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Mn-doped CeO2 and CeO2 with the same morphology (nanofiber and nanocube) have been synthesized through hydrothermal method. When applied to benzene oxidation, the catalytic performance of Mn-doped CeO2 is better than that of CeO2, due to the difference of the concentration of O vacancy. Compared to CeO2 with the same morphology, more oxygen vacancies were generated on the surface of Mn-doped CeO2, due to the replacement of Ce ion with Mn ion. The lattice replacement has been analyzed through XRD, Raman, electron energy loss spectroscopy and electron paramagnetic resonance technology. The formation energies of oxygen vacancy on the different exposed crystal planes such as (110) and (100) for Mn-doped CeO2 were calculated by the density functional theory (DFT). The results show that the oxygen vacancy is easier to be formed on the (110) plane. Other factors influencing catalytic behavior have also been investigated, indicating that the surface oxygen vacancy plays a crucial role in catalytic reaction.

The hydrogenation reaction of succinic acid in the liquid phase was studied using the supported metal catalysts, Fe/CeO2, Cu/CeO2, and Fe-Cu/CeO2. The CeO2 support was prepared by precipitation method and the supported metal solids by dry impregnation of support. For monometallic solids, a percentage of iron and copper of 10 wt.%, respectively, was considered. For the bimetallic solid, the metal content was 5 wt.% of each metal. The catalysts were characterized using atomic absorption spectroscopy, X-ray diffraction, nitrogen physisorption, and infrared spectroscopy techniques. The evaluation of the catalytic activity showed that the catalysts favor the formation of γ-hydroxybutyric acid (GHB), with the Cu/CeO2 system presenting the highest percentages of conversion of succinic acid and yield towards GHB. This catalytic behavior could be related to the smaller crystallite size and the greater surface area evidenced in the material compared to the other catalysts studied. Furthermore, the results obtained using the bimetallic material evidenced the role of iron as a promoter for obtaining γ-butyrolactone (GBL).

New chemical recycling processes for mitigating plastic pollution are being developed every day. Plastic depolymerization is typically conducted under high temperatures and pressures in pyrolysis, hydrogenolysis, ammonolysis, and glycolysis processes, which require robust heterogeneous catalysts that tolerate such extreme conditions. Furthermore, bifunctional metal/metal oxide catalysts offer synergistic effects emanating from metal–support interactions and hydrogen spillover. CeO2 is emerging as an effective material as depolymerization catalysts due to its Lewis acid–base properties and high reducibility for generating oxygen vacancies. This review summarizes the recent efforts of using CeO2‐based catalysts for plastic waste depolymerization. The intrinsic properties of CeO2 that reinforce its uniqueness as a catalytic material for substrate activation are examined, followed by an examination of how these properties manifest in metal–support catalysis, where CeO2 acts synergistically with the active metal, and its morphology plays an important role in determining product selectivity. In addition, cases in which CeO2 serves as the primary active species for plastic waste depolymerization are discussed, particularly in the thermal and photothermal glycolysis of heteroatom‐containing plastics. Finally, perspectives are provided on gaining a greater mechanistic understanding of CeO2‐based depolymerization processes and on facilitating their translation to industrial applications.

A novel, simple, and inexpensive technique, chemical coprecipitation, was employed to produce CeO2 nanoparticles and CeO2/CuO nanocomposite. It entailed reacting dehydrated metal nitrate salts with an aqueous extract of Ficus religiosa. The CeO2 and CeO2/CuO solids were identified by X-ray diffraction (XRD), FTIR,  and transmission electron microscopy (TEM). The diffraction peaks of the CeO2 and CeO2/CuO revealed cubic and monoclinic structures, respectively, with average crystallite sizes of 20.5 and 26.8 nm, based on the XRD data.  TEM examinations show that the mean sizes of CeO2 and CeO2/CuO particles were (39.8 and 66.5 nm, respectively). These results imply negligible agglomeration. This study evaluated the antimicrobial efficacy of CeO2/CuO nanocomposite and CeO₂/CuO NPs against bacterial and fungal pathogens. The nanocomposite exhibited superior activity, producing larger inhibition zones (Bacillus subtilis: 26 mm; Candida albicans: 28 mm) compared to CeO₂ NPs and the standard drugs ciprofloxacin (as antibiotic) and nystatin (as antifungal). MIC and MBC/MFC assays confirmed stronger potency, particularly against Gram-positive bacteria and C. albicans. Time–kill kinetics revealed complete eradication of B. subtilis and K. pneumoniae within 180 min, while partial survival occurred in S. aureus and S. typhi. Both materials were inactive against Aspergillus niger, indicating selective but potent antimicrobial effects.

Ni-based catalysts have been widely used for the CO2 reforming of methane (CRM) process, but deactivation is their main problem. This study created an alternative electronic Ni-NiO-CeO2 interaction on the surface of 5 wt% Ni-5 wt% CeO2/Al2O3-MgO (5Ni5Ce(xh)/MA) catalysts to enhance catalytic potential simultaneously with coke resistance for the CRM process. The Ni-NiO-CeO2 network was developed on Al2O3-MgO through layered double hydroxide synthesis via our ammonia vapor diffusion impregnation method. The physical properties of the fresh catalysts were analyzed employing FESEM, N2 physisorption, and XRD. The chemical properties on the catalyst surface were analyzed employing H2-TPR, XPS, H2-TPD, CO2-TPD, and O2-TPD. The CRM performances of reduced catalysts were evaluated at 600 °C under ambient pressure. Carbon deposits on spent catalysts were determined quantitatively and qualitatively by TPO, FESEM, and XRD. Compared to 5 wt% Ni-5 wt% CeO2/Al2O3-MgO prepared by the traditional impregnation method, the electronic interaction of the Ni-NiO-CeO2 network with the Al2O3-MgO support was constructed along the time of ammonia diffusion treatment. The electronic interaction in the Ni-NiO-CeO2 nanostructure of the treated catalyst develops surface hydroxyl sites with an efficient pathway of OH* and O* transfer that improves catalytic activities and coke oxidation.

Cerium dioxide (CeO2) was pretreated with reduction and reoxidation under different conditions in order to elucidate the role of surface Ce4+ and oxygen vacancies in the catalytic activity for direct synthesis of dimethyl carbonate (DMC) from CO2 and methanol. The corresponding catalysts were comprehensively characterized using N2 physisorption, XRD, TEM, XPS, TPD, and CO2-FTIR. The results indicated that reduction treatment promotes the conversion of Ce4+ to Ce3+ and improves the concentration of surface oxygen vacancies, while reoxidation treatment facilitates the conversion of Ce3+ to Ce4+ and decreases the concentration of surface oxygen vacancies. The catalytic activity was linear with the number of moderate acidic/basic sites. The surface Ce4+ rather than oxygen vacancies, as Lewis acid sites, promoted the adsorption of CO2 and the formation of active bidentate carbonates. The number of moderate basic sites and the catalytic activity were positively correlated with the surface concentration of Ce4+ but negatively correlated with the surface concentration of oxygen vacancies. The surface Ce4+ and lattice oxygen were active Lewis acid and base sites respectively for CeO2 catalyst, while surface oxygen vacancy and lattice oxygen were active Lewis acid and base sites, respectively, for metal-doped CeO2 catalysts. This may result from the different natures of oxygen vacancies in CeO2 and metal-doped CeO2 catalysts.

The lack of osteoinductive, angiogenic and antimicrobial properties of hydroxyapatite coatings (HA) on titanium surfaces severely limits their use in orthopedic and dental implants. Therefore, we doped SiO2, Gd2O3 and CeO2 nanoparticles into HA to fabricate a HASiGdCe coating with a combination of decent antibacterial, angiogenic and osteogenic properties by the plasma spraying technique.IntroductionThe lack of osteoinductive, angiogenic and antimicrobial properties of hydroxyapatite coatings (HA) on titanium surfaces severely limits their use in orthopedic and dental implants. Therefore, we doped SiO2, Gd2O3 and CeO2 nanoparticles into HA to fabricate a HASiGdCe coating with a combination of decent antibacterial, angiogenic and osteogenic properties by the plasma spraying technique.The HASiGdCe coating was analyzed by SEM (EDS), surface roughness tests, contact angle tests, XRD, FTIR spectroscopy, tensile tests and electrochemical dynamic polarization tests. Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO-1) were used as representative bacteria to verify the antibacterial properties of the HASiGdCe coating. We evaluated the cytocompatibility and in vitro osteoinductivity of the HASiGdCe coating by investigating its effect on the cell viability and osteogenic differentiation of MC3T3-E1 cells. We assessed the in vitro angiogenic activity of the HASiGdCe coating by migration assay, tube formation assay, and RT‒PCR analysis of angiogenic genes in HUVECs. Finally, we used infected animal femur models to investigate the biosafety, antimicrobial and osteointegration properties of the HASiGdCe coating in vivo.MethodsThe HASiGdCe coating was analyzed by SEM (EDS), surface roughness tests, contact angle tests, XRD, FTIR spectroscopy, tensile tests and electrochemical dynamic polarization tests. Methicillin-resistant Staphylococcus aureus (MRSA) and Pseudomonas aeruginosa (PAO-1) were used as representative bacteria to verify the antibacterial properties of the HASiGdCe coating. We evaluated the cytocompatibility and in vitro osteoinductivity of the HASiGdCe coating by investigating its effect on the cell viability and osteogenic differentiation of MC3T3-E1 cells. We assessed the in vitro angiogenic activity of the HASiGdCe coating by migration assay, tube formation assay, and RT‒PCR analysis of angiogenic genes in HUVECs. Finally, we used infected animal femur models to investigate the biosafety, antimicrobial and osteointegration properties of the HASiGdCe coating in vivo.Through various characterization experiments, we demonstrated that the HASiGdCe coating has suitable microscopic morphology, physical phase characteristics, bonding strength and bioactivity to meet the coating criteria for orthopedic implants. The HASiGdCe coating can release Gd3+ and Ce4+, showing strong antibacterial properties against MRSA and PAO-1. The HASiGdCe coating has been shown to have superior osteogenic and angiogenic properties compared to the HA coating in in vitro cellular experiments. Animal implantation experiments have shown that the HASiGdCe coating also has excellent biosafety, antimicrobial and osteogenic properties in vivo.ResultsThrough various characterization experiments, we demonstrated that the HASiGdCe coating has suitable microscopic morphology, physical phase characteristics, bonding strength and bioactivity to meet the coating criteria for orthopedic implants. The HASiGdCe coating can release Gd3+ and Ce4+, showing strong antibacterial properties against MRSA and PAO-1. The HASiGdCe coating has been shown to have superior osteogenic and angiogenic properties compared to the HA coating in in vitro cellular experiments. Animal implantation experiments have shown that the HASiGdCe coating also has excellent biosafety, antimicrobial and osteogenic properties in vivo.The HASiGdCe coating confers excellent antibacterial, angiogenic and osteogenic properties on titanium implants, which can effectively enhance implant osseointegration and prevent bacterial infections, and it accordingly has promising applications in the treatment of bone defects related to orthopedic and dental sciences.ConclusionThe HASiGdCe coating confers excellent antibacterial, angiogenic and osteogenic properties on titanium implants, which can effectively enhance implant osseointegration and prevent bacterial infections, and it accordingly has promising applications in the treatment of bone defects related to orthopedic and dental sciences.

CeO2 is an important rare earth (RE) oxide and has served as a typical oxygen storage material in practical applications. In the present study, the oxygen storage capacity (OSC) of CeO2 was enhanced by doping with other rare earth ions (RE, RE = Yb, Y, Sm and La). A series of Undoped and RE–doped CeO2 with different doping levels were synthesized using a solvothermal method following a subsequent calcination process, in which just Ce(NO3)3∙6H2O, RE(NO3)3∙nH2O, ethylene glycol and water were used as raw materials. Surprisingly, the Undoped CeO2 was proved to be a porous material with a multilayered special morphology without any additional templates in this work. The lattice parameters of CeO2 were refined by the least–squares method with highly pure NaCl as the internal standard for peak position calibrations, and the solubility limits of RE ions into CeO2 were determined; the amounts of reducible–reoxidizable Cen+ ions were estimated by fitting the Ce 3d core–levels XPS spectra; the non–stoichiometric oxygen vacancy (VO) defects of CeO2 were analyzed qualitatively and quantitatively by O 1s XPS fitting and Raman scattering; and the OSC was quantified by the amount of H2 consumption per gram of CeO2 based on hydrogen temperature programmed reduction (H2–TPR) measurements. The maximum [OSC] of CeO2 appeared at 5 mol.% Yb–, 4 mol.% Y–, 4 mol.% Sm– and 7 mol.% La–doping with the values of 0.444, 0.387, 0.352 and 0.380 mmol H2/g by an increase of 93.04, 68.26, 53.04 and 65.22%. Moreover, the dominant factor for promoting the OSC of RE–doped CeO2 was analyzed.

The increasing concentrations of emerging organic contaminants (EOCs) in wastewater threaten human health and the environment. Their complex structures, low concentrations, and conversion into secondary metabolites challenge current remediation techniques. This study presents the Z-scheme Ti3C2 MXene@CeO2 (MX@CeO2) heterostructures, synthesized by a facile in-situ sonochemical method, aimed at enhancing photocatalytic mineralization of highly toxic Doxorubicin (DOX) drug. Our findings reveal that the unique surface and structural properties of Ti3C2 MXene facilitated the effective nucleation and growth of the CeO2. The growth mechanisms involved the adsorption of Ce atoms through negatively charged functional groups, and anchoring to surface defects and vacancies in Ti3C2 MXene. The formation of intimate interfacial heterojunctions between Ti3C2 MXene and CeO2 not only facilitated the charge separation and utilization but also improved the photostability, thereby improving the catalytic performance of the composite. Photodegradation experiments demonstrated 96% removal of DOX within 240 minutes of visible light exposure. Moreover, high-performance liquid chromatography analysis confirmed the complete mineralization of DOX. The post degradation analysis revealed the minimal cytotoxicity induced by photodegraded residues. The stability and sustained catalytic efficiency of MX@CeO2 in degrading DOX into non-toxic residues position such Z-scheme heterostructures as promising candidates for long-term remediation of EOCs. Schematic: (Left) The schematic illustrates the synthesis of Ti3C2 MXene@CeO2 heterostructures through a mild etching method, followed by the growth of a CeO2 shell via a vacancy confined method. (Middle) This process enhances charge transfer dynamics as proposed in the Z-scheme, facilitating the degradation of pollutants. (Right) the visual representation highlights the degradation of Doxorubicin. [Display omitted]

In this work, the experimental investigations were piloted to study the influence of hybrid nanoparticles containing SiO2 and CeO2 nanoparticles on thermo-physical characteristics of the paraffin-based phase change material (PCM). Initially, the hybrid nanoparticles were prepared by blending equal mass of SiO2 and CeO2 nanoparticles. The hybrid-nano/paraffin (HnP) samples were prepared by cautiously dispersing 0, 0.5, 1.0, and 2.0 percentage mass of hybrid nanoparticles inside the paraffin, respectively. The synthesized samples were examined under different instruments such as field emission scanning electron microscope (FESEM), Fourier transform infrared spectrometer (FTIR), differential scanning calorimetry (DSC), thermogravimetric analyzer (TGA), and thermal properties analyzer to ascertain the influence of hybrid nanoparticles on thermo-physical characteristics of the prepared samples. The obtained experimental results proved that the hybrid nanoparticles were uniformly diffused in the paraffin matrix without affecting the chemical arrangement of paraffin molecules. Prominently, the relative thermal stability and relative thermal conductivity of the paraffin were synergistically enriched up to 115.49% and 165.56%, respectively, when dispersing hybrid nanoparticles within paraffin. Furthermore, the hybrid nanoparticles appropriately amended the melting and crystallization point of the paraffin to reduce its supercooling, and the maximum reduction in supercooling was ascertained as 35.81%. The comprehensive studies indicated that the paraffin diffused with SiO2 and CeO2 hybrid nanoparticles at 1.0 mass percentage would yield a better outcome compared to the next higher mass fractions without much diminishing the latent heat of paraffin. Hence, it is recommended to utilize the hybrid-nano/paraffin with 1.0 mass fraction of the aforementioned hybrid nanoparticles for effectively augmenting the thermal energy capacity of low-temperature solar thermal systems.