MnCO3 Precursors Research Articles

Regulation of oxygen vacancies in MnCO3-based catalysts by thermally inducing for efficiently catalytic benzene combustion

Tuning oxygen vacancies through carbon pyrolysis is an effective strategy for fabricating high-performance catalysts to oxidize volatile organic compounds (VOCs). Herein, a series of MnCO3-based catalysts were synthesized by pyrolyzing MnCO3 precursors with different morphologies including dumbbell-like (D), bayberry-like (B) and cubic (C) structures for the benzene oxidation. The catalyst (D-300) derived from dumbbell-like MnCO3 exhibited superior catalytic performance for the benzene oxidation with a T90 of 176 °C and remarkable stability in long-term, cycling and water-resistance tests. Abundant oxygen vacancies in D-300 improved lattice oxygen mobility and redox ability, resulting in superior oxygen uptake and release capabilities. Moreover, oxygen vacancies greatly facilitated the activation and replenishment of gaseous oxygens to generate active oxygen species, thereby dramatically accelerating the cleavage of benzene rings and deep mineralization. In situ DRIFTS analysis demonstrated that benzene preferentially adsorbed onto D-300 due to its abundant acidic sites, and the oxidation of phenolate species was a rate-determining step. H2O may hinder the activation of gaseous oxygen, suppressing the activity of the catalyst.

CuMn2O4 hierarchical microspheres as remarkable electrode of supercapacitors

This work firstly prepared CuMn2O4 hierarchical microspheres by using micro/nano MnCO3 precursor. Notably, a remarkable specific capacitance of 657 F g−1 at 1 A g−1, 368.8 F g−1 even at 5 A g−1 and an excellent capacitance retention of 96% after 3000 cycles are achieved for supercapacitors (SCs). In additional, the specific capacitances of this asymmetric capacitor are approximately 134.7, 110.5, 88, 75.8 and 71.7 F g−1 for 2, 3, 5, 8 and 10 A g−1, respectively. The result indicated a highly promising application in SCs.

Morphology-tunable hollow Mn2O3 nanostructures: highly efficient electrocatalysts and their electrochemical sensing for phenolic endocrine disruptors via toughening of graphene oxide

In the present study, three-dimensional hollow Mn2O3 polycrystals with various aggregation morphologies including spheres, dumbbells, cubes, and ellipsoids were selectively synthesized by modulating the shape of premade MnCO3 precursors with different manganese sources. Structural and electrochemical analyses demonstrated that the ellipsoidal Mn2O3 hollow structures had a higher specific surface area, wider pore diameter, and superior electron-transfer reactivity, thus, they exhibited greater electrocatalytic activity toward the oxidation of two phenolic endocrine disruptors, i.e., o-phenylphenol (OPP) and butylparaben (BP). In addition, the electro-oxidation of hollow Mn2O3 ellipsoids for OPP and BP was further enhanced when they were physically wrapped with graphene oxide (GO). This remarkable property is attributable to the dramatical increase of active sites and surface-chemisorbed oxygen species in these unique nanostructures. Highlights are presented for the simultaneous determination of OPP and BP within wide linear ranges of 0.002-20 and 0.003-24 μM, with low detection limits of 0.63 and 0.88 nM, respectively. Our findings not only offer a novel morphology-controllable synthesis strategy to better understand the morphology impact on the electrochemical performances of Mn2O3, but also represent a facile design of robust, active, and easy-to-obtain catalysts for sensors and other electrocatalytic systems.

Peanut-like yolk/core-shell MnO/C microspheres for improved lithium storage and the formation mechanism of MnCO3 precursors

The novel peanut-like yolk/core-shell MnO/C microspheres are prepared by combining hydrothermal reaction with precipitation polymerization and calcination technology. The formation mechanism of peanut-like MnCO3 is revealed and the determinant for the morphology of MnO/C microspheres is clarified. It can be obtained yolk-shell and core-shell MnO/C by controlling the thickness of resorcinol-formaldehyde (RF) layers. The electrochemical properties of MnO/C with different structures are evaluated. The enormous volume expansion/contractions of MnO in yolk-shell MnO/C microspheres are accommodated by abundant internal void. The thinner carbon shell provides a shorter path for Li+ diffusion and the Li+ transfer is accelerated. Yolk-shell MnO/C microspheres show high reversible capacity (1073.7 mAh/g after 500 cycles at 1.0 A/g), superior cyclic performance (885.6 mAh/g after 1000 cycles at 2.0 A/g) and rate performance (414.8 mAh/g at 5.0 A/g, 319.6 mAh/g at 10.0 A/g). For core-shell MnO/C microspheres, numerous channels spontaneously formed among MnO secondary particles are conducive to the entry of Li+. It can counteract the Li+ diffusion limitation. Therefore, a stable cyclic performance is maintained. Core-shell MnO/C microspheres exhibited discharge capacities of 712.3 and 514.1 mAh/g at 1.0 and 2.0 A/g after 500 cycles with unconspicuous attenuation.

Yttrium-doped LiMn2O4 spheres with long cycle life as Lithium-Ion Battery Cathode

Lithium manganese oxide (LiMn2O4) is one of the most promising material as lithium-ion battery cathodes owing to its significant advantages such as nontoxicity and low cost at present. However, LiMn2O4 exhibits insufficient cycling stability in practical application, which is an urgent problem to be figured out. In order to overcome this shortcoming, a facile method is presented which synthesized a yttrium-doped spherical LiMn2O4 whose diameter is about 5–6 μm using cubic MnCO3 precursors. The doped LiMn2O4 samples were investigated by XRD and SEM, which indicated that the spherical LiYxMn2−xO4 is a porous structure composed of LiYxMn2−xO4 nanoparticles with an average size of about 60–80 nm. The LiYxMn2−xO4 shows an excellent cycling performance when x = 0.01. At the current density of 1C (1C = 140 mAh g−1), LiYxMn2−xO4 shows a discharge specific capacity of 120 mAh g−1 at 1C with a specific capacity retention of 96% after 650 cycles.

Facile construction of Mn2O3@CeO2 core@shell cubes with enhanced catalytic activity toward CO oxidation

Heterogeneous core@shell nanostructures bring unique synergetic catalytic properties in comparison with their single-component materials, because the two-phase interface could render hybrid junctions with rich redox reactions. Herein, a series of Mn2O3@CeO2 core@shell cubes with tunable CeO2 shell thickness have been controllably synthesized by a facile multi-step process, which involved the annealing treatment of MnCO3 precursor to produce Mn2O3 microcubes, followed by a refuxing process to deposit a uniform CeO2 layer on the Mn2O3 surface. The CeO2 shell was assembled by nanoparticles with sizes in the range of 2–10 nm, and the thickness could be facilely manipulated by changing the Mn/Ce molar ratios of reactants used in the synthetic process. The Mn2O3@CeO2 core@shell cubes exhibited enhanced catalytic activity toward CO oxidation compared with both pure CeO2 and Mn2O3, which was attributed to the synergistic interaction between CeO2 and Mn2O3. Impressively, Mn2O3@CeO2-0.1 sample with a proper CeO2 thickness exhibited the highest catalytic performance, attaining 100% CO conversion at 220 °C.

Facile synthesis of hollow MnO microcubes as superior anode materials for lithium-ion batteries

Hollow MnO microcubes with edge length about 8 μm are prepared by a thermal decomposition process of MnCO3 precursor, which are obtained via a simple hydrothermal method. The morphologies of the final products are controlled by adjusting the amount of urea so as to achieve good electrochemical property. The microcube varies from hollow structure to solid structure and the pore size with the increasing amount of urea. The hollow MnO microcube exhibits a high reversible capability in the first cycle is 901.4 mA h g−1 at 0.1 C, slightly decreases to 722.9 mA h g−1 at 0.5 C in the 4th cycle and rises to 914.6 mA h g−1 at 0.5 C even after 200 cycles. Furthermore, the same porous MnO hollow microcube delivers high rate reversible specific capacities of 339.4 mA h g−1 at 4 C. The excellent performance of hollow MnO microcube can be attributed to its high surface area and stable hollow structure, which facilitates lithium-ion and electron rapid transport while simultaneously accommodating the drastic volumetric change during electrochemical cycling.

Synthesis of Si-Induced MnO/Mn2SiO4@C Cuboids as High-Performance Anodes for Lithium-Ion Batteries.

The exploration of anode materials of lithium-ion batteries (LIBs) is still a great challenge because of their low electrical conductivity and poor durability. Transition-metal oxides are proposed as a potential alternative, even though their dimension and structure greatly affect their electrochemical properties. In this study, MnO/Mn2SiO4@C cuboids were prepared via the polymerization-pyrolysis process. Larger MnCO3 precursor particles embedded into a monolithic carbon framework and formed smaller nanoparticles owing to the inducing effect of Si element in phthalocyanino silicon (SiPc), giving MnO/Mn2SiO4@C cuboids. The micron-scaled cuboid composite can lead to higher tap density and greater electrical performance due to lower interparticle resistance. Therefore, the as-prepared MnO/Mn2SiO4@C electrode exhibits stable specific capacities of 585.9 and 423.9 mA h g-1 after 1000 discharge/charge cycles at 1 and 2 A g-1, respectively. Meanwhile, an excellent rate capacity of 246.3 mA h g-1 was achieved even at 30 A g-1. Additionally, this facile and economical strategy to improve electrode performance provides a commercially feasible way for the construction of high-performance LIBs.

Surfactant-assisted synthesis of LiMn2O4 particles as high-rate and long-life cathode materials for lithium-ion batteries

Herein, we reported the synthesis of uniform LiMn2O4 submicroparticles by surfactant-assisted preparation of spherical MnCO3 precursor followed by solid-state reaction. Polyethylene glycol (Mw = 1000) was used as surfactant to control the morphology and size of the MnCO3 precursor as well as the MnO2 intermediate and LiMn2O4 product. The influence of particle size, homogeneity, and crystallinity on the electrochemical performance of LiMn2O4 was intensively investigated. The test results indicate that the LiMn2O4 sample using polyethylene glycol with weight as 10% of reactants shows the best rate capability and long-term cyclability. Due to the homogeneous particles with the average size of ca. 250 nm and high crystallinity, the discharge capacities are as high as 125, 118, 114, and 100 mAh g−1 at 1, 10, 20, and 50 C rates, respectively, along with high capacity retention of 74% after 1000 cycles at 20 C.

LiNi0.5Mn1.5O4 nano-submicro cubes as high-performance 5 V cathode materials for lithium-ion batteries

High-voltage spinel LiNi0.5Mn1.5O4 is considered the most promising cathode materials for large-scale lithium-ion batteries to meet the fast increasing high energy and power density requirements. However, its commercial applications are restricted due to rigorous capacity fading, particularly at high temperatures. Herein, we propose novel highly uniform nano/submicro LiNi0.5Mn1.5O4 cubes for the first time using cubic MnCO3 precursors, which are prepared via a facile co-precipitation route. The as-synthesized LiNi0.5Mn1.5O4 demonstrates excellent cycle stability and superior rate capability. Specifically, the materials retain a nearly 100% capacity retention after 100 cycles at 25°C. Moreover, under the elevated temperature of 55°C, it can deliver a discharge capacity of 131.7mAhg−1 with the specific energy of 605.1WhKg−1 and even over 98.4% of primal discharge capacity can be maintained for up to 100 cycles.

Effects of the starting materials of Na0.44MnO2 cathode materials on their electrochemical properties for Na-ion batteries

Na0.44MnO2 is one of the most promising cathode materials in the development of sodium ion batteries (SIBs). Here, a solid-state method is described for the synthesis of regular Na0.44MnO2 nanorods about 200nm in size at a low temperature without further annealing being required. In this work, we have investigated effects of different precursors on preparation of Na0.44MnO2 and found that the size and width of the Na0.44MnO2 nanorods were influenced by the MnCO3 precursors. The electrochemical properties for SIBs of Na0.44MnO2 nanorods synthesized from three different preparation methods were thoroughly researched. Na0.44MnO2 nanorods prepared by hydrothermal synthesis of MnCO3 (HS-Na0.44MnO2) produced a superior cathode material than other Na0.44MnO2 which uses commercial MnCO3 (C-Na0.44MnO2) and co-precipitation synthesis of MnCO3 (CP-Na0.44MnO2) as precursors. The HS-Na0.44MnO2 exhibits high discharge capacity (about 139.6mAhg−1), good cycling stability (98.2% after 40 cycles at the current density of 20mAg−1) and excellent rate performance, which is a much better performance than those in previous reports. The superior electrochemical performance of HS-Na0.44MnO2 is mainly due to the relatively smaller size, uniform morphology and excellent crystallinity. Furthermore, the electrochemical impedance spectroscopy (EIS) showed that the surface film resistance and charge transfer resistance of the HS-Na0.44MnO2 is smaller than others, which leading to the better electrochemical performance.

Growth behavior of LiMn2O4 particles formed by solid-state reactions in air and water vapor

Morphology control of particles formed during conventional solid-state reactions without any additives is a challenging task. Here, we propose a new strategy to control the morphology of LiMn2O4 particles based on water vapor-induced growth of particles during solid-state reactions. We have investigated the synthesis and microstructural evolution of LiMn2O4 particles in air and water vapor atmospheres as model reactions; LiMn2O4 is used as a low-cost cathode material for lithium-ion batteries. By using spherical MnCO3 precursor impregnated with LiOH, LiMn2O4 spheres with a hollow structure were obtained in air, while angulated particles with micrometer sizes were formed in water vapor. The pore structure of the particles synthesized in water vapor was found to be affected at temperatures below 700°C. We also show that the solid-state reaction in water vapor is a simple and valuable method for the large-scale production of particles, where the shape, size, and microstructure can be controlled.

Hierarchical LiMn2O4 Hollow Cubes with Exposed {111} Planes as High-Power Cathodes for Lithium-Ion Batteries.

Hierarchical LiMn2O4 hollow cubes with exposed {111} planes have been synthesized using cube-shaped MnCO3 precursors, which are fabricated through a facile co-precipitation reaction. Without surface modification, the as-prepared LiMn2O4 exhibits excellent cyclability and superior rate capability. Surprisingly, even over 70% of primal discharge capacity can be maintained for up to 1000 cycles at 50 C, and with only about 72 s of discharge time the as-prepared materials can deliver initial discharge capacity of 96.5 mA h g(-1). What is more, the materials have 98.4% and 90.7% capacity retentions for up to 100 cycles at 5 C under the temperatures of 25 and 60 °C, respectively. The superior electrochemical performance can be attributed to the unique hierarchical and interior hollow structure, exposed {111} planes, and high-quality crystallinity.

Mn2O3 microcubes with three-dimensional porous network structure as electrochemical sensing material for nitrite

Mn2O3 microcubes with three-dimensional (3D) micromesoporous network structure were synthesized by thermal decomposition of the as-prepared MnCO3 precursor. The structure, morphology, and textural property of the as-synthesized Mn2O3 microcubes were characterized. The electrochemical property and electrochemical sensing performance toward nitrite detection were investigated. Owing to the unique 3D micromesoporous network structure, the Mn2O3 microcubes could provide electrochemical sensing of nitrite with high sensitivity, selectivity, and reliability.

Hydrothermal Synthesis and Electrochemical Properties of Spherical α-MnO2 for Supercapacitors.

In the present work, spherical α-MnO2 with a high specific capacitance was synthesized by a two-step hydrothermal route. MnCO3 precursors were first prepared by a common hydrothermal method, and then converted to α-MnO2 via a hydrothermal reaction between the precursors and KMnO4 solutions. The effects of hydrothermal temperature on the morphology, crystal structure and specific area of the MnO2 were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and BET measurements. The electrochemical capacitive properties of the manganese dioxides with different morphologies and structures were evaluated by cyclic voltammetry and galvonostatic charge-discharge tests. The results showed that the temperature in the second hydrothermal step had prominent impact on the capacitive properties of a-MnO2. The MnO2 synthesized at 150 *C exhibited a highest specific capacitance of 328.4 Fx g(-1) at a charge-discharge current density of 100 mA x g(-1).

Morphologically controlled synthesis of porous Mn2O3 microspheres and their catalytic applications on the degradation of methylene blue

Porous Mn2O3 microspheres are controllably synthesized by selectively etching MnCO3 precursor with HCl solution. Morphologies and microstructures of Mn2O3 microspheres are analyzed by SEM, TEM, XRD, and N2 sorption technique. The catalytic performances of Mn2O3 microspheres for the degradation of methylene blue (MB) are investigated, and the reaction kinetics of MB degradation is also studied. The results show it is feasible to control the morphologies of Mn2O3 microspheres by adjusting the concentration of HCl solution, and the well-developed porous Mn2O3 microspheres demonstrate good potential on MB degradation. The degradation reactions follow the pseudo-first-order kinetic model, and the degradation capabilities for MB are great dependent on BET surface areas and pore volumes of Mn2O3 microspheres.

Highly dispersed Mn2O3 microspheres: Facile solvothermal synthesis and their application as Li-ion battery anodes

Nanostructured transition metal oxides are promising alternative anodes for lithium ion batteries. Li-ion storage performance is expected to improve if high packing density energy particles are available. Herein, Mn2O3 microspheres with a ca. 18μm diameter and a tapped density of 1.33g/cm3 were synthesized by a facile solvothermal–thermal coversion route. Spherical MnCO3 precursors were obtained through solvothermal treatment and they decomposed and converted into Mn2O3 microspheres at an annealing temperature of 700°C. The Mn2O3 microspheres consisted of Mn2O3 nanoparticles with an average 40nm diameter. These porous Mn2O3 microspheres allow good electrolyte penetration and provide an ion buffer reservoir to ensure a constant electrolyte supply. The Mn2O3 microspheres have reversible capacities of 590 and 320mAh/g at 50 and 400mA/g, respectively. We thus report an efficient route for the fabrication of energy particles for advanced energy storage.

Green synthesis of MnO x nanostructures and studies of their supercapacitor performance

Manganese oxides with different crystalline phases and morphologies were prepared by calcining MnCO3 precursors. The MnCO3 precursors with different morphologies were obtained through a green route under hydrothermal conditions with orange pericarp extracting solution as the reducing agent. By calcining the precursor under different temperatures and atmospheres, MnO x with different stoichiometric ratios (i.e., MnO, MnO2, Mn2O3, and Mn3O4) can be obtained. Electrochemical studies reveal that among these manganese oxides, MnO or MnO2 are more suitable as supercapacitor working electrodes than Mn2O3 or Mn3O4. They exhibit high specific capacitance up to 296.6 F/g and also possess good cycling stability, which make them potential electrode materials for supercapacitors.

Surfactant-assisted crystallization of porous Mn2O3anode materials for Li-ion batteries

MnCO3 precursors with different morphologies were crystallized using three kinds of surfactants as soft templates, i.e., cation surfactant cetyl trimethyl ammonium bromide (CTAB), anion surfactant sodium dodecyl sulfate (SDS) and neutral poly(vinyl pyrrolidone) (PVP). When PVP was used, the reaction manner was changed from only stirring at room temperature to a hydrothermal route. Under hydrothermal conditions, different ethanol/water ratios and sources of CO32− (NaHCO3 and urea) were used. Porous cubic, regular spherical and nut-like spherical Mn2O3 samples can be obtained by a simple post-annealing process. The correlation between the morphology of Mn2O3 and its performance as an anode material for Li-ion batteries was evaluated. The nut-like spherical Mn2O3 sample has the best cycling performance, with a specific discharge capacity of 925 mA h g−1 at a current density of 100 mA g−1 after 180 cycles. The sample composed of cubes and spheres has superior rate performance. The specific discharge capacity decreases with increasing current density from ~872 mA h g−1 at 100 mA g−1 to ~361 mA h g−1 at 2000 mA g−1.

Shewanella-mediated biosynthesis of manganese oxide micro-/nanocubes as efficient electrocatalysts for the oxygen reduction reaction.

Developing efficient electrocatalysts for the oxygen reduction reaction (ORR) is critical for promoting the widespread application of fuel cells and metal-air batteries. Here, we develop a biological low-cost, ecofriendly method for the synthesis of Mn2 O3 micro-/nanocubes by calcination of MnCO3 precursors in an oxygen atmosphere. Microcubic MnCO3 precursors with an edge length of 2.5 μm were fabricated by dissimilatory metal-reducing Shewanella loihica PV-4 in the presence of MnO4 (-) as the sole electron acceptor under anaerobic conditions. After calcining the MnCO3 precursors at 500 and 700 °C, porous Mn2 O3 -500 and Mn2 O3 -700 also showed microcubic morphology, while their edge lengths decreased to 1.8 μm due to thermal decomposition. Moreover, the surfaces of the Mn2 O3 microcubes were covered by granular nanoparticles with average diameters in the range of 18-202 nm, depending on the calcination temperatures. Electrochemical measurements demonstrated that the porous Mn2 O3 -500 micro-/nanocubes exhibit promising catalytic activity towards the ORR in an alkaline medium, which should be due to a synergistic effect of the overlapping molecular orbitals of oxygen/manganese and the hierarchically porous structures that are favorable for oxygen absorption. Moreover, these Mn2 O3 micro-/nanocubes possess better stability than commercial Pt/C catalysts and methanol-tolerance property in alkaline solution. Thus the Shewanella-mediated biosynthesis method we provided here might be a new strategy for the preparation of various transition metal oxides as high-performance ORR electrocatalysts at low cost.