chemical mechanical polishing performance

Mesoporous abrasive particles exhibit superior chemical mechanical polishing/planarization (CMP) performance, as compared with the corresponding bulk materials. Nevertheless, the lack of control over the shape and particle size or distribution extremely restricts the development of mesoporous abrasives and their potential applications. To overwhelm these drawbacks, pure and ytterbium-doped mesoporous ceria (mCeO2 and mCeYbO2) spheres with well-defined morphology and good uniformity were synthesized via a straightforward nanocasting strategy using high-quality mesoporous silica spheres as hard templates and metal nitrates as precursors. The resulting samples were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, selected area electron diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, UV–vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, Zeta potential, and N2 adsorption-desorption measurements. The as-prepared mCeO2 and mCeYbO2 products exhibited enriched surface defects (trivalent Ce, vacancy oxygen, hydroxyls) and polycrystalline porous frameworks with a surface area of up to 160 m2/g and pore size of 4–7 nm. Benefiting from these synergistic attributes, the flexible and defective particle abrasives enabled significant improvements in both surface quality and removal efficiency during oxide-CMP, as compared to commercial CeO2. A possible CMP mechanism was proposed on the basis of the physical contact state, adsorption and adhesion behavior, as well as tribochemical interaction occurred at CeO2–SiO2 interfaces. This work demonstrates highly promising abrasive materials advancement combining architecture and defect engineering towards high-performance oxide-CMP.

A p-n heterojunction PdO/CeO2 photocatalysts with enhanced photocatalytic ability for reduction of Hg(II) ions from aqueous solution

Heterostructured photocatalysts represent an essential role in the catalytic redox reactions in wastewater during illumination. In this contribution, p-n heterojunction PdO/CeO2 photocatalysts were constructed with enhanced photocatalytic ability for the reduction of Hg(II) utilizing HCOOH as hole scavengers under visible light. PdO NPs were uniformly spread on the mesoporous CeO2 surface, to act as potential separation centers of electrons and holes. The synthesized PdO/CeO2 nanocomposites exhibited an excellent photocatalytic ability, contrasted to the bare CeO2 NPs. The photocatalytic ability of PdO/CeO2 nanocomposites for reduction of Hg(II) has existed in the trends of 2%PdO ≥1.5%PdO >1%PdO >0.5 % PdO/CeO2 nanocomposites > bare CeO2 NPs. A photocatalytic ability of 100 % for Hg(II) reduction was achieved within 40 min utilizing 1.5 % PdO/CeO2 nanocomposites, which was 2.2 folds greater than that of bare CeO2 NPs. The rate constant of 1.5 % PdO/CeO2 nanocomposite (0.106 min−1) is more 9.9 times than that CeO2 NPs (0.0107 min−1). The enhancement photocatalytic ability of PdO/CeO2 can be interpreted to the wide surface area, narrow bandgap, numerous active sites, fast mobility, efficient diffusion of Hg(II), and the high separation rate of photocarriers. Considering the promotion photocatalytic ability of heterojunction PdO/CeO2 nanocomposites, the heterostructure photocatalyst is of magnificent importance to the photocatalytic redox reactions and exhibits a significant effect on our human health and ecological environment.

Boosted antibiotic elimination over 2D/2D mesoporous CeO2/BiOCl S-scheme photocatalyst

Exploring efficient photocatalysts holds significant importance for the prevention and treatment of antibiotic pollution. This research reports a 2D/2D CeO2/BiOCl S-scheme photocatalyst constructed by mesoporous CeO2 and BiOCl nanosheets (NSs). Efficient charge separation and transfer was achieved by the synergistic effect of large-area contact and S-scheme charge transfer mechanism, which significantly enhanced the photocatalytic performance of CeO2/BiOCl. Experimental results demonstrated that the CeO2/BiOCl photocatalyst displayed superior photocatalytic activity to the individual components, which could efficiently eliminate four types of antibiotics, namely tetracycline (TC), chlortetracycline (CTC), doxycycline (DOC), and oxytetracycline (OTC) under UV light irradiation. Particularly, the sample of 0.4CeO2/BiOCl exhibited the highest catalytic efficiency, with a TC degradation rate constant of 0.01524 min−1, which was 1.85 and 22.74 times higher than that of single CeO2 and BiOCl, respectively. Moreover, liquid chromatograph-mass spectrometer (LC-MS) analysis is employed to reveal the degradation pathways of TC. This work offers an insightful idea for the fabrication of novel S-scheme photocatalysts applied in environmental purification.

Differential Activation of Alkynes between Capped and Naked Ag Nanoclusters Anchored by Highly-Open Mesoporous CeO2 for Two Coupling Reactions with CO2.

The cyclization of 3-hydroxy alkynes and the carboxylation of terminal alkynes both with CO2 are two attractive strategies to simultaneously reduce CO2 emission and produce value-added chemicals. Herein, the differential activation of alkynes over atomically precise Ag nanoclusters (NCs) supported on Metal-organic framework-derivedhighly-open mesoporous CeO2 (HM-CeO2) by reserving or removing their surface captopril ligands is reported. The ligand-capped Ag NCs possess electron-rich Ag atoms as efficient π-activation catalytic sites in cyclization reactions, while the naked Ag NCs possess partial positive-charged Ag atoms as perfect σ-activation catalytic sites in carboxylation reactions. Impressively, via coupling with HM-CeO2 featuring abundant basic sites and quick mass transfer, the ligand-capped Ag NCs afford 97.9% yield of 4,4-dimethyl-5-methylidene-1,3-dioxolan-2-one for the cyclization of 2-methyl-3-butyn-2-ol with CO2, which is 4.5 times that of the naked Ag NCs (21.7%), while the naked Ag NCs achieve 98.5% yield of n-butyl 2-alkynoate for the carboxylation of phenylacetylene with CO2, which is 15.6 times that of ligand-capped Ag NCs (6.3%). Density functional theory calculations reveal the ligand-capped Ag NCs can effectively activate alkynyl carbonate ions for the intramolecular ring closing in cyclization reaction, while the naked Ag NCs are highly affiliative in stabilizing terminal alkynyl anions for the insertion of CO2 in carboxylation reaction.

Aerosol-assisted fabrication of mesoporous CeO2 nanoparticles for cargo controlled delivery application

This study presents a spray pyrolysis technique for fabricating mesoporous cerium oxide nanoparticles (MCNs) with tunable properties. The MCNs were extensively characterized by their morphology, crystallinity, optical properties, and surface area through transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Raman spectroscopy, UV−vis spectroscopy, and BET adsorption isotherms. We manipulated synthesis parameters to tailor these characteristics, and subsequently evaluated the ability of MCNs to load and release the cationic probe Rhodamine 6G, demonstrating their responsiveness to pH variations. The particles showed high entrapment efficiency (up to 40 %), pH-responsive release, and pore-size-dependent release performance. Additionally, the biocompatibility of MCNs was confirmed by assessing their impact on the viability of HEK293 cells. The findings indicate that the fabricated MCNs hold promise for targeted nano-therapeutic applications, particularly within acidic microenvironments such as tumor sites.

An insight on the role of Pr in the photocatalytic efficiency of mesoporous CeO2@C

Using Ce(NO3)3·6H2O and Pr(NO3)3·6H2O as raw materials, ammonium hydroxide as precipitate, acid red 14 (AR14) as carbon source, Ce-Pr-O@C was synthesized in this study. The structural properties of the resulted samples were characterized by XRD, N2 adsorption–desorption, Raman, TEM, UV–vis, FT-IR, and XPS techniques. The photocatalytic efficiency of Ce-Pr-O@C was evaluated by the degradation of AR14. Effect of Pr doping on the photocatalytic efficiency of Ce-Pr-O@C was focused on. The results show that 25% Pr doping amount is benefit for the formation of mesopores, improvement of hydroxyl group content, enhancement of bonding rate, resulting in the promotion of adsorption capacity of organic pollutants and separation of photogenerated electron and hole and thus increasing of photocatatlytic efficiency. Moreover, effect of carbon loading amount on the photocatatlytic efficiency was also investigated.

Lithium manganite anchored on mesoporous ceria photocatalyst for removal of Hg(II) ions from aqueous solution under visible illumination

The development of effective photocatalysts is critical for the photo/redox reaction of noxious Hg(II) ions and Hgo in environmental engineering and purification. In this contribution, Li2MnO3 nanoparticles (NPs) were anchored mesoporous CeO2 networks to design photocatalysts with high harvest of visible light, and the obtained Li2MnO3/CeO2 nanocomposites were utilized for photoreduction of Hg(II) ions under visible illumination. The TEM and XRD results showed the formation of Li2MnO3 and CeO2 with the monoclinic and cubic fluorite structures, and the particle size is about 10–20 nm. The enhancement of light absorption of Li2MnO3/CeO2 nanocomposites could create considerable photoinduced carriers during the photocatalytic reactions. The incorporation of Li2MnO3 and CeO2 NPs demonstrated outstanding photocatalytic performance compared with pristine CeO2 NPs, and the optimum 9%Li2MnO3/CeO2 nanocomposite achieved 98 % of the reduction Hg(II) ability within 60 min. The rate constant for 9 % Li2MnO3/CeO2 photocatalyst is ∼ 6.47 and 3.85 times greater than Li2MnO3 and CeO2 NPs. The superior photocatalytic performance of Li2MnO3/CeO2 nanocomposites was ascribed to the efficient separation of photocarriers due to the formation of S-scheme heterojunction, the large surface area, and mesoporous structures. The obtained Li2MnO3/CeO2 nanocomposite was highly stable and efficient for the Hg(II) photoreduction runs up to five successive experiments under similar conditions. Moreover, the possible mechanism over heterojunctions Li2MnO3/CeO2 nanocomposites toward the reduction of Hg(II) ions is examined as well. The formation of S-scheme heterojunction photocatalyst provides better photocatalytic applications in terms of air purification, hydrogen production, and water treatment.

Insights into Co and Fe-doping effects of mesoporous CeO2 catalysts for dry reforming of glycerol to syngas production

The dry reforming of glycerol (GDR) is one of the alternatives for syngas production by utilizing biodiesel byproduct glycerol and CO2. The development of highly active and stable catalyst is significantly important to achieve GDR process, and the current work provides insights into Co and Fe-doping effects of mesoporous CeO2 (CoFeCe) catalysts synthesized by the colloidal solution combustion method. The prepared catalysts presented the uniform mesoporous structure, the doping of Co and Fe metals resulted in stronger metal-support interaction. The GDR experimental data were compared with the non-stoichiometric thermodynamic equilibrium values. The conversions of glycerol and CO2 were increased with increasing the reaction temperatures due to the endothermic GDR reaction, and the H2/CO produced in syngas was in the range of 0.7–1.4. Due to the improvement of Co and Fe metals in the mesoporous structure of CeO2 catalyst, the 7CoFeCe catalyst exhibited excellent and stable GDR performance and no significant signs of deactivation were observed during 76 h test, and the results indicated that the enhanced interaction and high dispersion of Co and Fe in mesoporous CeO2 catalyst could inhibit carbon formation and promote GDR reaction.

Constructing Efficient CuO-Based CO Oxidation Catalysts with Large Specific Surface Area Mesoporous CeO2 Nanosphere Support.

CeO2 is an outstanding support commonly used for the CuO-based CO oxidation catalysts due to its excellent redox property and oxygen storage-release property. However, the inherently small specific surface area of CeO2 support restricts the further enhancement of its catalytic performance. In this work, the novel mesoporous CeO2 nanosphere with a large specific surface area (~190.4 m2/g) was facilely synthesized by the improved hydrothermal method. The large specific surface area of mesoporous CeO2 nanosphere could be successfully maintained even at high temperatures up to 500 °C, exhibiting excellent thermal stability. Then, a series of CuO-based CO oxidation catalysts were prepared with the mesoporous CeO2 nanosphere as the support. The large surface area of the mesoporous CeO2 nanosphere support could greatly promote the dispersion of CuO active sites. The effects of the CuO loading amount, the calcination temperature, mesostructure, and redox property on the performances of CO oxidation were systematically investigated. It was found that high Cu+ concentration and lattice oxygen content in mesoporous CuO/CeO2 nanosphere catalysts greatly contributed to enhancing the performances of CO oxidation. Therefore, the present mesoporous CeO2 nanosphere with its large specific surface area was considered a promising support for advanced CO oxidation and even other industrial catalysts.

A Novel Molten Salt Mediated Synthesis of Mesoporous Metal Oxides with High Crystallization.

The controlled synthesis of mesoporous metal oxides remains a great challenge because the uncontrolled assembly process and high-temperature crystallization can easily destroy the mesostructure. Herein, we develop a facile, versatile, low-cost, and controllable molten salt assisted assembly strategy to synthesize mesoporous metal oxides (e.g., CeO2, ZrO2, SnO2, Li2TiO3) with high surface area (115-155 m2/g) and uniform mesopore size (3.0 nm). We find this molten salt mediated assembly enables the desolvation of the precursors and forms bare metal ions, enhances their coordination interaction with the surfactant, and promotes their assembly into a mesostructure. Furthermore, the molten salt assisted crystallization process can lower the collision probability of the target metal atom, inhibit its further growth into large crystals, and achieve a well-maintained mesostructure with high crystallization. Furthermore, this method can be expanded to synthesize various structured mesoporous metal oxides, including hollow spheres, nanotubes, and nanosheets by introducing the carbon template. The obtained mesoporous CeO2 microspheres loaded with Cu species exhibit excellent antibacterial performance and superior catalytic activity for the hydrogenation of nitrophenol with high conversion and cycling stability.

Significant enhanced SO2 resistance of Ce-doped OMS-2 catalyst by building the CeO2 shell for the low-temperature SCR of NO with NH3

Developing highly SO2-resistance catalysts for the NOx reduction at low temperatures is a significant challenge. In this study, we fabricate a catalyst of Ce-doped manganese oxide octahedral molecular sieve by building the CeO2 shell (Ce-OMS-2@CeO2) to solve this problem. This catalyst showed high selective catalytic reduction with NH3 (NH3-SCR) activity and enhanced resistance to SO2-induced deactivation. Ce-OMS-2@CeO2 exhibited outstanding NH3-SCR activity and anti-sulfur performance at 200 °C. The mesoporous CeO2 shells exerted no influence on the transport of reactants to catalytic active sites. The NH3-SCR on Ce-OMS-2@CeO2 catalyst occurred via the Langmuir-Hinshelwood mechanism with adsorption of NH3 and NO on different sites, thus preventing competing adsorption. The CeO2 shell bound SO2 strongly in priority, thus protecting the Ce-OMS-2 core from SO2 poisoning. Moreover, a dynamic balance was established between NH4HSO4 formation and decomposition over our Ce-OMS-2@CeO2 catalyst at low temperatures, which also hindered the SO2 poisoning in NH3-SCR reaction.

Mesoporous CeO2-supported ultrafine PdCu nanoparticle catalyst for selective hydrogenation of alkynols

Bimetallic PdCu nanoparticles were anchored on mesoporous CeO2, the obtained PdCu@CeO2 catalyst showed high selectivity for alkynols hydrogenation to produce high value-added enols.

Facile design of mesoporous spherical cerium oxide@reduced graphene oxide nanocomposites with excellent microwave absorption

Mesoporous spherical CeO2 and unique conductive network structures of CeO2@RGO and CeO2@MWNCT nanocomposites.

Multiscale characterizations of structural evolution in mesoporous CeO2.

In situ ultra-small-angle and wide-angle X-ray scattering enables simultaneous tracking of the structural parameters of mesoporous CeO2 from the atomic scale to the micron-size scale. This multiscale approach provides a path to better understand structure-property relationships in mesoporous polycrystalline materials under dynamic conditions such as high temperature cycling.

Efficient optimization of the synthetic conditions for aerosol-assisted high-quality mesoporous CeO2 powders.

The morphology of surfactant-assisted mesoporous metal oxides was tuned to obtain high surface-area particles by utilizing the synthetic conditions for fabricating transparent thin films through an evaporation-induced self-assembly (EISA) process. For investigating their potential applications, especially for designing heterogeneous catalysts, mesoporous metal oxides should be obtained in powder forms; however, a serious limitation associated with their reproducibility persists. Herein, along with a rapid optimization approach, starting from determining and improving chemical composition for the fabrication of mesoporous metal oxide films, an advanced approach to obtain highly porous metal oxide powders is presented using a temperature-controlled spray-drying process with step-by-step but smooth optimization by combining several EISA processes, involving the utilization of a precursor solution optimized for a slow-drying process in the case of ceria (CeO2) using poly(styrene)-block-poly(ethylene oxide) (PS-b-PEO).

Pathogen-Activated Macrophage Membrane Encapsulated CeO2-TCPP Nanozyme with Targeted and Photo-Enhanced Antibacterial Therapy.

Nanozymes with peroxidase-mimic activity have recently emerged as effective strategies for eliminating infections. However, challenges in enhancing catalytic activities and the ability to target bacteria have hindered the broader application of nanozymes in bacterial infections. Herein, a novel nanozyme based on mesoporous CeO2 nanosphere and meso-tetra(4-carboxyphenyl)porphine (TCPP) encapsulated within pathogen-activated macrophage membranes, demonstrates photodynamic capability coupled with photo-enhanced chemodynamic therapy for selective and efficient antibacterial application against infected wounds. Interestingly, the expression of Toll-like receptors accordingly upregulates when macrophages are co-cultured with specific bacteria, thereby facilitating to recognition of the pathogen-associated molecular patterns originating from bacteria. The CeO2 not only serve as carriers for TCPP, but also exhibit intrinsic peroxidase-like catalytic activity. Consequently, Staphylococcus aureus (S. aureus)-activated macrophage membrane-coated CeO2-TCPP (S-MM@CeO2-TCPP) generated singlet oxygen, and simultaneously promoted photo-enhanced chemodynamic therapy, significantly boosting reactive oxygen species (ROS) to effectively eliminate bacteria. S-MM@CeO2-TCPP specifically targeted S. aureus via Toll-like receptor, thereby directly disrupting bacterial structural integrity to eradicate S. aureus in vitro and relieve bacteria-induced inflammation to accelerate infected wound healing in vivo. By selectively targeting specific bacteria and effectively killing pathogens, such strategy provides a more efficient and reliable alternative for precise elimination of pathogens and inflammation alleviation in microorganism-infected wounds.

Direct Operando Visualization of Metal Support Interactions Induced by Hydrogen Spillover During CO2 Hydrogenation.

The understanding of catalyst active sites is a fundamental challenge for the future rational design of optimized and bespoke catalysts. For instance, the partial reduction of Ce4+ surface sites to Ce3+ and the formation of oxygen vacancies are critical for CO2 hydrogenation, CO oxidation, and the water gas shift reaction. Furthermore, metal nanoparticles, the reducible support, and metal support interactions are prone to evolve under reaction conditions; therefore a catalyst structure must be characterized under operando conditions to identify active states and deduce structure-activity relationships. In the present work, temperature-induced morphological and chemical changes in Ni nanoparticle-decorated mesoporous CeO2 by means of in situ quantitative multimode electron tomography and in situ heating electron energy loss spectroscopy, respectively,are investigated. Moreover, operando electron energy loss spectroscopy is employed using a windowed gas celland reveals the role of Ni-induced hydrogen spillover on active Ce3+ site formation and enhancement of the overall catalytic performance.

Impact of Ce/Zr Ratio in the Nanostructured Ceria and Zirconia Composites on the Selective CO2 Adsorption.

High surface-area, mesoporous CeO2, ZrO2, and Ce-Zr composite nanoparticles were developed using the hydrothermal template-assisted synthesis method. Samples were characterized using XRD, N2 physisorption, TEM, XPS, and FT-IR spectroscopic methods. The CO2 adsorption ability of the obtained materials was tested under dynamic and equilibrium conditions. A high CO2 adsorption capacity in CO2/N2 flow or CO2/N2/H2O was determined for all studied adsorbents depending on their composition flow. A higher CO2 adsorption was registered for Ce-Zr composite nanomaterials due to the presence of strong O2- base sites and enriched surface oxygen species. The role of the Ce/Zr ratio is the process of the formation of highly active and selective adsorption sites is discussed. The calculated heat of adsorption revealed the processes of chemisorption and physisorption. Experimental data could be appropriately described by the Yoon-Nelson kinetic model. The composites reused in five adsorption/desorption cycles showed a high stability with a slight decrease in CO2 adsorption capacities in dry flow and in the presence of water vapor.

Biomass nanoarchitectonics with Annona reticulate flowers for mesoporous carbon impregnated on CeO2 nanogranular electrode for energy storage application

Metal oxide semiconductors with mesoporous nanoarchitecture are interesting new materials because they have more active sites and a substantially higher surface area, which makes them useful for a wide range of applications. Herein, we report the mesoporous carbon impregnated on CeO2 nanogranular using a pyrolysis method followed by a coprecipitation method. The ecological and affordable biowaste precursor, Annona reticulate flower, was used to prepare the mesoporous carbon. The effect of porous carbon in CeO2 nanogranular on the electrochemical properties of the mesoporous carbon impregnated on the CeO2 nanogranular electrode has been studied meticulously. A CeO2 electrode showed a specific capacitance of 332.9 F g-1 at 2 mA cm-2 current density and an excellent rate capability of 88.23 %. Then mesoporous carbon reveals a specific capacitance of 573.6 F g-1 at 2 mA cm-2 current density and an excellent rate capability of 92.10 %. Furthermore, the composition of mesoporous carbon and CeO2 electrodes showed an enhancement in the supercapacitor behavior. It showed a high specific capacitance of 753.2 % Fg-1 at 2 mA cm-2 current density and an excellent rate capability of 95.50 %. It is observed that the specific capacitance of the composite electrode is higher than that of the individual electrode because the specific area and porosity of the composite electrode are increased, which helps to adsorb more electrolytes and increase the supercapacitor’s behavior. The findings show that composite electrodes made from mesoporous carbon generated from waste biomass and nanogranular CeO2 can be significant electrode materials for energy storage applications.