Nanoparticles Of CeO2 Research Articles

Nickel-Doped Cerium Oxide Nanoparticles: Green Synthesis Using Stevia and Protective Effect against Harmful Ultraviolet Rays.

Nanoparticles of cerium oxide CeO2 are important nanomaterials with remarkable properties for use in both industrial and non-industrial fields. In a general way, doping of oxide nanometric with transition metals improves the properties of nanoparticles. In this study, nickel- doped cerium oxide nanoparticles were synthesized from Stevia rebaudiana extract. Both doped and non-doped nanoparticles were characterized by X-ray diffraction, Field Emission Scanning Electron Microscopy, Energy Dispersive X-ray, Raman spectroscopy, and Vibrating-Sample Magnetometry analysis. According to X-ray diffraction, Raman and Energy Dispersive X-ray crystalline and single phase of CeO2 and Ni doped CeO2 nanoparticles exhibiting fluorite structure with F2g mode were synthesized. Field Emission Scanning Electron Microscopy shows that CeO2 and Ni doped nanoparticles have spherical shape and sizes ranging of 8 to 10 nm. Ni doping of CeO2 results in an increasing of magnetic properties. The enhancement of ultraviolet protector character via Ni doping of CeO2 is also discussed.

Comparison of Mixing Strategies and Hybrid Ratio Optimization for Mechanical Properties Enhancement of Al-CeO2-GNP’s Metal Matrix Composite Fabricated by Friction Stir Processing

In this work, mechanical properties enhancement of AA6061 metal matrix composite (MMC) is carried out by synergizing nanoparticles mixing strategies and hybrid ratio. Dry mixing and solvent-based mixing of CeO2 and graphene nanoplatelets (GNP) are compared separately as well as in volume percentages of 75/25, 50/50, and 25/75, respectively. Solvent-based mixing proved to be more effective in separating particles agglomerates and mixing them uniformly due to polar nature of solvent and agitation of sonicator. Nanoparticles of CeO2 and graphene are embedded by friction stir processing (FSP) in metal matrix. Four numbers of passes are performed, and rotational and traverse speeds of 1000 rpm and 40 mm/min are kept for first three passes and 1000 rpm and 60 mm/min for fourth pass, respectively. Microstructure analysis of FSPed samples divulged the contribution of nanoparticles in refining grains due to their pinning effect in retarding grain growth. Because of grain refinements and obstacles posed by particles to dislocation movement, enhancements in hardness and tensile strength of MMC are observed. 50/50 volume percentage is recorded as optimum in improving tensile strength and microhardness. Fractography showed that fracture shifts from ductile to brittle with increasing content of graphene. It is suggested that formation of Al4C3 caused brittle failure. Highest improvement of 69.3% in microhardness and that of 12.9% in UTS are recorded as compared to base metal.

Poly vinyl alcohol-CeO2 nanocomposite films: a promising material for NO2 sensors at high temperatures

Nanoparticles of CeO2 were dispersed in Poly vinyl Alcohol to form nanocomposite films of various concentrations. Thick films of thickness around 100 μm were prepared by solution casting and pure PVA, PVA-2.5 wt% CeO2 and PVA-25 wt% CeO2 films were tested for their response as sensors to various gases. It was found that the PVA-2.5 wt% CeO2 film showed the best response of nearly 40% increase in resistance to 100 ppm of NO2 gas at 423 K. This indicated that it could be useful as a high temperature sensor for NO2 gas. Three of the above samples were also prepared by spin coating technique as thin films of thickness 1 μm, 5 μm and 50 μm, on a glass substrate and tested for sensing action of the same gases at 3 ppm concentration. It was seen that 2.5 wt% CeO2 film of 1 μm thickness gave the best response of 16% increase for NO2 gas, amongst all the films. The increase in resistance of the films in the presence of NO2 gas is due to chemisorption on the CeO2 nano fillers and the mechanism seems to be effective even at low concentration of the filler. The results of sensing in these films are better than that of other similar materials and suggest that they can be used as high temperature sensors.

Selective Hydrodeoxygenation of Guaiacol to Phenolics by Ni/Anatase TiO2 Catalyst Formed by Cross-Surface Migration of Ni and TiO2

The catalytic properties of physical mixtures of Ni particles (100–200 nm) with nanoparticles of anatase TiO2 (TiO2-A), ZrO2, Al2O3, rutile TiO2 (TiO2-R), and CeO2 were investigated for the hydrode...

Electric Conductivity of Li/Na Binary Molten Carbonate Coexisting with Nanoparticles of CeO2:Sm3+

The electrical conductivity calculated from ac impedance measurement and differential thermal analysis (DTA) are measured for molten (Li0.52Na0.48)2CO3 coexisting with nano-ordered CeO2 and ceria-based oxides such as CeO2:Sm3+. The influence of surface properties of the oxides with smooth surface, narrow particle size distribution, and large specific surface area at around the eutectic point is discussed. The specific surface area of the solid phase of used samples are ca. 50 m2g-1.Temperature dependence of the electrical conductivity for (Li0.52Na0.48)2CO3 coexisting with nano-ordered CeO2 and CeO2:Sm3+ at melt content less than ca. 15 vol% does not indicate a remarkable change in conductivity at the temperature range around the eutectic point of molten carbonate, whereas the transition point was observed obviously in Arrhenius plot’s for CeO2 (1.5 m2g-1)/(Li0.52Na0.48)2CO3 (5 vol%) coexisting system in previous study. Obtained DTA spectra indicate that the melting enthalpy disappeared below the melt content of 30 vol% or less. In such case, the apparent average thickness of the carbonate melts is less than ca 0.5 nm as remarkable influences of solid phase are observed. Sm3+ doping contributes an increase of electrical conductivity of composites below the eutectic points of molten carbonate.

Adsorption and Desorption Properties of CeO2 Nanoparticles for Concentrating Dilute CO2

A recent concern about an energy issue has encouraged investigation on photocatalytic [1] or electrochemical [2] conversion of CO2 to fuels such as methane and methanol. For the realization of the conversion of CO2 to fuels, a technique concentrating dilute CO2 in the atmosphere also becomes important. A rare-earth oxide of CeO2 is an excellent adsorbant against CO2 [3]. The advantage is that CeO2 adsorbs CO2 near room temperature and releases it until 300 °C. The mass of the CO2 adsorbed to 1 g of CeO2 reaches 0.04 g at most, although the adsorption and desorption properties are dependent on the natures of particles. The crucial factors have not been revealed yet. In this work, we prepared several CeO2 nanoparticles with different synthetic routes and characterized their properties with respect to the unit cell dimensions, morphologies, and specific surface areas. The CeO2 nanoparticles were prepared by (1) thermal decomposition of Ce2(CO3)2·8H2O or CeCO3OH, and (2) precipitation by raising the pH of Ce(NH4)2(NO3)6 aq with NH3 or CO(NH2)2. Some samples were heat-treated at 300 °C to improve the crystallinity and the effects of the heat treatment were examined. The adsorption and desorption properties were characterized by thermogravimetric (TG) analysis (Rigaku Thermo plus EVO), in which a powder sample was pretreated in TG in dry CO2 at 250 °C to remove the adsorbed CO2 and H2O and then kept at 25 °C in CO2 for adsorption equilibrium. The mass of the adsorbed CO2 was calculated from the weight change between 25 and 250 °C. XRD indicated the formation of fluorite type CeO2 regardless of the preparation routes. TEM observation revealed that the prepared samples were composed of nano-sized particles less than 10 nm. The TEM observation exhibited well crystallized nanoparticles of CeO2 with clear lattice fringes in the images. The broadened XRD peaks were attributed to the smallness of the grain size. The CeO2 particles prepared via thermal decomposition of Ce2(CO3)·8H2O or CeCO3OH showed better performance on CO2 adsorption. Quite interestingly, there was no distinct correlation between the specific surface areas evaluated by N2 adsorption and the CO2 adsorption. Rather, the nanoparticles which had a specific crystallite size around 5~6 nm appeared to be advantageous on the CO2 adsorption as shown in Fig. 1. Fig. 1 shows the adsorbed mass of CO2 to 1 g of the CeO2 powders prepared via the different synthetic routes. An increasing tendency can be seen in the adsorbed mass until 6 nm when the data was plotted against the crystallite size. [1] H. Rao et al., Nature 548 (2017) 74. [2] S. Kaneco et al., Ind. Eng. Chem. Res. 41 (2002) 5165. [3] C. Li et al., J. Chem. Soc. Faraday Trans 1 (1989) 3901. Figure 1

CHARACTERIZATION OF CeO2 DOPED MgAl2O4 PREPARED BY THE CHELATING AGENTS-ASSISTED IMPREGNATION METHOD

MgAl2O4 spinel employed as support of reforming catalysts was doped by CeO2. The samples were prepared by wet impregnation from aqueous solutions of cerium nitrate, with and without chelating agents. The chelating agents used were ethylenediamine-tetraacetic acid (EDTA), nitrilotriacetic acid (NTA) and citric acid (CA) at different pH of impregnation. The solids were characterized by TG, XRD, SBET, TPR, SEM-EDX and CO2-TPD. Nanoparticles of CeO2 between 5 and 6.8 nm were obtained by the thermal decomposition in air at 600 °C. The surface cerium reduction occurred in a wide temperature range of 450° to 670 °C. The use of citric acid at pH= 8 led to the lowest crystallite size of CeO2 and the lowest interaction with the spinel. The H2 consumption and extent of CeO2-support interaction did not show a clear dependence with the CeO2 crystallite sizes. The use of chelating agents in the impregnation step did not modify the total basicity. Slight changes in the strength of weak basic sites were observed.

Tuned charge-transfer between ceria and 1,4,5,8-naphthaldiimide as a function of pH

In this study, cerium oxide CeO2 was selected to exploit their applications with an also special class of organic compounds the naphthalene diimides. The 1,4,5,8-naphthaldiimides are known for their superior electrochemical activities comparable to those of Paraquat (Methyl Viologen) but with larger amplitude of photochemical applications. Cerium Oxide is a wide bandgap semiconductor well known for its catalytic capabilities and for its simple manipulation to prepare thin films and nanoparticles (NP). Aqueous suspensions containing positively charged diimide derivative N,N’-(N,N´-dimethylethyleneamine-N´´-butyl)−1,4,5,8-naphthaldiimide (NDI4) and NP of CeO2 were investigated. The UV–vis and fluorescent spectra of the NDI4 showed distinct features compared to those of that in bulk that arises from the sorption on the ceria surface. NDI4 interacted in a special manner with NP of CeO2 rendering a wide pH range hydrolytic inertness and novel photochromic behavior of the diimide. The organic dye is proposed to adsorb in the crevices of the NP and forming a charge transfer complex with CeO2 that accounts for the new photoactivities observed.

Inverse Catalysts for CO Oxidation: Enhanced Oxide–Metal Interactions in MgO/Au(111), CeO2/Au(111), and TiO2/Au(111)

Au(111) does not bind CO and O2 well. The deposition of small nanoparticles of MgO, CeO2, and TiO2 on Au(111) produces excellent catalysts for CO oxidation at room temperature. In an inverse oxide/metal configuration there is a strong enhancement of the oxide–metal interactions, and the inverse catalysts are more active than conventional Au/MgO(001), Au/CeO2(111), and Au/TiO2(110) catalysts. An identical trend was seen after comparing the CO oxidation activity of TiO2/Au and Au/TiO2 powder catalysts. In the model systems, the activity increased following the sequence: MgO/Au(111) < CeO2/Au(111) < TiO2/Au(111). Ambient pressure X-ray photoelectron spectroscopy (AP-XPS) was used to elucidate the role of the titania–gold interface in inverse TiO2/Au(111) model catalysts during CO oxidation. Stable surface intermediates such as CO(ads), CO32–(ads), and OH(ads) were identified under reaction conditions. CO32–(ads) and OH(ads) behaved as spectators. The concentration of CO(ad) initially increased and then decre...

Influence of Nano CeO2 on the Microstructures and Current Density of Preform Optimized Infiltration Growth-Processed Bulk YBa2Cu3 O 7−δ Superconductors

The effect of the addition of nanometric ceria (CeO2) on the physical properties of YBa2Cu3O7−δ superconductors is investigated. Preform optimized infiltration growth (POIG) process emerged as one of the advanced processing techniques to obtain the uniform distribution of fine Y2BaCuO5 (Y-211) particles of the order of ∼1 μ m. Nanoparticles of CeO2 were added to Y-211 in 0, 2, 5 and 10 wt% through a novel process called Nano Dispersive Sol Casting and subjected to POIG process. Nanometric CeO2 particles were distributed homogeneously throughout the Y-211 preform without any agglomeration. The micrographs of the final composites indicate refinement in Y-211 particle size and presence of defects in various length scales, starting from few nanometers to few microns. As the CeO2 content increased, the Y-211 particle size refined below 1 µm and, for 10 wt% of doping, even smaller than 0.5 µm. Elemental analysis confirmed the formation of different phases in the CeO2-added composites, due to which the superconducting transition is shown broadening. The sample with 10 wt% doping exhibited a stable Jc curve to high applied magnetic fields due to the presence of multiple peak fields. The present work demonstrates the introduction of fine microstructural defects for pinning the flux lines at different applied magnetic fields in POIG-processed YBCO composites.

Role of various nano-particles in prevention of fungal decay, mold growth and termite attack in wood, and their effect on weathering properties and water repellency

The resistance of Scots pine wood vacuum-treated with nano-particles of ZnO, B2O3, CuO, TiO2, CeO2, and SnO2 against decay, mold fungi and subterranean termites was evaluated. Weathering and water absorption properties were also studied. Nano-ZnO only was resistant against leaching, while the other compounds leached out from wood specimens at more than 60% release rates. Mold growth in wood specimens was significantly inhibited by treatment with nano-ZnO and nano-B2O3. In Petri dishes, all mold fungi were also inhibited by nano-ZnO and nano-B2O3; however, nano-SnO2 inhibited Trichoderma harzianum growth only. Weight loss from fungal attack by the brown-rot fungus was significantly inhibited by all nano-compounds tested, except for leached specimens of nano-B2O3 treatments. Considerably higher weight losses were obtained in decay resistance tests by the white-rot fungus; only nano-CuO and nano-SnO2 were effective against this fungus. Nano-CuO and nano-B2O3 treatments produced favorable termite resistance in both weathered and unweathered specimens, while nano-ZnO and nano-CeO2 resulted in decreased weight loss in specimens exposed to termites. Nano-ZnO was slightly effective in decreasing water absorption. Exposing untreated wood specimens to artificial weathering resulted in significant changes in the chemical structure as determined by FT-IR analysis; however, weathering effect was somewhat decreased by the incorporation of the nano-compounds.

Ceria based novel nanocomposites catalysts MnxCe1−xO2/α-Al2O3 for low-temperature combustion of methanol

A modified nanoemulsion method allowed obtaining nanoparticles (NPs) of the MnOx–CeO2 system within the whole range of the Mn:Ce atomic ratio. The NPs with excess of Ce consisted solely of MnxCe1−xO2 nanocrystallites (NCs) (fluorite structure) while the catalysts with excess of Mn were nanocomposite of MnxCe1−xO2 and of 3–4 times larger Mn3O4 (hausmannite) NCs. The obtained nanomaterials were mesoporous but the composite materials consisted thin slit-shaped pores of size close to the micropore range. The NPs of Mn3O4 were much more active in catalytic combustion of methanol than NPs of CeO2 obtained by the same nanoemulsion method. Nevertheless, incorporation of Mn into CeO2 lattice can improve these NPs to be more active than Mn3O4. The NPs of MnxCe1−xO2 deposited on α-Al2O3 micrograins via the nanoemulsion method preserved activity of the equivalent non-supported NPs. The comparable high activity of Mn0.25Ce0.75O2 monophasic NPs with the nanocomposite of the Mn:Ce=3:1 ratio suggests joint catalytic action of Mn- and Ce-assembles. Complementary XPS measurements showed a surface Mn-enrichment of the monophasic NPs associated with Mn4+ to Mn2+/3+ reduction and increase of the O2− share in O 1s signal. Such active assemblies have been postulated.

Cerium and yttrium oxide nanoparticles against lead-induced oxidative stress and apoptosis in rat hippocampus.

Due to numerous industrial applications, lead has caused widespread pollution in the environment; it seems that the central nervous system (CNS) is the main target for lead in the human body. Oxidative stress and programmed cell death in the CNS have been assumed as two mechanisms related to neurotoxicity of lead. Cerium oxide (CeO2) and yttrium oxide (Y2O3) nanoparticles have recently shown antioxidant effects, particularly when used together, through scavenging the amount of reactive oxygen species (ROS) required for cell apoptosis. We looked into the neuroprotective effects of the combinations of these nanoparticles against acute lead-induced neurotoxicity in rat hippocampus. We used five groups in this study: control, lead, CeO2 nanoparticles + lead, Y2O3 nanoparticles + lead, and CeO2 and Y2O3 nanoparticles + lead. Nanoparticles of CeO2 (1000 mg/kg) and Y2O3 (230 mg/kg) were administered intraperitoneally during 2 days prior to intraperitoneal injection of the lead (25 mg/kg for 3 days). At the end of the treatments, oxidative stress markers, antioxidant enzymes activity, and apoptosis indexes were investigated. The results demonstrated that pretreatments with CeO2 and/or Y2O3 nanoparticles recovered lead-caused oxidative stress markers (ROS, lipid peroxidation, and total thiol molecules) and apoptosis indexes (Bax/Bcl-2 and caspase-3 protein expression). Besides, these nanoparticles reduced the activities of lead-induced superoxide dismutase and catalase as well as the ADP/ATP ratio. Interestingly, the best recovery resulted from the compound of these nanoparticles. Based on these outcomes, it appears that this combination may potentially be beneficial for protection against lead-caused acute toxicity in the brain through improving the oxidative stress-mediated programmed cell death pathway.

Effect of dopants [Gd3+, Sm3+, Ca2+, Sr2+ and Ba2+] on the performance characteristics of ceria based electrolytes for application in solid oxide fuel cells

Doped CeO2 based materials are now-a-days proposed as alternate electrolyte materials for solid oxide fuel cells (SOFCs) working at low temperature (~723 – 873 K). In this research work, nanoparticles of CeO2 doped with Gd3+, Sm3+, Ca2+, Sr2+ and Ba2+were prepared by a simple homogeneous chemical precipitation method. The prepared materials (after heat treatment at 1023 K for 2 hours) were systematically characterized by XRD, EDAX analysis, FTIR , particle size analysis and SEM. Lattice parameters were calculated from the XRD data. The XRD results indicate that all the doped ceria samples studied are single phase with a cubic fluorite structure. The average particle size of the doped ceria powder was about 48 – 115 nm and the particles have shown narrow particle size distribution patterns. AC impedance spectroscopy studies performed on the sintered specimens have shown better oxide ion conductivity values and hence these materials may be suitable for application as electrolyte materials in solid oxide fuel cells working at low temperature (~723 – 873 K). ________________________________________GRAPHICAL ABSTRACT

Electronic structure study of Ce1-xAxO2 (A = Zr & Hf) nanoparticles: NEXAFS and EXAFS investigations.

Single phase nanoparticles (NPs) of CeO2, Ce0.5Zr0.5O2, Ce0.5Hf0.5O2 and Ce0.5Hf0.25Zr0.25O2 were successfully synthesized by co-precipitation method at constant pH and temperature. The X-ray diffraction results revealed that the additive atoms did not segregate to form secondary phases but led to grain size variation in the NPs. The 10 Dq values in the near edge X-ray absorption fine structure (NEXAFS) spectra at the O K-edge did not vary in the same way as the average grain size was changed for the doped CeO2 NPs. The deconvolution of Ce M5-edge and detailed analysis of O K pre-edge peak have shown the higher Ce(+3)/(Ce(+3) + Ce(+4)) ratio in the Zr- and Hf-doped samples. The local atomic structure around the Ce, Zr and Hf atoms was investigated using extended X-ray absorption fine structure (EXAFS) spectroscopy at Ce K-edge, Zr K-edge and Hf L3-edge, respectively, and the EXAFS data were fitted with the theoretical calculations. The 4f occupancy, Ce(+3)/(Ce(+3) + Ce(+4)) ratio of Ce ions, coordination number of Ce and Ce-Ce/Ce-O bond distances were sensitive to the additive atoms but not explicitly changed according to the grain size variation in the NPs.

Assemblies of nanoparticles of CeO2–ZnTi-LDHs and their derived mixed oxides as novel photocatalytic systems for phenol degradation

Self-assemblies of nanoparticles of CeO2/ZnTi layered double hydroxides (CeO2/ZnTi-LDH) and the derived CeO2/Zn2TiO4 systems are reported as novel efficient nano-photocatalysts for phenol degradation. The spontaneous formation and organization of nanoparticles of CeO2 on ZnTi-LDH matrix is based on a cheap, nontoxic and facile technique that invokes the manifestation of the structural memory effect of LDH in aqueous solution of Ce(SO4)2. It was found that the composition of the brucite-type layer has a major effect on establishing the performances of the phenol photodegradation process. Moreover the LDH layered matrix offers multiple advantages, such as manipulation of the brucite-like layer composition and the insertion of key cations, like Zn2+ and Ti4+, but also the possibility to supply a good dispersion of the metal cations within the layers, which may act as charge separation centers enhancing the efficiency in subsequent applications. These results open new opportunities in the development of hybrid nano-assemblies systems able to utilize their collective properties for facilitating cumulative photocatalytic properties for “green” removal of dangerous pollutants.

Microsomal Glutathione Transferase 1 Protects Against Toxicity Induced by Silica Nanoparticles but Not by Zinc Oxide Nanoparticles

Microsomal glutathione transferase 1 (MGST1) is an antioxidant enzyme located predominantly in the mitochondrial outer membrane and endoplasmic reticulum and has been shown to protect cells from lipid peroxidation induced by a variety of cytostatic drugs and pro-oxidant stimuli. We hypothesized that MGST1 may also protect against nanomaterial-induced cytotoxicity through a specific effect on lipid peroxidation. We evaluated the induction of cytotoxicity and oxidative stress by TiO2, CeO2, SiO2, and ZnO in the human MCF-7 cell line with or without overexpression of MGST1. SiO2 and ZnO nanoparticles caused dose- and time-dependent toxicity, whereas no obvious cytotoxic effects were induced by nanoparticles of TiO2 and CeO2. We also noted pronounced cytotoxicity for three out of four additional SiO2 nanoparticles tested. Overexpression of MGST1 reversed the cytotoxicity of the main SiO2 nanoparticles tested and for one of the supplementary SiO2 nanoparticles but did not protect cells against ZnO-induced cytotoxic effects. The data point toward a role of lipid peroxidation in SiO2 nanoparticle-induced cell death. For ZnO nanoparticles, rapid dissolution was observed, and the subsequent interaction of Zn2+ with cellular targets is likely to contribute to the cytotoxic effects. A direct inhibition of MGST1 by Zn2+ could provide a possible explanation for the lack of protection against ZnO nanoparticles in this model. Our data also showed that SiO2 nanoparticle-induced cytotoxicity is mitigated in the presence of serum, potentially through masking of reactive surface groups by serum proteins, whereas ZnO nanoparticles were cytotoxic both in the presence and in the absence of serum.

Fabrication of Ag–CeO2 core–shell nanospheres with enhanced catalytic performance due to strengthening of the interfacial interactions

Interfacial interactions are often found in human medical devices, hybrid solar cells, and catalysis. However, there is a lack of control of these interactions when tailoring the materials properties for many technological applications. As a case study, we reported on the synthesis of Ag–CeO2 core–shell nanospheres with the aim of strengthening the interfacial interactions to give enhanced catalytic performance. All core–shell nanospheres were synthesized by a surfactant-free method with a subsequent annealing redox reaction. Systematic sample characterizations indicate that metallic Ag cores with a diameter of 50–100 nm were wrapped by assembled nanoparticles of CeO2 with a shell thickness of 30–50 nm to form a nano-scale core–shell structure. The interfacial interactions between the Ag core and CeO2 shell were strengthened by annealing, surprisingly, as followed by generation of oxygen vacancies to provide abundant of absorption sites for oxygen species. As a consequence, the temperature for oxygen spilling was lowered to 79 °C, and the catalytic performance was abnormally enhanced, as indicated by complete CO oxidation at 120 °C with no sign of deactivation, even when the reaction time is beyond 100 h. The reaction products were desorbed quickly from the surfaces of the core–shell nanospheres, which accounts for their superior stability during catalytic reactions.

Room Temperature Ferromagnetism in Fe-Doped CeO&lt;SUB&gt;2&lt;/SUB&gt; Nanoparticles

RT ferromagnetism was observed in nanoparticles of Fe-doped CeO2 (i.e., Ce(0.97)Fe(0.03)O2) synthesized by a sol-gel method. The undoped and Fe-doped CeO2 were characterized by XRD, Raman spectroscopy, TEM, and VSM. The undoped samples and Ce(0.97)Fe(0.03)O2 precursor exhibit a diamagnetic behavior. The 673 K-calcined Ce(0.97)Fe(0.03)O2 sample is paramagnetic whereas 773 and 873 K-calcined Ce(0.97)Fe(0.03)O2 samples are ferromagnetism having the magnetizations of 4.65 x 10(-3) emu/g and 6.20 x 10(-3) emu/g at 10 kOe, respectively. Our results indicate that the ferromagnetic property is intrinsic to the Fe-doped CeO2 system and is not a result of any secondary magnetic phase or cluster formation.

The Nanomorphology-Controlled Palladium-Support Interaction and the Catalytic Performance of Pd/CeO2 Catalysts

Nanorods and nanoparticles of CeO2 were successfully synthesized and used as support of Pd/CeO2 catalysts. It is found that the nanorods show obvious advantages as the support, compared with the nanoparticles. Low efficiency in the formation of reduced Pd, and partial encapsulation of Pd species account for the poor activity of Pd supported on CeO2 nanoparticles. On the contrary, a favorable interaction between Pd and the crystal planes [1 1 0] and [1 0 0] of CeO2 nanorods effectively promotes the reducibility of Pd species, resulting in much better catalytic performance of Pd/CeO2 catalyst for CO oxidation.