Praseodymium Oxide Research Articles

Synthesis and Characterization of Platinum-Praseodymium Oxide Nanocatalysts for Methanol Oxidation

Direct methanol fuel cells (DMFCs) are promising energy conversion devices, which can provide high efficiency and energy density, and as such, have been studied intensively. Due to the poisoning of Pt catalysts during methanol oxidation, various co-catalysts have been studied. Ruthenium has been studied extensively and good results have been obtained. More recently various oxide materials have been proposed and studied. Of these materials, rare earth metal oxides have been shown to be promising co-catalysts, although of the various oxides, CeO2 has perhaps received most attention. In this study, praseodymium oxide containing catalyst materials have been synthesised and characterized. Praseodymium oxide containing nanocatalysts were obtained via deposition of praseodymium hydroxide onto a carbon support material and calcination of the resulting material. Thereafter, platinum nanoclusters were deposited onto the praseodymium oxide containing composite material by impregnation of the Pt precursor into the support material and further reduction with hydrogen. The studied materials were electrochemically characterized using rotating disk electrode, cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy methods. Physical properties of the materials were characterized using X-ray diffraction, thermogravimetric analysis, scanning electron microscopy with EDX, inductively coupled plasma mass spectrometry and specific surface area measurements. The studied materials exhibit high currents for methanol oxidation even at low Pt loadings. Compared to a commercial Pt-C(Vulcan) material, the overpotential was drastically reduced, and the peak potential for methanol oxidation is at E = 0.15 V vs mercury-mercurous sulfate electrode. The good results of the study are a continuation of the investigation of nanocatalysts containing rare earth metal oxides for electrooxidation of alcohols. Acknowlegements This work was supported by the EU through the European Regional Development Fund Project TK141 “Advanced materials and high-technology devices for energy recuperation systems” (2014-2020.4.01.15-0011) and by the Estonian Research Council (institutional research grant IUT20-13, and PUT1581). P. Valk thanks Estonian Students Fund in USA for financial support.

Synthesis and Characterization of Platinum-Praseodymium Oxide Nanocatalysts for Methanol Oxidation

In this study, platinum-praseodymium oxide nanoparticles have been deposited onto a carbon support material. The praseodymium oxide nanoparticles were synthesized by calcination of deposited Pr(OH)3 and Pt nanoparticles were synthesized by reduction of H2PtCl6 with hydrogen. The physical properties were characterized using X-ray diffraction, thermogravimetric analysis and inductively coupled plasma mass spectrometry. The materials were electrochemically characterized using cyclic voltammetry and chronoamperometry. The materials exhibited high activity towards methanol electrooxidation, as well as relatively low overpotential.

The structure and performance of (Ni4Fe)mAg(PrZr4)nOx catalyst for ethanol steam reforming

Co-precipitation method is used to synthesize PrpZrqOx composite oxide support and impregnation method is adopted in preparing (Ni4Fe)mAgPrpZrqOx catalysts. X-ray power diffraction (XRD), Temperature programmed reduction (TPR) and Temperature programmed oxidation (TPO) are used to characterize the catalysts. The results indicate that not only the improvement of catalytic activity is remarkable, but also an excellent capacity of resistance to carbon deposition when Ag dropped into the Ni-Fe bimetallic catalysts. XRD spectrum of the fresh (Ni4Fe)mAg(PrZr4)nOx catalysts present characteristic diffraction peak of tetragonal crystal phase ZrO2, rhombohedral Fe2O3, hexagonal NiO and cubic Ag2O while no diffraction peak of praseodymium oxide appears because the doped praseodymium ions can enter the ZrO2 lattice. After 823K’s pretreatment by H2, the main active components are cubic Ni0 and cubic Ag0. TPR shows that the presence of Ag is of great benefit to the reduction of Fe2O3 and NiO: the peaks maximum due to the Fe2O3→Fe3O4 and NiO→Ni0 reduction of the Ag-containing sample are shifted by more than 150K to lower temperatures in comparison with Ni-Fe bimetallic metallic catalysts. (Ni4Fe)16Ag(PrZr4)64.8Ox catalyst shows its best catalytic activity in ethanol steam reforming. Under the following conditions, reaction temperature 773K, ethanol/water with molar ratio of 1:6, weight hourly space velocity (WHSV) of 11.8 h−1, the ethanol conversion rates are nearly 100% and the molar percentage of H2, CO, CH4, CO2 are 70.5%, 1.8%, 7.9%, and 19.6% respectively.

Bare and nonionic surfactant-functionalized praseodymium oxide nanoparticles: Toxicological studies

The applications of praseodymium oxide (Pr6O11) nanomaterials in catalysis, oxygen storage materials, and optical devices are the emergent areas that possess an urgent requirement for the toxicological evaluation of these nanomaterials to determine their impact on the ecology. In the present work, we have employed a multiassay approach for the toxicological profiling of bare and nonionic surface-modulated Pr6O11 nanoparticles (NPs). The contemporary analysis in this work has presented a great prospect to develop efficient indicators and inspect the toxic nature of bare and functionalized Pr6O11 NPs. The effect of Pr6O11 NPs was analyzed on germination parameters by the wheat seed germination assay and on algal growth by the paper disc approach. The influence of Pr6O11 NPs on the percentage viability of four different types of bacteria, namely, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi, was investigated. The substantial effect of different concentrations of Pr6O11 NPs on Allium cepa was investigated at the genomic level by using the chromosomal aberration assay. The functionalized NPs exhibited 41.05%-400% higher biocompatibility by the wheat seed germination assay and 27.1%-47.3% by the A. cepa chromosomal aberration assay than the bare NPs. In algal growth assay and antibacterial activity testing, biocompatibility of the developed functionalized NPs enhanced by 23.1%-37.1% and 10%-70.6%, respectively. The current work evaluated the toxicity of the NPs and measured the competence of the obtained data to characterize possibilities of probable threats, prominence of data requirement, and breaches that must be filled to diminish the ambiguities about the safe use of Pr6O11 NPs.

Rare earth elements price forecasting by means of transgenic time series developed with ARIMA models

A time series can be thought of as a numerical organism with a continuous nature from a chronological point of view and something that is permanently updated. Up to this moment time series research related with their features, traits, and characteristics, is mainly focused on data mining, in order to discover hidden information or specific knowledge within the time series or their transformations. However, time series representation is crucial, as they are difficult to handle in their original structure due to their high dimensionality.In this paper, the “theory of transgenic time series” is developed, and applied to the forecasting of several rare earth oxide prices: dysprosium, europium, terbium, neodymium, and praseodymium oxides. This theory addresses, specifically, the existence of metal price cycles and the presence of anomalous phenomena that the theory allows to eliminate from the time series, improving the accuracy of the forecast.After representing the time series in a way that allows their genome to be sequenced, a restriction enzyme is defined in order to create a genetically modified time series. There was no need to develop DNA ligases as time series can be cut and pasted without further considerations.Results clearly state that transgenic time series lead to more accurate short term forecasts in cases where a consistent time series genome can be represented. Further research should address the feasibility of developing more accurate long term forecasts by adding new gene sequences based on the time series genome, in order to achieve greater confidence from investors and professional advisers in the feasibility studies developed for future mining investment projects.Finally, it has to be remarked that this theory has nothing to do with “genetic algorithms”, a metaheuristic that was inspired by the natural selection process and not by the sequencing and manipulation of the genome.

Single SOFC with Supporting Ni-YSZ Anode, Bilayer YSZ/GDC Film Electrolyte, and La2NiO4 + δ Cathode

Characteristics of fuel cells with supporting Ni-YSZ anode, bilayer YSZ/GDC electrolyte with the thickness of 10 μm, and La2NiO4 + δ cathode are studied. It is shown that when humid (3% water) hydrogen is supplied to the anode and air is supplied to the cathode, the maximum values of cell’s power density are 1.05 and 0.75 W/cm2 at 900 and 800°С, respectively. After the introduction of praseodymium oxide and ceria into the cathode and the anode, respectively, the power density is ca. 1 W/cm2 at 700°С. It is found that the power density of a cell with impregnated electrodes weakly increases with the increase in temperature to ca. 1.4 W/cm2 at 900°С. The analysis of impedance spectra by the distribution of relaxation times shows that such behavior is associated with the gas-diffusion resistance of the SOFC anode. The latter is explained by the low porosity of the anode and the high rate of fuel consumption.

Influence of Pr6O11 on oxygen electroreduction kinetics and electrochemical performance of Sr2Fe1.5Mo0.5O6-δ based cathode

Oxygen electroreduction kinetics and electrochemical performance of the Pr6O11-impregnated Sr2Fe1.5Mo0.5O6-δ – Ce0.8Sm0.2O1.9 (SFM–SDC) cathode have been first studied. By means of distribution of relaxation times and non-linear least squares analysis of impedance spectra were shown that the addition of Pr6O11 into the cathode leads to the increase in the rate of the low-frequency step. It is suggested that the observed phenomenon is associated with the increase in the rate of surface oxygen exchange. It is shown that the introduction of praseodymium oxide into the cathode results in a decrease in the area specific polarization resistances of the cathode at equilibrium potentials from 0.23 to 0.06 Ω cm2 at 800 °C in air. The maximum power density of symmetrical solid oxide fuel cell (SOFC) with impregnated SFM–SDC electrodes and supporting 760 μm La0.85Sr0.15Ga0.85Mg0.15O3-δ electrolyte without buffer/barrier and collector layers under air/wet hydrogen (dry CH4) condition was about 0.5 (0.26) W cm−2 at 800 °С. The overvoltage of the cathode was higher than that of the anode under air/wet hydrogen and vice versa when methane was supplied to the anode. The obtained results elucidate that the impregnated SFM–SDC is a promising cathode for SOFC application.

Ceramics based on zirconium dioxide stabilized with indium oxide and praseodymium oxide

The solid solutions based on Zirconia doped with indium oxide and praseodymium oxide with different concentration was obtained by the method of inverse heterophase co-deposition. The physico-chemical properties of obtained samples were examined. The highest properties have been achieved in samples of the composition Zr1-xRxO2-δ (R=23 mol .% In). This composition has a density of 5.38 g/cm3; open porosity is 0 %, the bending strength is 203 MPa.

Thermal decomposition of praseodymium nitrate hexahydrate Pr(NO3)3·6H2O

The hexahydrate of praseodymium nitrate hexahydrate Pr(NO3)3·6H2O does not show phase transitions in the range of 233–328 K when the compound melts in its own water of crystallization. It is suggested that the thermal decomposition is a complex step-wise process, which involves the condensation of 6 mol of the initial monomer Pr(NO3)3·6H2O into a cyclic cluster 6[Pr(NO3)3·6H2O]. This hexamer gradually loses water and nitric acid, and a series of intermediate amorphous oxynitrates is formed. The removal of 68% HNO3–32% H2O azeotrope is essentially a continuous process occurring in the liquid phase. At higher temperatures, oxynitrates undergo thermal degradation and lose water, nitrogen dioxide and oxygen, leaving behind normal praseodymium oxide Pr2O3. The latter absorbs approximately 1 mol of atomic oxygen from N2O5 disproportionation, giving rise to the non-stoichiometric higher oxide Pr2O3.33. All mass losses are satisfactorily accounted for under the proposed scheme of thermal decomposition.

New detailed insights on the role of a novel praseodymium nanofilm on the polymer/steel interfacial adhesion bonds in dry and wet conditions: An integrated molecular dynamics simulation and experimental study

Abstract The adhesion improvement and surface-bonding nature at epoxy polymer/steel interface decorated with novel rare earth element nanofilms based on praseodymium (Pr) and its composite cerium-praseodymium (Ce-Pr) oxides were studied by molecular dynamics (MD) simulation and experimental approaches. The steel surface morphology and chemistry after depositing praseodymium and cerium oxides were examined by field-emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The adhesion characteristics of epoxy coating applied over surface-treated steel were assessed by pull-off adhesion and Fourier transform infrared (FT-IR) spectroscopy. Results revealed that the adhesion strength at polymer/steel interface substantially improved upon steel surface treatment by Pr and Ce-Pr (100%) nanofilms. The strongest interfacial adhesion and the lowest adhesion loss in wet conditions were observed for steel samples decorated by Ce and Pr oxides. The simulation results further evidenced the stronger epoxy resin adhesion onto surface-treated steel (represented by praseodymia Pr2O3 and ceria CeO2) as compared with untreated sample (represented by iron oxides) particularly under wet conditions.

The influence of steel surface treatment by a novel eco-friendly praseodymium oxide nanofilm on the adhesion and corrosion protection properties of a fusion-bonded epoxy powder coating

The effect of steel surface treatment by an eco-friendly praseodymium (Pr) oxide nanofilm on the corrosion protection properties and cathodic delamination of a fusion-bonded epoxy coating (FBE) was studied. The results of AFM, FE-SEM and contact angle tests revealed that a crack free praseodymium oxide nanofilm uniformly covered the steel surface. Results of EIS and salt spray tests revealed that the steel surface treatment by Pr film significantly enhanced the FBE coating corrosion protection performance. Results of cathodic delamination test showed significant decrease in the FBE cathodic delamination rate. Results of pull-off test revealed the FBE/Steel interfacial adhesion bonds promotion.

Pr6O11-Functionalized SnO2Flower-Like Architectures for Highly Efficient, Stable, and Selective Acetone Detection

Pristine and different amounts of praseodymium oxide (Pr6O11)-functionalized tin oxide (SnO2) flower-like architectures were synthesized by a facile one-step hydrothermal method. Their crystal structure, surface morphology, and chemical compositions were analyzed by XRD, SEM, TEM, and XPS. Measured results showed that Pr existing was in the form of Pr6O11. Compared with pristine SnO2 architectures, the gas sensing properties toward acetone of Pr6O11-functionalized SnO2 architectures could significantly be enhanced under different working temperatures. The response of the as-synthesized Pr6O11/SnO2 (Pr(mol):Sn(mol) = 1:50) sensor to 100 ppm acetone was about 27, which was about three times higher than that of pristine SnO2 architectures. The response/recovery time was 2/36 s at 200 °C. When acetone concentration was down to 1 ppm, Pr6O11/SnO2 (Pr(mol):Sn(mol) = 1:50) sensor also exhibited an obvious response. Meanwhile, the enhanced gas sensing mechanism of Pr6O11-functionalized SnO2 architectures was discussed, and the results indicated that the architectures are promising candidates for the practical acetone sensing.

Boron and praseodymium doped bismuth oxide nanocomposites: Preparation and sintering effects

Boron and praseodymium doped bismuth oxide nanocomposites were prepared through polymeric precursor technique. The nanocomposites were then sintered to identify the changes in the microstructures of the nanocomposites. The microstructural properties of the nanocomposites were investigated by means of Brunauer-Emmett-Teller nitrogen adsorption, a Scanning Electron Microscope, a Fourier Transform Infrared Spectrometer, and an X-Ray Diffractometer. The Fourier Transform Infrared Spectra of nanocomposites was attested from the presence of boron, praseodymium, and bismuth oxides. According to the X-Ray Diffractometer results, β-bismuth oxide was formed after calcination. Moreover, sintering affected on the crystalline structure of the boron undoped nanocomposite. The sintered boron doped nanocomposite was mainly consisted of the hexagonal bismuth praseodymium oxide while the β-bismuth oxide phase was dominant for the sintered boron doped nanocomposite. The Scanning Electron Microscope micrographs of the nanocomposites showed the plate-like structures. The surface areas of the nanocomposites were decreased because of sintering in accordance with the Brunauer-Emmett-Teller results.

ОБРАЗОВАНИЕ СОЕДИНЕНИЙ НА ОСНОВЕ ФЕРРИТА ВИСМУТА ПРИ ЧАСТИЧНОМ ЗАМЕЩЕНИИ ИОНОВ ВИСМУТА ИОНАМИ ЛАНТАНА И ПРАЗЕОДИМА

Using the solid-phase reaction method we obtained bismuth ferrite based compounds generated by partial substitution of bismuth ions with rare earth metal ions (lanthanum and praseodymium). We used thermogravimetric analysis and X-ray analysis at the temperature range from 297 to 1123 K to study the peculiarities of the processes of phase formation of reaction-products synthesis in the systems which contain oxides of iron, bismuth, lanthanum, and praseodymium; their compositions were also determined. For the final synthesis temperature of 1123 K we determined a homogeneous concentration area, where bismuth ferrite solid solutions with the structure of distorted perovskite exist. We studied the influence of lanthanum and praseodymium oxides on phase composition of bismuth ferrite compounds in the process of isovalent alloying of a part of bismuth ions by lanthanum and praseodymium ions. In the frequency range of 20 Hz – 1 MHz we determined the key parameters, which characterize electrical and magnetic properties of perovskite-like phases. We found that for the considered samples the frequency dependencies of complex magnetic permeability and electrical parameters (real and alleged part of permittivity) are of almost the same type. We showed that for the given frequency range both electrical (complex permittivity) and magnetic (complex magnetic permeability) parameters decrease with the frequency increase

The role of Praseodymium oxide-Impregnated Clinoptilolite Zeolite Catalyst to Increase Octane Number in Gasoline

In the present work, the role of praseodymium oxide as a promotor of active site in zeolite base as catalyst for increasing the octance number in gasoline were investigated. In this study, we used three types of catalyst, namely the activated clipnotilolite zeolite (catalyst 1), Pr6O11-impregnated clinoptilolite zeolite 0.01 (w/w%) (catalyst 2) and Pr6O11-impregnated clinoptilolite zeolite 0.1 (w/w%) (catalyst 3). Both catalyst 2 and 3 were prepared by impregnation method. The calcination temperature for all of catalysts was set at 500°C for 2 hours to remove the organic impurities and stabilize the structure of catalyst. The Si/Al ratio increased from 5.1 to 5.85 with prasedymium nitrate hexahydrate percentage in catalysts 2 and 3 were 0.14 and 0.05%, respectively. The surface area of catalysts 1 - 3 are 19.42, 18.09 and 15.22 m2/g, respectively. The activity performance of catalyst 3 with 1 and 3 % loading at 27.7°C for 2 min have increased the octane number of 0.1. Increasing octane number of 0.1 was also confirmed by GC-MS data which showed the presence of decreasing C4-C11 hydrocarbon compounds and increasing of aromatic compounds. Pr6O11-impregnated clinoptilolite zeolite catalyst is potential for application in fuel system to increase octane number at room temperature (27.7°C).

Synthesis, physicochemical and catalytic properties of Ni/PrCeZrO catalysts for water-gas shift reaction

AbstractMixed nanocrystalline ceria-zirconia oxides doped with praseodymium containing 5, 7.5, 10, and 12.5 wt. % nickel were prepared by the incipient wetness impregnation of the oxide support. Complex physicochemical characterization by X-ray diffraction analysis, ultraviolet-visible diffuse reflectance spectroscopy, high resolution transmission electron microscopy and Fourier-transform infrared spectroscopy of adsorbed CO revealed that the nickelcontaining samples are comprised of a solid solution of praseodymium, cerium and zirconium oxides with the fluorite structure as well as nickel oxide particles with a size up to 100 nm. All prepared nanocomposite catalysts show a high catalytic activity in the water-gas shift reaction. The optimum content of nickel in the catalyst providing the maximum activity was found to be 10 wt. %. A high oxygen mobility in these catalysts estimated by the temperature-programmed oxygen isotope heteroexchange with C18O2 provides required coking stability. To eliminate local overheating of the catalyst and decrease the pressure drop in the reactor, as required for further up-scaling, the active component was supported on a metal plate made of Ni-Al foam alloy. At a fixed contact time, the same level of CO conversion with a fraction of the active component was achieved with an approximately 50 wt% loading on the support.

Corrosion and magnetic properties of encapsulated carbonyl iron particles in aqueous suspension by inorganic thin films for magnetorheological finishing application

Magnetorheological fluid is composed of micro-size carbonyl iron (CI) particles for polishing of optical substrates. In this paper, the corrosion resistance of carbonyl iron (CI) particles modified with three inorganic thin films based on rare earth elements, including cerium oxide (CeO2), lanthanum oxide (La2O3) and praseodymium oxide (Pr2O3), was investigated. The morphology and chemistry of the CI-Ce, CI-Pr and CI-La particles were examined by high resolution Field Emission-Scanning Electron Microscopy (FE-SEM), X-ray energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization tests were carried out to investigate the corrosion behavior of CI particles in aquatic environment. In addition, the Vibrating Sample Magnetometer (VSM) technique was utilized for determination of magnetic saturation properties of the coated particles. Afterwards, gas pycnometry and contact angle measurement methods were implemented to evaluate the density and hydrophilic properties of these particles. The results showed that deposition of all thin films increased the hydrophilic nature of these particles. In addition, it was observed that the amount of magnetic saturation properties attenuation for Pr2O3 and La2O3 films is greater than the CeO2 film. The EIS and polarization tests results confirmed that the CI-Ce had the maximum corrosion resistant among other samples. In addition, the thermogravimetric analysis (TGA) showed that the ceria coating provided particles with enhanced surface oxidation resistance.

Combustion synthesis, structural and magnetic characterization of Ce1−xPrxO2 system

The current work describes the synthesis of Ce1−xPrxO2 (x = 0.0, 0.2, 0.4, 0.6, 0.8) and Pr6O11 systems by the combustion method, using citric acid as chelating agent. The obtained solids after combustion and calcination processes were characterized by thermal analysis (TGA-DTA) and infrared spectroscopy (FT-IR) to evaluate the chemical process during the combustion reaction. The surface area analysis using isotherms of nitrogen adsorption, reveal that all samples exhibit values between 70 and 135 m2 g−1, with a pore volume that allows its classification as mesoporous materials. The structural analysis by X-ray diffraction (XRD) and Rietveld refinement, revealed the obtention of a pure cubic structure Fm3m (225) along all cerium oxide modifications with nanocrystalline domain sizes, except for the praseodymium oxide that shows two crystalline phases in a monoclinic crystalline phase P12 1 /c 1 (14) in the case of Pr6O11 and a cubic phase Fm3m (225) for PrO2 oxide. The oxygen storage capacity measurements performed in all samples, demonstrate that exchange of Ce ions by Pr increases the storage capacity of samples over the reference values in accordance with the synthesis method. The characterization by high-resolution transmission electron microscopy, confirmed that the solids are composed by nanometric aggregates with d spacing between 0.29 and 0.31 nm along main diffraction signals, in accordance with the experimental XRD results. Finally, the magnetic characterization in a ZFC configuration and a M-H mode, shows a strong paramagnetic behavior in all systems except in CeO2 oxide, which exhibited a prevalent diamagnetic behavior.

Structural investigation and sonocatalytic efficiency of Ce0.9Nd0.1O1.95 and Ce0.9Pr0.1O1.95 nanocatalysts

The cost-effective low-frequency ultrasound (42 kHz) producing bath type sonicator was utilized to demonstrate the synthesis of sequential (SP) and co-precipitated (CP) Ce0.9Pr0.1O1.95, Ce0.9Nd0.1O1.95 and their bare catalysts. The analytical characterizations of the catalysts showed that the 42 kHz ultrasound fetches the interesting physicochemical properties with unusual sonocatalytic efficiency in the resulting catalysts. In addition, the ultrasound introduced the nanoporous structure in the CeO2, Ce0.9Pr0.1O1.95 (SP, CP) and Ce0.9Nd0.1O1.95 (SP, CP) catalysts, however, the nanoporous structure was not observed for the bare praseodymium and neodymium oxides. The sonocatalytic efficiency of the catalysts was evaluated by studying the degradation kinetics of Acid Blue 113 (AB113) dye. The sonocatalytic degradation of AB113 followed the first-order kinetic rate law and the r2 (linear regression coefficient) was >0.92. The extended ultrasound irradiation of AB113 was studied for 7 h in the presence of various nanocatalysts in order to evaluate the total organic carbon (TOC) removal from the sonocatalytic microenvironment. The rapid development of cost-effective technology based on 42 kHz ultrasound assisted degradation of various environmental pollutants significantly contributes to reducing the cost required for the commercialization of advanced oxidation processes.

Nanoscale analysis of the oxidation state and surface termination of praseodymium oxide ultrathin films on ruthenium(0001)

The complex structure and morphology of ultrathin praseodymia films deposited on a ruthenium(0001) single crystal substrate by reactive molecular beam epitaxy is analyzed by intensity-voltage low-energy electron microscopy in combination with theoretical calculations within an ab initio scattering theory. A rich coexistence of various nanoscale crystalline surface structures is identified for the as-grown samples, notably comprising two distinct oxygen-terminated hexagonal Pr2O3(0001) surface phases as well as a cubic Pr2O3(111) and a fluorite PrO2(111) surface component. Furthermore, scattering theory reveals a striking similarity between the electron reflectivity spectra of praseodymia and ceria due to very efficient screening of the nuclear charge by the extra 4f electron in the former case.