CeO2 Particles Research Articles

Thermal decomposition kinetics and combustion performance of paraffin-based fuel in the presence of CeO2 catalyst

In recent years, significant developments have been made in solid-fuel combustion. Paraffin-based fuels could be a potential solid fuel for hybrid and ramjet applications due to their high regression rate, low cost, and minimal environmental impact. This study examines the thermal and combustion performance of paraffin-based fuels loaded with CeO2 combustion catalysts and Al additive. A typical melt-cast technique was used to prepare three different fuel formulations, which are paraffin/10 wt.% of Al (S2), paraffin/10 wt.% of CeO2 (S3), and CeO2-Al (10:10 wt.%) binary composite (S4). The pure paraffin (S1) fuel was manufactured as a reference formulation. The CeO2-Al binary composite powder was prepared by ball-milling of CeO2 and Al powders. The CeO2 and Al nanoparticles were characterized by X-ray diffraction (XRD), particle size distribution (PSD), and scanning electron microscope (SEM). The PSD study revealed that the majority of CeO2, Al, and CeO2-Al binary composite particles are 29 nm, 34 nm, and 26 nm in size, respectively. The thermogravimetric analysis (TGA) was used to investigate the effect of CeO2 and Al on the thermal decomposition of paraffin. The results indicate that the paraffin decomposes faster and at a higher rate when CeO2 and CeO2-Al binary composite additives were added. The activation energy of paraffin-based fuel (S4) was reduced from 254 kJ/mol to 214 kJ/mol when a CeO2-Al combustion catalyst was added. The lab-scale ballistic tests showed that the average regression rate of paraffin-Al (S2) and paraffin-CeO2(S3) samples increased in the range of 1.1-1.4 mm/s and 1.12-1.38 mm/s, respectively, whereas, with the CeO2-Al binary composite (S4) sample, a reasonable improvement of 1.15 mm/s to 1.49 mm/s was reported.

Tailoring metal-support interactions via tuning CeO2 particle size for enhancing CO2 methanation activity over Ni/CeO2 catalysts

Interfaces derived from metal-support interaction (MSI) and related oxygen vacancies are generally recognized as main factors affecting on CO2 methanation performance, but the interaction between these two factors is not yet very clear. To better understand the role of complicated MSI and associated oxygen vacancy for CO2 methanation, we designed the CeO2 nanocubes with different sizes as support and prepared supported Ni catalysts to study the relationship between MSI and catalytic performance. HRTEM, XRD, BET, Raman and XPS characterization results confirmed that the MSI and related oxygen vacancy concentration could be modulated by CeO2 size. The impact of oxygen vacancy and phase interface on activating reactant molecules (CO2/H2) was evidenced by HRTEM and CO2/H2-TPD results. The CO2 conversion rate on the Ni/CeO2-6M at 548 K is about three times that on the Ni/CeO2-12M, which is attributed to its lower activation energy. Furthermore, in-situ FT-IR results for CO2 hydrogenation on the Ni/CeO2-6M proved that CO2 methanation followed the formate pathway and the methoxy/carbonyls are key intermediates to produce CH4. The structure-effect relationship was further explored to show the size effect on Ni-CeO2 interaction interfaces and enhanced methanation performance.

Defect generation and morphology transformation mechanism of CeO2 particles prepared by molten salt method

Ceria is widely used in industrial fields due to its unique chemical properties. In this work, a series of CeO2 particles with controllable morphology, size, and defect concentration were obtained by a simple molten salt method. The adjustment of temperature and molten salt concentration has a considerable effect on the morphology and particle size of the final CeO2 particles while prolonging the holding time has little effect. Ion doping and reducing atmosphere calcination were used to regulate the defect concentration to improve the chemical activity of CeO2 particles. SEM results show that the morphology of CeO2 particles transforms from sphere to octahedron under the two treatments. The Rietveld refinement results and the XPS spectra indicate that increasing calcination temperature, reducing atmosphere calcination and ion doping are beneficial to improving the oxygen vacancies and Ce3+ concentration of CeO2 samples, which are the reason for enhancing the photocatalytic activity of the samples. Moreover, the oriented attachment, agglomeration and merging of crystals formed by the decomposition of cerium precursors are the key to the growth of CeO2 particles. Aggregates with exposed low-energy planes merge directly to form particles of various morphologies to maintain their own low energy.

Determination of Intrinsic Active Sites on CuO–CeO2–Al2O3 Catalysts for CO Oxidation and NO Reduction by CO: Differences and Connections

Based on a CeO2–Al2O3 support (CA-T) prepared by two-step incipient wetness impregnation (T-IWI) method, an efficient CuO catalyst supported on CA-T (Cu/CA-T) was successfully developed, which showed better catalytic performance in CO oxidation and NO reduction by CO (NO + CO reaction) together with higher thermal stability than the CuO catalyst loaded on conventional CeO2–Al2O3 support (Cu/CA). Based on the results of HAADF-STEM, Raman spectra, electron paramagnetic resonance, X-ray absorption spectroscopy, ex situ and quasi in situ X-ray photoelectron spectroscopy, in situ diffuse reflectance infrared Fourier transform spectroscopy, and dynamic oxygen storage capacity (OSC) testing, etc., the microstructure of CuO–CeO2–Al2O3 catalysts, especially the state of Cu species, was systemically investigated. The mechanisms of CO oxidation and NO + CO reactions on Cu/CA and Cu/CA-T catalysts were collaboratively revealed. It was found that the CA-T support with smaller CeO2 particles could facilitate the formation of more highly dispersed CuOx clusters with better redox property. In CO oxidation, more active Cu+ species could be formed on Cu/CA-T under reaction conditions due to the higher reducibility of CuOx clusters on CeO2, which contributed to its superior CO removal efficiency. After aging, a significant decrease in CO oxidation activity was observed on Cu/CA catalyst, which was mainly resulted from the disappearance of highly dispersed CuOx clusters. In clear contrast, for aged Cu/CA-T catalyst, the highly dispersed CuOx clusters could be well preserved, well explaining its much higher catalytic activity and thermal stability than the aged Cu/CA counterpart as probed by the CO oxidation reaction. In NO + CO reaction, besides the formation of more Cu+ sites for CO adsorption and activation, much higher OSC function was also achieved on the Cu/CA-T catalyst. This was due to the higher concentration of surface oxygen vacancies and moderate strength of CuOx–CeO2 interaction on Cu/CA-T, which could effectively promote the NO dissociation into [N] for N2 formation and the transfer of dissociated [O] to CO@Cu+ sites to complete the CO depletion.

Catalytic Dye Oxidation over CeO2 Nanoparticles Supported on Regenerated Cellulose Membrane

A novel regenerated cellulose (RC) membrane containing cerium oxide (CeO2) nanoparticles is described in detail. In this work, CeO2 nanoparticles with high surface area and mesoporosity were prepared by a modified template-assisted precipitation method. Successful synthesis was achieved using cerium nitrate as a precursor, adjusting the final pH solution to around 11 by ammonium hydroxide and ethylene diamine, and annealing at 550 °C for 3 hours under a protective gas flow. This resulted in a surface area of 55.55 m².g–1 for the nanoparticles. The regenerated cellulose membrane containing CeO2 particles was synthesized by the novel and environmentally friendly method. The catalyst CeO2 and cellulose/CeO2 membrane were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Electron paramagnetic resonance (EPR), and Brunauer-Emmett-Teller (BET) measurements. The g-value of 2.276 has confirmed the presence of the surface superoxide species of CeO2 nanoparticles in EPR. The photocatalytic activity of the catalyst and the membrane containing the catalyst was evaluated through the degradation of methylene blue under visible light irradiation by UV-VIS measurements. The cellulose/CeO2 membrane degraded 80% of the methylene blue solution in 120 minutes, showing a better photocatalytic activity than the CeO2 catalyst, which degraded approximately 62% in the same period. It has been proven that the RC membrane is not only a good transparent supporting material but also a good adsorption for high-performance of CeO2 catalyst. Copyright © 2022 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

The Effect of Ceo2 Addition on Transformation Temperatures and Wear Resistance of Cu-Al-Ni Shape Memory Alloys

SMAs can switch from one crystallographic structure to another in response to temperature or stress stimuli. When SMAs are exposed to mechanical cyclic stress, they can absorb and discharge mechanical energy by experiencing a reversible hysteretic shape change. SMAs are widely used for sensing, actuation, impact absorption, and vibration damping. This work studied the effect of CeO2 addition on the transformation temperature and wear resistance of Cu-Al-Ni SMAs. WhereCeO2 was added at different percent’s 0.5, 1, and 3 wt% to the base alloy, followed by casting and homogenization at 900oC. Some tests were carried out: Differential scanning calorimeter, Optical Microscope, Scanning Electron microscopy, Energy dispersion spectrometer, X-Ray Diffraction, and Wear and Hardness tests. OM and SEM tests reveal that both phases of martensite β and γ are found. Also, the additions of CeO2 show a visible effect on phase formation and transformation temperatures. It was observed that increasing of CeO2 particles in Cu-based SMAs owing to improve interfacial bonding between matrix and reinforcement and also observed that the variants become thicker with increasing in percent. Additions of different percentages of cerium oxide increase the hardness of Cu-Al-Ni SMAs. Due to the addition of CeO2 particles, the sample's wear rate decreases compared to pure SMAs.

High-performance CeO2:Co nanostructures for the elimination of accidental poisoning caused by CO intoxication

Owing to the global upward trend of accidental carbon monoxide (CO) poisoning in the past 30 years, this work aimed to develop Cobalt-doped CeO2 particles by the microwave-assisted hydrothermal route under distinct conditions. Their structural, morphological, spectroscopic and electrical behaviors were investigated to correlate the influence of Co on their properties with the introduction of oxygen vacancies and their sensing capability to assist in the mitigation of CO poisoning cases. The samples were crystalline and had no secondary phases. Two distinct activation energies for the electrical conduction processes were observed due to dopant influence, corroborating the local cluster-to-cluster charge transfer (CCCT) mechanism, resulting in a response time of only 3s for the 4% Co-doped sample. On the other hand, through positron annihilation studies we showed that the oxygen vacancies are preferentially formed near Co ions, reducing the Co ion charge and leading to the formation of neutral VO-Co+2 complex clusters.

Cyclability enhancement of CeO2/Sb2O3 composite electrode via ternary Na-storage reactions

As a Na-ion battery anode material, we newly designed CeO2/Sb2O3 composites ternary Na-storage mechanisms: insertion, conversion, and alloying reactions. The structural analyses confirmed that the CeO2 particles were incorporated well into the Sb2O3 matrix, on a microscopic scale, in the composites obtained via mechanical milling. The Sb2O3 electrode showed a high initial reversible capacity of 610 mA h g−1 because of the conversion reaction of Sb2O3 and its subsequent alloying reaction of Sb, whereas it very poor cyclability owing to large volume changes during these reactions. Furthermore, we newly confirmed reversible Na-insertion reaction of an CeO2 electrode and its excellent cyclability. It was revealed for the first time that reversible Na-insertion and Na-extraction reactions occur, accompanied by lattice expansion and contraction. For the CeO2/Sb2O3 composite electrodes, the rapid capacity decay behavior was significantly improved. This indicates that CeO2 contributes to stress relaxation and Na-ion conduction through the insertion reaction. An increase in the Sb2O3 content in the composite improved the anode performance. The CeO2/Sb2O3 (10/90 wt%) composite electrode exhibited excellent anode performance with a capacity of 400 mA h g−1 at the 120th cycle despite its low CeO2 content. Notably, the cyclability could be effectively enhanced using a small amount of CeO2.

A general strategy towards improving the strength and thermal shock resistance of glass-ceramics through microstructure regulation

Glass-ceramics are usually obtained through controlled crystallization. In this work, we propose a new strategy to add an appropriate amount of oxide particles to the parent glass to improve the performance of glass-ceramics. Different amounts of Al2O3 or/and CeO2 particles were added into a SiO2-Al2O3-ZnO-CaO-ZrO2-TiO2 based glass, and crystallization behavior, fracture strength, and thermal shock behavior were systematically evaluated. The results indicate that with the addition of Al2O3 or/and CeO2 particles of moderate amount, the unfavorable needle-like ZrSiO4, Zn2SiO4, and CaTiSiO5 crystals were largely inhibited when annealed at 900 °C. Accordingly, fracture strength is maintained high after heating at high temperatures. The thermal shock resistance is also enhanced drastically. The additive Al2O3 is thermodynamically favorable to react with the glass, forming particulate ZnAl2O4 instead of precipitating the needle-like crystals of Zn2SiO4 and CaTiSiO5; while CeO2 will combine with ZrO2 to form a solid solution and promote the precipitation of primary crystal CaZrTi2O7 that will not transform to ZrSiO4 with prolonging thermal exposure.

Facile One-Pot Synthesis of α–MnO2/CeO2 Nanowires for Mg-Air Batteries

In this work, we synthesized MnO2/CeO2 electrocatalysts by in situ decoration of α–MnO2 with CeO2 particles during a one-step hydrothermal process. The morphology, composition, and electrochemical properties were studied in the context of application to the oxygen reduction reaction (ORR) and Mg-air battery. According to the results, α–MnO2/CeO2 microfibres exhibited better ORR performance than α–MnO2 microfibres due to the synergistic result between the introduction of Ce3+ in CeO2 lattice and the enhancement of Mn3+ content in MnO2 lattice. α–MnO2/CeO2 microfibres provided a higher surface area and more catalytic active sites than α–MnO2 microfibres by controlling the molar ratio of Ce3+/Mn7+ for the precursor. When the mole ratio of Ce3+ and Mn7+ in the precursors was 10%, the four-electron transfer process of the MnO2/CeO2 microfibres (MC-140-12-10) was found to be similar to that of the 20 wt% Pt/C commercial catalysts. MC-140-12-10 microfibres also showed the excellent long-term stability after 25,000 s and superior Mg–air battery performances than α–MnO2. Hence, the work paves the way for developing Mg-air batteries through a simple synthesis and cost-effective ORR catalyst.

In-situ electron loss spectroscopy reveals surface dehydrogenation of hydrated ceria nanoparticles at elevated temperatures

Ceria (CeO2) exhibits high reversible oxygen storage capacity at intermediate temperatures (500–800 °C) related to an extraordinary and not fully understood reduction of its surfaces. We have investigated pristine and alcohol-dispersed commercially available ceria nanoparticles by in-situ scanning transmission electron microscopy with electron energy loss spectroscopy (STEM-EELS) to examine the dynamic changes during the initial redox reaction process of ceria nanoparticles in an ultra-high vacuum atmosphere using an in-situ heating holder. High spatially resolved EELS was used to estimate the amounts of Ce3+ and Ce4+ in the nanoparticles as a function of temperature, based on the white-line ratios M5/M4 of the EELS spectra. The results show a nm-range thick surface layer rich in Ce3+ on pristine particles prior to heating. During heating, this oxidises to Ce4+. Heating in high vacuum should normally not lead to oxidation, but the observed results can be understood if the surface layer has an oxyhydroxide composition such as CeOOH, which by heating in the vacuum dehydrogenates and hence oxidises to CeO2, a process that requires diffusion of hydrogen only. This process occurred for all samples, but was more pronounced for the particles that were previously dispersed in ethanol. Thermogravimetric analysis (TGA) by heating the pristine powder in dry atmosphere yielded a considerable weight loss confirming the content of hydroxide and probably water in and on the CeO2 particles. The results suggest that CeO2 surfaces are reduced to a layer of oxyhydroxide by hydrogen-containing molecules like water vapour or alcohols.

Effect of Ni active site position and synthesis route on activity, stability, and morphology of Ce promoted Ni/Al2O3 catalyst for clean H2 production

The main object of this research is investigation the effect of Ni active site position and synthesis route on the activity, stability, and morphology of Ce promoted Ni/Al2O3 catalyst applied in the steam reforming of methane (SRM) for producing H2-rich syngas with low CO2 contents. In the first step, the Ce promoted Ni/Al2O3 catalysts are synthesized via co-impregnation and co-precipitation methods with different Ni loading 10–25 % and Ce loading 0–3.0 %. The performance of synthesized catalysts to progress steam reforming reaction are tested in an experimental setup at temperature range 600–700 °C and steam to methane ratio 1.5–3.5. Besides the influence of CeO2 particles on the catalytic activity of Ni-based catalysts, their effect on Ni active sites dispersion is also investigated. The results depicted that integrated Ni-Al structure synthesized via co-precipitation method has a higher surface area, higher catalytic activity and stability, as well as stronger Ni-Al interaction compared to un-promoted impregnated samples. However, the 20Ni-1.5Ce/Al2O3 catalyst exhibits higher NiO crystallinity, stronger Ni-Al interaction, higher oxygen storage capacity (OSC), lower deposited coke, and thus higher catalytic activity during the SRM process. Based on the activity tests, 20Ni-1.5Ce/Al2O3 catalyst depicted the best performance for producing environmentally-friendly H2-rich syngas with the lowest amount of CO2 and CH4.

Influence of CeO2 and TiO2 Particles on Physicochemical Properties of Composite Nickel Coatings Electrodeposited at Ambient Temperature.

The Ni-TiO2 and Ni-CeO2 composite coatings with varying hydrophilic/hydrophobic characteristics were fabricated by the electrodeposition method from a tartrate electrolyte at ambient temperature. To meet the requirements of tight regulation by the European Chemicals Agency classifying H3BO3 as a substance of very high concern, Rochelle salt was utilized as a buffer solution instead. The novelty of this study was to implement a simple one-step galvanostatic electrodeposition from the low-temperature electrolyte based on a greener buffer compared to traditionally used, aiming to obtain new types of soft-matrix Ni, Ni-CeO2, and Ni-TiO2 coatings onto steel or copper substrates. The surface characteristics of electrodeposited nickel composites were evaluated by SEM, EDS, surface contact angle measurements, and XPS. Physiochemical properties of pure Ni, Ni-CeO2, and Ni-TiO2 composites, namely, wear resistance, microhardness, microroughness, and photocatalytic activity, were studied. Potentiodynamic polarization, EIS, and ICP-MS analyses were employed to study the long-term corrosion behavior of coatings in a 0.5 M NaCl solution. Superior photocatalytic degradation of methylene blue, 96.2% after 6 h of illumination, was achieved in the case of Ni-TiO2 composite, while no substantial change in the photocatalytic behavior of the Ni-CeO2 compared to pure Ni was observed. Both composites demonstrated higher hardness and wear resistance than pure Ni. This study investigates the feasibility of utilizing TiO2 as a photocatalytic hydrophilicity promoter in the fabrication of composite coatings for various applications.

A facile emulsion-combustion processing of IR reflective, antibacterial and antifungal ceria for surface engineered functional textiles

Emulsion-combustion reaction was performed using cerous carbonate-urea emulsion prepared in hexane/water medium by mechanical milling with CTAB surfactant. Prolonged exposure of the urea-cerous carbonate emulsion mixture at 90 °C, undergoes slow and steady flameless, ‘smouldering’ that caused localized micro-thermal heating. Ultimately simultaneous decomposition of cerous carbonate and urea occurred, finally produced crystalline, soft ceria agglomerates consisting of fluorite CeO2 particles. Ceria thus obtained was studied for the optical reflectance in the wavelength 700–2400 nm to understand the total solar reflectance quality [TSR]. The product was also systematically characterized for phase purity, morphology, UV absorbance, band gap as well as surface chemistry using XPS analysis. The Near IR reflectance data confirms 94% reflectance in the IR region. Antibacterial and antifungal studies were conducted against Escherichia coli, Staphylococcus aureus, Klebsiella, Candida albicans, and Aspergillus Niger. Subsequently, this IR reflective, antimicrobial ceria was dispersed in an acrylic-sodium silicate hybrid dispersant cum binder system for ceria spray coatings on fabrics used for making face masks. The IR reflectance and hydrophobic properties of ceria coated masks were examined. This study explored the beneficial properties of IR reflective, antimicrobial, hydrophobic CeO2 for the processing of surface engineered, multifunctional textiles for the medical sector.

Ptirm (M=Zn, Ni) Ammonia Oxidation Catalysts for Anion-Exchange Membrane Direct Ammonia Fuel Cells

Low-temperature direct ammonia fuel cells (DAFCs) use carbon-neutral ammonia as a fuel, which has attracted increasing attention recently due to ammonia's low source-to-tank energy cost, easy transport and storage, and wide availability. However, current DAFC technologies are greatly limited by the kinetically sluggish ammonia oxidation reaction (AOR) at the anode. Herein, we report an AOR catalyst, in which ternary PtIrZn nanoparticles with an average size of 2.3 ± 0.2 nm were highly dispersed on a binary composite support comprising cerium oxide (CeO2) and zeolitic imidazolate framework-8 (ZIF-8)-derived carbon (PtIrZn/CeO2-ZIF-8) through a sonochemical-assisted synthesis method. The PtIrZn alloy, with the aid of abundant OHad provided by CeO2 and uniform particle dispersibility contributed by porous ZIF-8 carbon (surface area: ∼600 m2 g−1), has shown highly efficient catalytic activity for the AOR in alkaline media, superior to that of commercial PtIr/C. The rotating disk electrode (RDE) results indicate a lower onset potential (0.35 vs. 0.43 V), relative to the reversible hydrogen electrode at room temperature, and a decreased activation energy (∼36.7 vs. 50.8 kJ mol−1) relative to the PtIr/C catalyst. Notably, the PtIrZn/CeO2-ZIF-8 catalyst was assembled with a high-performance hydroxide anion-exchange membrane to fabricate an alkaline DAFC, reaching a peak power density of 91 mW cm−2. Unlike in aqueous electrolytes, supports play a critical role in improving uniform ionomer distribution and mass transport in the anode. PtIrZn nanoparticles on silicon dioxide (SiO2) integrated with carboxyl-functionalized carbon nanotubes (CNT–COOH) were further studied as the anode in a DAFC. A significantly enhanced peak power density of 314 mW cm−2 was achieved.

Synthesis and Characterization of Novel NiW–CeO2 Composite Coating with Enhanced Corrosion and Wear Resistance

Compact and uniform NiW composite coatings filled with ceramic particles such as CeO2 were electrodeposited on brass substrates using direct current (DC) and a well–designed pulse reverse current waveforms (PRC). PRC coatings exhibited the noblest corrosion potential and lowest current density compared to DC–electrodeposited coatings. Among all PRC coatings, PRC–NiW–CeO2 demonstrated the highest corrosion potential (−4.72 × 10−1 V) and the lowest current density (5.32 × 10−6 V). It also seems that the addition of CeO2 particles to the NiW matrix enhanced the wear resistance of the coatings, and the lowest wear volume of (133.10 × 103 µm3) and friction coefficient of 0.25 were obtained due to the formation of the uniform, void free and compact structures with a high content of CeO2 particles in the coating.

Strong Ru-CeO2 interaction boosts catalytic activity and stability of Ru supported on CeO2 nanocube for soot oxidation

Cerium oxide based catalysts are active for soot oxidation, while serious catalyst deactivation feasibly occurs due to thermal sintering. In this study, Ru and Ag supported on CeO2 were prepared and their catalytic performances as well as thermal durability for soot oxidation were evaluated. Characterization results show that thermal treatment at 800 °C leads to substantial crystalline growth of CeO2 and Ag particles in Ag/CeO2. In contrast, crystalline growth of CeO2 is remarkably alleviated and high dispersion of Ru particles is effectively maintained on Ru/CeO2 owing to the formation of RuOCe bonds. As a result, catalyst recycling and thermal pretreatment at 800 °C lead to remarkably catalyst deactivation of CeO2 and Ag/CeO2, but slightly declined activity on Ru/CeO2. The combination of experiments and DFT calculations clearly indicates that the strong interactions between Ru and CeO2 account for the high catalytic activity and strong thermal duration of Ru/CeO2 for soot oxidation.

Antioxidant colloids via heteroaggregation of cerium oxide nanoparticles and latex beads

Antioxidant colloids were developed via controlled heteroaggregation of cerium oxide nanoparticles (CeO2 NPs) and sulfate-functionalized polystyrene latex (SL) beads. Positively charged CeO2 NPs were directly immobilized onto SL particles of opposite surface charge via electrostatic attraction (SL/Ce composite), while negatively charged CeO2 NPs were initially functionalized with poly(diallyldimethylammonium chloride) (PDADMAC) polyelectrolyte and then, aggregated with the SL particles (SPCe composite). The PDADMAC served to induce a charge reversal on CeO2 NPs, while the SL support prevented nanoparticle aggregation under conditions, where the dispersions of bare CeO2 NPs were unstable. Both SL/Ce and SPCe showed enhanced radical scavenging activity compared to bare CeO2 NPs and were found to mimic peroxidase enzymes. The results demonstrate that SL beads are suitable supports to formulate CeO2 particles and to achieve remarkable dispersion storage stability. The PDADMAC functionalization and immobilization of CeO2 NPs neither compromised the peroxidase-like activity nor the radical scavenging potential. The obtained SL/Ce and SPCe artificial enzymes are foreseen to be excellent antioxidant agents in various applications in the biomedical, food, and cosmetic industries.

Ceria-silica mesoporous catalysts for CO preferential oxidation in H2-rich stream: The effect of Ce:Si ratio and copper modification

In this work mesoporous CeO2-SiO2 catalysts with the Ce:Si molar ratios of 1:1 and 4:1 were synthesized by template method and modified with copper to elucidate the role of copper-ceria and ceria-silica interactions in the catalyst efficiency in CO-PROX. The catalysts were characterized by SEM-EDS, AAS, XRD, TPR-H2, TEM, and spectroscopic methods (Raman, EPR and in situ DRIFT of adsorbed CO). The binary catalyst with the equimolar Ce:Si ratio demonstrated better catalytic performance in CO-PROX due to its favorable textural properties and strong ability to anion vacancy formation as confirmed by N2 physisorption and Raman spectroscopy. CuOx/CeSiOy (Ce:Si = 4:1) demonstrated better low-temperature activity, CO2 selectivity and stability than CuOx/CeSiOy (Ce:Si = 1:1) and both binary systems because of its unique structure, comprising fine CeO2 particles with a narrow size distribution of 2–3 nm well dispersed on a large surface area, high concentration of the most active in CO oxidation Cu+ sites, formed on CuOx-CeO2 interfaces, and improved ability to surface reoxidation after reduction with the reagents resulted in the decreased Ce3+ concentration. It was also stable in the presence of CO2 and H2O in the reaction mixture. These properties would be difficult to achieve via template preparation methods without SiO2 addition.

Enhanced mechanical and tribological properties of AA6061/CeO2 composite fabricated by friction stir processing

Friction stir processing (FSP) with single and double pin tools was successfully utilized with the aim of fabrication of Al 6061/CeO2 surface composite layer. It was found that pin geometry (pin number) has played a pivotal role in the improvement of mechanical properties and extra grain refinement. Moreover, results indicated that using a double-pin tool during the process impressively enhanced the distribution of CeO2 particles in the matrix and, subsequently, the ultimate tensile strength was increased about 20% compared to the single pin tool.