Manganese Pyrophosphate Research Articles

Manganese pyrophosphate with multiple coordinated water molecules for electrocatalytic water oxidation

Manganese pyrophosphate with multiple coordinated water molecules for electrocatalytic water oxidation

A novel mechanochemical synthesis of LiMnPO4 with manganese violet and ammonium manganese phosphate as precursors

Olivine lithium manganese phosphate was synthesized by a mechanochemical method. Inorganic cathode materials can be divided into three kinds of lithium metal oxide layered, spinel oxide and olivine metal phosphate. One important of the cathode materials used in Li-ion cells is LiMnPO4. In this paper two different precursors, manganese violet and ammonium manganese phosphate proposed as reactant in the synthesis of LiMnPO4 nanostructures. Reaction between NH4MnP2O7 and Li2CO3 takes placed in solid state at room temperature. In this mechanochemical process, a solid acid and base reaction occurred between ammonium and carbonate ions. In addition, MnIII is unstable oxidation state and convert to crystalline β-MnO2, Li2MnP2O7 and NH4H2PO4 in the disproportionation reaction. Results showed that mechanochemical reaction between NH4MnP2O7 with Li2CO3 as precursors lead to concurrent redox and acid-base reaction. As a result, we observed there is a tendency for manganese violet to disproportionation into MnO2 and manganese pyrophosphate salt in a solid-state reaction. Finally, a redox reaction between β-MnO2 and Li2MnP2O7 in pyrolysis reaction under inert atmosphere give LiMnPO4. In the other hand in the mechanochemical reaction between NH4MnPO4 and Li2CO3, only acid and base reaction occurred and the NH4+ ions were replaced with Li+ ions and amorphous LiMnPO4 was prepared. The amorphous LiMnPO4 convert to crystalline LiMnPO4 by annealing the powder under inert atmosphere. The chemical changes in formation of LiMnPO4 compound was characterized by X-Ray diffraction analysis (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and energy dispersion x-ray analyses (EDX). FTIR spectra showed that the NH4+ ions were replaced with Li+ ions. X-ray diffraction show that by variation of precursor from manganese violet to ammonium manganese phosphate in the mechanochemical reaction the crystalline pattern changes to amorphous and also the reaction pathway was changed. The SEM images of LiMnPO4 nanoparticles that obtained by two precursors exhibit squamous morphologies with well-defined grain boundaries and nonuniform particle size distributions. The particle size distributions of crystalline LiMnPO4 obtained by NH4MnP2O7 and NH4MnPO4 were found in the region 60–260 and 20–130 nm respectively.

An enhanced capacitive storage of hybrid supercapacitor based on interconnected nitrogen-doped graphene encapsulated honeycomb cobalt manganese pyrophosphate

Herein, the circular ring-like cobalt manganese pyrophosphate (Co0.55Mn0.45)2P2O7 wrapped by nitrogen-doped graphene (NG) are synthetized through a facile one-step microwave method with numerous open porous structures as electrochemically active sites. The circular ring-like (Co0.55Mn0.45)2P2O7 possess honeycomb-like structures to storage more ions and have more electrochemically active sites from the honeycomb edges, which faster ion/electron transporting through the pores. Therefore, these honeycomb-like hybrids obtain an excellent specific capacity of 236.21 mA h g−1 at 1 A·g−1 under three-electrode conditions, contribution a wonderful cycle stability of 86.7% after 10,000 cycles. Anode material of asymmetric supercapacitor (ASC) is assembled with biomass hierarchical glucose carbon (HGC), the maximum energy density of the ASC device is 75.72 Wh·kg−1 at a power density of 800 W·kg−1 (remained 60.08 Wh·kg−1 at 8000 W·kg−1). The enhanced capacitive storage of the ASC device can be attributed to the interconnected circular ring-like structure and the perfect combination of nitrogen-doped graphene.

New synthesis strategies to improve Co-Free LiNi0.5Mn0.5O2 cathodes: Early transition metal d0 dopants and manganese pyrophosphate coating

In this work, we report solution-based doping and coating strategies to improve the electrochemical performance of the Co-free layered oxide cathode LiNi0.5Mn0.5O2 (NM-50/50). Small amounts of d0 dopants (e.g., Mo6+and Ti4+, 0.5–1 at. %) increase the cathode's specific capacity, cycling stability, and rate capability. For example, a Mo-doped cathode with the nominal composition LiNi0.495Mn0.495Mo0.01O2 exhibits a high reversible capacity of 180 mA h/g at 20 mA/g compared to only 156 mA h/g for undoped NM-50/50. Effects of 1 at.% Mo dopant on the cathode structure were studied using a suite of characterization tools including X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy. These measurements demonstrate that Mo6+ dopant is enriched near the particle surface and improves the electrochemical performance of LiNi0.5Mn0.5O2 by: (i) reducing Li+/Ni2+ cation mixing which facilitates Li+ transport, (ii) mitigating undesirable phase transformations near the cathode surface, and (iii) altering the cathode/electrolyte interfacial chemistry. This work also reports the use of an inorganic Mn2P2O7 coating which enhances the cycling stability of Mo-doped NM-50/50, presumably through formation of a stable cathode electrolyte interphase (CEI) layer. Overall, the synthesis approaches reported herein are quite general and can potentially be expanded to other high voltage Li-ion battery cathodes.

Effect of preparation methodology on the colour and the NIR reflectance of nickel doped manganese pyrophosphate

Nickel doped Mn2P2O7 pigments of the formula NixMn2-xP2O7 (x = 0.0.5, 1.0, 1.5, 2.0) were prepared by precipitation and hydrothermal methods and characterized by PXRD, FT-IR, UV-DRS and SEM - EDX. The colour parameters were studied using CIE-LAB parameters. It is noteworthy that when x = 0 reddish pink colour was observed in precipitation method whereas in hydrothermal method pale pink colour was noticed. The colour hue change from pink to yellow was observed when x value is increased from 0 to 2.0. Well defined morphology was obtained in hydrothermal method, whereas precipitation method leads to the formation of irregular morphology. NIR Solar reflectance (R*) was found to be 79% for x = 0 prepared by hydrothermal method but by precipitation method it was reduced to 65%. Increased lightness (L*) value (less intense) was noticed for the all samples prepared by hydrothermal method compared to precipitation method (more intense). A yellow pigment which is free of chromium, cadmium and lead was obtained.

Unique crystallization behavior of sodium manganese pyrophosphate Na2MnP2O7 glass and its electrochemical properties

sCrystallization behavior of Na2MnP2O7 precursor glass was examined. Layered type Na2MnP2O7 was formed at 461 °C for 3 h in N2 filled electric furnace. Irreversible phase change was confirmed from layered Na2MnP2O7 to β-Na2MnP2O7 over 600 °C. At 650 °C crystallized phase was completely changed to β-phase. By means of charge and discharge testing it is found that layered Na2MnP2O7 is also active as cathode in sodium ion batteries. We found glass-ceramics technology is one of the suitable process for the synthesis of layered Na2MnP2O7 cathode without any complicate process.

The synthesis, structure and properties of a new lithium-rich manganese(ii) phosphate Li5CsMn(P2O7)2: a congruently melting compound with a 'lithium hamburger' structure.

The crystals of the title compound have been grown in molten salt media. Single-crystal X-ray diffraction experiment revealed that the compound crystallizes in an orthorhombic space group Pbcn (no. 60) with cell parameters: a = 5.1023(10) Å, b = 19.717(4) Å, c = 12.557(3) Å, and Z = 4. The structure of Li5CsMn(P2O7)2 consists of one-dimensional manganese pyrophosphate chains [MnP4O14]∞ interleaved with Cs(+) and Li(+) cations. A pseudo-two-dimensional layer [CsMnP4O14]∞ parallel to the ab plane is made up of [MnP4O14]∞ chains and Cs-O polyhedra through sharing the oxygen atoms. The three crystallographically distinct Li atoms are all located in the interlayered space to form a 'lithium hamburger' structure. Magnetic studies demonstrated that the compound shows paramagnetic behavior. DSC and XRD investigations revealed that the compound melts congruently. AC impedance studies show that the conductivity is 1.3 × 10(-5) S cm(-1) at 573 K and the activation energy is 0.42 eV. In addition, Li ion diffusional pathways were obtained using the bond valence map.

Mechanochemical effects on formation and properties of zinc - manganese pyrophosphates

Mechanochemical effects on formation and properties of zinc - manganese pyrophosphates

Development of optically transparent water oxidation catalysts using manganese pyrophosphate compounds

One challenge in artificial photosynthetic systems is the development of active oxygen evolution catalysts composed of abundant elements. The oxygen evolution activities of manganese pyrophosphate compounds were examined in electrochemical and photochemical experiments. Electrocatalysis using calcium–manganese pyrophosphate exhibited good catalytic ability under neutral pH and an oxygen evolution reaction was driven with a small overpotential (η<100mV). UV–vis diffuse reflectance measurements revealed that manganese pyrophosphates exhibit weak absorption in the visible light region while commonly used oxygen evolution catalysts exhibit intense absorption. Therefore, the efficient light absorption of a photocatalyst was retained even after surface modification with a manganese pyrophosphate, and photochemical oxygen evolution was achieved by using magnesium ferrite modified with manganese pyrophosphate nanoparticles under the illumination of visible light at wavelength of over 420nm.

ChemInform Abstract: A New Water Oxidation Catalyst: Lithium Manganese Pyrophosphate with Tunable Mn Valency.

AbstractInductively coupled plasma mass spectrometry, XPS, XANES, galvanostatic charging—discharging, and cyclic voltammetry analysis indicate that Li2‐xMnP2O7 (x = 0.3, 0.5, 1) exhibits high catalytic stability for water oxidation without additional delithiation or phase transformation.

A New Water Oxidation Catalyst: Lithium Manganese Pyrophosphate with Tunable Mn Valency

The development of a water oxidation catalyst has been a demanding challenge for the realization of overall water-splitting systems. Although intensive studies have explored the role of Mn element in water oxidation catalysis, it has been difficult to understand whether the catalytic capability originates mainly from either the Mn arrangement or the Mn valency. In this study, to decouple these two factors and to investigate the role of Mn valency on catalysis, we selected a new pyrophosphate-based Mn compound (Li2MnP2O7), which has not been utilized for water oxidation catalysis to date, as a model system. Due to the monophasic behavior of Li2MnP2O7 with delithiation, the Mn valency of Li(2-x)MnP2O7 (x = 0.3, 0.5, 1) can be controlled with negligible change in the crystal framework (e.g., volume change ~1%). Moreover, inductively coupled plasma mass spectrometry, X-ray photoelectron spectroscopy, ex-situ X-ray absorption near-edge structure, galvanostatic charging-discharging, and cyclic voltammetry analysis indicate that Li(2-x)MnP2O7 (x = 0.3, 0.5, 1) exhibits high catalytic stability without additional delithiation or phase transformation. Notably, we observed that, as the averaged oxidation state of Mn in Li(2-x)MnP2O7 increases from 2 to 3, the catalytic performance is enhanced in the series Li2MnP2O7 < Li(1.7)MnP2O7 < Li(1.5)MnP2O7 < LiMnP2O7. Moreover, Li2MnP2O7 itself exhibits superior catalytic performance compared with MnO or MnO2. Our study provides valuable guidelines for developing an efficient Mn-based catalyst under neutral conditions with controlled Mn valency and atomic arrangement.

A new polymorph of lithium manganese(ii) pyrophosphate β-Li2MnP2O7

A new polymorph of lithium manganese pyrophosphate was synthesized by low-temperature solid-state synthesis, and the crystal structure was determined. The new phase has a new type of three-dimensional framework structure, which is completely different from that found in the previous study by Adam et al., J. Solid State Chem., 2008, 181, 3110. Electrochemical measurement with a Li cell demonstrated a reversible electrochemical activity at around 4 V.

Synthesis and characterization of a series of cobalt–manganese pyrophosphate CoxMn2 − xP2O7 (x = 0, 0.25, 0.5, and 1) compounds

Cobalt–manganese pyrophosphate nanostructures with formula CoxMn2−xP2O7 (x=0, 0.25, 0.5, and 1) were successfully prepared via two different methods: the precipitation and the hydrothermal at 150°C using poly-ethylene-glycol-5000 (PEG-5000), with further calcinations at 500°C. The Rietveld refinement of the XRD data confirms that CoxMn2−xP2O7 nanoparticles crystallize in the monoclinic system with space group C2/m. The crystallite size obtained from X-ray line broadening was found to be 41nm for the Mn2P2O7 compound. The grain size of CoxMn2−xP2O7 varies when increasing the degree of substitution. IR and Raman studies show characteristic bands of the P2O74− anion. A correlation between the partial replacement of Mn by Co and the dependent lattice parameters, the microstructure and the spectroscopic properties was observed. An effort has been made to explain the observed correlation with a qualitative model.

Oxidation of L-Valine by Manganese(III) in Pyrophosphate Medium: Kinetics and Mechanism

Kinetics of oxidation of L-valine (Val) by manganese(III) pyrophosphate has been studied as a function of pH (0.94-1.90) at 313 K. The reaction shows a first-order dependence of rate each on (Mn(III)) and (Val), a fractional-order on (H + ), and an inverse fractional-order each on (Na4P2O7) and (Mn(II)). Effects on the rate of anions, such as (F - ), (Cl - ) and (ClO4 - ), and the dielectric constant of the solvent medium have been studied. Solvent isotope studies have been performed in D 2O medium. Activation parameters have been determined from Arrhenius and Eyring plots. A mechanism consistent with the observed kinetics is proposed and discussed.

A mechanistic study on the disproportionation and oxidative degradation of phenothiazine derivatives by manganese(III) complexes in phosphate acidic media

The oxidative degradation of phenothiazine derivatives (PTZ) by manganese(III) was studied in the presence of a large excess of manganese(III)-pyrophosphate (P2O7 2−), phosphate (PO4 3−), and H+ ions using UV–vis. spectroscopy. The first irreversible step is a fast reaction between phenothiazine and manganese pyrophosphate leading to the complete conversion to a stable phenothiazine radical. In the second step, the cation radical is oxidized by manganese to a dication, which subsequently hydrolyzes to phenothiazine 5-oxide. The reaction rate is controlled by the coordination and stability of manganese(III) ion influenced by the reduction potential of these ions and their strong ability to oxidize many reducing agents. The cation radical might also be transformed to the final product in another competing reaction. The final product, phenothiazine 5-oxide, is also formed via a disproportionation reaction. The kinetics of the second step of the oxidative degradation could be studied in acidic phosphate media due to the large difference in the rates of the first and further processes. Linear dependences of the pseudo-first-order rate constants (k obs) on [MnIII] with a significant non-zero intercept were established for the degradation of phenothiazine radicals. The rate is dependent on [H+] and independent of [PTZ] within the excess concentration range of the manganese(III) complexes used in the isolation method. The kinetics of the disproportionation of the phenothiazine radical have been studied independently from the further oxidative degradation process in acidic sulphate media. The rate is inversely dependent on [PTZ+.], dependent on [H+], and increases slightly with decreasing H+ concentration. Mechanistic consequences of all these results are discussed.

Solvothermal synthesis of Mn 2P 2O 7 and its application in lithium-ion battery

Manganese pyrophosphate, Mn 2P 2O 7 was synthesized by a simple solvothermal method using Mn metal powder and P 2S 5 in ethylene glycol medium at 190–220 °C. Morphology and crystalline structure of the products were characterized by X-ray diffraction and scanning electron microscopy. The flower-like microspheres with diameters of about 2–5 μm are composed of a number of nanoplatelets with thickness of 20–40 nm. The effect of reaction temperature and reaction time on the microstructure of Mn 2P 2O 7 was investigated. The samples were used as active anode materials for lithium-ion battery and their electrochemical properties were examined by constant current charge–discharge cycling. The Mn 2P 2O 7 electrodes exhibited initial reversible capacities of 440–330 mAh g − 1 depending on the synthetic conditions. From these results, a possible reaction mechanism of Mn 2P 2O 7 with lithium was proposed.

ChemInform Abstract: Iron and Manganese Pyrophosphates as Cathodes for Lithium‐Ion Batteries.

AbstractThe compounds Li2Mn1‐yFeyP2O7 (y = 0, 0.2, 0.5, 0.8, 1) are synthesized by evaporation of aqueous solutions of LiOAc, Fe(OAc)2, Mn(OAc)2, and NH4H2PO4, followed by annealing (H2/He, 400—700 °C).

Iron and Manganese Pyrophosphates as Cathodes for Lithium-Ion Batteries

The mixed-metal phases, (Li2Mn1−yFeyP2O7, 0 ≤ y ≤ 1), were synthesized using a “wet method”, and found to form a solid solution in the P21/a space group. Both thermogravimetric analysis and magnetic susceptibility measurements confirm the 2+ oxidation state for both the Mn and Fe. The electrochemical capacity improves as the Fe concentration increases, as do the intensities of the redox peaks of the cyclic voltammogram, indicating higher lithium-ion diffusivity in the iron phase. The two Li+ ions in the three-dimensional tunnel structure of the pyrophosphate phase allows for the cycling of more than one lithium per redox center. Cyclic voltammograms show a second oxidation peak at ∼5 V and ∼5.3 V, indicative of the extraction of the second lithium ion, in agreement with ab initio computation predictions. Thus, electrochemical capacities exceeding 200 Ah/kg may be achieved if a stable electrolyte is found.

Synthesis and characterization of nanocrystalline manganese pyrophosphate Mn 2P 2O 7

Mn 2P 2O 7 polyhedral particles were synthesized by simple and cost-effective method using manganese nitrate hydrate and phosphoric acid in the presence of nitric acid with further calcinations at the temperature of 800 °C. The crystallite size obtained from X-ray line broadening is 31 ± 13 nm for the Mn 2P 2O 7. The X-ray diffraction and SEM results indicated that the synthesized nanoparticles have only the structure without the presence of any other phase impurities. The FT-IR and FT-Raman spectra show characteristic bands of the P 2O 7 4− anion. The UV–Vis–NIR spectrum confirms the octahedral coordination of Mn 2+ ion.

Polymer and oligomer phosphazene cymantrene derivatives as solid state precursors of nanostructured manganese pyrophosphate

Pyrolysis under air at 800 °C, of the cyclic N3P3[OC6H4PPh2·Mn(CO)2(η-MeC5H4)]6 (1) and the polymer {[NP(O2C12H8)]0.5[NP(OC6H4COOPrn)(OC6H4PPh2·Mn(CO)2(η-MeC5H4))]0.5}n (2) phosphazene with pendant OC6H4PPh2·Mn(CO)2(η-MeC5H4) units affords nanostructured Mn2P2O7. The morphology of the pyrolytic products is highly dependent on the phosphazene support. Dense structures were observed from pyrolysis of cyclic (1) while most porous materials were obtained from pyrolysis of polymer (2). The new polymeric complex (2) was prepared from reaction of the phosphine containing polymer {[NP(O2C12H8)]0.5[NP(OC6H4COOPrn)(OC6H4PPh2)]0.5}n and the photochemically generated [Mn(THF)(CO)2(η-MeC5H4)] and was fully characterized.