Phosphorus Sites Research Articles

Phosphorus-Modulated Generation of Defective Molybdenum Sites as Synergistic Active Centers for Durable Oxygen Evolution.

It is well known that electrocatalytic oxygen evolution reaction (OER) activities primarily depend on the active centers of electrocatalysts. In some oxide electrocatalysts, high-valence metal sites (e.g., molybdenum oxide) are generally not the real active centers for electrocatalytic reactions, which is largely due to their undesired intermediate adsorption behaviors. As a proof-of-concept, molybdenum oxide catalysts are selected as a representative model, in which the intrinsic molybdenum sites are not the favorable active sites. Via phosphorus-modulated defective engineering, the inactive molybdenum sites can be regenerated as synergistic active centers for promoting OER. By virtue of comprehensive comparison , it is revealed that the OER performance of oxide catalysts is highly associated with the phosphorus sites and the molybdenum/oxygen defects. Specifically, the optimal catalyst delivers an overpotential of 287mV to achieve the current density of 10mAcm-2 , accompanied by only 2% performance decay for continuous operation up to 50h. It is expected that this work sheds light on the enrichment of metal active sites via activating inert metal sites on oxide catalysts for boosting electrocatalytic properties.

Insight into direct phosphorus release from simulated wastewater ferric sludge: Influence of physiochemical factors

Phosphorous recovery from chemical phosphorus removal (CPR) plants is limited. CPR plants that use iron salts for phosphorous removal generate iron phosphate (Fe-P) rich sludge. This study investigates the influence of pH and competing anions (chloride), on phosphorus and soluble iron release from lab simulated Fe-P sludge. Factors influencing recovery, such as sludge age and Fe/P molar ratio are also investigated. Results showed that alkaline treatment of Fe-P sludge was not effective in releasing Fe (<3%) but effective in releasing P, particularly at controlled pH value of 10 where the %P release was (90 ± 2%). Sludge ageing time did not affect P release from Fe-P sludge at ages less than 5 days. However, a remarkable decrease in %P release (i.e., 50% reduction) was observed at ages of 9 and 11 days for pH values of 9–10. Arsenic extraction of exchangeable surface bound P from Fe-P sludge and surface area determination of hydrous ferric oxide (HFO) under different aging times supported qualitatively the internalization of surface bound P during aging, which is a proposed mechanism responsible for the decrease in P release for older sludge. Chloride effect in releasing P from Fe-P sludge was negligible. The reduction in P release by aging was best described by a zero-order kinetic model. Modeling with the PHREEQC geochemical software did not always agree with the measured release of phosphorus from the Fe-P sludge. PHREEQC assumes all surface sites for phosphorus are exchangeable and has no mechanism to represent phosphorus trapped within HFO particles.

Structure of amorphous materials in the NASICON system NaTi2Si x PO12

The structure of glasses in the sodium (Na) super-ionic conductor (NASICON) system NaTi2Si x PO12 with x = 0.8 and x = 1.0 was explored by combining neutron and high-energy x-ray diffraction with 29Si, 31P and 23Na solid-state nuclear magnetic resonance (NMR) spectroscopy. The 29Si magic angle spinning (MAS) NMR spectra reveal that the silica component remains fully polymerized in the form of Si4 units, i.e. the silicon atoms are bound to four bridging oxygen atoms. The 31P{23Na} rotational echo adiabatic passage double resonance (REAPDOR) NMR data suggest that the 31P MAS NMR line shape originates from four-coordinated P n units, where n = 1, 2 or 3 is the number of bridging oxygen atoms per phosphorus atom. These sites differ in their 31P-23Na dipolar coupling strengths. The results support an intermediate range order scenario of a phosphosilicate mixed network-former glass in which the phosphate groups selectively attract the Na+ modifier ions. Titanium takes a sub-octahedral coordination environment with a mean Ti–O coordination number of 5.17(4) for x = 0.8 and 4.86(4) for x = 1.0. A mismatch between the P–O and Si–O bond lengths of 8% is likely to inhibit the incorporation of silicon into the phosphorus sites of the NASICON crystal structure.

Isovalent substitution of vanadium in LiFePO4: Evolution of monoclinic α-Li3Fe2(PO4)3 phase

We report the synthesis and characterization of isovalent substitution of vanadium at phosphorus site in orthorhombic lithium iron phosphate (LiFePO4) nanoparticles by non-aqueous sol–gel method. Detailed analysis of X-ray diffraction patterns reveals the evolution of monoclinic α-Li3Fe2(PO4)3 phase and its formation is favored for the vanadium content higher than 20%. A continuous increase in unit cell volume of LiFePO4 is observed with increase in vanadium content from x = 0.05 to 0.20, followed by rapid decrease above x = 0.20, due to the creation of a greater number of Li-ion vacancies. FTIR studies demonstrate that the wavenumbers of various absorption maxima and the covalency strength parameter do not show a variation with x, thus confirm the substitution of vanadium in the form of VO4. Our results through Mössbauer and electron paramagnetic resonance spectroscopy unambiguously demonstrate the enhancement in the formation of α-Li3Fe2(PO4)3 phase for vanadium content higher than 20%.

Atom Substitution Defects of Hexagonal Boron Phosphide Suppress Charge Recombination.

Point defects, during e-h recombination, are a key factor in impacting optoelectronic device performance. Using nonadiabatic molecular dynamics (NAMD), here we investigate the nonradiative recombination of pristine, missing atom defects, including phosphorus vacancies (VP) and phosphorus and boron vacancies (VBP), and atom substitution defects, containing boron on the phosphorus site (BP) and phosphorus on the boron site (PB) of 2D monolayer hexagonal boron phosphide (h-BP). Carrier dynamics in the pristine h-BP and the defect engineered systems reveal that atom substitution defects BP and PB can suppress e-h nonradiative recombination. This is caused by the introduction of several low-frequency phonons in defect states. Electron-phonon coupling between the electronic state and these low-frequency phonons shortens the decoherence time and the nonadiabatic coupling. Also, the atom substitution systems with one defect state introduce fewer carrier recombination channels. Such a mechanism can be extended to other 2D materials with the same structure as h-BP.

Enhanced formation of multi-branched isoparaffins in syngas conversion by ZnCrOx-MCM-22 composites

Direct syngas conversion to gasoline-range hydrocarbons particularly environmental-friendly, high octane number multi-branched isoparaffins attracts wide attention from both academia and industry but remains challenging. We report herein that ZnCrOx-HMCM-22 upon phosphorus modification enables selective syngas conversion to gasoline (C5-C11) with a selectivity of 77%. Following a simple hydrogenation in the same reactor, the fraction of isoparaffins among gasoline reaches 67%, particularly multi-branched isoparaffins as high as 27.5%, which is three times higher than that obtained by FTS-zeolites and four times higher than that in commercial 92# gasoline. This is attributed to the inhibited hydrogenation of olefins over the acid sites of phosphorus modified MCM-22 with weakened strength. Thus, methylation of olefins is significantly facilitated leading to formation of multi-branched isohydrocarbons. The fundamental understanding gained here will allow further optimization and development of catalysts for direct syngas conversion to high-quality gasoline.

Treatment of high-concentration phosphorus wastewater based on foamed concrete

Phosphorus is a nonrenewable resource, and the recovery of phosphorus from wastewater containing high concentrations of phosphorus is of great importance. In this work, a novel method for highly efficient treatment of high-concentration phosphorus-containing wastewater (50 mg/L, 100 mg/L and 150 mg/L) with low energy consumption was developed by using the block waste foam concrete (FC) as a potential phosphorus recovery material. The results showed that acid leaching significantly improved the accumulation efficiency of phosphorus in calcium hydroxyphosphate (HAP) via accelerating the release of calcium in wastewater. The recovery rate of phosphorus could reach 99.0% under the pH value of 9.0 at 25 °C, using 2.0 g FC. It was also found that the microporous structure of the surface of FC provided the adsorption sites for phosphorus, resulting in the adsorption rate in different concentrations of phosphorus-containing wastewater up to 14.5%. It indicated that FC achieved the recovery of phosphorus from high-concentration phosphorus-containing wastewater by coupling HAP crystallization and physical adsorption to polyphosphorus.

Chemical shielding and electric field gradient tensors of disodium 5′-adenosine triphosphate trihydrate determined by solid-state NMR spectroscopy and ab initio calculations

The tri-phosphate and sodium ion environments in well crystallized disodium 5′adenosine triphosphate trihydrate (ATP•3H2O) are investigated using high-resolution solid-state NMR spectroscopy and ab initio calculations. The six inequivalent phosphorus sites resolved in 31P MAS spectra have been assigned on the basis of experimentally obtained results and theoretical ab initio quantum chemical calculations of 31P chemical shielding tensors with increased numerical accuracy. Aided by 31P-31P dipolar connectivity established in DQ-SQ correlation experiment and DFT calculations carried out at the B3LYP/(aug-cc-pDVZ(3s,2p,1d), 6–31G(d,p)) level, phosphorus resonance assignments in MAS spectra have been made and the 31P chemical shielding anisotropies and tensor orientations in the molecule-fixed frame have been determined. 31P shielding tensors are found to be oriented with the most shielded direction nearly perpendicular to the O-P-O plane involving the two adjoining oxygens. The complete resolution of the four sodium sites has been achieved from 3Q-MAS experiments performed at 7.05 T and this has enabled 23Na quadrupole parameters to be determined experimentally and compared with theoretical calculations. Besides aiding a partial resonance assignment of the 23Na 3Q-MAS spectrum, our HF/6–311++G(2d,2p) calculations of 23Na EFG tensors show that for two sodium sites which are tightly coordinated the orientation of the EFG tensor is distinct. These exhibit unique directions along which the field gradient is the smallest and largest.

Iron in Hydroxyapatite: Interstitial or Substitution Sites?

Iron-doped hydroxyapatite (Fe-HAp) is regarded as a promising magnetic material with innate biocompatibility. Despite the many studies reported in the literature, a detailed theoretical description of Fe inclusions is still missing. There is even no consensual view on what kind of Fe defects take place in Fe-HAp—iron interstitial or calcium substitutions? In order to address these questions, we employ modern first-principles methodologies, including hybrid density functional theory, to find the geometry, electronic, magnetic and thermodynamic properties of iron impurities in Fe-HAp. We consider a total of 26 defect configurations, including substitutional (phosphorus and calcium sites) and interstitial defects. Formation energies are estimated considering the boundaries of chemical potentials in stable hydroxyapatite. We show that the most probable defect configurations are: Fe and Fe substitutions of Ca(I) and Ca(II) sites under Ca-poor conditions. Conversely, Fe interstitials near the edge of the hydroxyl channel are favored in Ca-rich material. Substitutional Fe on the P site is also a probable defect, and unlike the other forms of Fe, it adopts a low-spin state. The analysis of Fe K-XANES spectra available in the literature shows that Fe-HAp usually contains iron in different configurations.

Digestibility of phosphorus in growing pigs as influenced by source and concentration of dietary phosphorus and collection site.

The current study examined the influence of source and concentration of dietary phosphorus (P) on the apparent ileal digestibility (AID) and apparent total tract digestibility (ATTD) of P in growing pigs. Eighteen cannulated barrows (25±5kg) were allotted to a triplicate 6×3 incomplete Latin square design with six diets and three periods. The diets comprised of soybean meal (SBM) or distillers' dried grain with solubles (DDGS) as sole sources of dietary P, and three concentrations of P (2.0, 2.5 or 3.0g/kg) in a 2×3 factorial arrangement. The AID and ATTD of P were not different (p=0.37) in all diets. Apparent digestibility of P was affected (p<0.01) by source and concentration of P. There was no interaction between source and concentration of dietary P on the apparent digestibility of P. Determined by regression analysis, the true ileal digestibility of P was 58.3% or 57.6%, and true total tract digestibility of P was 56.0% or 62.6%, for SBM or DDGS, respectively. The regression-derived ileal endogenous P loss (EPL) was 0.61 or 0.13g/kg DM intake, and total tract EPL was 0.53 or 0.35g/kg DM intake, for SBM or DDGS, respectively. In conclusion, the study demonstrated that both the source and concentration of dietary P affect the digestibility of P in growing pigs.

Enthalpy-Controlled Insertion of a "Nonspectator" Tricoordinate Phosphorus Ligand into Group 10 Transition Metal-Carbon Bonds.

Insertion of a tricoordinate phosphorus ligand into late metal-carbon bonds is reported. Metalation of a P^P-chelating ligand (L1), composed of a nontrigonal phosphorous (i.e., P(III)) triamide moiety, P(N(o-N(Ar)C6H4)2, tethered by a phenylene linker to a -PiPr2 anchor, with group 10 complexes L2M(Me)Cl (M = Ni, Pd) results in insertion of the nontrigonal phosphorus site into the metal-methyl bond. The stable methylmetallophosphorane compounds thus formed are characterized spectroscopically and crystallographically. Metalation of L1 with (cod)PtII(Me)(Cl) does not lead to a metallophosphorane but rather to the standard bisphosphine chelate (κ2-L1)Pt(Me)(Cl). These divergent reactivities within group 10 are rationalized by reference to periodic variation in M-C bond enthalpies.

Roles of metabolic regulation in developing Quercus variabilis acorns at contrasting geologically-derived phosphorus sites in subtropical China

BackgroundPhosphorus (P) -rich soils develop in phosphorite residing areas while P-deficient soils are ubiquitous in subtropical regions. Little has been reported that how metabolites participate in the seed development and the processes involved in their coping with contrasting-nutrient environments.ResultsHere we quantified the metabolites of Quercus variabilis acorns in the early (July), middle (August), late (September) development stages, and determined element (C, H, O, N, P, K, Ca, Mg, S, Fe, Al, Mn, Na, Zn, and Cu) concentrations of acorns in the late stage, at geologically-derived contrasting-P sites in subtropical China. The primary metabolic pathways included sugar metabolism, the TCA cycle, and amino acid metabolism. Most metabolites (especially C- and N-containing metabolites) increased and then decreased from July to September. Acorns between the two sites were significantly discriminated at the three stages, respectively, by metabolites (predominantly sugars and organic acids). Concentrations of P, orthophosphoric acid and most sugars were higher; erythrose was lower in late-stage acorns at P-rich sites than those at P-deficient sites. No significant differences existed in the size and dry mass of individual acorns between oak populations at the two sites.ConclusionsOak acorns at the two sites formed distinct metabolic phenotypes related to their distinct geologically-derived soil conditions, and the late-stage acorns tended to increase P-use-efficiency in the material synthesis process at P-deficient sites, relative to those at P-rich sites.

Native Point Defects in Monolayer Hexagonal Boron Phosphide from First Principles

In this paper, we have investigated the electronic and magnetic properties of four types of native defects under neutral and charged states in a hexagonal boron phosphide (h-BP) monolayer, including boron vacancy ( $$ V_{\rm{B}} ) $$ , phosphorus vacancy ( $$ V_{\rm{P}} ) $$ , boron on the phosphorus site ( $$ B_{\rm{P}} ) $$ and phosphorus on the boron site ( $$ P_{\rm{B}} ) $$ within the framework of the density functional theory. For the four types of defects, various charge states were investigated, and only 0 and 1 + charge states for all defects are stable within the electronic chemical potential range (i.e. Fermi level range). It is found that $$ B_{\rm{P}} $$ with the smallest defect formation energy is the most stable defect under both phosphorus-rich and -poor conditions in the whole range of electronic chemical potential. $$ V_{\rm{P}} $$ and $$ P_{\rm{B}} $$ are found to be shallow donors (i.e. 1 +/0) but could not be effectively introduced into the h-BP monolayer due to a rather high formation energy, while $$ V_{\rm{B}} $$ and $$ B_{\rm{P}} $$ are found to be holes trap centers. Especially, $$ B_{\rm{P}} $$ with a low defect formation energy, will be produced easily and seriously affect the p-type doping efficiency and conductivity of h-BP. Additionally, $$ V_{\rm{B}} $$ and $$ V_{\rm{P}} $$ induce a nonzero magnetic moment while $$ P_{\rm{B}} $$ and $$ B_{\rm{P}} $$ show non-magnetic nature in the h-BP monolayer.

Phosphorus-doping activates carbon nanotubes for efficient electroreduction of nitrogen to ammonia

The electrochemical nitrogen reduction reaction (NRR) as an energy-efficient approach for ammonia synthesis is hampered by the low ammonia yield and ambiguous reaction mechanism. Herein, phosphorus-doped carbon nanotube (P-CNTs) is developed as an efficient metal-free electrocatalyst for NRR with a remarkable NH3 yield of 24.4 μg·h−1·mg−1cat. and partial current density of 0.61 mA·cm−2. Such superior activity is found to be from P doping and highly conjugated CNTs substrate. Experimental and theoretical investigations discover that the electron-deficient phosphorus sites with Lewis acidity should be genuine active sites and NRR on P-CNTs follows the distal pathway. These findings provide insightful understanding on NRR processes on P-CNTs, opening up opportunities for the rational design of highly-active cost-effective metal-free catalysts for electrochemical ammonia synthesis.

The effects of native defects and carbon dopant on AlP nanosheet

Developing n- and p-type low dimensional semiconductors is crucial for fabrication high circuit integration density and high speed devices. About how to realize the n- and p-type doping for recently proposed monolayer AlP, we propose the possible schemes. Our investigation shows that aluminum and phosphorus vacancies could render monolayer AlP to be p- and n- type semiconductor. When carbons substitute aluminum or adsorb on phosphorus sites, monolayer AlP is n-type semiconductor. Carbons adsorbed on aluminum sites, the band gap would reduce to 0.98 eV. Carbons substituting phosphorus make monolayer AlP be ferromagnetic semiconductors, and the Curie temperature is estimated to be 403.59 K. Adsorption energies imply carbons chemically adsorb on phosphorus and aluminum sites. Formation energies show carbons substituting phosphorus and phosphorus vacancies can be realized experimentally. Our research provides a useful strategy to tailor monolayer AlP’s properties, even opens up the possibility of applications based on its semiconductors’ properties.

Preferable Adsorption of Nitrogen and Phosphorus from Agricultural Wastewater Using Thermally Modified Zeolite–Diatomite Composite Adsorbent

Nitrogen and phosphorus adsorbents are widely used to mitigate agricultural non-point source pollution. However, research on adsorbents mainly involves studying chemical adsorption properties, and analyzes of the effects of adsorbent on pollutant removal has not considered the surface morphology of the adsorbent or the surface distribution of pollutants. In this study, we focus on the surface morphology of the adsorbent and the surface distribution of contaminants while examining chemical adsorption properties. The crystal composition of the adsorbent was evaluated by x-ray diffraction (XRD) characterization. Kinetic adsorption data and adsorption isotherms demonstrated that thermally modified zeolite exhibits better nitrogen adsorption. The optimal removal of nitrogen and phosphorus by thermally modified zeolite and diatomite occurred at a 3:2 ratio, reaching a removal rate of 92.07% and 84.61%, respectively. The potential adsorption mechanism of a composite adsorbent for nitrogen and phosphorus capture was investigated by Fourier transform infrared spectroscopy. Scanning electron microscopy mapping, grey image recognition, and gradient recognition confirmed a relationship between the surface morphology of the adsorbent and the distribution of surface pollutants. The larger the surface of the gradient, the more uneven it is, the more nitrogen and phosphorus sites are adsorbed on the surface, and the more nitrogen and phosphorus are adsorbed. These results suggest that thermally modified zeolite/diatomite can serve as a promising adsorbent for nitrogen and phosphorus removal in practical applications.

Correlated metabolic and elemental variations between the leaves and seeds of oak trees at contrasting geologically derived phosphorus sites.

The leaves and seeds of plants frequently function as the source and sink organs for distinct metabolites, which can interactively vary in response to adverse site conditions. Subtropical soils are typically characterized as having deficient phosphorus (P), calcium (Ca), and magnesium (Mg), with enriched aluminum (Al) and iron (Fe), while Al and manganese (Mn) are toxic at low pH. It remains largely unknown how leaf- and seed-sourced metabolites are synergistically linked to adapt to P-variable soils for trees in subtropical areas. Here we quantified the metabolic and elemental profiling in the mature leaves and immature seeds of Quercus variabilis at contrasting geologically-derived phosphorus sites in subtropical China. The results revealed that carbon (C) and nitrogen (N) based metabolites (primarily sugars and organic acids), as well as enzyme- and protein/nucleic acid-related elements (N, P, Mg, and Mn) played important roles toward characterizing the profiling of metabolites and ionomes in leaves and seeds at two site types, respectively. These metabolites (sugars, amino acids, and fatty acids) and elements (N, P, Mg, and Mn) of seeds were closely related to the sugars, organic acids, and elements (N, P, Mg, and Mn) of leaves at the two site types. For the most part, the content of N and P in the soil affected the accumulation of materials (such as, starchs and proteins) in seeds, as well as N and P assimilation in leaves, by influencing C- and N-containing metabolites in leaves. These results suggested that correlated disparities of C- and N-containing metabolites, along with enzyme- and protein/nucleic acid-related elements in both leaves and seeds played important roles in plants to facilitate their adaptation to nutrient-variable sites in subtropical zones.

Element contents of acorns, weevil larvae and feces at contrasting geological-derived phosphorus sites

element contents of acorns, weevil larvae and feces at contrasting geological-derived phosphorus sites

Metabolite and element interactions of developing seeds for adaptation to variable soil nutrients at contrasting geological phosphorus sites

Metabolite and element interactions of developing seeds for adaptation to variable soil nutrients at contrasting geological phosphorus sites

Response of nutrients in submergence-prone rainfed lowland rice ecosystem with different flood histories

Site specific nutrient management approach was used to understand response of rice (variety Swarna Sub-1) yields to applied nutrients in soils with different flood histories of Bihar. Trials on nutrient omission plot technique (NOPT) were conducted in four sites for nitrogen, phosphorus, potassium and zinc with four replications at each site. Per cent response of yield as compared to nutrient omission plots ranged from 36.4 to 77.2%, 10.9 to 37.2%, 5.8 to 17.0% and 4.3 to 32.9% with addition of N, P, K and Zn respectively. Differences in response of applied nutrients were found due to difference in submergence condition and soil-nutrient status. The variation in nitrogen use efficiency was from 24.1 to 37.9%, phosphorus use efficiency from 22.1 to 33.6%, potassium use efficiency from 65.5 to 71.8% and zinc use efficiency from 2.72 to 3.93%. It may be concluded that soil nutrient contributions and level of submergence affected nutrient use efficiency and crop yield response to applied nutrients.