High-resolution Solid-state 31P Research Articles

Deciphering the potassium storage phase conversion mechanism of phosphorus by combined solid-state NMR spectroscopy and density functional theory calculations

Phosphorus is the potential anode material for emerging potassium-ion batteries (PIBs) owing to the highest specific capacity and relatively low operation plateau. However, the reversible delivered capacities of phosphorus-based anodes, in reality, are far from the theoretical capacity corresponding to the formation of K3P alloy. And, their underlying potassium storage mechanisms remain poorly understood. To address this issue, for the first time, we perform high-resolution solid-state 31P NMR combined with XRD measurements, and density functional theory calculations to yield a systemic quantitative understanding of (de)potassiation reaction mechanism of phosphorus anode. We explicitly reveal a previously unknown asymmetrical nanocrystalline-to-amorphous transition process via rP ↔ (K3P11, K3P7, beta-K4P6) ↔ (alpha-K4P6) ↔ (K1−xP, KP, K4−xP3, K1+xP) ↔ (amorphous K4P3, amorphous K3P) that are proceed along with the electrochemical potassiation/depotassiation processes. Additionally, the corresponding K-P alloys intermediates, such as the amorphous phases of K4P3, K3P, and the nonstoichiometric phases of “K1−xP”, “K1+xP”, “K4−xP3” are experimentally detected, which indicating various complicated K-P alloy species are coexisted and evolved with the sluggish electrochemical reaction kinetics, resulting in lower capacity of phosphorus-based anodes. Our findings offer some insights into the specific multi-phase evolution mechanism of alloying anodes that may be generally involved in conversion-type electrode materials for PIBs.

Synthesis, Characterization, and Stability of Americium Phosphate, AmPO4.

AmPO4 was prepared by a solid-state reaction method, and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. The purity of the monazite-like phase was confirmed by spectroscopic (high-resolution solid-state 31P NMR and Raman) and microscopic (SEM-EDX and TEM) techniques. The thermal and self-irradiation stability have been studied. The compound is stable under argon and air atmosphere at least up to 1773 K. It remains crystalline under self-irradiation for circa two months, with a crystallographic volume swelling of ∼1.5%, and then is amorphizing over a year. However, microcrystals are present in the amorphous material even after a two year period of time. All these characteristics are discussed in relation to the potential application of AmPO4 as a stable form of Am in radioisotope power sources for space exploration and of behavior of the monazites under irradiation.

Structural investigations of PuIII phosphate by X-ray diffraction, MAS-NMR and XANES spectroscopy

PuPO4 was prepared by a solid state reaction method and its crystal structure at room temperature was solved by powder X-ray diffraction combined with Rietveld refinement. High resolution XANES measurements confirm the +III valence state of plutonium, in agreement with valence bond derivation. The presence of the americium (as β− decay product of plutonium) in the +III oxidation state was determined based on XANES spectroscopy. High resolution solid state 31P NMR agrees with the XANES results and the presence of a solid-solution.

NMR and X-ray diffraction study of the phases of zirconium phosphate incorporated in a composite membrane Nafion®-ZrP

Zirconium Phosphate (ZrP) inside a composite membrane Nafion-ZrP was studied by combining wide angle X-ray diffraction (XRD) and high-resolution solid-state 31P Nuclear Magnetic Resonance (NMR) under magic angle spinning conditions (MAS). We have, at first, investigated the physical features of ZrP powders that were prepared ex situ under different conditions leading to either amorphous or crystalline α-ZrP. ZrP incorporated into Nafion® membranes (in situ ZrP) was then studied. Informations obtained from X-ray and NMR data clearly show that the in situ ZrP is not in a purely crystalline phase. The presence of broad peaks in the X-ray spectra proves that the compound inside the membrane is semi-crystalline. This result is confirmed by MAS 31P NMR since the NMR spectra of in situ ZrP and ex situ semi-crystalline ZrP powder are alike. Moreover, the NMR analyses demonstrate that the phosphate groups can be found in three different connectivities with phosphorous atoms surrounded by either 2, 3 or 4 OZr bonds., with predominantly 3 OZr bonds being favored.

Surface Modification of Boron Nitride Nanoparticles by Decylphosphonic Acid Characterized by Solid-state NMR

Abstract We have attempted to modify the surface of boron nitride (BN) nanoparticles by decylphosphonic acid and have characterized the surface layer of BN nanoparticles by means of high-resolution solid-state 31P NMR. The surface of BN nanoparticles was successfully modified, and the 31P NMR spectra showed two types of bonding states for the organic modifier. They are tentatively assigned to P–B and P–N bonding states from consideration of the residual line broadening due to interaction with quadrupole nuclei.

A solid-state 31P NMR study of 1:1 silver–triphenylphosphine complexes — Interpretation of 1J(107,109Ag,31P) values,

High-resolution solid-state 31P NMR spectroscopy was used to investigate a series of 1:1 silver–triphenylphosphine complexes, [Ph3PAgX]n, where X is a monovalent anion and n = 1, 2, 3, 4, or ∞. The 31P CP MAS NMR spectra reveal the number of distinct phosphorus sites in these complexes as well as the |1J(109Ag,31P)| values, which range from 401 ± 10 Hz (X = N3–) to 869 ± 10 Hz (X = SO3CF3–). The data obtained here and in earlier investigations indicate that |1J(109Ag,31P)| values for silver–tertiary phosphine complexes decrease as Ag–P bond lengths increase. This experimental conclusion is supported by DFT calculations, which also indicate that the Fermi-contact mechanism is the only important spin–spin coupling mechanism for 1J(109Ag,31P) in these complexes. In addition, the crystal structure of a silver–triphenylphosphine trifluoroacetate tetramer was determined using X-ray crystallography, and the structure of a silver–triphenylphosphine chloride tetramer was reinvestigated.

Straightforward detection of the secondary ionisation of the phosphate group and pK determinations by high-resolution solid-state 31P NMR

The suitability of high-resolution solid-state 31P NMR for a straightforward determination of the protonation state of phosphate groups as well as of their pK2 values extracted from solid state mono : dianionic ratios has been demonstrated.

Understanding the structural properties of a homologous series of bis-diphenylphosphine oxides

A homologous series of bis-diphenylphosphine oxides (C6H5)2PO(CH2)(n)PO(C6H5)2 (with n = 2-8; denoted 2-8] have been investigated to explore the effects of a range of competing and cooperative intermolecular and intramolecular interactions on the structural properties in the solid state. The important factors influencing the structural properties include intramolecular aspects such as the conformation of the aliphatic chain and the intramolecular interaction between the two P=O dipoles in the molecule, and intermolecular aspects such as long-range electrostatic interactions (dominated by the arrangement of the P=O dipoles), C-H...O interactions, C-H...pi interactions and pi...pi interactions. Compounds 3 and 5 could be crystallized only as solvate co-crystals (3 water and 5 x (toluene)2], whereas the crystal structures of all the other compounds contain only the bis-diphenylphosphine oxide molecule. The crystal structures have been determined from single-crystal X-ray diffraction data, with the exception of 7 (which has been determined here from powder X-ray diffraction data) and 4 (which was known previously). The compounds with even n represent a systematic structural series, exhibiting characteristic, essentially linear P=O...P=O...P=O dipolar arrays, together with C-H...O and C-H...pi interactions. For the compounds with odd n, on the other hand, uniform structural behaviour is not observed across the series, although certain aspects of these crystal structures contribute in a general sense to our understanding of the structural properties of bis-diphenylphosphine oxides. Importantly, for the compounds with odd n, there is "frustration" with regard to the molecular conformation, as the preferred all-anti conformation of the aliphatic chain gives rise to an unfavourable parallel alignment of the two P=O dipoles within the molecule. Clearly the importance of avoiding a parallel alignment of the P=O dipoles becomes greater as n decreases. Local structural aspects (investigated by high-resolution solid-state 31P NMR spectroscopy) and thermal properties of the bis-diphenylphosphine oxide materials are also reported.

X-ray diffraction and phosphorus-31 NMR studies of the dynamically disordered 3:2 phenol–triphenylphosphine oxide complex

The 3:2 phenol–triphenylphosphine oxide (phenol–TPPO) adduct was studied by means of X-ray diffraction together with high-resolution solid-state 31P NMR spectroscopy. The X-ray results showed that the crystalline structure, which belongs to the triclinic P[1 with combining macron] space group, involves disorder. There are two molecules of TPPO and three phenol molecules per unit cell. One of the latter is disordered across an apparent inversion centre. Analysis of NMR data in conjunction with the crystal structure allowed the origin of such disorder to be established, showing that it is dynamic in nature. Variable-temperature NMR experiments were performed and a coalescence temperature was found at 247 K. Spectra recorded below this temperature showed two phosphorus signals. The kinetics for the phenol residue exchanging between two different TPPO moieties (two-site exchange with equal populations) were determined. Thermodynamic parameters for the motion were calculated from Eyring plots. For temperatures ranging from 262.9 to 221.5 K, the bandshape analysis technique was used to derive the required data. For lower temperatures, the selective polarisation inversion experiment (SPI) was performed, whilst high temperature values were derived from variable-temperature T1ρ studies. The activation enthalpy (ΔH‡), calculated using the results obtained by bandshape analysis, T1ρ and SPI, was determined as 38 kJ mol−1, while the activation entropy (ΔS‡) was found to be −23 J mol−1 K−1 (assuming the transmission coefficient is ½). Phosphorus-31 shielding tensor anisotropies have been derived for this system by spinning sideband analysis at both fast and slow-exchange limits and it has been shown that the tensor is axially symmetric. Single-crystal experiments show that the symmetry axis of the tensor is along the P[double bond, length half m-dash]O bond (within experimental error).

2-THIOXO-1,3,2-DITHIAPHOSPHOLANES -SOLID-STATE MAS NMR AND CRYSTAL STRUCTURE INVESTIGATIONS AS WELL AS IGLO CALCULATIONS OF 31P SHIELDING TENSORS

2-Thioxo-1,3,2-dithiaphospholanes with P-substituents R = Me, Et, i-Pr, t-Bu, Ph, 3,5-Me2C6H3, and 4-MeOC6H4 were prepared and characterized by solution and high resolution solid-state 31P and 13C NMR spectroscopy. The influence of different alkyl and aryl substituents at the phosphorus atom on the anisotropy of 31P chemical shift and on the molecular structure is discussed. The orientation of the principal axes with respect to the molecular frame is predicted from the solid-state 31P NMR results. Quantum chemical calculations of the 31P shielding tensors by the IGLO method confirm these results. The crystal structures of 2-tert-butyl-2-thioxo-1,3,2-dithiaphospholane and 2-(3,5-dimethylphenyl)-2-thioxo-1,3,2-dithiaphospholane are presented and discussed.

Local structure and connectivity in lithium phosphate glasses: a solid-state 31P MAS NMR and 2D exchange investigation

High resolution solid-state 31P magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectroscopy has been used to investigate the local structure and connectivity for three xLi 2O·(1 - x)P 2O 5 glasses. The principal components of the 31P chemical shift anisotropy (CSA) tensors for the different phosphate tetrahedron sites (Q n ) and the relative populations of each Q n species were determined from simulation of the MAS spectra. The medium range structure and connectivity between similar or different Q n units in these lithium phosphate glasses were probed using novel two-dimensional (2D) MAS exchange experiments. Radio-frequency dipolar recoupling (RFDR) techniques allowed the reintroduction of the through space 31P- 31P dipolar-dipolar interaction even in the presence of fast MAS. For these binary phosphate glasses the connectivity and medium range structure for different Q n species is described well by a statistical distribution, and is consistent with a model of random depolymerization.

Topotactic synthesis of α-zirconium phenylphosphonate from α-zirconium phosphate

α-Zirconium phenylphosphonate has been synthesised by a reaction between α-zirconium phosphate and molten phenylphosphonic acid. The reaction produces a physical mixture of the ‘pure’ phases of α-zirconium phenylphosphonate and α-zirconium phosphate, with the ratio dependent on the ratio of phenylphosphonic acid to α-zirconium phosphate in the synthesis mixture. Detailed characterization of the reaction products has been carried out by powder X-ray diffraction, high-resolution solid-state 31P NMR spectroscopy, thermogravimetric analysis and FT-IR spectroscopy, and by considering experiments involving the selective intercalation of n-butylamine.

Structural study of phosphate groups in layered metal phosphates by high-resolution solid-state31P NMR spectroscopy

In studies of a series of crystals of layered metal phosphate compounds by magic angle spinning (MAS) NMR spectroscopy, it has been found that there is a distinct correlation between the 31 P isotropic chemical shift value and the type of phosphate group. The isotropic 31 P chemical shifts of (H 2 PO 4 ) - , (HPO 4 ) 2- and (PO 4 ) 3- groups appear around δ -10, -20 and -30, respectively. These assignments were made unambiguously by measuring the 31 P MAS NMR spectra with and without 1 H high-power decoupling together with the cross-polarization transfer technique between 1 H and 31 P nuclei (CP MAS spectra).

Chemical characterization and agronomic effectiveness of phosphorus applied as a polyphosphate-chitosan complex

This work was undertaken to characterize a chitosan-polyphosphate complex (CH-PP) and to evaluate its agronomic effectiveness as a source of phosphorus for ryegrass (Lolium perenne) grown on loamy and clayey soils. High resolution solid state31P and13C nuclear magnetic resonance were used to characterize this complex and to monitor the structural changes occurring to it during an 8-week incubation period in a loamy soil. A pot experiment was conducted on the two soils after labelling the available P with32PO4 ions. This experiment allowed for the determination of the agronomic effectiveness of the chitosan-polyphosphate complex compared to polyphosphate and to monocalcium phosphate. Results showed that chitosan immobilized up to 147 mg P kg−1 as pyrophosphate and hexametaphosphate. This reaction did not involve major structural changes in the pyrophosphate or hexametaphosphate groups nor in the chitosan. The chitosan-polyphosphate complex was as efficient as the polyphosphate alone to sustain the P nutrition of ryegrass. The relative agronomic effectiveness of these P sources was slightly lower compared to that of monocalcium phosphate. The high P fertilizing value of the chitosan-polyphosphate complex was attributed to its gradual hydrolysis in the soil. The potential interest of chitosan to remove polyphosphates from waste waters while preserving the high P fertilizing value of polyphosphates was addressed.

Probing hydrogen-bonding patterns in cocrystals of amides and triarylphosphine oxides using high-resolution solid-state 31P NMR spectroscopy

The isotropic 31P chemical shift for hydrogen-bonded cocrystals formed between aryl sulfonamides and triarylphosphine oxides shows a linear corrleation with the number of hydrogen-bonds, N–H ⋯ O–P, formed by each triarylphosphine oxide fragment; this result can now be applied as a means of deriving information on the hydrogen-bonding patterns in related cocrystals of unknown structure.

High resolution 31P solid state NMR in phosphorus-transition metal compounds

The use of a high resolution solid state 31P NMR technique to investigate the coordination of phopshorus ligands bound to transition metal atoms is reviewed using examples which include information on molecular structure and crystallographic sites in organometallic solids, and characterization of supported transition metal complexes on surfaces. Moreover 31P CPMAS (cross polarization magic angle spinning) experiments can afford a wealth of information such as chemical shift anisotropy, isotropic coupling constants with quadrupolar nuclei and quadrupole coupling constants that are often obscured in solution state due to the rapid isotropic motion of the molecules.

High resolution solid state 31P and 15N magic angle spinning nuclear magnetic resonance studies of amorphous and microcrystalline, layered metal (IV) hydrogenphosphates

High resolution solid state 31P and 15N MAS NMR have been used to probe the structure of amorphous and microcrystalline layered hydrogenphosphates and their amine intercalation compounds. A linear relationship between δ 31P and electronegativity of the metal centre was observed. In the case of both forms of the titanium and zirconium hydrogenphosphates a linear relationship was seen between isotropic chemical shift and the number of bridging P-O-M oxygens (connectivity) of the phosphate groups. In a further study of the intercalation compounds of tin (IV) hydrogenphosphate monohydrate, the NMR data indicated there to be more proton transfer in the propylamine intercalation (SnP-PrA) compound than is the case with trans-N,N'-diethyl 2-butene-1, 2-diamine (NNBD) and that there is more proton transfer in the case of NNBD that in the ammonium intercalation compound. The extent of protonation of ammonia by different strength acids has also been observed by 15N MAS NMR and has been correlated to the isotropic chemical shift.

High-resolution solid-state 31P and 119Sn magic-angle spinning nuclear magnetic resonance studies of amorphous and microcrystalline layered metal(IV) hydrogenphosphates

High-resolution solid-state 31P and 119Sn magic-angle spinning nuclear magnetic resonance (MAS NMR) and Mössbauer spectroscopies have been used to probe the structure of amorphous and microcrystalline layered hydrogenphosphates and some of their intercalation compounds. A linear relationship between δ(31P) and the Allred–Rochow electronegativity of the metal atom was observed. In the case of both α and γ forms of titanium and zirconium hydrogenphosphates, a linear relationship was seen between the isotropic chemical shift (δiso) and the number of bridging P—O—M oxygens (connectivity) of the phosphate groups. In a further study of the intercalation compounds of tin(IV) hydrogenphosphate monohydrate (SnP), the NMR data indicated there to be more electron transfer in the propylamine intercalation compound than is the case with E-N,N′-diethylbut-2-ene-1,4-diamine (NNBD) and that there is more electron transfer in the case of NNBD than in the ammonium intercalation compound. A linear relationship was observed when δ(119Sn) was plotted as a function of δ(31P). The Sn Mössbauer spectrum of the host material was indicative of ionic character around the metal atom and similar to that of SnF4.

High-Resolution Solid-State 31P NMR of Alkali Phosphates

Abstract High-resolution solid-state 31P NMR spectra have been measured for inorganic alkali phosphates with different condensations in the PO4 units, and the isotropic chemical shift and anisotropy have been determined. The isotropic chemical shifts in alkali orthophosphates do not correlate directly with the cation size. The hydration effects have been carefully examined by means of a 1H decoupling experiment and by the heat treatment of the materials, accompanied by thermogravimetric analysis. Hydration causes an upfield shift in Na3PO4, K3PO4, and Na4P2O7, while it causes a downfield shift in Rb3PO4 and Cs3PO4. All the five peaks observed in the K4P2O7 sample can be ascribed to anhydrous species; this is in contrast to the findings of previous works. The field-dependence experiments definitely demonstrate that the splittings in K4P2O7 and (KPO3)n are caused by inequivalent sites.

High-resolution solid-state 31P NMR study of network structure in AgIAg 2OP 2O 5 glass

High-resolution solid-state 31P NMR spectra have been measured for AgIAg 2OP 2O 5 glasses using magic-angle sample spinning. Three types of PO 4 units can be identified: isolated, end chain, and middle chain groups. Quantitative analysis has been carried out for the three groups, and the average length of the PO 3 chain has been estimated. The NMR results have confirmed that the network structure is determined by the two components, Ag 2O and P 2O 5, and that AgI does not modify the network.