Praseodymium Oxide Research Articles

Effect of rare-earth Pr6O11 insulating layer on the electrical properties of Au/n-GaN Schottky electrode and its chemical and structural characterization

An Au/Pr6O11/n-GaN metal/insulator/semiconductor (MIS) junction was prepared with a high-k praseodymium oxide insulator layer and probed its structural, chemical and electrical characteristics by XRD, TEM, XPS, I–V and C–V approaches. XRD, TEM and XPS examinations confirm the Pr6O11 film growth on n-type GaN surface. Electrical results demonstrate the fabricated junctions show a good rectifying nature with a low leakage current. The series resistance (RS) and shunt resistance (RSh) were derived for the Au/n-GaN Schottky electrode (SE) and MIS junction. MIS junction possesses a higher barrier height (BH) compared to the Au/n-GaN SE, implying the insulator layer altered the BH. By employing Cheung’s, Norde and surface potential plots, the BH, ideality factor and RS were evaluated and the results were comparable. Lower interface state density (NSS) was obtained for the MIS junction than the SE, which confirmed that the Pr6O11 insulator layer plays a vital role in lowering the NSS. Results demonstrated the Poole–Frenkel emission controls the current conduction mechanism in reverse-bias of both SE and MIS junction. Observations stated that the Pr6O11 thin film is a suitable high-k insulating material for the fabrication of GaN-based MIS devices.

Facile synthesis of a novel ultra-low density praseodymium oxide aerogel for catalyst and adsorbent

The pure praseodymium oxide aerogel with ultra-low density (about 10.7 mg/cm3) was prepared by using solution-freeze-drying-calcination method for the first time. The results of BET, SEM and TEM indicated that the pure praseodymium oxide aerogel belonged to the mesoporous material, which showed a typical three-dimensional porous structure. The results of TG/DSC showed that the praseodymium oxide aerogel could decrease the ammonium perchlorate decomposition temperature by 54.7 °C and enhance the heat production from 121.3 J/g to 838.5 J/g. The maximum adsorption amounts of praseodymium oxide aerogel reached 251.1 mg/g for uranium. This method provides a new strategy for preparation of low density metal oxide aerogels.

Promotion of SOFC Cathode Performance and Durability by the Addition of Mixed Conducting Praseodymium Oxides

Solid oxide fuel cells (SOFCs) convert the chemical energy from a fuel into electricity at elevated temperatures with a high efficiency and in an environment-friendly manner. The high polarization resistance of the oxygen electrode, corresponding to a low electrode activity and a low cell performance, can be reduced by introducing various catalysts to the electrode. In this work, praseodymium oxides are introduced into the LSCF cathode by infiltration. In addition, the barrier layer, Gd0.2Ce0.8O1.9, was replaced with Pr0.1Gd0.1Ce0.8O1.9. The increase of power density at 0.8 V is approximately 0.2 W/cm2 by applying a PGCO buffer, 0.13 W/cm2 by infiltration, and 0.34 W/cm2 through implementation of both. Current-voltage plots and electrochemical impedance spectroscopy were used to examine the electrochemical performance of SOFCs. The distribution of relaxation time was used to analyze the mechanism for which the polarization resistance was decreased and was attributed to the mixed conduction nature in PrOx.

Raman and EXAFS study of neodymium and praseodymium included alumino-germanate glass

Germanate glass has been synthesised keeping Al2O3 fixed at 10 mol% with Neodymium oxide and Praseodymium oxide varying from 5 mol% to 10 mol%. The effect of the rare-earth inclusion on the structure of the host matrix was examined by several techniques. Extended x-ray Absorption Fine Structure showed tetrahedral coordination of oxygen around Ge for all the glasses and gave the oxygen coordinations around Nd and Pr to be 8.7 and 8.9 respectively which is in contrast to the often quoted octahedral coordination for these ions. Raman spectroscopic studies have shown the Qn linkages of the GeO4 tetrahedra in these glasses as predominantly Q2 and Q3. The distribution of relative fractions of these linkages shows the Pr containing glass as having a few Q° and maximum Q2 connectivities while for the Nd and Nd-Pr containing glasses, these distributions peak for the Q3 connected linkages. These observations lead to the view that the Pr containing glass has a less well connected network than the Nd containing glasses. The presence of Pr in these glasses results in a decrease in electronic band gap energy and an increase in the electronic polarizability.

New series of organic–inorganic polymer nanocomposite membranes for fuel cell applications

Flexible organic–inorganic polymer nanocomposite membranes with uniformly distributed metal oxide nanoparticles were prepared using sulfonated poly(ether ether ketone) (SPEEK) as a base material and praseodymium oxide (PSO) as an inorganic additive. The degree of sulfonation of SPEEK was determined by proton nuclear magnetic resonance (NMR) analysis and found to be 60%. The characteristic properties of the polymer nanocomposite membranes were examined by thermogravimetric analysis, X-ray diffraction, ion exchange capacity, water uptake ability, and proton conductivity. The incorporation of metal oxide into the polymer matrix was confirmed by scanning electron microscope with energy dispersive X-ray spectroscopy and X-ray diffraction analyses. The nanocomposite membrane exhibits good thermal stability when compared to that of the pristine membrane and SPEEK with 10 wt% of PSO loading was found to be stable up to 450°C. The assessment of polymer electrolyte membrane is accomplished by fabricating membrane electrode assemblies of pure SPEEK and SP-PSO-10 membranes and the latter produced maximum peak power density of 622 mW cm−2. The constructed SPEEK/PSO nanocomposite membranes offered superior physicochemical properties while applying these materials in an H2-O2 fuel cell.

PrBaMn2O5+δ with praseodymium oxide nano-catalyst as electrode for symmetrical solid oxide fuel cells

PrBaMn2O5+δ (PBMO) is one of the promising electrode materials for symmetrical solid oxide fuel cells, but suffers from limited electrocatalytic activity. In this work, nanosized Pr6O11 particles were introduced into PBMO backbone on both anode and cathode as synergic catalysts and to optimize the electrode reactions. The as-prepared electrode was investigated by X-ray diffraction, H2-temperature programmed reduction (H2-TPR), O2-temperature programmed desorption (O2-TPD), X-ray photoelectron spectroscopy (XPS), field emission scanning electron microscope (FESEM) and the electrochemical measurements. After coated with Pr6O11, the cathode polarization resistance (Rp) of PBMO decreased from 0.25 to 0.016 Ω cm2, the anode Rp reduced from 0.46 to 0.20 Ω cm2 and the power outputs of symmetrical cells improved by ∼75% at 800 °C. The TPR and TPD results indicate that the electrode catalytic activity was significantly promoted by Pr6O11. Furthermore, the stability tests show that PBMO with Pr6O11 is highly stable in redox conditions.

Smoke sensing applications of Brij 58 functionalized Praseodymium oxide (Pr6O11) nanostructures

Herein, we report, for the first time, the fabrication and characterization of smoke sensors based on Brij 58 functionalized Praseodymium oxide (Pr6O11) nanostructures. Various Pr6O11 nanostructures such as nano-aggregates, spherical particles, nano-ellipsoids and nanoflowers were synthesized by facile solution process by varying the concentration of Brij 58 in different mass ratios (Pr salt: Brij 58 = 1:1, 1:2, 1:3 and 1:4). Detailed characterizations confirmed that the synthesized nanomaterials exhibited well-crystallinity and good optical properties. Interestingly, the Pr6O11 nanostructures have showed a significant chromogenic shift thereby acting as efficient smoke sensors. Pr6O11 nanomaterials have shown significant lowering in the optical absorbance when exposed to smoke and hence have the effective tendency to oxidize the smoke gases. The Pr6O11 nanomaterials successfully brought down the concentrations of CO by 99% and a 100% eradication of NOx and SO2 gases was achieved. The use of least chemicals, external energy deprived operation and recovery of the spent nanomaterials-oriented protocol, advocates the cost effectiveness of the presented system.

Praseodymium oxides. Complete characterization by determining oxygen content

Praseodymium ions are available in many oxidation states, so they are capable to form a huge number of different oxides, which make them an interesting and versatile material in many industries, such as ceramics or optics.Although praseodymium oxides behavior has been studied, the information found in the literature is sometimes contradictory. The different conditions of experimentation have led to opposite results due to rapid praseodymium oxide transformations. Many authors have pointed out the high oxygen mobility upon phase transformations during heating and cooling processes.Four materials based on praseodymium oxide compounds were characterized by physicochemical analysis. Praseodymium concentration was determined by WD-XRF and oxygen content was determined by the elemental analyzer TC-436, while XRD gave crystalline phases information and thermal analysis was carried out to obtain information about phase transformations. The combination of these analytical techniques allowed to have the real and accurate praseodymium concentration of a determined product, as it was found out that, two products that intended to have the same praseodymium concentration, were actually different.PrO2 and Pr2O3 were the major phases identified in these materials by XRD, although Pr(OH)3, and Pr6O11 were also found as minor phases in the original materials. From the results obtained by WD-XRF, XRD and simultaneous thermal analysis; crystalline phases concentration was calculated, but the determination of oxygen content by the elemental analyzer TC-436 was the key to validate the results obtained from WD-XRF, XRD and simultaneous thermal analysis. The oxygen determination method was optimized by increasing a 400% the sample weight introduced into the piece of equipment, which resulted in a precision improvement.In addition, one sample underwent different thermal treatments at the temperatures of 500, 650, 760, 980 and 1040 °C and two different cooling processes (slow cooling and quenching), to study phase transformations at these temperatures by measuring the oxygen content and determine the crystalline phases by XRD. It was found that, when the sample was quenched, different phases were formed at different temperatures, such as Pr9O16 and Pr7O12, while cooling slowly the calcined sample was always giving Pr6O11 because the intermediate phases were not stable enough to be determined.Thus, the aim of this work was to devise an adequately robust test method and use it to expand the present knowledge base concerning the praseodymium oxide physicochemical characterization and its behavior across different heating and cooling processes.

Enhancing Mechanical and Corrosion Properties of Electrodeposited Ni- Pr6O11 Composite Coatings Via Stabilizing Agents

Integrating nanoparticles into nickel coatings has been shown to increase the corrosion and mechanical properties of these coatings. The structures of CeO2 and Pr6O11 nanoparticles are similar, and extensive studies on Ni-CeO2 composite coatings have shown increased mechanical and corrosion properties, but there is sparse research on Ni-Pr6O11 composite coatings. However, praseodymium oxide has the potential to change phases upon heating or cooling, increasing the oxygen vacancies and affecting corrosion resistance in certain environments. Praseodymium oxide nanoparticles naturally agglomerate in the electrolyte solution making it difficult to disperse in electroplating solutions. This research studies various stabilizing agents for praseodymium oxide in electrolyte solutions. Electrodeposition of nickel-praseodymium oxide nanocomposites onto metal substrates has been performed with varying concentrations of praseodymium oxide nanoparticles present in the nickel plating bath. Sodium citrate (SC) addition acts as a stabilizing agent for the nanoparticles when added to the electrolytic bath. Up to 30 g/L praseodymium oxide nanoparticles were incorporated into the nickel coating using electrodeposition. The morphology, formation, composition, and hardness of the produced nickel-praseodymium oxide nanocomposite were investigated using scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and microhardness measurements. Potentiodynamic polarization, electrochemical impedance spectroscopy, and exposure to chloride solutions were used to investigate the corrosion resistance properties of the nanocomposites. Figure 1

Metal‐Supported Solid Oxide Electrolysis Cell with Significantly Enhanced Catalysis

High‐temperature electrolysis (HTE) using solid oxide electrolysis cells (SOECs) is a promising hydrogen production technology and has attracted substantial research attention over the last decade. While most studies are conducted on hydrogen electrode‐supported type cells, SOEC operation using metal‐supported cells has received minimal attention. The development of metal‐supported SOECs with performance similar to the best conventional SOECs is reported. These cells have stainless steel supports on both sides, 10Sc1CeSZ electrolyte and electrode backbones, and nano‐structured catalysts infiltrated on both hydrogen and oxygen electrode sides. Samarium‐doped ceria (SDC) mixed with Ni is infiltrated as a hydrogen electrode catalyst, and the effect of ceria:Ni ratio is studied. On the oxygen electrode side, catalysts including lanthanum strontium manganite (LSM), lanthanum strontium cobalt ferrite (LSCF), praseodymium oxide (Pr6O11), and their composite catalysts with SDC (i.e., LSM‐SDC, LSCF‐SDC, and Pr6O11‐SDC) are compared. Using the materials with highest catalytic activity (Pr6O11‐SDC and SDC40‐Ni60) and optimizing the catalyst infiltration processes, excellent electrolysis performance of metal‐supported cells is achieved. Current densities of −5.31, −4.09, −2.64, and −1.62 A cm−2 are achieved at 1.3 V and 50 vol% steam content at 800, 750, 700, and 650 °C, respectively.

Development of a nanostructured Ce(III)-Pr(III) film for excellently corrosion resistance improvement of epoxy/polyamide coating on carbon steel

Chemical treatment of carbon steel (CS) specimens was done by an eco-friendly Ce (III)-Pr(III) composite nanofilm. The impact of composite film deposition on CS on the epoxy coating (EP) capability for reduction of CS corrosion and delamination rates was examined. The Ce (III)-Pr (III) thin film morphology was studied by field emission-scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS) methods. The EP anti-corrosion capacity promotion on CS by deposition of Ce(III)-Pr(III) composite film was investigated by electrochemical impedance spectroscopy (EIS) and salt spray test. Cathodic delamination (CD) rate of EP/Ce (III)-Pr (III) system was also examined. Furthermore, molecular dynamics (MD) simulations were applied to get microscopic-level insights into the aminoamide hardener/epoxy coating interaction mechanism with Ce (III)-Pr (III) film. It was shown that the film uniformly deposited is mainly composed of oxide/hydroxide of cerium (III) and praseodymium (III) and without crack and defect. Results revealed that the Ce (III)-Pr (III) composite thin film significantly promoted the EP anti-corrosion capability and decreased the CD rate. The computational results proved that the curing agent and crosslinked EP resin adsorbed to praseodymium and cerium oxide surfaces mostly through electrostatic interactions of N and O heteroatoms with surface metal atoms.

Interfacial adhesion and corrosion protection properties improvement of a polyester-melamine coating by deposition of a novel green praseodymium oxide nanofilm: A comprehensive experimental and computational study

The effects of steel surface treatment by a novel nanofilm based on praseodymium oxide on the interfacial adhesion, corrosion protection properties and cathodic delamination rate of a polyester-melamine coating were studied by combined experimental and theoretical molecular dynamics (MD) and quantum mechanics (QM) techniques. Field emission-scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS) were employed to characterize the surface morphology and chemical composition of nanofilm. The results obtained from electrochemical impedance spectroscopy, cathodic delamination and pull-off tests demonstrated the significant improvement of steel/polymer interfacial adhesion, the decrease of coating disbonding rate and the increase of corrosion protection performance by the aid of steel surface decoration by nanofilm. Furthermore, the theoretical outcomes derived from atomistic MD simulations of metal/polymer interface conducted in dry and wet environments further evidenced the strengthened coating adhesion onto surface-treated steel. It was also theoretically observed that the interfacial electrostatic interactions were the major force in coating binding to untreated/treated steel substrate.

Boosting the oxygen reduction reaction of the misfit [Ca2CoO3-δ]q[CoO2] (C349) by the addition of praseodymium oxide

We report the effect of PrOx addition on the oxygen reduction reaction (ORR) mechanism of a [Ca2CoO3-δ]q[CoO2] SOFC cathode (also known as Ca3Co4O9-δ, C349) obtained by solid-state synthesis of a stoichiometric mixture of mollusk shell powder (a natural source of calcium carbonate) and cobalt oxide. Symmetrical cells of screen-printed pristine C349 and PrOx-infiltrated C349 compositions are analyzed by electrochemical impedance spectroscopy (EIS) as a function of oxygen partial pressure (pO2 = 1-10−2 atm) in the temperature range 600–800 °C. The results show a decrease in total polarization resistance (Rp) of ∼8 times by the addition of PrOx to the C349 phase in pure oxygen at 700 °C. This improvement is shown to be mainly due to a large decrease (∼13 times) in the charge-transfer processes occurring at the surface of electrode, which dominate the total polarization resistance. The polarization resistance of the PrOx-impregnated C349 cathode is also demonstrated to be very competitive in comparison to typical Ca-cobaltite-based cathodes.

Facile preparation of praseodymium oxide coated peanut-like lithium nickel cobalt manganese oxide microspheres for lithium ion batteries with high voltage capabilities

Praseodymium oxide (Pr6O11) coated peanut-like lithium nickel cobalt manganese oxide (LiNi1/3Co1/3Mn1/3O2) microspheres has been prepared by a simple dip-dry method. The structure and morphology of the as-prepared samples were characterized by X-ray diffraction and electron microscopy. The results show that the composites can be indexed as hexagonal layered structure with peanut-like morphology, and the LiNi1/3Co1/3Mn1/3O2 were successfully coated with Pr6O11 particles. The samples exhibit superior high voltage capabilities, the discharge capacity of the coated sample (Pr6O11 content is 1 wt%) is 139.9 mA h g−1 at 1 C between 2.5 and 4.5 V after 100 cycles. However, the discharge capacity still maintains 96.7 mA h g−1 at 10 C within the voltage range of 2.5–4.6 V over 50 cycles. The improved high voltage capabilities could be ascribed to the positive impact of Pr6O11, which can increase the electronic conductivity between microspheres, the lithium-ion diffusion coefficient, in conjunction with inhibit the undesirable side reaction between electrode and electrolyte.

Synthesis and characterization of novel Pr6O11/Mn3O4 nanocomposites for electrochemical supercapacitors

This study presents the successful synthesis of praseodymium oxide, Pr6O11 and hausmannite manganese oxide, Mn3O4 nanoparticles, along with a novel synthesis of (Pr6O11/Mn3O4) nanocomposites by employing the hydrothermal route followed by post thermal annealing. X-ray Diffraction, Field Emission Scanning Electron Microscopy and Energy Dispersive X-ray characterization techniques are being adapted to analyze the physical characteristics of all the synthesized materials. XRD results reveal the crystalline nature of the synthesized materials. FE-SEM results display the irregular nanograins of Mn3O4 and a regular network of interconnected Pr6O11 nanoparticles. Nitrogen adsorption/desorption tests confirm the mesoporous nature of all the synthesized electrode materials. The Pr6O11/Mn3O4 − 2 electrode material exhibits an outstanding specific capacitance of 794.58 F/g at a current density of 0.5 A/g, as compared to the 521.24 F/g for the Pr6O11 electrode material. These investigations provide an easy and efficient method to develop nanocomposites (Pr6O11/Mn3O4) with better electrochemical characteristics, as electrode materials for supercapacitor applications.

Advanced three-dimensional hierarchical Pr6O11@Ni-Co oxides-based core-shell electrodes for supercapacitance application

A facile solvothermal method is used to fabricate hierarchical core-shell nanostructures based on praseodymium, nickel and cobalt oxides supported on nickel foam. The Pr6O11 nanoparticles were first grown on the nickel foam and then utilized as a backbone for anchoring NiO, Co3O4 and NiCo2O4 nanostructures to form a core-shell structure. The core-shell electrodes exhibit superior electrochemical performance than single Pr6O11 nanoparticles electrodes. A superior specific capacitance of 1635 F/g at a current density of 0.5 mA/cm2 with good cycling stability was obtained for the Pr6O11@NiCo2O4 electrode. Moreover, a solid-state supercapacitor was fabricated by assembling Pr6O11@NiCo2O4 electrodes using KOH/PVA as the solid electrolyte. The as-prepared solid-state device demonstrated impressive energy density of 6.6 W h/kg and a power density of 150 W/kg. This optimal performance could be attributed to the high conductive nickel foam current collector and synergistic effects generated from the core-shell architecture of NiCo2O4 and the Pr6O11 nanoparticles.

Controlled synthesis of praseodymium oxide nanoparticles obtained by combustion route: Effect of calcination temperature and fuel to oxidizer ratio

This investigation focuses on the employment of the solution combustion route for synthesis of praseodymium oxide nanoparticles. The fabrication was be carried out by using the solution combustion of a fuel (urea) and oxidizer (praseodymium nitrate) mixture. The influence of fuel/oxidizer ratio and the temperature of calcination on the phases formed, morphological changes and the crystallite size of Pr6O11 have been checked. Various characterization tools have been used for the identification of the thermal behaviour of the precursors, structure and morphology of the prepared Pr6O11 nanoparticles, which include TGA-DTA, XRD, FT-IR, XPS, SEM, and TEM. With respect to the effect of the fuel content, it was found that using F/O ratio ≥4.0 at 500 °C praseodymium carbonate starts to form at the expense of the oxide phase. These phase changes were, also, companied by a noticeable morphological modifications. On the other hand, it was shown that Pr6O11 can be obtained as a single phase upon calcining at temperatures ≥500 °C. The electrical conductivity of Pr6O11 nanoparticles synthesized at 400–700 °C has been investigated over a measuring temperature range of 200–400 °C. The obtained results have led to a better understanding of the factors influencing the electrical conductivity behaviour of Pr6O11 nanoparticles, viz. the availability of Pr3+/Pr4+ pairs and the crystallite size.

High performance metal-supported solid oxide fuel cells with infiltrated electrodes

High power density is required to commercialize solid oxide fuel cells for vehicular applications. In this work, high performance of metal supported solid oxide fuel cells (MS-SOFCs) is achieved via catalyst composition, electrode structure, and processing optimization. The full cell configuration consists of a dense ceramic electrolyte and porous ceramic backbones (electrodes) sandwiched between porous stainless steel metal supports. The conventional YSZ electrolyte and backbones are replaced with more conductive and thinner 10Sc1CeSZ ceramics. MS-SOFCs are co-sintered in a single step and subsequently infiltrated with nanocatalysts. Five categories of cathode catalysts are screened in full cells, including: perovskites, nickelates, praseodymium oxide, binary layered composites, and ternary layered composites. Various anode compositions are also tested. The conventional LSM cathode catalyst is replaced with more active Pr6O11 and the Ni content of the SDC-Ni anode is increased. The resulting cells achieve a peak power of 1.56, 2.0, and 2.85 W cm−2 at 700, 750, and 800 °C, respectively, with 3%H2O/H2 as fuel and cathode exposed to air. Multiple cells show reproducible performance (Pmax = 1.50 ± 0.06 W cm−2) and OCV (1.10 ± 0.02 V). The performance is further increased with cathode exposed to pure oxygen (2.0 W cm−2 at 700 °C).

Three-dimensionally ordered macroporous PrOx: An improved alternative to ceria catalysts for soot combustion

The synthesis and use for soot combustion of praseodymium oxide with three-dimensionally ordered macroporous (3DOM) structure is described. This novel PrOx-3DOM catalyst is presented as an improved noble-metal-free alternative to CeO2 as soot combustion catalyst. The PrOx-3DOM catalyst presents a defined 3DOM structure with high macropores volume, which significantly enhances the solid-solid soot-catalyst contact. This enhanced contact, together with the improved reducibility of PrOx regarding CeO2, ameliorate the active oxygen production and its transfer to soot particles, improving the soot combustion with O2. In addition, the higher ability of PrOx to oxidize NO to NO2, improves the soot combustion in a higher extent than CeO2 in presence of NOx. The catalytic activity of PrOx-3DOM after several soot combustion cycles is also confirmed.

Improving Thermal Stability of Solution-Processed Indium Zinc Oxide Thin-Film Transistors by Praseodymium Oxide Doping.

Praseodymium-doped indium zinc oxide (PrIZO) channel materials have been fabricated by a solution process with conventional chemical precursor. The PrIZO-based thin-film transistors (TFTs) exhibited a field-effect mobility of 10.10 cm2/V s, a subthreshold swing value of 0.25 V/decade, and an Ion/ Ioff ratio of 108. The as-fabricated PrIZO-TFTs showed an improved device performance against positive bias temperature stress (PBTS shift of 1.97 V for 7200 s), which was evidently better than the undoped IZO-TFTs (PBTS shift of 9.52 V). This result indicates that the organic residual (-OCH3 and -CH2-) in metal-oxide semiconductor, which is confirmed to be a dominant effect on the performance of PBTS, can be passivated by the rare earth of praseodymium element. The residual is intended to be oxidized with a more stable ester group with the assistant of PrOx, weakening the electron-withdrawing characteristic during the thermal bias stress.