Reduction Of Ce Research Articles

Synthesis, Crystal Structure, and Photocatalytic Properties of Two Isoreticular Ce(IV)-MOFs with an Infinite Rod-Shaped Inorganic Building Unit.

The use of the V-shaped linker molecules 4,4'-oxydibenzoic acid (H2ODB) and 4,4'-carbonyldibenzoic acid (H2CDB) led to the discovery of two isoreticular Ce(IV)-based metal-organic frameworks (MOFs) of composition [CeO(H2O)(L)], L = ODB2-, CDB2-, denoted CAU-58 (CAU = Christian-Albrechts-University). The recently developed Ce-MOF synthesis approach in acetonitrile as the solvent proved effective in accessing Ce(IV)-MOF structures with infinite rod-shaped inorganic building units (IBUs) and circumventing the formation of the predominantly observed hexanuclear [Ce6O8] cluster. For the structure determination of the isoreticular MOFs, three-dimensional electron diffraction (3D ED) and powder X-ray diffraction (PXRD) data were used in combination with density functional theory (DFT) calculations. [CeO(H2O)(CDB)] shows reversible H2O adsorption by stirring in water and thermal treatment at 190 °C, which leads to a unit cell volume change of 11%. The MOFs feature high thermal stabilities (T > 290 °C), which exceed those of most Ce(IV)-MOFs and can be attributed to the infinite rod-shaped IBU. Surface and bulk oxidation states of the cerium ions were analyzed via X-ray photoelectron spectroscopy (XPS) and X-ray absorption near-edge spectroscopy (XANES). While Ce(III) ions are observed by the highly surface-sensitive XPS method, the bulk material contains predominantly Ce(IV) ions according to XANES. Application of the MOFs as catalysts for the catalytic degradation of methyl orange in aqueous solutions was also studied. While degradation activity for both MOFs was observed, only CAU-58-ODB revealed enhanced photocatalytic activity under ultraviolet (UV) light. The photocatalytic mechanism likely involves a ligand-to-metal charge transfer (LMCT) from the linkers to the Ce(IV) centers. Analyses by XANES and inductively coupled plasma-optical emission spectroscopy (ICP-OES) demonstrate that leaching of Cerium ions as well as partial reduction of Ce(IV) to Ce(III) takes place during catalysis. At the same time, PXRD data confirm the structural stability of the remaining MOF catalysts.

Synthesis and Reactivity of Redox-Active Cerium(IV) Aryloxide Complexes

The steric and electronic effects on the stability and reactivity of cerium(IV) aryloxide complexes supported by the Kläui tripodal ligand [Co(η5-C5H5){P(O)(OEt)2}3]− (LOEt–) have been investigated. A Ce(IV) oxo species (1) prepared in situ from [Ce(LOEt)2Cl2] and Ag2O has been used as a starting material for the synthesis of Ce(IV) aryloxide complexes. The reactions of 1 with aryl alcohols (ArOH) in hexane resulted in formation of three possible products: (A) [CeIV(LOEt)2(OAr)2] for Ar = Ph (2-H), 2,4-X2C6H3 [X = Br (2-Br2,4), Cl (2-Cl2,4)], 3,5-Br2C6H2 (2-Br3,5), or 2,6-F2C6H3 (2-F2,6); (B) [CeIII(LOEt)2(OAr)] for Ar = 2,4,6-X3C6H2 (X = tBu) or 2,6-X2C6H3 (X = tBu, Cl); or (C) [CeIV(LOEt)2(OAr)Cl] (3-Cl2,4,6) for Ar = 2,4,6-Cl3C6H2. The Ce(IV) aryloxide chloride complex [CeIV(LOEt)2(OC6H3Cl2-2,4)Cl] (3-Cl2,4) has been synthesized by ligand exchange between 2-Cl2,4 and [CeIV(LOEt)2Cl2]. No obvious correlation was found between the Ce–O bond lengths [2.138(6)–2.215(3) Å]/Ce–O–C angles [138.6(3)–166.8(3)°] and the substituents of the aryloxide ligands in 2-H, 2-Br2,4, 2-Br3,5, 2-Cl2,4, and 2-F2,6. Among the Ce(IV) bis(aryloxide) complexes synthesized, 2-F2,6 was found to be most reactive with respect to Ce(IV/III) reduction. In hexane, 2-F2,6 is capable of oxidizing 2,4,6-tri-tert-butylphenol (tbp) and 9,10-dihydroanthrancene, presumably via an H-atom abstraction pathway. Density functional theory calculations indicated that 2-F2,6 has a triplet excited state lying 7.1 kcal mol–1 above the singlet ground state. The oxidation of tbp by 2-F2,6 involves Ce–Oaryl bond homolysis of the triplet excited state and H-atom transfer between the resulting 2,6-difluorophenoxyl radical and tbp. This work highlights the influence of the steric effect on the stability and reactivity of redox-active Ce(IV) aryloxide complexes.

Engineering oxygen vacancy-rich CeOx overcoating onto Ni/Al2O3 by atomic layer deposition for bi-reforming of methane

Atomic layer deposition (ALD) was applied to develop CeOx-overcoated Ni/Al2O3 catalyst for bi-reforming of methane (BRM), as the combination of dry reforming of methane (DRM) and steam reforming of methane (SRM). Non-stoichiometric CeOx thin films were successfully deposited on Ni/Al2O3 particles by ALD, which constructed a beneficial Ni-CeOx interface and modified the catalyst property. Ascribed to the unique ALD growth mode, a high amount of Ce(III) and oxygen vacancies existed in the ALD-deposited CeOx overcoating. A reduction process before the BRM reaction contributed to the further reduction of Ce(IV) to Ce(III), resulting in more oxygen vacancies. The oxygen vacancies at the Ni-CeOx interface enabled a high rate of CO2 activation and enabled the balance between the activation of CO2 and H2O for BRM. Due to its oxygen vacancies as activation sites for CO2 and H2O, CeOx ALD overcoating significantly improved the activity of Ni/Al2O3 catalyst and achieved a better control in the H2/CO ratio with a suitable ratio of H2O/CO2/CH4 feed. CeOx overcoatings enhanced the reducibility of Ni(II) sites and assisted in preventing Ni from oxidation during the BRM reaction. Less carbon deposition was achieved by the Ni/Al2O3 catalyst with CeOx overcoating as ascribed to its better reactant activation capacity.

Selective and green oxidation of alcohols and sulfides using mesostructured Cux/Cey mixed oxides

Mesostructured mixed metal oxides are one of the best candidates for various oxidations. Here, mesostructured Cux/Cey mixed oxides with various Cu/Ce ratios were prepared using mesoporous silica as a hard template to improve their selectivity and efficiency as the oxidative catalysts. Investigation of the different ratios of Cu/Ce showed that all catalysts are significantly more active than their salts in the oxidation of alcohols and sulfides with some green oxidants. The results demonstrated that the balance of the number of active catalytic centers (concentration of Cu) and the structural characteristics (surface area and oxygen vacancy) determine the activity of the catalysts. It also seems to be a powerful interplay among copper and cerium ions that helps the reduction of both Cu (II) and Ce (IV).

MOF-Derived CeO2 and CeZrOx Solid Solutions: Exploring Ce Reduction through FTIR and NEXAFS Spectroscopy.

The development of Ce-based materials is directly dependent on the catalyst surface defects, which is caused by the calcination steps required to increase structural stability. At the same time, the evaluation of cerium's redox properties under reaction conditions is of increasing relevant importance. The synthesis of Ce-UiO-66 and CeZr-UiO-66 and their subsequent calcination are presented here as a simple and inexpensive approach for achieving homogeneous and stable CeO2 and CeZrOx nanocrystals. The resulting materials constitute an ideal case study to thoroughly understand cerium redox properties. The Ce3+/Ce4+ redox properties are investigated by H2-TPR experiments exploited by in situ FT-IR and Ce M5-edge AP-NEXAFS spectroscopy. In the latter case, Ce3+ formation is quantified using the MCR-ALS protocol. FT-IR is then presented as a high potential/easily accessible technique for extracting valuable information about the cerium oxidation state under operating conditions. The dependence of the OH stretching vibration frequency on temperature and Ce reduction is described, providing a novel tool for qualitative monitoring of surface oxygen vacancy formation. Based on the reported results, the molecular absorption coefficient of the Ce3+ characteristic IR transition is tentatively evaluated, thus providing a basis for future Ce3+ quantification through FT-IR spectroscopy. Finally, the FT-IR limitations for Ce3+ quantification are discussed.

Isolation and redox reactivity of cerium complexes in four redox states.

The chemistry of lanthanides is limited to one electron transfer reactions due to the difficulty of accessing multiple oxidation states. Here we report that a redox-active ligand combining three siloxides with an arene ring in a tripodal ligand can stabilize cerium complexes in four different redox states and can promote multielectron redox reactivity in cerium complexes. Ce(iii) and Ce(iv) complexes [(LO3)Ce(THF)] (1) and [(LO3)CeCl] (2) (LO3 = 1,3,5-(2-OSi(OtBu)2C6H4)3C6H3) were synthesized and fully characterized. Remarkably the one-electron reduction and the unprecedented two-electron reduction of the tripodal Ce(iii) complex are easily achieved to yield reduced complexes [K(2.2.2-cryptand)][(LO3)Ce(THF)] (3) and [K2{(LO3)Ce(Et2O)3}] (5) that are formally "Ce(ii)" and "Ce(i)" analogues. Structural analysis, UV and EPR spectroscopy and computational studies indicate that in 3 the cerium oxidation state is in between +II and +III with a partially reduced arene. In 5 the arene is doubly reduced, but the removal of potassium results in a redistribution of electrons on the metal. The electrons in both 3 and 5 are stored onto δ-bonds allowing the reduced complexes to be described as masked "Ce(ii)" and "Ce(i)". Preliminary reactivity studies show that these complexes act as masked Ce(ii) and Ce(i) in redox reactions with oxidizing substrates such as Ag+, CO2, I2 and S8 effecting both one- and two-electron transfers that are not accessible in classical cerium chemistry.

Effect of Metal Dopant on the Performance of Ni@CeMeO2 Embedded Catalysts (Me = Gd, Sm and Zr) for Dry Reforming of Methane

Biogas upgrading by a catalytic process has been studied in order to obtain syngas using renewable source of methane. This work evaluates the influence of metal dopant (Gd, Sm, and Zr) on the CeO2 structure for the dry reforming of methane over Ni nanoparticle embedded catalysts. The doping with Zr improved the thermal stability of the catalyst, leading to the formation of small Ni nanoparticles, while Ni metal sintering was observed for Ni@CeO2, Ni@CeGdO2, and Ni@SmO2, according to in situ XRD under reduction conditions. The ceria reducibility was affected by the dopant nature, for which the addition of Zr caused distortions in the ceria lattice, promoting the diffusion of oxygen bulk to surface. The doping with Gd and Sm created oxygen vacancies by charge compensation, and the saturation of oxygen vacancies in the fresh samples decreased the degree of Ce reduction, according to TPR results. The larger Ni particles and poor redox behavior for Ni@CeGdO2 and Ni@CeSmO2 were responsible for the high carbon formation on these catalysts during the DRM reaction. The Ni@CeZrO2 catalyst did not present coke formation because of smaller Ni crystallite size and higher ceria reducibility. Therefore, the control of Ni particle size and the high oxygen mobility in the Ni@CeZrO2 catalyst inhibits carbon deposition and enhances the mechanism of carbon removal, promoting the catalyst stability.

Characterisation of a Complex CaZr0.9Ce0.1Ti2O7 Glass–Ceramic Produced by Hot Isostatic Pressing

The behaviour of Ce-containing zirconolites in hot isostatically pressed (HIPed) materials is complex, characterised by redox interactions between the metallic HIP canister that result in reduction of Ce4+ to Ce3+. In this work, a glass–ceramic of composition 70 wt.% CaZr0.9Ce0.1Ti2O7 ceramic in 30 wt.% Na2Al2Si6O16 glass was produced by HIP (approx. 170 cm3 canister) to examine the extent of the material–canister interaction. A complex material with six distinct regions was produced, with the extent of Ce reduction varying depending on the distance from the canister. Notably, the innermost bulk regions (those approximately 7 mm from the canister) contained only Ce4+, demonstrating that a production-scale HIPed glass–ceramic would indeed have a bulk region unaffected by the reducing environment induced by a ferrous HIP canister despite the flow of glass at the HIP temperature. Each of the six regions was characterised by XRD (including Rietveld method refinements), SEM/EDX and linear combination fitting of Ce L3-edge XANES spectra. Regions in the lower part of the canister were found to contain a significantly higher fraction of Ce4+ compared to the upper regions. Though zirconolite-2M was the major crystalline phase observed in all regions, the relative abundances of minor phases (including sphene, baddeleyite, rutile and perovskite) were higher in the outermost regions, which comprised a significantly reduced Ce inventory.

Bacterial Metabolites and Particle Size Determine Cerium Oxide Nanomaterial Biotransformation.

Soil is a major receptor of manufactured nanomaterials (NMs) following unintentional releases or intentional uses. Ceria NMs have been shown to undergo biotransformation in plant and soil organisms with a partial Ce(IV) reduction into Ce(III), but the influence of environmentally widespread soil bacteria is poorly understood. We used high-energy resolution fluorescence-detected X-ray absorption spectroscopy (HERFD-XAS) with an unprecedented detection limit to assess Ce speciation in a model soil bacterium (Pseudomonas brassicacearum) exposed to CeO2 NMs of different sizes and shapes. The findings revealed that the CeO2 NM's size drives the biotransformation process. No biotransformation was observed for the 31 nm CeO2 NMs, contrary to 7 and 4 nm CeO2 NMs, with a Ce reduction of 64 ± 14% and 70 ± 15%, respectively. This major reduction appeared quickly, from the early exponential bacterial growth phase. Environmentally relevant organic acid metabolites secreted by Pseudomonas, especially in the rhizosphere, were investigated. The 2-keto-gluconic and citric acid metabolites alone were able to induce a significant reduction in 4 nm CeO2 NMs. The high biotransformation measured for <7 nm NMs would affect the fate of Ce in the soil and biota.

Development of Responsive Polymeric Nanocomposites for Enhanced CeO2 Removal in Post-Chemical Mechanical Planarization (p-CMP)

As integrated circuits (ICs) and logic devices continue to shrink according to Moore’s Law, the demand for enhanced Chemical Mechanical Planarization (CMP) processes has increased dramatically. More specifically, an area that has gained tremendous attention is Shallow Trench Isolation (STI) CMP. The process of STI involves the electrical isolation of active components that require exposure by removing the bulk oxide (i.e., TEOS) overburden from the deposition process. Traditional STI slurry formulations are comprised of a CeO2 nanoparticle dispersion, rate enhancers, selectivity and rheology modifiers, and pH adjusters. Due to the presence of defect states (i.e., oxygen vacancies (Ovacs)) on the surface of CeO2 nanoparticles, their photocatalytic properties can be exploited to induce redox reactions. Specifically, the reduction of Ce4+ to Ce3+ leads to the formation of additional Ovacs on the surface of CeO2, which causes hard adsorption of CeO2 nanoparticles to TEOS surfaces. Significant work has been conducted on optimizing the post-CMP (p-CMP) cleaning process by creating low shear force environments via charge transfer chemistries to remove CeO2 adsorbed to TEOS. As a result, this work presents the design of responsive polymeric composites that may be employed in the brush scrubbing of TEOS to enhance particle removal while minimizing shear and compressive forces. This will ultimately limit secondary defectivity and induce more efficient cleaning of nanoparticles from the dielectric material. To monitor the cleaning process, coefficient of friction (CoF), shear force (SF), defect measurements via profilometry, particle removal efficiency (PRE), and Ce4+/Ce3+ ratio measurements will be utilized. Using a UV/Vis spectroscopic technique to monitor the Ce4+/Ce3+ ratio, initial results show a correlation between the oxidation state of CeO2 and PRE. Additionally, using a non-traditional polymeric brush during cleaning has shown higher PRE while maintaining lower shear force environments.

Synthesis of Ceria (CeO2) Nanoparticles and Their Application in Colorimetric Probes for the Determination of Ascorbic Acid

AbstractNanoceria (CeO2 nanoparticles) are among the most unique and promising lanthanide nanomaterials with sensing applicability. In this study, the redox reactivity of nanoceria was exploited for biomedical application based on changes in the physicochemical properties of the nanoparticles on interaction with ascorbic acid (Vitamin C). Nanoceria were synthesized by the microwave‐assisted method using ammonium ceric nitrate [(NH4)2Ce(NO3)6] as the precursor and diethylene glycol (DEG) as the stabilizer and capping agent. The powder X‐ray diffraction (p‐XRD) studies of the nanoparticles showed that the synthesized particles are of a pure single‐phase matched with a cubic structure. Data from Scanning Electron Microscopy (SEM) &amp; Transmission Electron Microscopy (TEM) analysis were also used to estimate the average size of the particles, and a range of value between 6.8‐7.1 nm was obtained which agrees with the value obtained using Debye‐Sherrer's relation (6.8±0.2 nm). On interacting the nanoceria with ascorbic acid, a color change from light yellow to reddish orange (oxidation of ascorbic acid) was observed, and at the same time, the Ce4+ is being reduced to Ce3+. The reaction between the nanoceria and ascorbic acid was done at a constant concentration of nanoceria with varying amounts of ascorbic acid. This reaction was monitored using the UV‐Vis Spectrometry, and the spectra obtained showed that the intensity of the peak decreases with decreasing concentration of the ascorbic acid. Furthermore, the reduction of Ce4+ to Ce3+ was justified by the blue shift in the λmax from 344 nm to 254 nm. Data obtained also showed a detection limit of 20 ppm ascorbic acid. The nanoceria were also used to fabricate a paper strip which tested positive for the colorimetric detection of ascorbic acid.

How Natural Gas Infrastructure Affects Carbon Emission Indicators in Guangdong Province?

As a public infrastructure, the West to East Natural Gas Pipeline Project (WENGPP), acting as a key supplier of energy, has adopted a potential approach to reduce CE by expanding Natural gas (NG) power in the developed areas in China. However, the literature pertaining to the effects of the efforts made by WENGPP to reduce CE remains scant. Therefore, this study applied the causal inference framework—Regression Discontinuity Design (RDD) to the Guangdong province, which was chosen as a case in point that provides empirical evidence related to the nexus between WENGPP and CE. Remarkably, our results disclosed that WENGPP had caused the total volume of CE in Guangdong province to decline notably. Both short and long-term emission inhibition effects approximated 10.68–14.96%. We revealed two CE reduction mechanisms: (i) through the low-carbon emission trade-off effect, wherein NG consumers were able to gain emission advantages under policy pressure; and (ii) through price comparison effect, where high combustion efficiency of NG consumers combined with low energy consumption costs could provide the incentive of promoting the optimization of regional emission structure. The article suggests a substitutable channel upgrading public energy infrastructure to improve the low-carbon alternative process, to policy makers.

Phase evolution and valence state change in Gd-Ce co-doped zirconolite glass-ceramics

Zirconolite based glass-ceramic is widely researched for the immobilization of actinide-rich high-level waste (HLW). The research of the co-doping effect has important guiding significance for the waste disposal processes. In this study, the co-doping effects of gadolinium and cerium in the zirconolite glass-ceramics were investigated systematically by using X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS). The results revealed that the high amount of Gd can be well incorporated in the Ce-bearing zirconolite particles. The zirconolite was transformed from 2M to 3T structure with the increase of the Gd-doping concentration. The further addition of Gd caused the formation of Gd2Ti2O7 pyrochlore with the doping concentration of about 10.0 wt%, while the zirconolite was still the dominant ceramic phase. The reduction of Ce from Ce4+ to Ce3+ was firstly inhibited and then stabilized with the doping of Gd in this system, indicated that the redox equilibrium of cerium (Ce4+ ↔ Ce3+) was established in the sample with the high amount of Gd doping. This work aimed to further understand the co-doping effect of actinides in zirconolite glass-ceramics, which is expected to provide an important basic scientific basis for underground disposal of HLW.

Synthesis of Ni-doped ceria nanoparticles and their unusual surface reduction in hydrogen

This work presents an original approach to preparing pure and Ni-doped CeO2 nanoparticles (NPs) that can be directly drop-casted on a substrate or calcined to form powders. The reduction of the NPs in H2 is very different than the one usually anticipated for supported Ni–CeO2 catalysts. In situ soft X-ray absorption and infrared spectroscopies revealed that the reduction of Ce4+ into Ce3+ in H2 proceeds via simultaneous oxidation of Ni2+ ions into Niδ+ (2<δ<3). Comparison with reference samples indicates that Ce4+ ions reduction is promoted over Ni-doped CeO2 NPs, whereas that of Ni2+ is hindered. Theoretical simulation of Ni L-edge spectra suggested that Ni dopant into ceria is in a square planar four-coordinate environment, in contrast to the familiar octahedral symmetry of bulk nickel oxides. Our results reveal that the surface chemistry of Ni-doped CeO2 is quite distinct as compared to that of the individual bulk oxides, which potentially can lead to a different performance of this material, notably in catalytic applications.

Electrocoagulation: operational parameters, sludge & economic analysis

ABSTRACT The performance of electrocoagulation (EC) was studied by conducting experiments for the removal of Reactive Orange 4 dye from its synthetic aqueous solution. The effect of operational parameters (initial solution pH, current density, inter-electrode distance, electrolysis time and retention time, solution temperature, conductivity and different electrode combinations) on the efficiency of EC was studied and the results were analysed in terms of colour removal efficiency (CRE), electrical energy consumption (EEC) and operating cost (OC). The effect of different anions on the efficiency of EC was studied by conducting experiments with electrolytes containing chloride, sulphate, carbonate and nitrate ions. The characterisation of EC generated sludge was performed using XRD. A maximum CRE of 95% was obtained for EEC of 1.7 kWh/m3 and OC of 0.45 US $/m3. It was found that the addition of electrolyte containing chloride ions resulted in higher CRE (93–95%) compared to electrolytes containing sulphate and carbonate ions as their presence can lead to passivation of the electrode surface & thereby resulting in a reduction in CRE (60% and 41%, respectively). The addition of sodium chloride as an electrolyte resulted in minimum EEC and OC. The Al/Al electrode combination provided the maximum CRE and least EEC & OC. The increase in solution temperature leads to reduction in CRE and CE due to formation of passive layer on the surface of electrodes. However, a reduction in cell potential and EEC was noticed with an increase in solution temperature.

CeO2-clay composites for ultra-long cycle life electrochemical capacitive energy storage application

The lattice expansion caused by the reduction of Ce(IV) to Ce(III) impeded the development of the CeO2 as an effective electrode material for electrochemical supercapacitors. Herein, we prepared CeO2-clay composites through a one-step hydrothermal method. The interlayer structures of clays efficiently accommodate volume changes induced by crystal lattice expansion to achieve ultra-long cycle stability. After 60000 charge–discharge cycles, the capacitance retention rate of the assembled asymmetric supercapacitors is as high as ∼100%. The key findings of this work reveal the potential application of clays in achieving ultralong cycle stability of the CeO2 electrode material, paving the way for further application of the CeO2 in electrochemical energy storage.

γ-Zirconium Titanium-Phosphates – Fibrous Cerium Phosphate / Polyaniline, Polyindole, Polycarbazole and Polyimidazole Nanocomposite Membranes

Layered nanosized mixed γ-zirconium titanium phosphates and fibrous cerium phosphate, γ-ZrxTi(1-x)..PO4.H2PO4.2H2O (γ-ZTP), Ce(HPO4)2.2.9H2O(nCePf), respectively, (x= 0.95, 0.89), and their [γ-ZrxTi(1-x).PO4. H2PO4]0.3 [Ce(HPO4)2]0.70. 2H2O nanocomposite membranes were prepared and characterized by chemical, x-ray diffraction (XRD), thermogravimetric analysis (TGA) and Fourier transform spectroscopy (FT-IR). Novel [γ-ZrxTi(1-x).PO4.H2PO4]0.3[Ce(HPO4)2]0.70 /polyaniline, polyindole, polycarbazole, and polyimidazole nanocomposite membranes were prepared via in-situ chemical oxidation of the monomers aniline, indole, carbazole and imidazole, respectively, that was promoted by the reduction of Ce(IV) ions present on the surface of the inorganic matrix composite. A possible explanation is nCePf occurs at the surface of the composite was attacked by the monomers, respectively, converted to cerium (III) orthophosphate (CePO4). The resultant novel composites were characterized by elemental (C,H,N) analysis and FT-IR. From elemental (C,H,N) analysis the % in weight of the resultant conducting polymers present in [γ-Zr0.95Ti0.05.PO4.H2PO4]0.3 [Ce(HPO4)2]0.70 composite were [ Pani 19.35, PIn 5,72. PCz 5.8, PIm 23.7]%. The % in weight of the conducting polymers in the composite [γ-Zr0.9Ti0.11.PO4.H2PO4]0.3[[Ce(HPO4)2]0.70 were [Pani 8.54, PIn 8.02, PCz 7.72, PIm 22.27]%. The conductivity of the resultant conducting polymers found to be in the range of semiconductors.

Study on the Extraction of Cerium(IV) from Nitric Acid Medium with tri-Isoamyl Phosphate

This paper studied the extraction behavior of tri-isoamyl phosphate (TiAP)/n-dodecane as extractant for Ce(IV) in a nitric acid medium. In the study of extraction of pure Ce(IV) solution, the test results show that when the organic phase and the water phase ratio is 1: 1, the organic phase and the water phase are mixed and contacted for 90 s, and the pH value is 0-2.0, the extraction tends to be balanced, and the complexes formed by the extraction are theoretically deduced and obtained the theoretical molecular formula of the complex is Ce(NO3)4·nTiAP, where n is between 2 and 3; under this condition, the extraction rate of pure Ce(IV) can reach 99.45% after 16-stage countercurrent extraction test; the relative standard deviation is less than 2%. In the extraction of Ce(IV) solution containing other metal ions, the test results show that the extraction rate of 0.05 mol·L-1 TiAP/n-dodecane solution to the material liquid containing Ce(IV) 0.005 g·L-1 is about 64%. However, the experiment found that the extraction rate tends to decrease with the increase of the material liquid’s standing time. After 24 hours, the extraction rate is close to 0. Then, the experiment researched the influence of each metal ion component on the extraction after standing and obtained the metal. In the presence of ionic components, the extraction rate tends to decrease with the increase of the liquid standing time. Considering the strong oxidizing property of Ce4+ under acidic conditions, the experimental study of TiAP on Ce3+ and Ce4+ mixtures with different percentages. The results show that as the percentage of Ce3+ in the feed liquid increases, the extraction rate is in a downward trend, and the trend is consistent with the increase in the standing time on the extraction rate. The original liquid contains impurity Ce4+ is slowly reduced to Ce3+, which affects the extraction results. Studies have shown that TiAP of 0.05 mol·L-1 performs well for the extraction of Ce4+ in pure Ce(IV) solution; TiAP of 0.05 mol·L-1 is effective for extraction of Ce(III) solution of 0 ~ 5 mg·L-1. The effect of Ce3+ is not obvious; because Ce4+ is too oxidizing, when other metal ions studied are present at the concentration studied, it will accelerate the reduction of Ce4+ and affect the extraction results.

Characterization of innovative Pt-ceria catalysts for PEMFC by means of ex-situ and operando X-Ray Absorption Spectroscopy

As the demand for energy is rising, the role of batteries and fuel cells in everyday life is undeniable, but fuel cell systems are still currently not employed worldwide mainly because of their cost, which is due to the large amount of Pt used in catalyst layers. Recently, it was demonstrated that catalysts composed by low Pt loading (around 10 μg/cm 2 ) onto ceria (CeO x ) matrix are a promising alternative, showing comparable performances with respect to catalysts made by Pt only. Indeed, a strong metal to support interaction between Pt and ceria has been already observed and exploited for application in direct methanol fuel cells. In this context, the aim of the present study is to investigate the stability of innovative Pt-CeO x anode catalyst deposited on two different supports and characterized by means of X-ray Absorption Spectroscopy (XAS). The XANES ex-situ data collected at the Ce L 3 -edge highlighted the stability of ceria when directly deposited onto the nano-Gas Diffusion Layer (nGDL) whereas it is particularly unstable when deposited onto the so-called Carbon Ionomer Layer (CIL), where Ce was found irreversibly reduced to Ce 3+ upon contact with the air. These behaviors are confirmed also by preliminary test experiments conducted in operando conditions, using a modified fuel cell designed on purpose. In addition, EXAFS data collected ex-situ at the Pt L 3 -edge evidenced an increase in the fraction of Pt 2+ as the overall amount of Pt (or the Pt/Ce ratio) is decreasing, in agreement with existing literature. Our results provide an extended picture about characterization of Pt-CeOx catalyst, focusing on the effects of the hosting support, in order to improve the fabrication of more stable Membrane Electrode Assemblies (MEAs) with low Pt contents to be employed with PEMFCs. The lower efficiency and stability of ptceO 2 anode catalyst sputtered on carbon-lonomer-Layer has been linked to the quick reduction of Ce. • 2 kind of Pt-ceria anode catalyst were prepared using a novel sputtering technique. • Differences in the efficiency are visible in the first days of operation. • Samples were studied both ex situ and in operando conditions through XAS and SAXS. • When sputtered on Carbon Ionomer Layer, the catalyst is less stable. • Pt 2+ fraction increases as the Pt/Ce ratio decreases.

X-ray photoelectron spectroscopy study of Pt-cluster-induced electronic-state change of CeO2(111) surfaces

We investigated the reduction of a CeO2(111) surface after the deposition of size-selected Pt8 clusters on it via x-ray photoelectron spectroscopy (XPS). Electron transfer from Pt to CeO2(111) results in the reduction of Ce4+ to Ce3+ and the subsequent formation of Ptδ+ atoms at the interface. We quantitatively estimated the reduction from the Ce3+/(Ce3+ + Ce4+) ratio determined from the Ce3d spectra. Approximately 30% of Ce4+ under or in the perimeter of the Pt8 cluster was reduced to Ce3+. The XPS spectra showed an increase in the ratio of Ce3+/(Ce3+ + Ce4+) with an increase in the amount of Pt8 clusters deposited on the CeO2(111) surface. The reduction of 3.7 Ce4+ to Ce3+ per Pt8 clusters, followed by the formation of 3.7 Ptδ+ atoms per Pt8 clusters was observed at 0.006 ML (mono layer) Pt coverage. The actual Ce3+ formation influenced by Pt deposition was approximately 2.5%. We estimate that approximately 30% of Ce4+ under or in the perimeter of a Pt8 cluster was reduced to Ce3+. At a higher coverage of 0.015 ML, the reduction of 2.2 Ce4+ to Ce3+ per Pt8 cluster, followed by the formation of 3.2 Ptδ+ atoms per Pt8 cluster was observed. This implies the aggregation of Pt clusters occurred at a higher Pt coverage. Atomically precise quantification of the electron transfer across the Pt–CeO2(111) interface can enable an improved understanding of the metal-support interaction.