Praseodymium Atoms Research Articles

Synergistic effects of nitrogen-doped carbon and praseodymium oxide in electrochemical water splitting

Hybrid materials featuring perovskite-type metal oxide in conjunction with heteroatom-doped graphene hold immense promise as alternatives to costly noble metal catalysts for electrochemical water splitting, facilitating the generation of environmentally friendly hydrogen. In this study, perovskite-type oxide containing praseodymium, barium, strontium, cobalt, and iron atoms dispersed in a carbon matrix as a catalyst is synthesized via annealing of the carbon material with substrates for the preparation of perovskite oxide. The mass ratio of reagents regulates the porous structure and elemental composition. The result of the hydrogen evolution reaction (HER), suggests that the hybrid catalysts exhibit intermediate HER kinetics compared to the commercial Pt/C and the catalyst without carbon. The Tafel slope for HER is lower for materials containing carbon, because of the improved reaction kinetics, facilitated proton transfer, and enhanced electrochemical surface area. Therefore, the study provides an effective strategy for the preparation of catalyst and their use as the active catalyst of water splitting.

Ultraviolet-C persistent luminescence and defect properties in Ca2Al2SiO7:Pr3+

In recent years, significant attention has been focused on the study of materials with ultraviolet (UV) persistent luminescence (PersL) due to their prospective application possibilities. Although novel UV persistent phosphors are being developed, reports on defect properties and PersL mechanisms are limited. In this study, the incorporation of Pr3+ ions in Ca2Al2SiO7 is analyzed using X-ray diffraction (XRD) and X-ray absorption techniques, whereas PersL properties are characterized by photoluminescence (PL), thermostimulated luminescence (TSL) and electron paramagnetic resonance (EPR) methods. Analysis of the Pr L3-edge X-ray absorption spectra suggests that praseodymium atoms substitute for calcium atoms. The UV-C PersL of the host results from thermally assisted recombination of charge carriers with trap depths within the 0.50–0.87 eV range. Moreover, a partial correlation of PersL and TSL with the decay of X-ray-induced paramagnetic centers was observed. This study expands the knowledge base on the structure of Ca2Al2SiO7 and establishes the optimal Pr3+ concentration for efficient UV-C PersL.

Rare earth praseodymium-based single atom catalyst for high performance CO2 reduction reaction

Rare earth single-atom catalysts (SACs) can be used to obtain atomically dispersed species on supports to provide the maximum number of well-defined active sites, which would subsequently maximize the utilizationof rare earth metals. However, the design and synthesis of SACs are mostly based on transition metals, and rare earth SACs have been rarely explored. Herein, we report a rare earth praseodymium SAC dispersed on a porous carbon substrate by utilizing the cascade anchoring strategy, with a metal loading of up to 5.07 wt%. This praseodymium SAC exhibits excellent catalytic performance for the electrochemical CO2 reduction reaction (CO2RR) and achieves high selectivity for CO, with a faradaic efficiency (FECO) of up to 93% at a low potential of −0.43 V vs RHE. Experiments and theoretical calculations confirm that the isolated praseodymium atoms on the substrate are critical for improving the CO2RR performance of the material.

Praseodymium polyhydrides synthesized at high temperatures and pressures

Rare earth element polyhydrides have been predicted to exhibit high-${T}_{c}$ superconductivity at extreme compressions. Through a series of in situ high-pressure high-temperature x-ray powder diffraction experiments combined with density functional theory calculations, we report the emergence of polyhydride species in the praseodymium-hydrogen system. We initially observe the formation of ${\mathrm{PrH}}_{3}$, which continuously increases in hydrogen content on compression towards ${\mathrm{PrH}}_{4}$. Laser heating ${\mathrm{PrH}}_{4}$ in a hydrogen medium at pressures of 85 GPa leads to the synthesis of both ${\mathrm{PrH}}_{9}$ and ${\mathrm{PrH}}_{7}$. Both structures are characterized by hexagonal arrays of praseodymium atoms surrounded by hydrogen clathrate cages.

ChemInform Abstract: Investigation of Praseodymium Fluorides: A Combined Matrix‐Isolation and Quantum‐Chemical Study.

AbstractReaction products of laser‐ablated praseodymium atoms with fluorine in excess neon, argon, krypton, or neat fluorine at 4—10 K are investigated by IR spectroscopy and quantum chemical DFT and coupled‐cluster calculations.

Investigation of Praseodymium Fluorides: A Combined Matrix-Isolation and Quantum-Chemical Study.

The chemistry of the lanthanides is mostly dominated by compounds in the oxidation state +III. Only few compounds of Ce, Pr, and Tb are known with the metal in the +IV oxidation state. Removal of the last f-electron on praseodymium +IV would lead to a closed-shell system with formal oxidation state V. In this work we investigated the stability of the PrF5 molecule by theory and matrix-isolation techniques through the reaction of laser-ablated praseodymium atoms with fluorine in excess of neon, argon, krypton, or neat fluorine. Besides the known PrF3 molecule, unreported IR bands for PrF4 could be observed, and there is evidence for the formation of PrF and PrF2 but not for the formation of PrF5.

Synthesis, crystal structure and luminescence properties of lanthanide complexes with a new semirigid bridging furfurylsalicylamide ligand

We present here new lanthanide coordination polymers based on a semirigid bridging furfurylsalicylamide ligand which were synthesized and characterized by elemental analysis, X-ray powder diffraction and IR measurements. The coordination polymer [Pr2L3(NO3)6]∞ displays a two-dimensional honeycomb-like framework, which can be regarded as a (6,3) topological network with praseodymium atoms acting as “three-connected” centers. The photoluminescence analysis indicates that there is an efficient ligand-to-LnIII energy transfer in TbIII complex and the ligand is an efficient “antenna” for TbIII. From a more general perspective, the results demonstrated herein provide the possibility of controlling the formation of the desired lanthanide coordination structure to enrich the crystal engineering strategy and enlarges the arsenal for developing excellent luminescent lanthanide complexes of salicylamide derivatives.

Di-μ-pivalato-κ3O,O′:O′;κ3O:O,O′-bis[(methanol-κO)bis(2,2,6,6-tetramethylheptane-3,5-dionato)praseodymium(III)

In the centrosymmetric dimeric title compound, [Pr2(C5H9O2)2(C11H19O2)4(CH3OH)2], the two praseodymium(III) atoms are eight-coordinate and are bridged by O atoms from the two pivalate anions. Each PrIII ion is further coordinated by two chelating 2,2,6,6-tetra­methyl-3,5-hepta­nedionate (thd−) ligands and one methanol mol­ecule. The distance between the two PrIII ions is 4.273 (5) Å. Intra­molecular hydrogen bonds exists between the methanol hy­droxy group on one PrIII atom and a chelating O atom of a thd− ligand coordinated to the symmetry-related PrIII atom.

Synthesis and Crystal Structure of the Praseodymium Orthoborate λ -PrBO3

The praseodymium orthoborate λ -PrBO3 was synthesized from Pr6O11, B2O3, and PrF3 under high-pressure / high-temperature conditions of 3 GPa and 800 °C in a Walker-type multianvil apparatus. The crystal structure was determined on the basis of single-crystal X-ray diffraction data, collected at room temperature. The title compound crystallizes in the orthorhombic aragonite-type structure, space group Pnma, with the lattice parameters a = 577.1(2), b = 506.7(2), c = 813.3(2) pm, and V = 0.2378(2) nm3, with R1 = 0.0400 and wR2 = 0.0495 (all data). Within the trigonal-planar BO3 groups, the average B-O distance is 137.2 pm. The praseodymium atoms are ninefold coordinated by oxygen atoms.

Quantum-chemical features of Ln—O interatomic interactions in LnNb x O y (Ln=La, Ce, Pr, Nd, Pm, Sm, Eu) systems

Properties of the lanthanide—oxygen bonds in lanthanide niobates LnNb7O12(Ln=La, Ce, Pr, Nd, Pm, Sm, Eu) have been studied using the ab initio cluster X α discrete variational method with two different basis sets of molecular orbitals. It has been found that the structural instability of lanthanides LnNb7O12 (Ln=Nd, Sm) observed in experiments is due to the combined effect of decrease in the stability of [LnO8] cluster and increase in quantum-mechanical Ln—O repulsion when the minimum near neodymium (in the first model of the basis set of molecular orbitals) or praseodymium (in the second model of the basis set of molecular orbitals) atoms is passed.

Postdeposition annealing induced transition from hexagonal Pr2O3 to cubic PrO2 films on Si(111)

Films of hexagonal praseodymium sesquioxide (h-Pr2O3) were deposited on Si(111) by molecular beam epitaxy and thereafter annealed in 1 atm oxygen at different temperatures, ranging from 100 to 700 °C. The films of the samples annealed at 300 °C or more were transformed to PrO2 with B-oriented Fm3¯m structure, while films annealed at lower temperatures kept the hexagonal structure. The films are composed of PrO2 and PrO2−δ species, which coexist laterally and are tetragonally distorted due to the interaction at the interface between oxide film and Si substrate. Compared to PrO2, PrO2−δ has the same cubic structure but with oxygen vacancies. The oxygen vacancies are partly ordered and increase the vertical lattice constant of the film, whereas the lateral lattice constant is almost identical for both species and on all samples. The latter lattice constant matches the lattice constant of the originally crystallized hexagonal praseodymium sesquioxide. That means that no long range reordering of the praseodymium atoms takes place during the phase transformation.

Synthesis and Crystal Structure of the Novel Compound Mg4.5Pr79.5Mo126O312 Containing Mo3, Mo7 and Mo19 Clusters

The synthesis and crystal structure of the novel reduced molybdenum oxide Mg4.5Pr79.5Mo126O312 are presented. This compound crystallizes in the trigonal space group R-3 m with a = 11.3061(2) A, c = 58.242(1) A, V = 6447.5(2) A3, and Z = 1. Refinements yield R(F 2) = 0.0433 and wR(F 2) = 0.0931 for 2827 unique reflections. The structure is built up from alternating slabs made up of molybdenum forming Mo3, Mo7 and Mo19 clusters, praseodymium and oxygen atoms, and slabs containing isolated MoO6 octahedra. The Pr3+ cations are localized either within the slabs or at their borderlines to ensure the cohesion between the slabs. Of the six crystallographically independent sites occupy by the Pr3+ cations, two of them also contain randomly about 15% and 20% of Mg2+ cations while the remaining four are fully occupied by the Pr3+ cations.

Structure and Chemical Bonding of PrRuSn

The new ternary stannide PrRuSn was synthesized from the elements via arc-melting. PrRuSn is isopointal to the orthorhombic TiNiSi-type structure, space group Pnma. The structure was characterized by X-ray powder and single crystal diffraction: a = 761.7(2), b = 483.9(2) and c = 730.3(3) pm, wR2 = 0.0386, 433 F2 values, 20 variables. The ruthenium and tin atoms in PrRuSn build up a three-dimensional [RuSn] polyanionic network with Ru-Sn distances in the range 268 - 274 pm. The praseodymium atoms fill channels within the polyanion. They bind to the network via short Pr-Ru distances of 301 and 302 pm. Electronic structure calculations on PrRuSn and isopointal PrPdSn underline these features and reveal strong T-Sn (T = Ru, Pd) interactions within both solid state structures.

Praseodymium silicide formation at the Pr 2O 3/Si interface

The interface and layer structure of praseodymium (Pr) oxide layers grown on Si(0 0 1) from a high-temperature effusion cell are studied using grazing incidence X-ray diffraction. Due to the interdiffusion of praseodymium and silicon atoms, Pr silicide forms in the layers. We find that Pr silicide is the favorable structure under oxygen deficient growth conditions in the Pr oxide layer. To avoid the silicidation, additional oxygen must be supplied. The formation of Pr silicide is suppressed for layers grown with an oxygen partial pressure of 10 −7 mbar at a substrate temperature of 700 °C.

3D-[Pr(Im)3(ImH)]@ImH: Ein dreidimensionales Netzwerk mit vollständiger Stickstoffkoordination aus einer Imidazolschmelze / 3D-[Pr(Im)3(ImH)]@ImH: A Three-Dimensional Network with Complete Nitrogen Coordination Obtained from an Imidazole Melt

The reaction of a melt of unsubstituted imidazole with praseodymium metal yields bright green crystals of 3D-[Pr(Im)3(ImH)]@ImH. Imidazolate ligands coordinate η1 via both N atoms their 1,3 positioning within the heterocycle being responsible for the connection of praseodymium atoms. A 3-dimensional network is formed with imidazole molecules from the melt intercalated in the crystal structure. The imidazole molecules can be released and temperature dependent reversibly be exchanged with gas molecules including argon. Thus the solvent free high temperature synthesis of rare earth elements with amine melts can also be utilized for “crystal engineering” and the synthesis of compounds with material science aspects. Furthermore 3D-[Pr(Im)3(ImH)]@ImH is the first unsubstituted imidazolate of the lanthanides.

Properties of cerium–zirconium mixed oxides partially substituted by neodymium: Comparison with Zr–Ce–Pr–O ternary oxides

CeO 2 doped with praseodymium, neodymium and/or zirconium atoms were prepared by coprecipitation and by the sol–gel method. Structural properties were investigated by in situ XRD and Raman spectroscopy while oxygen storage capacity (OSC) was measured by transient CO oxidation. All the compounds, except pure Nd 2O 3, have a fluorite-type structure as well as a Raman band at 560 cm −1 characteristic of the oxygen vacancies involving non-stoichiometric oxides. The lattice parameter under hydrogen, being dependent on the temperature, revealed two reduction mechanisms: one at a low temperature at the surface and another at a high temperature in the bulk. Ce–Nd binary oxides show a strong tendency towards crystallite aggregation, which reduces accessibility to gases and OSC properties. Zirconium improves the thermal resistance to sintering of both Ce–Nd and Ce–Pr oxides. The Zr–Ce–Pr–O followed by Zr–Ce–Nd–O compounds displaying high oxygen mobility at a low temperature, appear to be very promising for practical applications such as OSC materials.

Structure, magnetic properties and 119Sn Mössbauer spectroscopy of PrRhSn

PrRhSn was synthesized in polycrystalline form by a reaction of praseodymium, rhodium, and tin in an arc-melting furnace. The sample was investigated by powder and single crystal X-ray diffraction: ZrNiAl type, space group P 6 ¯ 2 m , a = 742.49 ( 7 ) , c = 415.05 ( 5 ) pm, w R 2=0.0737, 353 F 2 values and 14 variables. The PrRhSn structure has two crystallographically independent rhodium sites with a tricapped trigonal prismatic coordination, i.e. [Rh1Sn 3Pr 6] and [Rh2Sn 6Pr 3]. The rhodium and tin atoms build up a three-dimensional [RhSn] network with short Rh–Sn contacts (278 and 285 pm), in which the praseodymium atoms fill distorted hexagonal channels. The magnetic and electronic properties of PrRhSn have been studied by means of AC and DC magnetic susceptibility measurements as well as 119Sn Mössbauer spectroscopy. A transition from a paramagnetic to a ferromagnetic state was found at T C = 3.0 K .

The Stereochemical Activity of the Lone Pair in [Bi(NO3)3{(iPrO)2(O)PCH2P(O)(OiPr)2}2] — Comparison of Bismuth, Lanthanum and Praseodymium Nitrate Complexes

AbstractFive coordination compounds of bismuth, lanthanum and praseodymium nitrate with the oxygen‐coordinating chelate ligand (iPrO)2(O)PCH2P(O)(OiPr)2 (L) are reported: [Bi(NO3)3(L)2] (1), [La(NO3)3(L)2] (2), [Pr(NO3)3(L)2] (3), [La(NO3)3(L)(H2O)] (4) and [Pr(NO3)3(L)(H2O)] (5). The compounds were characterized by means of single crystal X‐ray crystallography, 1H and 31P NMR spectroscopy in solution, solid‐state 31P NMR spectroscopy, IR spectroscopy, DTA‐TG measurements (1, 2 and 4), conductometry and electrospray ionization mass spectrometry (ESI‐MS). In addition, DFT calculations for model compounds of 1 and 2 support our experimental work. In the solid state mononuclear coordination compounds were observed for 1—3, whereas compounds 4 and 5 gave one‐dimensional hydrogen‐bonded polymers via water‐nitrate coordination. Despite of the similar ionic radii of bismuth(III), lanthanum(III) and praseodymium(III) for a given coordination number the bismuth and lanthanide compounds 1—3 are not isostructural. The bismuth compound 1 shows a 9‐coordinate bismuth atom whereas lanthanum(III) and praseodymium(III) atoms are 10‐coordinate in the lanthanide complexes 2—5. The general LnO10 coordination motif in compounds 2—5 is best described as a distorted bi‐capped square antiprism. The BiO9 polyhedron might be deduced from the LnO10 polyhedron by replacing one oxygen ligand with a stereochemically active lone pair. The one‐to‐one complexes 4 and 5 dissociate in solution to give the corresponding one‐to‐two complexes 2 and 3, respectively, and solvated Ln(NO3)3. In contrast to the lanthanides, the one‐to‐two bismuth complex 1 is less stable in CH3CN solution and partially dissociates to give solvated Bi(NO3)3 and (iPrO)2(O)PCH2P(O)(OiPr)2.

Structural changes of Ce–Pr–O oxides in hydrogen: a study by in situ X-ray diffraction and Raman spectroscopy

Ce–Pr–O mixed oxides prepared by coprecipitation and calcined at 1173 K reveal a non stoichiometric structure with oxygen vacancies in the bulk. In situ XRD and Raman spectroscopy were used to investigate these properties simultaneously and identified a thermal expansion coefficient twice as high as that of pure ceria at room temperature and the presence of a Raman band at 560 cm−1, characteristic of the oxygen vacancies. These results confirm that praseodymium atoms are able to induce oxygen mobility in the bulk at 298 K. This is due to a structure containing a high number of anionic vacancies pre-existing at ambient temperature.

Indides LnNiIn2 (Ln=Pr, Nd, Sm) and Ferromagnetic PrRhIn

The title compounds were synthesized by reacting the elements in an arc-melting apparatus under purified argon and subsequent annealing at 970 K. The nickel containing compounds crystallize with a new structure type which was determined for PrNiIn2: Cmcm, a=440.0(2) pm, b=1833.9(6) pm, c=2164.6(5) pm, wR2=0.0550, 1451 F2 values, and 66 parameters. From a geometrical point of view, the structure of PrNiIn2 may be described as an intergrowth of small distorted CaCu5-, CsCl-, and Cu3Au-related slabs. The structure is also related to the MgCuAl2 type by chemical twinning. The shortest interatomic distances within the PrNiIn2 structure occur for the Ni–In and In–In contacts. The nickel and indium atoms form a three-dimensional [NiIn2] polyanion in which the praseodymium atoms fill distorted pentagonal channels. To a first approximation the formula may be written as Pr3+[NiIn2]3−. PrRhIn adopts the ZrNiAl type structure: P62m, a=755.6(2) pm, c=404.8(1) pm, wR2=0.0285, 361 F2 values, and 14 parameters. Structural motifs of PrRhIn are tricapped trigonal prisms [Rh1In6Pr3] and [Rh2Pr6In3]. The rhodium and indium atoms form a three-dimensional [RhIn] polyanion in which the praseodymium atoms are located in distorted hexagonal channels. Susceptibility measurements reveal Curie–Weiss behavior with a magnetic moment of 3.69(5) μB/Pr. PrRhIn orders ferromagnetically at TC=5.8(6) K and shows a saturation magnetization of 1.60(5) μB/Pr at 2 K and 5.5 T. Resistivity measurements indicate metallic behavior with a specific resistivity of 105±20 μΩ cm at room temperature.