CeO2 Nanocomposites Research Articles

Characterization of hydrogen storage behavior of the as-synthesized p-type NiO/n-type CeO2 nanocomposites by carbohydrates as a capping agent: The influence of morphology

This study proposes a p-type/n-type heterojunction system for electrochemically hydrogen storage. The electrochemical investigation was done as a simple method to evaluate storage capacity. The p-type NiO/n-type CeO2 mesoporous nanocomposites were prepared via a facile thermal decomposition way that is better than the carbohydrates as a green capping agent. For the first time, the electrochemical hydrogen storage behavior of this nanocomposite was evaluated by chronopotentiometry technique in a potassium hydroxide aqueous solution (6 M KOH) under 1 mA current. The electrochemical measurements display that the hydrogen storage capacity is largely dependent on the design of the nanostructures. Sample No. 2 with the plate-like architecture has higher hydrogen storage capacity than sample No. 1 having particle architecture. The plate-like architecture increases the storage capacity by reducing the diffusion pathway, increasing the surface area, and buffering the volume change during cycling. The hydrogen storage capacity for sample No. 1 and 2 was obtained ≈5500 and 6850 mAh/g, respectively.

On the Surface Nature of Bimetallic PdZn Particles Supported on a ZnO–CeO2 Nanocomposite for the Methanol Steam Reforming Reaction

CO adsorption—as a molecular probe—was studied by transmission IR spectroscopy on pre-reduced Pd and bimetallic PdZn nanoparticles. Palladium was supported (2 wt% Pd) on pure CeO2, ZnO and a ZnO–CeO2 composite (atomic ratio Zn:Ce = 1:2). The Pd 3d5/2 binding energy shift, together with the formation of metallic zinc were consistent with the development of a PdZn alloy over the zinc-containing supports at increasing reduction temperature, as revealed by XPS. Following H2 reduction at 623 K the bimetallic particles showed only linear CO adsorption (COL) at initial contact time (10 Torr CO, 298 K), giving rise to a convoluted IR band ascribed to different Pd sites, where it was assumed that the Pd–Pd distances were larger than for pure Pd crystallites, indicating the presence of a PdZn alloyed surface. However, for longer exposure time to CO and/or higher superimposed pressure, the appearance of bridge and hollow coordinated CO (COB and COH, respectively) on the Pd sites suggested the degradation of the PdZn surface alloy, most likely due to the segregation of Pd surface patches. The temperature-programmed, dynamic isobaric adsorption of CO (TPA-CO), under flowing CO(1%)/He on the catalysts pre-reduced at 623 K (that is, for similar conditions to those found in the methanol steam reforming—MSR-process) showed faster desorption of COL as compared to COB + COH species for supported Pd/CeO2, as expected. However, the TPA-CO results on Pd/ZnO–CeO2 were atypical: even under the superimposed, low CO partial pressure, and for a temperature range similar to those found at high methanol conversion in the MSR reaction, the PdZn bimetallic surface nature was recovered, which could be an explanation of the good selectivity to CO2 of Pd/ZnO-based catalysts and—in particular—of the catalytically stable Pd/ZnO–CeO2 materials.

Superior Photocatalytic Performance of CeO₂ Nanoparticles and Reduced Graphene Oxide Nanocomposite Prepared by Low Cost Co-Precipitation Method.

In this article, cerium oxide nanoparticles (CeO2 NPs) and reduced graphene oxide nanocomposite have been fabricated through simple, easy and cost effective co-precipitation method. The structural, optical and morphological characterization provides the evidence of successful synthesis of CeO2 NPs and nanocomposite. X-ray photoelectron spectroscopic characterization provides useful information about the concentrations and proportions of Ce3+ and Ce4+ ions in nanoparticles as well as in nanocomposite. These studies provide an insight to understand enhanced photocatalytic activity of nanocomposite. The nanocomposite produces 81% photocatalytic degradation of methyl orange compared to only 45% degradation by CeO2 NPs alone.

Rapid photo-degradation of toxic dye pollutants: green synthesis of mono-disperse Fe3O4–CeO2 nanocomposites in the presence of lemon extract

Fe3O4 nanoparticles were first synthesized via a fast precipitation method. CeO2 and Fe3O4–CeO2 nanocomposites then were prepared using hydrothermal method with a green procedure in the presence of lemon extract. The effect of time, pH and applied magnetic field on the size and shape of nanostructures were investigated. The prepared products were characterized using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. Vibrating sample magnetometer was used to study the magnetic property of the products. The results illustrated super-paramagnetic behaviour of Fe3O4 nanoparticles. The photo-catalytic behaviour of Fe3O4–CeO2 nanocomposites was evaluated using the degradation of two azo dyes under ultraviolet light irradiation. The results show that the prepared nanocomposites have potential application for magnetic and photo-catalytic performance.

Enhanced photocatalytic activity of hybrid reduced graphene oxide–CeO2 hierarchical flower-like nanostructures

The combination of the unique properties of graphene with functional characteristics of metal oxides is an interesting pathway to achieve desirable properties for various applications. Herein, reduced graphene oxide (rGO) hybridized with CeO2 nanoparticle (CeO2-NPs) or CeO2 hierarchical flower-like nanostructure (CeO2-HFNs) composites were synthesized by a facile hydrothermal or solvothermal processes. The microstructure, morphology and photocatalytic performance of the synthesized rGO–CeO2 nanocomposites were systematically investigated under simulated sun irradiation, using methylene blue (MB) as a test dye. The results show that rGO can prevent the aggregation, support the CeO2-NPs distribution or wrap the CeO2-HFNs. The rGO–CeO2-HFNs exhibit an enhanced photodegradation rate (96%) in comparison with bare CeO2-HFNs (73%) and bare CeO2-NPs (67%) towards the degradation of MB. The enhancement can be attributed to separation of electron–hole pairs and large specific area for the rGO–CeO2-HFNs. The low rGO-to-CeO2 mass fraction makes this high-performance catalyst more economical and promising for environmental application.

Facile Synthesis of CeO2 Nanosheets Decorated upon BiOI Microplate: A Surface Oxygen Vacancy Promoted Z-Scheme-Based 2D-2D Nanocomposite Photocatalyst with Enhanced Photocatalytic Activity

Construction of a visible light driven Z-scheme-based photocatalytic system is a hot topic of research because of the potential to alleviate both energy and environmental issues. In the present study a series of surface vacancy mediated BiOI–CeO2 nanocomposites were prepared and their crystallographic, morphological, optical, and electrochemical behavior were characterized through XRD, TEM, FESEM, UV–vis DRS, PL, ESI, and Mott–Schottky techniques. From the XPS analysis, it could be said that a high amount of oxygen defects and metallic bismuth were present on the composite than neat CeO2 which was the major cause of enhancement in the photocatalytic activity. Further the photocatalytic efficiency of the as prepared samples was tested toward RhB decolorization/phenol oxidation as well as for O2 gas evolution. It was observed that 40 wt % BiOI–CeO2 nanocomposite exhibited highest photocatalytic activity among neat and other composites, i.e., 89% decolorization of 100 ppm RhB and produces 323 μmol/2h of O2 u...

Cu/Mn Double-Doped CeO2 Nanocomposites as Signal Tags and Signal Amplifiers for Sensitive Electrochemical Detection of Procalcitonin.

Nanomaterials themselves as redox probes and nanocatalysts have many advantages for electrochemical biosensors. However, most nanomaterials with excellent catalytic activity cannot be directly used as redox probe to construct electrochemical biosensor because the redox signal of these nanomaterials can only be obtained in strong acid or alkali solution at high positive or negative potential, which greatly limits their applications in biologic assay. In this study, Cu/Mn double-doped CeO2 nanocomposite (CuMn-CeO2) was synthesized to use as signal tags and signal amplifiers for the construction of electrochemical immunosensor for sensitive assay of procalcitonin (PCT). Herein, CuMn-CeO2 not only possesses excellent catalytic activity toward H2O2 for signal amplification, but also can be directly used as redox probe for electrochemical signal readout achieved in neutral mild buffer solution at low positive potential. Importantly, since doping Cu, Mn into CeO2 lattice structure can generate extra oxygen vacancies, the redox and catalytic performance of obtained CuMn-CeO2 was much better than that of pure CeO2, which improves the performance of proposed immunosensor. Furthermore, CuMn-CeO2 can be implemented as a matrix for immobilizing amounts of secondary antibody anti-PCT by forming ester-like bridging between carboxylic groups of Ab2 and CeO2 without extra chemical modifications, which greatly simplifies the preparative steps. The prepared immunosensor exhibited a wide linear range of 0.1 pg mL-1 to 36.0 ng mL-1 with a low detection limit of 0.03 pg mL-1. This study implements nanomaterial themselves as redox probes and signal amplifiers and paves a new way for constructing electrochemical immunosensor.

Investigation of Mn2O3 as impurity on the electrochemical hydrogen storage performance of MnO2[sbnd]CeO2 nanocomposites

The electrochemical hydrogen adsorption/desorption properties of MnO2CeO2 and MnO2CeO2/Mn2O3 nanocomposites are studied and discussed in this paper for the first time. MnO2CeO2 nanocomposites have been prepared via thermal decomposition route using fructose as a green capping agent under various reaction conditions. Two parameters contain calcination time and temperature were evaluated to achieve the product with specific composition and morphology. In hydrogen storage process, the charge/discharge cycles were investigated via chronopotentiometry technique. According to the results, the Mn2O3 impurity can improve the electrochemical hydrogen storage performances of the MnO2CeO2 nanocomposite. Also, the hydrogen storage capacity of samples is enhanced with repeating the cycles, it was observed 1000 and 980 mA h/g for one cycle, 6100 and 5950 mA h/g after 20 cycles for samples No. 3 and 4, respectively. The increase of hydrogen storage capacity is because of the creation of new sites during charge/discharge process in the working electrode.

Nanostructured conducting polyaniline (NSPANI)/CeO2 nanocomposites for humidity sensors application

This paper reports the electrochemical activity of nanostructured conducting polyaniline (NSPANI) whose properties were enhanced by adding inorganic ceria (CeO2) nanoparticles that has excellent electro catalytic ability and biocompatibility properties. The method of synthesis employed for the nanocomposites of NSPANI and Cerium oxide (CeO2) was by in-situ polymerization method with different weight percentage of cerium oxide in aniline monomer. The metal oxide CeO2 nanoparticles were prepared by co-precipitation method. The effects of addition of ceria in weight percentage of 10, 20, 25 and 30 were investigated by various characterization techniques like X-ray diffraction, functional groups by Fourier Transform Infrared Spectroscopy, Thermal stability by Thermal Gravimetric Analysis, Morphology by Scanning Electron Microscope and Transmission electron microscope. Application of NSPANI/CeO2 nanocomposites in the field of humidity sensors were studied where different weight percentages of the CeO2 in aniline were compared along with the NSPANI without ceria. The material that showed the maximum sensitivity and also good linearity was the nanocomposite of NSPANI with 20% ceria.

Semiconductor-ionic Membrane of LaSrCoFe-oxide-doped Ceria Solid Oxide Fuel Cells

A novel semiconductor-ionic La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF)-Sm/Ca co-doped CeO2 (SCDC) nanocomposite has been developed as a membrane, which is sandwiched between two layers of Ni0.8Co0.15Al0.05Li-oxide (NCAL) to construct semiconductor-ion membrane fuel cell (SIMFC). Such a device presented an open circuit voltage (OCV) above 1.0V and maximum power density of 814mWcm−2 at 550°C, which is much higher than 0.84V and 300mWcm−2 for the fuel cell using the SCDC membrane. Moreover, the SIMFC has a relatively promising long-term stability, the voltage can maintain at 0.966V for 60hours without degradation during the fuel cells operation and the open-circuit voltage (OCV) can return to 1.06V after long-term fuel cell operation. The introduction of LSCF electronic conductor into the membrane did not cause any short circuit but brought significant enhancement of fuel cell performances. The Schottky junction is proposed to prevent the internal electrons passing thus avoiding the device short circuiting problem.

Thermal decomposition synthesis, characterization and electrochemical hydrogen storage characteristics of Co3O4–CeO2 porous nanocomposite

Particle-like Co3O4–CeO2 nanocomposite was synthesized via a facile thermal decomposition process in the presence of fructose as a green capping agent and ammonium cerium(IV) nitrate as Ce source. The effect of various parameters such as different cobalt sources, calcination temperature and time were investigated on the size and morphology of products. The transmission electron microscopy observations indicated that the synthesized products have a particle-like shape with an average diameter of 18–35 nm. For the first time, the electrochemical hydrogen storage performance of Co3O4–CeO2 porous nanocomposite was investigated via chronopotentiometry method in aqueous KOH solution in this paper. The electrochemical measurements showed that this product has a good hydrogen storage capacity at room temperature. Its maximum discharge capacity was 5200 mAh/g after 20 cycles. Therefore, Co3O4–CeO2 porous nanocomposite showed that it is a good candidate for electrochemical hydrogen storage.

Synthesis, characterization and investigation of the electrochemical hydrogen storage properties of CuO–CeO2 nanocomposites synthesized by green method

Pure CuO–CeO2 nanocomposites were synthesized by simple thermal decomposition method in presence of various Cu salts as a copper source and fructose as a green capping agent. In this study, the effect of various parameters such as the type of copper sources, temperature and time of reaction on the morphology and the particles size were studied. The products were characterized via X-ray diffraction (XRD) pattern, scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX), transmission electron microscopy (TEM), N2 adsorption (BET), vibrating sample magnetometer (VSM), and infrared spectrum (FT-IR). The optical property of the nanocomposite was examined via UV–vis (DRS) spectroscopy and the band gap was calculated to 3 eV. Also, the hydrogen storage capacity of CuO–CeO2 nanocomposites and CeO2 nanoparticles were investigated via chronopotentiometry method for the first time. The discharge capacity of CeO2 nanoparticles and CuO–CeO2 nanocomposites in 1 mA current and 20 cycles obtained 2150 and 2450 mAh/g, respectively.

Editorial expression of concern on intermediate Ce3+ defect level induced photoluminescence and third-order nonlinear optical effects in TiO2–CeO2 nanocomposites by S. Divya, V. P. N. Nampoori, P. Radhakrishnan, and A. Mujeeb

Editorial expression of concern on intermediate Ce3+ defect level induced photoluminescence and third-order nonlinear optical effects in TiO2–CeO2 nanocomposites by S. Divya, V. P. N. Nampoori, P. Radhakrishnan, and A. Mujeeb

Facile hydrothermal procedure to synthesize sheet-on-sheet reduced graphene oxide (RGO)/CuxO[sbnd]CeO2 nanocomposites for preferential oxidation of carbon monoxide

The sheet-on-sheet reduced graphene oxide (RGO)/CuxOCeO2 catalysts were synthesized by a facile hydrothermal procedure and systematically characterized by X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, hydrogen temperature-programmed reduction, X-ray photoelectron spectroscopy and N2 adsorption–desorption techniques. It is found that there is a large amount of reduced copper species in the RGO/CuxOCeO2 catalysts, and the addition of RGO was beneficial for the dispersion of particles and the improvement of textural properties. The spherical nanoparticles of copper species can be served as spacers to prevent the stacking of RGO. Copper and cerium species are homogenously distributed on the surface of RGO sheets. The introduction of RGO improves the formation of high Ce3+ concentration and oxygen vacancies. Therefore, the RGO/CuxOCeO2 catalysts show higher catalytic activity than the CuOCeO2 catalyst at low temperature (below 135 °C). Moreover, good resistance to H2O and CO2 of the RGO/CuxOCeO2 may be from for the formation of hydroxyl groups by dissociative adsorption of H2O on the surface of RGO, which can improve the WGS reaction and the decomposition of carbonates.

Ultrasonic assisted synthesis of nanocomposite materials based on resole resin and surface modified nano CeO2: Chemical and morphological aspects

In this study, phenol-formaldehyde (PF)/CeO2 nanocomposites (NC)s were prepared by in-situ polymerization of phenol and formaldehyde in alkali solution in the presence of surface modified CeO2 nanoparticles (NP)s by sonochemical assisted synthesis. The morphology and structure of PF/CeO2 NCs were characterized by using fourier transform infrared spectroscopy (FT-IR), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), and thermal analyses methods. It was found that due to the good dispersion of surface modified NPs in polymer matrix and the strong interfacial interaction between the CeO2 NPs and PF matrix, the thermal stability and thermo-mechanical properties of the PF/CeO2 NCs were greatly enhanced. FE-SEM and AFM analyses showed the uniform distribution of CeO2 NPs in PF matrix. The XRD patterns of NCs show the presence of crystalline CeO2 NPs in amorphous matrix. The thermal analysis results reveal that, with increases in the content of CeO2 NPs in PF matrix, the thermally stability factors of samples were drastically enhanced.

Self-Organized Epitaxial Vertically Aligned Nanocomposites with Long-Range Ordering Enabled by Substrate Nanotemplating.

Vertically aligned nanocomposites (VAN) thin films present as an intriguing material family for achieving novel functionalities. However, most of the VAN structures tend to grow in a random fashion, hindering the future integration in nanoscale devices. Previous efforts for achieving ordered nanopillar structures have been focused on specific systems, and rely on sophisticated lithography and seeding techniques, making large area ordering quite difficult. In this work, a new technique is presented to produce self-assembled nanocomposites with long-range ordering through selective nucleation of nanocomposites on termination patterned substrates. Specifically, SrTiO3 (001) substrates have been annealed to achieve alternating chemical terminations and thus enable selective epitaxy during the VAN growth. La0.7 Sr0.3 MnO3 :CeO2 (LSMO):CeO2 nanocomposites, as a prototype, are demonstrated to form well-ordered rows in matrix structure, with CeO2 (011) domains selectively grown on SrO terminated area, showing enhanced functionality. This approach provides a large degree of long-range ordering for nanocomposite growth that could lead to unique functionalities and takes the nanocomposites one step closer toward future nanoscale device integration.

Synthesis of the novel β-cyclodextrin supported CeO2 nanoparticles for the catalytic degradation of methylene blue in aqueous suspension

Nanoceria (CeO2) and a new β-cyclodextrin coated CeO2 nanocomposite (β-CD-CeO2) materials were prepared by using a combination of precipitation and sol-gel method for efficient degradation of organic dyes from aqueous solutions at room temperature. The prepared catalysts were characterized by using various analytical techniques such as XRD, FT-IR, Pyridine adsorbed FT-IR, Raman spectroscopy, FESEM, TEM and HRTEM. The XRD study suggests the formation of nanocrystalline materials which is further confirmed from the TEM photographs. The presence of oxygen vacancies and lattice defects of the samples were confirmed by Raman analysis. The thermal stability of the prepared catalysts was tested by TGA measurements. UV–Vis analyses were performed to find out the band gap energy and absorbance in the solid state. The β-CD-CeO2 has the particle diameter of 14 ± 2 nm with band gap of 4.93 eV. The degradation of the methylene blue (MB) was performed by using the prepared catalysts at room temperature in the presence of H2O2 without light irradiation. The process of degradation produces LMB sulfone with m/z = 317 amu, which further lost one or both of its dimethylamine groups to produce substances with m/z = 273 amu and m/z = 229 amu. It was observed that β-CD-CeO2 efficiently degrades the MB solution completely within 1 h whereas CeO2 degrades the solution partially giving a higher rate constant value for the former.

Kinetic Analysis of the Reduction of 4-Nitrophenol Catalyzed by CeO2 Nanorods-Supported CuNi Nanoparticles

CuxNi100–x (x = 0, 20, 40, 60, 80, and 100) nanoparticles were uniformly grown on the surface of CeO2 by the liquid impregnation method. The as-prepared nanocomposite abbreviated CuxNi100–x–CeO2 was characterized by various techniques including, X-ray powder diffraction, field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, Brunauer–Emmett–Teller surface area analyzer, and transmission electron microscopy. The catalytic activity of CuxNi100–x–CeO2 nanocomposites was investigated in 4-nitrophenol (4-NP) reduction reaction. Among the synthesized nanocomposites, Cu60Ni40–CeO2 exhibited the best catalytic activity (rate constant as 0.1654 s–1) with high recyclability for five consecutive runs. The mechanism of the reduction was studied, and the adsorption equilibrium constant of 4-NP (K4-NP) and borohydride (KBH4–) was calculated by using the Longmuir–Hinshelwood model. The energy of activation (Ea) and thermodynamic parameters such as activation enthalpy (ΔH⧧), entropy (ΔS⧧), and...

Nanoporous Platinum Doped Cerium Oxides Thin Films Grown on Silicon Substrates: Ionic Platinum Localization and Stability

In this study, the characterization of nanostructured Pt‐doped CeO2 films with low platinum content and porous structure is reported, deposited on silicon substrate by direct liquid injection chemical vapor deposition. The platinum localization and concentration in the nanocomposite are determined by scanning transmission electron microscopy associated with energy dispersive X‐ray spectroscopy. Films are made of ≈3 nm diameter CeO2 particles and platinum is homogeneously dispersed through the layers. X‐ray photoelectron spectroscopy (XPS) also shows that platinum is mainly in an ionic Pt2+ state. After diffusion through the preformed porous structure of ceria films, the platinum precursor decomposes at the surface of each ceria particle forming the films, producing a homogeneous platinum‐doped CeO2 nanocomposite. This result is supported by synchrotron radiation XPS experiment, where the measured relative Pt concentration demonstrates that platinum is decomposed only at the surface of ceria particles. Finally, when the saturation of Pt2+ sites at the surface of ceria particles is reached, metallic nanoclusters are formed from platinum excess.

A novel route for synthesis of α-Fe2O3–CeO2 nanocomposites for ethanol conversion

In this study, a series of α-Fe2O3–CeO2 nanocomposites containing 5, 15, 30, and 50 % Fe as well as the pure oxides, α-Fe2O3 and CeO2, were synthesized by a novel route of auto-combustion method at temperatures lower than those reported previously. The as-synthesized catalysts were characterized by several techniques such as XRD, XRF, N2 physisorption, DSC/TGA, NH3-TPD, TEM, and EDX. The catalytic activity of the synthesized nanocomposites was examined under ethanol conversion. The results revealed that the solid-solution formation was established for all the Fe-substituted CeO2 samples while maintaining the fluorite structure of ceria. Only a hardly noticeable segregation of α-Fe2O3 was appreciated for the catalyst samples with higher iron content (30 and 50 wt% Fe). The results confirmed that the adopted auto-combustion method allowed a good control of the chemical composition of the prepared composites with the proper structural and textural characteristics. The 30 % Fe–Ce sample was the most active and selective catalyst toward ethylene production compared with the other samples under study, owing to the pronounced Bronsted acid sites. The overall data collected through this work revealed that the synthesized nanocomposites are promising candidates for the production of ethylene from ethanol.