Highly efficient adsorption of congo red and methyl orange dyes using mesoporous α-Mn2O3 nanoparticles synthesized with Pyracantha angustofolia fruit extract

Due to the many applications of manganese oxides in water treatment, this research aimed to synthesize α-Mn2O3 nanoparticles through a green method and investigate the dye adsorption capacity of them. The α-Mn2O3 nanoparticles were successfully synthesized using KMnO4 and aqueous extract of Pyracantha angustofolia fruits under hydrothermal conditions and calcination. The products were identified using Fourier transform infrared (FTIR), X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), and scanning electron microscopy (SEM) analyses. The adsorption capacity of methyl orange (MO) and Congo red (CR) dyes were evaluated at different concentrations (25, 50, and 75 ppm) using α-Mn2O3 nanoparticles. Results revealed the spherical and porous structure of α-Mn2O3 nanoparticles with a specific surface area of 21.7 m2.g-1. Dye removal significantly increased with pH decrement. The adsorption capacity for MO and CR was 73.07 and 70.70 mg.g-1, respectively. The adsorption data of both dyes followed a pseudo-second-order kinetic model. The best fitted models for MO and CR adsorption were the Langmuir isotherm and the Dubinin-Radushkevich, respectively. In addition, a possible adsorption mechanism was proposed for both dyes. The findings showed that α-Mn2O3 nanoparticles are very efficient adsorbents for removing anionic dyes.

Temperature dependent structural properties of Mn1.90M0.10O3(M = Cr and Fe)

The polycrystalline samples of Mn1.90Cr0.10O3(MCO) and Mn1.90Fe0.10O3(MFO) have been investigated for their temperature dependent magnetic and structural properties. The Cr and Fe substitutions have significant effect on the magnetic and structural properties of Mn2O3. Like pristine Mn2O3, the Cr and Fe substituted samples MCO and MFO also exhibit two antiferromagnetic transitions; one at ∼77 K, ∼80 K, respectively and another at ∼40 K. Our room temperature synchrotron x-ray powder diffraction (SXRD) results confirm that both the MCO and MFO samples crystallize in cubic symmetry. The temperature dependent SXRD results demonstrate the cubic to orthorhombic structural transition for the studied samples. The pristine Mn2O3shows cubic to orthorhombic transition around 310 K, whereas this structural transition shifted towards lower temperature side with these substitutions i.e. around 240 K for MCO and 260 K for MFO. Interestingly, the centrosymmetricPcabto non-centrosymmetricPca21change in symmetry is also resolved at the ferroelectric ordering temperature for MCO.

Facile synthesis of nanosized Mn3O4 powder anodes for high capacity Lithium-Ion battery via flame spray pyrolysis

Mn₃O₄ powders with nanometer size are successfully synthesized by a simple one-step method via flame spray pyrolysis. The precursor droplet is generated by heating under high temperature flame with fixed flow rate, and the exothermic reaction is induced to form nanosized Mn₃O₄ powders. When used as anode material for lithium-ion battery, the Mn₃O₄ exhibits good cycling capacity and rate performance. It delivers a specific capacity of 1,182 mA h g⁻¹ over 110 cycles at a current density of 200 mA g⁻¹, and has a high capacity of 140 mA h g⁻¹ at 5,000 mA g⁻¹.

Non-equilibrium metal oxides via reconversion chemistry in lithium-ion batteries

Binary metal oxides are attractive anode materials for lithium-ion batteries. Despite sustained effort into nanomaterials synthesis and understanding the initial discharge mechanism, the fundamental chemistry underpinning the charge and subsequent cycles-thus the reversible capacity-remains poorly understood. Here, we use in operando X-ray pair distribution function analysis combining with our recently developed analytical approach employing Metropolis Monte Carlo simulations and non-negative matrix factorisation to study the charge reaction thermodynamics of a series of Fe- and Mn-oxides. As opposed to the commonly believed conversion chemistry forming rocksalt FeO and MnO, we reveal the two oxide series topotactically transform into non-native body-centred cubic FeO and zincblende MnO via displacement-like reactions whose kinetics are governed by the mobility differences between displaced species. These renewed mechanistic insights suggest avenues for the future design of metal oxide materials as well as new material synthesis routes using electrochemically-assisted methods.

Structural Diversity of Zinc(II), Manganese(II), and Gadolinium(III) Coordination Polymers Based on Two Isomeric N-Heteroaromatic Polycarboxylate Ligands: Structures and Their Derived Mn2O3 for Lithium Storage Applications

Tuning the coordination sites of two isomeric semirigid ligands, 5-(4-pyridin-3-yl-benzoylamino)isophthalic acid (3-H₂PBI) and 5-(4-pyridin-4-yl-benzoylamino)isophthalic acid (4-H₂PBI), afforded six new coordination polymers (CPs), [Zn(3-PBI)(H₂O)]_n (1), {[Mn₂(3-PBI)₂(H₂O)]·DMF·2H₂O}_n (2), {[Gd₂(3-PBI)₃(H₂O)₃]·DMF·3H₂O}_n (3), {[Zn₂(4-PBI)₂]·H₂O}_n (4), {[Mn₂(4-PBI)₂(H₂O)₂]·4H₂O}_n (5), and {(Me₂NH₂)[Gd(4-PBI)₂]·H₂O}_n (6). Structural analysis shows that 1 consists of 2D honeycomb (6,3) net, three sets of networks interlace mutually, generating an unexpected 2D + 2D + 2D → 3D polycatenating interesting system. 2 exhibits a 3D pcu topology. 3 presents a unique 3D with 3,3,6T13 network topology. 4 possesses 3D 2-fold interpenetrated structure with rutile topology. 5 presents an alluring 2D architecture comprising two distinct topologies (kgd and hcb), stacked arrangement in an unexpected ABBABB mode. 6 displays 2D (4,4)-grid network. A differentiation of these structural features indicate that coordination connectivity of metals, together with binding modes of two ligands are accountable for the fascinating structural contrast. In addition, 2 and 5 were then transformed into Mn₂O₃ via a simple heat treatment. Electrochemical test results show that both of the obtained Mn₂O₃ moieties exhibit stable lithium storage properties and excellent rate capabilities.

Hierarchical structured Mn2O3 nanomaterials with excellent electrochemical properties for lithium ion batteries

A series of Mn₂O₃ nanomaterials with hierarchical porous structures was synthesized using three types of leaves as templates. In addition to their different morphologies, different porous nanostructures were achieved by choosing different leaves. The Mn₂O₃ nanomaterial prepared by using gingko leaves as a template provides a larger pore volume and a higher Brunauer–Emmett–Teller (BET) surface area. At the same time, this material also displays excellent electrochemical performance, that is, the specific capacities are 1274.6 mA h g⁻¹ after 300 cycles and 381.5 mA h g⁻¹ at current densities of 300 and 3000 mA g⁻¹, respectively.

A series of Mn₂O₃ nanomaterials with hierarchical porous structures was synthesized using three types of leaves as templates.

Recent Advances in Designing High-Capacity Anode Nanomaterials for Li-Ion Batteries and Their Atomic-Scale Storage Mechanism Studies

Lithium-ion batteries (LIBs) have been widely applied in portable electronics (laptops, mobile phones, etc.) as one of the most popular energy storage devices. Currently, much effort has been devoted to exploring alternative high-capacity anode materials and thus potentially constructing high-performance LIBs with higher energy/power density. Here, high-capacity anode nanomaterials based on the diverse types of mechanisms, intercalation/deintercalation mechanism, alloying/dealloying reactions, conversion reaction, and Li metal reaction, are reviewed. Moreover, recent studies in atomic-scale storage mechanism by utilizing advanced microscopic techniques, such as in situ high-resolution transmission electron microscopy and other techniques (e.g., spherical aberration-corrected scanning transmission electron microscopy, cryoelectron microscopy, and 3D imaging techniques), are highlighted. With the in-depth understanding on the atomic-scale ion storage/release mechanisms, more guidance is given to researchers for further design and optimization of anode nanomaterials. Finally, some possible challenges and promising future directions for enhancing LIBs' capacity are provided along with the authors personal viewpoints in this research field.

Embedding MnO@Mn3 O4 Nanoparticles in an N-Doped-Carbon Framework Derived from Mn-Organic Clusters for Efficient Lithium Storage

The first synthesis of MnO@Mn₃ O₄ nanoparticles embedded in an N-doped porous carbon framework (MnO@Mn₃ O₄ /NPCF) through pyrolysis of mixed-valent Mn₈ clusters is reported. The unique features of MnO@Mn₃ O₄ /NPCF are derived from the distinct interfacial structure of the Mn₈ clusters, implying a new methodological strategy for hybrids. The characteristics of MnO@Mn₃ O₄ are determined by conducting high angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) and electron energy loss spectroscopy (EELS) valence-state analyses. Due to the combined advantages of MnO@Mn₃ O₄ , the uniform distribution, and the NPCF, MnO@Mn₃ O₄ /NPCF displays unprecedented lithium-storage performance (1500 mA h g^-1 at 0.2 A g^-1 over 270 cycles). Quantitative analysis reveals that capacitance and diffusion mechanisms account for Li⁺ storage, wherein the former dominates. First-principles calculations highlight the strong affiliation of MnO@Mn₃ O₄ and the NPCF, which favor structural stability. Meanwhile, defects of the NPCF decrease the diffusion energy barrier, thus enhancing the Li⁺ pseudocapacitive process, reversible capacity, and long cycling performance. This work presents a new methodology to construct composites for energy storage and conversion.

Formation of Mn–Cr mixed oxide nanosheets with enhanced lithium storage properties

Novel carbon-free Mn₂O₃/MnCr₂O₄ hybrid nanosheets are synthesized. As an anode for lithium-ion batteries, they deliver a wonderful electrochemical performance.

Hierarchical porous ZnMnO3 yolk–shell microspheres with superior lithium storage properties enabled by a unique one-step conversion mechanism

ZnMnO₃ has attracted enormous attention as a novel anode material for rechargeable lithium-ion batteries due to its high theoretical capacity. However, it suffers from capacity fading because of the large volumetric change during cycling. Here, porous ZnMnO₃ yolk–shell microspheres are developed through a facile and scalable synthesis approach. This ZnMnO₃ can effectively accommodate the large volume change upon cycling, leading to an excellent cycling stability. When applying this ZnMnO₃ as the anode in lithium-ion batteries, it shows a remarkable reversible capacity (400 mA h g⁻¹ at a current density of 400 mA g⁻¹ and 200 mA h g⁻¹ at 6400 mA g⁻¹) and excellent cycling performance (540 mA h g⁻¹ after 300 cycles at 400 mA g⁻¹) due to its unique structure. Furthermore, a novel conversion reaction mechanism of the ZnMnO₃ is revealed: ZnMnO₃ is first converted into intermediate phases of ZnO and MnO, after which MnO is further reduced to metallic Mn while ZnO remains stable, avoiding the serious pulverization of the electrode brought about by lithiation of ZnO.

ZnMnO₃ has attracted enormous attention as a novel anode material for rechargeable lithium-ion batteries due to its high theoretical capacity.

Nano-particle assembled porous core-shell ZnMn2O4 microspheres with superb performance for lithium batteries

Porous ZnMn₂O₄ microspheres were prepared via a facile co-precipitation method followed by calcination at various temperatures and evaluated as anode materials for lithium ion batteries. The sample prepared at 600 °C outperformed the other samples in terms of electrochemical performance with high reversible capacity, high-rate capability, and excellent cycling performance. The capacity of the sample remained as high as 999 mAh g^-1 at a current rate of 100 mA g^-1 after 50 cycles-one of the best ever reported for ZnMn₂O₄-based materials. A high reversible capacity of 400 mAh g^-1 was retainable at a current density of 2000 mA g^-1 after 2500 cycles. A novel electrochemical reaction mechanism of ZnMn₂O₄ anodes was established and investigated at length. The Mn₃O₄ observed during the charge process was largely responsible for the enhanced performance, as confirmed by x-ray photoelectron spectroscopy, scanning electron microscopy, and transmission electron microscopy. The relatively large surface area, abundant porosity, large ion exchange space, and strong mechanical stability of the porous connected 3D framework were responsible for the unique oxidation/reduction Mn²⁺ ↔ Mn³⁺ process we observed.

Partial-Redox-Promoted Mn Cycling of Mn(II)-Doped Heterogeneous Catalyst for Efficient H2O2-Mediated Oxidation

The development of a heterogeneous catalyst with high catalytic activity and durability for H₂O₂-mediated oxidation is one of the most important industrial and environmental issues. In this study, a Mn(II)-doped TiO₂ heterogeneous catalyst was developed for H₂O₂-mediated oxidation. The TiO₂ substrate-dependent partial-redox behavior of Mn was identified on the basis of our density functional theory simulations. This unique redox cycle was induced by a moderate electron transfer from Ti to Mn, which compensated for the electron loss of Mn and finally resulted in a high-efficiency cycling of Mn between its oxidized and reduced forms. In light of the theoretical results, a Mn(II)-doped TiO₂ composite with well-defined morphology and large surface area (153.3 m² g^-1) was elaborately fabricated through incorporating Mn(II) ions into a TiO₂ nanoflower, and further tested as the catalyst for oxidative degradation of organic pollutants in the presence of H₂O₂. Benefiting from the remarkable textural features and excellent Mn cycling property, this composite exhibited superior catalytic performance for organic pollutant degradation. Moreover, it could retain 98.40% of its initial activity even in the fifth cycle. Our study provides an effective strategy for designing heterogeneous catalytic systems for H₂O₂-mediated oxidations.

Ternary Porous Sulfur/Dual-Carbon Architectures for Lithium/Sulfur Batteries Obtained Continuously and on a Large Scale via an Industry-Oriented Spray-Pyrolysis/Sublimation Method

Ternary composites with porous sulfur/dual-carbon architectures have been synthesized by a single-step spray-pyrolysis/sublimation technique, which is an industry-oriented method that features continuous fabrication of products with highly developed porous structures without the need for any further treatments. A double suspension of commercial sulfur and carbon scaffolding particles was dispersed in ethanol/water solution and sprayed at 180 °C using a spray pyrolysis system. In the resultant composites, the sulfur particles were subjected to an ultrashort sublimation process, leading to the development of a highly porous surface, and were meanwhile coated with amorphous carbon, obtained through the pyrolysis of the ethanol, which acts as an adhesive interface to bind together the porous sulfur with the scaffolding carbon particles, to form a ternary composite architecture. This material has an effective conducting-carbon/sulfur-based matrix and interconnected open pores to reduce the diffusion paths of lithium ions, buffer the sulfur volumetric expansion, and absorb electrolyte and polysulfides. Because of the unique chemistry and the structure, the composites show stable cycling performance for 200 cycles and good rate capability of 520 mAh g(-1) at 2 C. This advanced spray-pyrolysis/sublimation method is easy to scale up and shows great potential for commercialization of lithium/sulfur batteries.

Conversion Reaction-Based Oxide Nanomaterials for Lithium Ion Battery Anodes

Developing high-energy-density electrodes for lithium ion batteries (LIBs) is of primary importance to meet the challenges in electronics and automobile industries in the near future. Conversion reaction-based transition metal oxides are attractive candidates for LIB anodes because of their high theoretical capacities. This review summarizes recent advances on the development of nanostructured transition metal oxides for use in lithium ion battery anodes based on conversion reactions. The oxide materials covered in this review include oxides of iron, manganese, cobalt, copper, nickel, molybdenum, zinc, ruthenium, chromium, and tungsten, and mixed metal oxides. Various kinds of nanostructured materials including nanowires, nanosheets, hollow structures, porous structures, and oxide/carbon nanocomposites are discussed in terms of their LIB anode applications.

Reconstruction of Mini-Hollow Polyhedron Mn2O3 Derived from MOFs as a High-Performance Lithium Anode Material

A mini-hollow polyhedron Mn2O3is used as the anode material for lithium-ion batteries. Benefiting from the small interior cavity and intrinsic nanosize effect, a stable reconstructed hierarchical nanostructure is formed. It has excellent energy storage properties, exhibiting a capacity of 760 mAh g-1 at 2 A g-1 after 1000 cycles. This finding offers a new perspective for the design of electrodes with large energy storage.

Porous Mn2O3 microcubes with exposed {001} facets as electrode for lithium ion batteries

Porous Mn₂O₃ microcubes with exposed {001} facets have been obtained and the Li-ion batteries in which they are applied deliver a high reversible capacity.

A thermally activated manganese 1,4-benzenedicarboxylate metal organic framework with high anodic capability for Li-ion batteries

Mn-1,4-BDC@200 was synthesized, with a capacity of 974 mA h g⁻¹after 100 cycles at a rate of 100 mA g⁻¹.

A simple synthesis of hollow Mn2O3 core–shell microspheres and their application in lithium ion batteries

Hollow Mn₂O₃ core–shell microspheres were successfully fabricated via a mixed method including a solution method and a subsequent thermal decomposition.

Enhanced anode performance of manganese oxides with petal-like microsphere structures by optimizing the sintering conditions

Herein, the rational design and synthesis of manganese oxides (MnO₂ and MnO) have been achieved and both of them show petal-like microsphere structures.

Electrochemical energy storage in Mn2O3 porous nanobars derived from morphology-conserved transformation of benzenetricarboxylate-bridged metal–organic framework

MOF-derived Mn₂O₃ shows a high capacity of ∼410 mA h g⁻¹ as a 2 V anode and an ultrahigh energy density of 147.4 W h kg⁻¹ as a supercapacitor.

Three-Dimensional (3D) Bicontinuous Hierarchically Porous Mn2O3 Single Crystals for High Performance Lithium-Ion Batteries

Bicontinuous hierarchically porous Mn₂O₃ single crystals (BHP-Mn₂O₃-SCs) with uniform parallelepiped geometry and tunable sizes have been synthesized and used as anode materials for lithium-ion batteries (LIBs). The monodispersed BHP-Mn₂O₃-SCs exhibit high specific surface area and three dimensional interconnected bimodal mesoporosity throughout the entire crystal. Such hierarchical interpenetrating porous framework can not only provide a large number of active sites for Li ion insertion, but also good conductivity and short diffusion length for Li ions, leading to a high lithium storage capacity and enhanced rate capability. Furthermore, owing to their specific porosity, these BHP-Mn₂O₃-SCs as anode materials can accommodate the volume expansion/contraction that occurs with lithium insertion/extraction during discharge/charge processes, resulting in their good cycling performance. Our synthesized BHP-Mn₂O₃-SCs with a size of ~700 nm display the best electrochemical performance, with a large reversible capacity (845 mA h g⁻¹ at 100 mA g⁻¹ after 50 cycles), high coulombic efficiency (>95%), excellent cycling stability and superior rate capability (410 mA h g⁻¹ at 1 Ag⁻¹). These values are among the highest reported for Mn₂O₃-based bulk solids and nanostructures. Also, electrochemical impedance spectroscopy study demonstrates that the BHP-Mn₂O₃-SCs are suitable for charge transfer at the electrode/electrolyte interface.

Hierarchical Mn₂O ₃Hollow Microspheres as Anode Material of Lithium Ion Battery and Its Conversion Reaction Mechanism Investigated by XANES

Hierarchical Mn2O3 hollow microspheres of diameter about 6-10 μm were synthesized by solvent-thermal method. When serving as anode materials of LIBs, the hierarchical Mn2O3 hollow microspheres could deliver a reversible capacity of 580 mAh g(-1) at 500 mA g(-1) after 140 cycles, and a specific capacity of 422 mAh g(-1) at a current density as high as 1600 mA g(-1), demonstrating a good rate capability. Ex situ X-ray absorption near edge structure (XANES) spectrum reveals that, for the first time, the pristine Mn2O3 was reduced to metallic Mn when it discharged to 0.01 V, and oxidized to MnO as it charged to 3 V in the first cycle. Furthermore, the XANES data demonstrated also that the average valence of Mn in the sample at charged state has decreased slowly with cycling number, which signifies an incomplete lithiation process and interprets the capacity loss of the Mn2O3 during cycling.

The controlled synthesis and improved electrochemical cyclability of Mn-doped α-Fe2O3 hollow porous quadrangular prisms as lithium-ion battery anodes

The controlled synthesis of anode material Mn-doped α-Fe₂O₃ hollow porous quadrangular prisms with an enhanced electrochemical cycling stability is reported.

Ni-enhanced Co3O4 nanoarrays grown in situ on a Cu substrate as integrated anode materials for high-performance Li-ion batteries

3D Co₃O₄ nanoarrays fabricated on a Cu substrate surface with a Ni-nanoseed-layer as the interface were synthesized by a two-step approach, combining electrodeposition and hydrothermal synthesis. This integrated anode exhibited excellent performance in Li-ion batteries.

Pristine hollow microspheres of Mn2O3 as a potential anode for lithium-ion batteries

Ascorbic acid aided inside-out Ostwald ripening promotes the formation of Mn₂O₃ microspheres with a hollow interior surface that exhibits an appreciable capacity of 610 mA h g⁻¹, even after completing 100 cycles.

A self-assembled Si/SWNT 3D-composite-nanonetwork as a high-performance lithium ion battery anode

A Si/SWNT 3D-composite-nanonetwork integrated anode for high-performance lithium storage, through a combined process of electrostatic induced self-assembly and film transfer.

Nanoflake driven Mn2O3 microcubes modified with cooked rice derived carbon for improved electrochemical behavior

Mn₂O₃ microcubes, symmetrically formed out of the systematic stacking of nanoflakes, built with nanoparticles in the 30–50 nm range have been obtained from a simple co-precipitation method.