Abstract: Efficient catalysts for the oxygen-evolution reaction, especially in alkaline media, are highly desired because of their application in various energy technologies. Now, a gold-supported NiCeOx catalyst is shown to have excellent catalytic activity due to synergistic geometric and electronic effects.

Abstract: We investigated the effect of various oxide supports on the catalytic activity of rhodium nanoparticles in hydrogen generation from the hydrolysis of ammonia borane. Among the oxide supports (CeO2, SiO2, Al2O3, TiO2, ZrO2, HfO2) ceria provides the highest catalytic activity for the rhodium(0) nanoparticles in the hydrolysis of ammonia borane. Rhodium(0) nanoparticles supported on nanoceria (Rh0/CeO2) were prepared by the impregnation of rhodium(III) ions on the surface of ceria followed by their reduction with sodium borohydride in aqueous solution at room temperature. They were isolated from the reaction solution by centrifugation and characterized by a combination of advanced analytical techniques. The catalytic activity of Rh0/CeO2 samples with various rhodium loading in the range of 0.1–4.0% wt. Rh was also tested in hydrogen generation from the hydrolysis of ammonia borane at room temperature. The highest catalytic activity was achieved by using 0.1% wt. rhodium loaded nanoceria. The resulting Rh0/CeO2 with a metal loading of 0.1% wt. Rh show superb catalytic activity in hydrogen generation from the hydrolysis of ammonia borane with a record turnover frequency value (TOF) of 2010 min−1 at 25.0 ± 0.1 °C. The superb catalytic activity of Rh0/CeO2 is ascribed to the reducible nature of ceria. The reduction of cerium(IV) to cerium(III) leads to a build-up of negative charge on the oxide surface which favors the bonding of rhodium(0) nanoparticles on the surface and, thus, their catalytic activity. Rh0/CeO2 are also reusable catalysts preserving 67% of their initial catalytic activity even after the fifth use in hydrogen generation from the hydrolysis of ammonia borane at room temperature (TOF = 1350 min−1. The work reported here also includes the kinetic studies depending on the temperature to determine the activation energy (Ea = 43 ± 2 kJ/mol) and the effect of catalyst concentration on the rate of hydrolysis of ammonia borane.

Abstract: We report the synthesis of high quality CeO2-CdO binary metal oxide nanocomposites were synthesized by a simple chemical precipitation and hydrothermal method. Cerium nitrate and cadmium nitrate were used as precursors. Composition, structure and morphology of the nanocomposites were analyzed by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM). XRD pattern proves that the final product has cubic phase and the particle size diameter of the nanocomposites are 27nm, XRD results also indicated that the crystalline properties of the nanocomposite were improved without affecting the parent lattice, FESEM analysis indicates that the product is composed of spherical particles in clusters. The morphological and optical properties of CeO2-CdO nanosamples were characterized by HRTEM and DRS spectroscopy. The IR results showed high purity of products and indicated that the nanocomposites are made up of CeO2 and CdO bonds. Absorption spectra exhibited an upward shift in characteristic peaks caused by the addition of transition metal oxide, suggesting that crystallinity of both the metal oxide is improved due to specific doping level. TGA plots further confirmed the purity and stability of nanomaterials prepared. Hence the nanocomposite has cubic crystal lattice and form a homogeneous solid structure. From the result, Cd(2+) ions are embedded in the cubic crystal lattice of ceria. The growth rate increases which are ascribed to the cationic doping with a lower valence cation. Ce-Cd binary metal oxide nanocomposites showed antibacterial activity, it showed the better growth inhibition towards p.aeruginosa. Exploit of photodegradation and photocatalytic activity of large scale synthesis of CeO2-CdO binary metal oxide nanocomposites was reported.

Abstract: In the current study and attempt is made to synthesized the cerium-doped copper ferrite nanoparticles (CuFe2−xCexO4) through an auto-combustion method with the aid of nitrate precursors such as copper(II), iron(III), and cerium(III (in an aqueous solution. Besides, the effect of different concentrations of various type of capping agents such as lactose and glucose on the morphology and particle size of final products was investigated. The structural, morphological, and optical properties of as-obtained products were characterized extensively by techniques such as FT-IR, XRD, EDX, SEM, TEM, and UV–vis. Furthermore, the magnetic property of as-prepared CuFe2−xCexO4 nanoparticles was also investigated with vibrating sample magnetometer at room temperature. Moreover, the as-prepared Ce-doped CuFe2O4 nanoparticles were used as efficient photocatalyst for the photocatalytic degradation of harmful organic dye, i.e. methyl orange under ultraviolet light.

Abstract: Optical and magneto-optical behavior of Cerium Yttrium Iron Garnet thin films at wavelengths of 200–1770 nm

Abstract: The mechanisms of sulfur dioxide poisoning on Mn/TiO2 and Mn-Ce/TiO2 catalysts are studied and poisoning resistance effect of cerium is revealed Both two kinds of catalysts were deactivated to reduce NOx removal in the presence of SO2, however, the sulfur resistance performance of the Ce doping catalysts was obviously improved From the result of DRIFT and DFT, SO2 can first adsorb on the manganese-terminal (Lewis acid sites) to form sulfates, which inhibit the adsorption of NH3 in the SCR reaction Deactivation of Bronsted acid sites was due to the formation of bisulfite, which can react with NH4+ form NH4HSO4 For the Mn-Ce/TiO2 catalysts, SO2 preferentially adsorbed on Ce atom as sulfate species, alleviating the sulfation of the main active sites (Lewis acid sites and Broosted acid site on MnOx) under the effect of SO2 Furthermore, cerium sulfate can produce new Bronsted acid site and contribute to the low-temperature SCR processes

Abstract: Catalytic oxidation of carbon monoxide (CO) is of great importance in many different fields of industry. Until now it still remains challenging to use non-noble metal based catalysts to oxidize CO at low temperature. Herein, we report a new class of nanoporous, uniform, and transition metal-doped cerium (IV) oxide (ceria, CeO2) microsphere for CO oxidation catalysis. The porous and uniform microsphere is generated by sacrificed polymer template. Transition-metals, like Cu, Co, Ni, Mn and Fe, were doped into CeO2 microspheres. The combination of hierarchical structure and metal doping afford superior catalytic activities of the doped ceria microspheres, which could pave a new way to advanced non-precious metal based catalysts for CO oxidation.

Abstract: Ultrafine 5 nm ceria isotropic nanoparticles were prepared using the rapid chemical precipitation approach from cerium(III) nitrate and ammonium hydroxide aqueous solutions. The as-prepared nanoparticles were shown to contain predominantly Ce(IV) species. The solubility of nanocrystalline CeO2 at several pH values was determined using ICP-MS and radioactive tracer methods. Phase composition of the ceria samples remained unchanged upon partial dissolution, while the shape of the particles changed dramatically, yielding nanorods under neutral pH conditions. According to X-ray absorption spectroscopy investigation of the supernatant, Ce(III) was the main cerium species in solution at pH < 4. Based on the results obtained, a reductive dissolution model was used for data interpretation. According to this model, the solubility product for ceria nanoparticles was determined to be log Ksp = −59.3 ± 0.3 in 0.01 M NaClO4. Taken together, our results show that the pH dependence of ceria anti- and pro-oxidant activit...

Abstract: Nanostructured ceria-praseodymia catalysts with different praseodymium contents have been prepared through hydrothermal synthesis to study the effect of Pr as a dopant and the effect of morphology towards soot combustion under “loose” and “tight” soot-catalyst conditions. Samples synthesized through solution combustion synthesis (SCS) have also been prepared as comparative materials. Studies in physicochemical properties of the catalysts have been carried out using complementary techniques. The present work also resorts to soot-TPR as an unconventional method of investigating the ability of solid catalysts to initiate soot oxidation in the absence of bulk oxygen. Ce50Pr50 catalyst (where 50 indicates the atomic percentage of cerium as well as of praseodymium) with mixed structures of nanorods and nanocubes has attained the best catalytic performances, thanks to the high lattice oxygen mobility and the easy reducibility. The insertion of Pr cations to the ceria framework enhances the number of redox sites on the surface, thus generating more oxygen vacancies. As a whole, activity tests in general have proven that despite having relatively low surface areas, ceria-praseodymia nanocubes and nanorods facilitated soot combustion reaction more actively than SCS-based ceria-praseodymia catalysts with larger surface areas. This evidences the beneficial effect of well-defined nanostructures in soot combustion, due to their possession of highly reactive low-index facets (1 0 0) and (1 1 0). Within SCS-based samples, however, the specific surface area overshadows the importance of praseodymium. This eventually marks the synergistic combination of well-defined nanostructures and praseodymium as a dopant.

Abstract: TiO2 and Ce/TiO2 were synthesized and subsequently used for the catalytic combustion of DCM. TiO2 had abundant Lewis acid sites and was responsible for the adsorption and the rupture of C-Cl bonds. However, TiO2 tended to be inactivated because of chloride poisoning due to the adsorption and accumulation of Cl species over the surface. While, Ce/TiO2 obtained total oxidation of CH2Cl2 at 335°C and exhibited stable DCM removal activity on 100h long-time stability tests at 330°C without any catalyst deactivation. The doped cerium generated Ce(3+) chemical states and surface active oxygen, and therefore played important roles from two aspects as follows. First of all, the poisoning of Cl for Ce/TiO2 was inhibited to some extent by CeO2 due to the rapid removal of Cl on the surface of CeO2, which has been verified by NH3-IR characterization. In the other hand, CeO2 enhanced the further deep oxidation of C-H from byproducts and retained the certain oxidation of CO to CO2. Based on the DRIFT characterization and the catalysts activity tests, a two-step reaction pathway for the catalytic combustion of DCM on Ce/TiO2 catalyst was proposed.

Abstract: A new and an existing Ce-based metal–organic framework (MOF) having a UiO-66 framework topology and incorporating azide and nitro functional groups in their frameworks have been successfully used as turn-on fluorescent probes for the sensing of H2S under physiological conditions. The azide (1-N3) and nitro (2-NO2) functionalized Ce MOFs have been synthesized under similar solvothermal conditions (100 °C, 15 min) using ammonium cerium(IV) nitrate and H2BDC-X (BDC = 1,4-benzenedicarboxylate; X = –N3 for 1-N3 and –NO2 for 2-NO2) linkers in DMF/H2O (DMF = N,N-dimethylformamide) mixtures. The phase purity of both compounds has been confirmed by X-ray powder diffraction (XRPD) analyses, infrared spectroscopy and thermogravimetric (TG) analyses. The thermally activated forms of both compounds (1′-N3 and 2′-NO2) show fast response time, excellent selectivity and sensitivity for the detection of H2S under physiological conditions (HEPES buffer, pH 7.4) through the fluorescence ‘turn-on’ mechanism. The detection limits (12.2 μM for 1′-N3 and 34.8 μM for 2′-NO2) of both materials lie within the range of the H2S concentration observed in biological systems. The materials can selectively detect H2S even in the presence of other competing biomolecules. Apart from the sensing of H2S, both compounds exhibit high uptake of CO2 (2.6 mmol g−1 for 1′-N3 and 3.7 mmol g−1 for 2′-NO2) at 0 °C and 1 bar. Thus, the materials are promising candidates in the fields of H2S sensing and CO2 capture.

Abstract: We report comparable levels of covalency in cerium– and uranium–carbon multiple bonds in the iso-structural carbene complexes [M(BIPMTMS)(ODipp)2] [M = Ce (1), U (2), Th (3); BIPMTMS = C(PPh2NSiMe3)2; Dipp = C6H3-2,6-iPr2] whereas for M = Th the MC bond interaction is much more ionic. On the basis of single crystal X-ray diffraction, NMR, IR, EPR, and XANES spectroscopies, and SQUID magnetometry complexes 1–3 are confirmed formally as bona fide metal(IV) complexes. In order to avoid the deficiencies of orbital-based theoretical analysis approaches we probed the bonding of 1–3via analysis of RASSCF- and CASSCF-derived densities that explicitly treats the orbital energy near-degeneracy and overlap contributions to covalency. For these complexes similar levels of covalency are found for cerium(IV) and uranium(IV), whereas thorium(IV) is found to be more ionic, and this trend is independently found in all computational methods employed. The computationally determined trends in covalency of these systems of Ce ∼ U > Th are also reproduced in experimental exchange reactions of 1–3 with MCl4 salts where 1 and 2 do not exchange with ThCl4, but 3 does exchange with MCl4 (M = Ce, U) and 1 and 2 react with UCl4 and CeCl4, respectively, to establish equilibria. This study therefore provides complementary theoretical and experimental evidence that contrasts to the accepted description that generally lanthanide–ligand bonding in non-zero oxidation state complexes is overwhelmingly ionic but that of uranium is more covalent.

Abstract: Two different trapping and detrapping processes of charge carriers have been investigated in GdAlO3:Ce3+,Ln3+ (Ln = Pr, Er, Nd, Ho, Dy, Tm, Eu, and Yb) and GdAlO3:Ln3+,RE3+ (Ln = Sm, Eu, and Yb; RE = Ce, Pr, and Tb). Cerium is the recombination center and lanthanide codopants act as electron-trapping centers in GdAlO3:Ce3+,Ln3+. Different lanthanide codopants generate different trap depths. The captured electrons released from the lanthanide recombine at cerium via the conduction band, eventually producing the broad 5d–4f emission centered at ∼360 nm from Ce3+. On the other hand, Sm3+, Eu3+, and Yb3+ act as recombination centers, while Ce3+, Pr3+, and Tb3+ act as hole-trapping centers in GdAlO3: Ln3+,RE3+. In this situation, we find evidence that recombination is by means of hole release instead of the more commonly reported electron release. The trapped holes are released from Pr4+ or Tb4+ and recombine with the trapped electrons on Sm2+, Eu2+, or Yb2+ and yield characteristic trivalent emission from Sm3...

Abstract: The new, dimethyl-functionalized Ce(IV)-based UiO-66 (UiO = University of Oslo) metal–organic framework (MOF) material Ce-UiO-66-(CH3)2 (1) was successfully synthesized under solvothermal conditions (100 °C, 15 min) by employing ammonium cerium(IV) nitrate and the 2,5-dimethyl-1,4-benzenedicarboxylate (H2BDC-(CH3)2) ligand in a DMF/H2O (DMF = N,N-dimethyl formamide) mixture. The phase purity of the as-synthesized and thermally activated form (1′) of the compound was confirmed by a combination of X-ray powder diffraction (XRPD) analysis, Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric (TG) analysis. As verified by the thermogravimetric analysis, the compound is thermally stable up to 300 °C in air atmosphere. Based on the XRPD measurements, the material retains its crystallinity after treatment with water, methanol, acetic acid and 1 M HCl. As confirmed by the gas sorption experiments, the compound shows significant microporosity towards N2 (BET surface area = 845 m2 g−1) and CO2 (adsorption capacity = 34 cm3 g−1 at 0 °C and 1 bar). The catalytic activity of 1′ has been studied in the oxidation of styrene and cyclohexene using tert-butylhydroperoxide (TBHP) as the terminal oxidant. The catalyst is reusable for four cycles with no significant drop in its activity which is further confirmed by a hot filtration experiment.

Abstract: A carbon paste electrode was modified with a Ce(III)-imprinted polymer (Ce-IP) and used for voltammetric determination of Ce(III) ions in real water samples. Precipitation polymerization was used for synthesis of the nano-sized Ce-IP from vinylpyridine and methacrylic acid (acting as the complexing ligands and functional monomers), divinylbenzene (cross-linker) and AIBN as the radical starter. The Ce-IP was characterized by scanning electron microscopy and zeta potentials. A carbon paste electrode (CPE) was then impregnated with the Ce-IP and used for the extraction and subsequent determination of Ce(III). Oxidative square wave voltammetry showed the electrode to give a significantly better response than an electrode modified with the non-imprinted polymer. The addition of multiwalled carbon nanotubes to the Ce-IP-modified electrode further improves the signal, thereby increasing the sensitivity of the method. The effects of electrode composition, extraction pH value, volume and time were optimized. The electrode, if operated at a voltage of 1.05 V (vs. Ag/AgCl), displays a linear response to Ce(III) in the 1.0 μM to 25 pM concentration range, and the detection limit is 10 pM (at an S/N ratio of 3). The relative standard deviation of 5 separate determinations is 3.1 %. The method was successfully applied to the determination of Ce(III) in the spiked samples of drinking water and sea water.

Abstract: Cerium-modified Cu-SSZ-13 catalysts were synthesized by an in situ hydrothermal method, and Ce was incorporated through ion exchange. The catalytic performance and N2 selectivity over prepared catalysts were evaluated in the selective catalytic reduction (SCR) of NOx by NH3. The physicochemical properties of the samples were characterized using XRD, SEM, H2-TPR, XPS, NMR, XAS, and N2 adsorption. The results indicated that Cu-SSZ-13 modified by Ce showed better NOx removal efficiency and aging resistance. The optimized condition was ion exchanged for 2 h in a cerous nitrate solution. The introduction of Ce effectively restrained the conversion of an active Cu component (Cu2+ → Cu+) during the hydrothermal aging. Ce3+ species strongly associated with molecular sieve carriers and only slight skeleton dealumination was observed on the sample exchanged for 2 h, thus resulting in the further stabilization of catalyst active centers, which consequently maintained the catalytic activity and antiaging ability.

Abstract: Cerium is a radical scavenger which improves polymer electrolyte membrane (PEM) fuel cell durability. During operation, however, cerium rapidly migrates in the PEM and into the catalyst layers (CLs). In this work, membrane electrode assemblies (MEAs) were subjected to accelerated stress tests (ASTs) under different humidity conditions. Cerium migration was characterized in the MEAs after ASTs using X-ray fluorescence. During fully humidified operation, water flux from cell inlet to outlet generated in-plane cerium gradients. Conversely, cerium profiles were flat during low humidity operation, where in-plane water flux was negligible, however, migration from the PEM into the CLs was enhanced. Humidity cycling resulted in both in-plane cerium gradients due to water flux during the hydration component of the cycle, and significant migration into the CLs. Fluoride and cerium emissions into effluent cell waters were measured during ASTs and correlated, which signifies that ionomer degradation products serve as possible counter-ions for cerium emissions. Fluoride emission rates were also correlated to final PEM cerium contents, which indicates that PEM degradation and cerium migration are coupled. Lastly, it is proposed that cerium migrates from the PEM due to humidification conditions and degradation, and is subsequently stabilized in the CLs by carbon catalyst supports.